Radiation Safety Manual

This page contains the official text of the Princeton University Radiation Safety Manual.  The Manual is provided to the NJ Department of Environmental Protection as part of the University's application for a license to possess and use radioactive materials.  It is also provided to radioactive materials users during radiation safety training.  The Manual is presented here because it is an important part of the documentation of our radiation safety program.  Some of the information contained in the Manual is presented elsewhere on the Radiation Safety pages, but generally the Manual provides greater detail. To request a copy of the Manual, contact the Radiation Safety Officer.


The Princeton University Radiation Safety Manual is a handbook of procedures and useful information for the radiation worker who uses either radioactive materials or radiation-producing machines in a laboratory setting at Princeton University. The Manual also reflects the requirements of relevant federal and state regulations. The Manual supplements but does not replace the required radiation safety training which all radiation workers must receive.

Introduction: Radiation Safety at Princeton University

The radiation safety program at Princeton University combines the best efforts of its Radiation Safety Committee, its radiation safety staff and all of its employees, students and visitors to ensure the safe use of radioactive materials.

Princeton University is licensed by the New Jersey Department of Environmental Protection (NJDEP) to possess and use many different radioisotopes. This license has been issued by NJDEP only because the University has established policies and procedures designed to ensure the accountability of radioactive materials and which will minimize the exposure of people to radioactive materials.

There are four key components to Princeton University’s radiation safety program:

The roles and responsibilities of each are described below:

The Radiation Safety Committee (RSC)

The Committee

  • oversees the radiation safety program
  • authorizes the use of radioactive materials
  • reviews incidents involving radioactive materials
  • sets policies for the use of sources of radiation
  • gives general supervision to the implementation of those policies.

The Environmental Health and Safety Office

The day-to-day operation of the radiation safety program is managed within the Environmental Health & Safety Office (EHS) by the University’s Radiation Safety Officer (RSO). The RSO and the Radiation Safety staff are available to advise Authorized Users and radiation workers on radiation safety and regulatory compliance issues and to provide the following services:

  • training
  • personal monitoring and dosimetry services
  • bioassay
  • pregnancy counseling
  • laboratory radiation surveys
  • incident, spill and contamination management
  • radioactive waste management

Appendix D lists the names, phone numbers, e-mail addresses and primary areas of responsibility of the Radiation Safety Staff.

The Authorized User

Authorized Users are faculty members or senior staff members who have been approved by the Radiation Safety Committee to use radioactive materials under specific conditions. An Authorized User is granted approval to possess and use specific isotopes only for the uses described in the authorization application and is issued a possession limit for each of those isotopes. Any person using radioactive materials at Princeton University is either an Authorized User or is a radiation worker using radioactive materials under an Authorized User’s supervision. Each Authorized User is responsible for:

  • the health and safety of anyone using or affected by the use of radioactive materials under his or her direction or supervision.
  • personally attending initial and annual refresher training and ensuring that his/her employees, staff and visitors receive appropriate training.
  • ensuring that his/her employees, staff and visitors comply with relevant regulations, policies and procedures.

The Radiation Worker

A radiation worker is anyone who uses radioactive materials or radiation-producing machines. The radiation worker’s thorough training, compliance with regulations and procedures, careful work habits and respect for the health and safety of fellow workers are an integral part of the radiation safety program. A radiation worker’s responsibilities include the following:

  • Complete the initial radiation safety training program and, for open source users, attend annual refresher radiation safety training offered by EHS.
  • Be familiar with the isotopes in use; know their radiological, physical and chemical properties, methods of detection, the types of hazards presented by each one, and the specific precautions and handling requirements for each isotope.
  • Be familiar with all the relevant procedures of the radiation safety program, including isotope purchasing and waste disposal procedures.
  • Know how to properly use the appropriate radiation survey meter.
  • Know how to use radiation monitoring badges and exchange them promptly at the end of the monthly or quarterly wear period.
  • Maintain appropriate inventory, disposal and survey records.
  • Secure radioactive materials by making sure that radioactive materials are locked away or are under immediate supervision within the laboratory.
  • Inform coworkers and visitors to the work area about the presence of radioactive materials and of any precautions they should take.
  • Know who to call in any incident involving sources of radiation and how to handle spills and personal contamination.

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Section 1: Spills & Incidents

Who to Notify

What to Do

An accident may happen to even the most careful of workers, and any worker may be called upon to assist in the case of a spill, a contamination incident, or an emergency. Be prepared and know how to respond before an incident happens. The following procedures provide an overview of who to notify and how to respond to several different types of incidents. Emergency Response Guidelines books which list incident contact phone numbers and procedures are posted near a telephone in every lab.

NOTE: Problems involving radioactive materials, such as spills or personal contamination, do not typically create emergencies. Generally such incidents can be readily handled with laboratory or other University resources instead of calling non-University emergency responders. A situation involving radioactive materials is only an emergency if it also involves fire, explosion or serious injury.

Who To Notify


An incident can be readily handled with laboratory or other University resources and may include a spill of radioactive materials, an incident of personal contamination or a possible exposure to an x-ray source.

  • During normal working hours, call Environmental Health & Safety (EHS) at 609-258-5294, or
  • Outside normal working hours, call EHS at 609-258-5294. You will hear a menu directing you to either leave a message or speak to a safety officer directly. Note: The immediate contact option should be used for radioactive materials incidents only. 


In the event of a fire, explosion or serious injury:

  • Call Public Safety at 911 anytime (use a campus phone to dial 911 or, if using a cell phone, dial 609-258-3333).
  • During normal working hours, also call EHS at 609-258-5294.
  • Also contact any Laboratory or Departmental Emergency contacts listed on the Emergency Information poster found on or near the entrance to the laboratory.

Reporting Requirements

You must notify immediately EHS if:

  • You have a spill exceeding 10 µCi.
  • You have widespread contamination.
  • You have contamination on skin or clothing (other than a lab coat) or shoes.

What to Do

When a Spill Occurs or Contamination is Found

Assess the extent of the contamination or the spill and ask:

  • Is this a minor spill or contamination incident?  Can I realistically handle this incident without help and without undue risk to me?  Do I have the resources I need to deal with this incident?
    If so, see Table 1 below.
  • Is contamination widespread?  Does this involve more than 10 µCi? Has a spill caused radioactive material to splatter?   Do I need help to manage and clean up this incident?
    If so, see Table 2 below.

Table 1: Minor Spill or Contamination

Spill Decontamination Procedure

Supplies: a lab coat, protective eyewear, sturdy disposable gloves, shoe covers (if appropriate), paper towels, decon solution, a rad waste container, and a survey meter.

Decon Solution:  For most isotopes (H-3, C-14, P-32, P-33, S-35, etc.), lab detergent, commercial products such as Count-Off, or mild acids such as acetic acid, may be used as decon solutions.  For I-125 contamination, do not use hot water, acids or acidic detergents, because volatile iodine may be produced.  A basic decon solution such as Count-Off or Dekasol may be used.

  1. Get supplies ready before cleanup.
  2. Use a survey meter or a wipe survey to carefully define the extent of the contaminated area.
  3. Mark the contaminated area with tape or other marking.
  4. Start the clean-up at the edge of the contaminated area and work inward.
  5. Clean wet spills or contamination using absorbent paper towels.
  6. Change paper towels frequently to avoid smearing contamination around.
  7. Change gloves frequently and watch out for rips and tears.
  8. Survey all personnel involved in the clean-up.  survey shoes as wella s hands and lab coats.
  9. Record the clean-up and personnel surveys in the lab survey log.
  10. Call EHS for assistance and information.
Table 2: Major Spill or Contamination
  1. Notify all personnel within the lab and in the vicinity of the lab, as appropriate.
  2. Notify EHS and deprtmental safety contacts.
  3. Assess the need for personnel protection measures such as removing contaminated clothing or cleaning contaminated skin.
  4. Block off the area.  Keep bystanders out of the area.  Assemble persons who were in the lab at the time of the incident.  Keep them close enough to the contaminated area to limit the spread of contamination but far enough away that no one is at risk of getting further contaminated.
  5. Do not track contamination beyond the area.  Remove contaminated shoes and put on clean shoes or put protective covers over shoes before leaving the contaminated area.
  6. Survey everyone and anything leaving the contaminated area.
  7. Decontamination is the responsibility of the Authorized User's lab personnel.  Clean-up should be performed under the supervision of EHS radiation safety staff.

For Skin and Body Contamination

  1. Notify EHS immediately whenever any case of skin or body contamination occurs.
  2. Note the original survey meter reading, the location of the contaminated area and the time of the contamination was discovered. EHS will use this information to calculate dose.
  3. Wash skin using mild soap and warm water for 2-3 minutes. Do not abrade skin or use hot water.
  4. Measure and record the count rate after the initial attempt at decontamination. Survey and repeat decontamination until the count rate cannot be reduced any further.
  5. If the skin becomes irritated, discontinue decontamination.
  6. When decontamination efforts are not immediately successful, often a substantial reduction in count rate is achieved during the next 24 hours with periodic washings with soap and water, combined with normal flaking of the skin.

A Serious Injury with Radioactive Contamination

Serious injury and life-or-death situations always take priority over radiological concerns. In all cases of physical injury, even minor injuries, medical attention and hospitalization take precedence over contamination concerns. There are no radiation sources at the University that produce contamination and radiation exposure risks large enough to prevent first aid from being given.

  1. Follow the Fire, Explosion & Serious Injury notification procedure. Public Safety responders are trained to provide first aid.
  2. If possible, have someone meet emergency response personnel and escort them to the accident scene.
  3. Remove contaminated items and clothing from the victim only if these actions will cause no further harm.
  4. If time permits, attempt to provide an uncontaminated pathway for the emergency crew.
  5. Have someone who can provide useful additional information accompany the victim to the emergency room.

Possible Overexposure to Sources of Radiation

The most likely scenario for a serious overexposure to radiation involves exposure to the primary beam of an x-ray diffractometer or to a high activity sealed source. In any case, notify EHS, who will provide additional instructions, based on the exposure conditions.

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Section 2: Using Radioisotopes Safely

In some cases the practices described below are required by regulation or by license conditions but in all cases these practices represent good laboratory practices that will promote the safe use of radioactive materials.

Protective Clothing

Lab accidents often involve spills or splashes which can readily contaminate exposed wrists, legs and feet. For any work with an open radioactive source, wear:

  • gloves (the longest length available)
  • a full-length lab coat (worn closed with sleeves rolled down)
  • close-toed shoes. Do NOT wear sandals or other open-toed shoes while working with radioactivity

It is strongly recommended that you wear safety glasses for any procedure, but it is essential that you wear safety glasses whenever there is a potential for the build-up of pressure.

Keep an extra set of clothing and shoes in the lab in the event that clothing becomes contaminated.

Avoid using petroleum-based hand creams when wearing gloves because petroleum-based hand creams may increase glove permeability.

Food and Beverages

  • Do not eat, drink or smoke in any room in which open sources of radioactive materials are used.
  • Do not store food, beverages, or medicines in refrigerators, freezers or coldrooms where open sources of radioactive materials are used or stored.
  • Do not store food, beverages, medicines, cosmetics, coffee cups, eating utensils, etc. on open surfaces near lab benches where contamination can be
    readily spread.

Mouth Pipetting

Never mouth pipet radioactive solutions.


  • Lock radioactive stock materials and sealed sources in a secured container or a secured storage area when not in use. Stock material is radioactive material as provided by the vendor and does not include material withdrawn from the original stock for experimental use.
  • Do not leave radioactive materials unsecured in an unattended lab, even for a short time, unless the lab is locked.
  • Supervise visitors to the lab.
  • When visitors who are not accompanied by authorized lab personnel enter the lab, find out who they are and why they are there.
  • If you discover that radioactive material is missing or lost and cannot be accounted for, notify EHS no later than the next business day.

Signs and Labels

For the radioisotopes commonly used at Princeton University, labeling of rooms and containers is mandatory under the following conditions:


Activity for Which Labeling

is Required (uCi)

H-3 1000
C-14 100
P-32 10
P-33 100
S-35 100
Ca-45 100
Cr-51 1000
Fe-59 10
Zn-65 10
I-125 1
U-238 100
  • Labeling contaminated items and containers of radioactive material is an important tool for contamination control and is a courtesy to other laboratory personnel.
  • Any container of radioactive material, any room or piece of equipment in which radioactive material is stored and any contaminated area or item, regardless of the level of radioactivity, should be labeled as Radioactive.
  • Caution Radioactive Material tape is available from the Molecular Biology Department and Chemistry Department stockrooms.

Fume Hoods and Biosafety Cabinets

Work with certain radioactive materials, such as volatile I-125 or millicurie amounts of S-35 methionine/cysteine, must be performed in a designated radioactive materials (RAM) fume hood.

  • A RAM hood must be posted with an Environmental Health & Safety (EHS) RAM sticker, and a Class A or a Class B hood. For radioiodine work, a RAM hood must be a Class A hood with an average face velocity of at least 100 lfpm. The hood class is shown on the EHS hood survey sticker.
  • To verify that the hood is functioning properly, compare the current reading for the hood’s continuous flow monitoring device (e.g., magnehelic) with the expected reading shown on the EHS hood survey sticker.
  • Biological safety cabinets (or laminar flow hoods) may not be suitable for radioisotope work, since the air from the cabinet may be exhausted back to the room. Consult with EHS before performing work with volatile radioactive materials in a biological safety cabinet.

Biological and Chemical Hazards

In addition to radiation hazards, some experimental protocols may pose biological and chemical hazards as well. Be familiar with all the risks associated with an experiment, follow any necessary precautions, and know the proper disposal techniques for the resulting wastes.

Keeping Radiation Exposure ALARA

The acronym ALARA, which stands for As Low As Reasonably Achievable, means that radiation workers should make every reasonable effort to keep radiation exposures as far below regulatory dose limits as practical. Adhering to the following practices can help keep radiation doses ALARA.

  • Be familiar with the properties of the radioisotope to be used and with any precautions and concerns specific to that radioisotope and material. (See Appendix B for detailed information about the radioisotopes most commonly used at the University).
  • Unfamiliar radioisotope procedures should be rehearsed before radioactive material is actually used.
  • Wear protective clothing.
  • Wear radiation monitor badges when appropriate.
  • Have all the necessary materials and equipment available and ready at the start of a procedure.
  • For those radioisotopes with significant external radiation levels, use remote handling tools, such as tongs, to limit direct handling of stock and sample vials.
  • Survey frequently and extensively. Don't assume that contamination will only be found on the benchtop.
  • Clean up contamination in the work area promptly.
  • Change gloves and lab coats as they become contaminated.
  • Work in a hood during procedures using volatile materials such as I-125 or millicurie amounts of S-35 methionine/cysteine.
  • Cover radioactive waste cans at all times and store waste cans away from areas in which people spend substantial amounts of time. Provide shielding for waste cans with significant external radiation levels.
  • Do not store contaminated materials, including gels, at any desk area.
  • Survey yourself and your clothing when radioisotope work is finished and before leaving the lab.

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Section 3: Acquiring Radioactive Materials

Princeton University must track and control all radioactive materials received to ensure that the University’s possession limits for radioactive materials (under the license issued by the state of New Jersey) are not exceeded. Therefore, the ordering and acquisition of radioisotopes must follow very specific rules and procedures. There are a few important rules for the purchase and acquisition of radioactive materials that laboratory workers must keep in mind:

Rule #1: Never place orders for radioactive materials directly with a vendor. All radioisotope orders must be placed in PRIME and must be coded as Radioactive. Replacements for incorrect orders or unusable shipments must be negotiated by the Purchasing Department.

Rule #2: Each laboratory using radioactive materials has been issued an Authorization for each isotope. This Authorization spells out the lab’s possession limit for that isotope and the conditions of use. EHS will not approve an order if the order will cause the lab’s Authorization limit to be exceeded.

Ordering Procedures

Note:  The procedures provided in the Manual for ordering radioactive materials no longer apply since the University's transition to Princeton PRIME.  Click here for updated procedures.

Free Vendor Samples and Samples from Other Institutions

Any person who plans to acquire radioactive material as a gift, loan or transfer from a vendor, another institution or company must contact EHS before the material is shipped to the University. Just as with regular radioisotope orders, EHS must approve any shipments before they are shipped. In addition, EHS arranges the shipment with the other institution and sends a copy of our radioactive materials license. Failure to notify EHS in advance about the shipment of radioactive materials may cause a lab’s authorization to be suspended or revoked.

Loans or Other Transfers of Radioactive Material

Transfers of radioactive material between Princeton University labs are permitted under the following conditions:

  • Transfers of sealed sources or plated sources are not permitted without written authorization from EHS.
  • The lab transferring the material is responsible for ensuring that the recipient lab is authorized to possess the radioisotope in question.
  • Transfers of open source radioactive material in amounts of 100 µCi or more must be reported to EHS no later than the next business day.

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Section 4: Package Receipt & Inventory

Receiving a Package

  1. All radioactive material packages are delivered to a central radioisotope receiving area. Environmental Health & Safety (EHS) staff open the package, check the packaging for contamination, inspect the packing list and vial label to verify that the vial contains the material actually ordered, and enter the shipment into the University’s radioisotope inventory and tracking database (RITA). RITA assigns a unique ID Number to each vial or source, and EHS staff place a label bearing the ID Number on the vial or source.
  2. When EHS has finished its survey of the package and has entered it into the inventory database, the vial or source is repackaged in its original package. The package is taped securely closed, and an EHS Package Release Label is placed on the package. In addition, EHS supplies a Vial Use Log or Sealed Source Inventory Log with each vial or source of radioactive material.
  3. Although EHS staff delivers packages to each department, the respective departments are responsible for establishing departmental procedures for transferring packages to laboratory personnel.
  4. When a package is delivered to the lab or picked up from the department’s receiving room, the person who accepts the package is asked to sign a receipt log (in some departments only designated lab representatives may sign for radioisotope packages). Before signing for a package, examine the packing list and the labels on the package to verify that this package is the same package described on the receipt log.
  5. Although EHS staff checks the vial and packing list against the requisition to look for errors in the shipment, recheck the packing list to verify that the package contains the expected material.
  6. After signing for any package, make sure that the package is immediately placed in a secured location.
  7. After signing for a package, promptly notify the person who ordered the material or who will use it that the package has arrived.

Opening Packages

The precautions described below are necessary because packages are occasionally delivered with the wrong materials, may contain highly contaminated inner vials, or vials may unintentionally become pressurized during transport.

  1. Wear protective clothing and open the stock vial in a fume hood when practical.
  2. Verify that the stock vial contains the material you ordered in the amount you ordered. If there are any discrepancies, call EHS and the Purchasing Office immediately.
  3. Before the package is delivered to the laboratory, EHS surveys the packing materials or packing containers for contamination. However, you should wipe test the inner container or stock vial to check for gross contamination (See Section 5 for information on performing a survey).
  4. Extensive contamination on the inner vial should be reported immediately to EHS.

Discarding Packaging Materials

  1. Survey any box or packaging material to be sure it is not contaminated before placing it out for the regular trash or sending it for recycling.
  2. Completely mark out, tape over, or remove all radioactive material labels on any empty packaging before placing the package out for pickup as non-radioactive trash. This is a specific NJDEP regulatory requirement.

Inventory Control

All stock vials, sealed sources and plated sources are assigned a unique identification number through the Princeton University radioisotope inventory and tracking database, known as RITA. Sources are tracked in RITA through the use of this ID number. In order to maintain adequate inventory control over the use and disposal of radioactive materials at the University, the following procedures have been established. EHS provides the laboratory with detailed written procedures for all phases of the inventory control and tracking process.

  • Record all withdrawals of material from a stock vial on the Vial Use Log.
  • When a stock vial is placed into radioactive waste, mail the Vial Use Log for that vial back to EHS. When EHS receives the Vial Use Log, EHS deletes the stock vial in RITA from the Authorized User’s active inventory.
  • An Authorized User’s active inventory can be viewed online through PeopleSoft. RITA performs decay calculations so that lab members can see the amount of radioactivity available, corrected for decay. Detailed procedures for using RITA are found in the Laboratory User’s Guide to RITA, available from EHS.
  • Once each quarter, labs must perform a physical inventory of radioactive materials stored in the lab, compare the actual inventory to the online inventory in RITA and report any discrepancies to EHS.
  • The procedure for handling transfers of radioactive material is described in Section 3.
  • If a lab discovers that radioactive material is missing or lost and can not be accounted for, EHS must be notified immediately.

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Section 5: Surveys & Contamination Control

Frequent surveys performed by knowledgeable laboratory personnel are the main line of defense to detect spills and to prevent the spread of contamination within and beyond the laboratory. This section summarizes the requirements for performing surveys. See Appendix A for detailed information about the types of contamination surveys, how to use a survey meter, how to perform a survey using a survey meter and how to perform a wipe test.

Survey Instrumentation

Table 5.1 summarizes the instrumentation and method of choice for the isotopes most commonly used at Princeton University.

Performing a Meter Survey

Appendix A provides detailed instructions on the use of a survey meter and how to perform a survey. The following list is a brief survey checklist:

  • Perform a battery test
  • Perform an operational check the first time you use the meter each day
  • Check meter background. Meter background should be < 100 counts per minute (cpm) for a G-M meter and < 300 cpm for a sodium iodide (NaI) scintillation meter.
  • Perform the survey
  • Decontaminate or label contaminated areas and items.
  • Document survey results in your personal survey log or in the lab survey log.

Defining Contamination

If an item or area with a sustained count rate of three times background or more is found, the item or area should be considered to be contaminated.

When to Survey

Laboratory personnel must conduct individual work area surveys (surveys of floors, workbenches, handles, experimental equipment, etc.) and personal surveys (surveys of one’s person and clothing) under the following conditions:

  • at the end of an experimental procedure;
  • at the end of each day for multi-day procedures;
  • frequently during the manipulation of millicurie quantities of open sources;
  • following the opening of radioactive material packages;
  • following withdrawals from stock vials containing more than 1 mCi;
  • prior to exiting the laboratory (for personal surveys)

Where to Survey

Survey areas where splashes or spills may have occurred and areas where a person could unknowingly transfer contamination. Typical survey locations include:

  • Benchtops, including the edges
  • Fume hoods (aprons, sashes, sash handles)
  • Beta shields
  • Refrigerator and freezer door handles
  • Sinks designated for radioactive material disposal (sink basin, surrounding bench, faucet handles)
  • Floors: at working areas, laboratory entrances, waste containers, fume hoods
  • Communal equipment, such as pipettors, timers, incubators, centrifuges, water baths, etc.
  • Non-radioactive trash (to ensure that contaminated waste is not disposed of as regular trash)
  • Clean areas (offices, desks, doorknobs, phones, computers)

When to Document Surveys

Document the survey results:

  • when radioactivity in amounts of 250 µCi or more have been handled,
  • whenever contamination is discovered, regardless of the amount used, and
  • to show follow-up actions, whenever contamination has been cleaned up.

How to Document Surveys

Record survey results in a personal survey log or in the laboratory survey log. Appendix A contains a copy of a blank survey log page. Each log entry should contain the following information:

  • Name of person performing the survey
  • Date of survey
  • Brief description of the area surveyed
  • Survey meter results (in cpm), even for background count rates
  • Meter identification (model, serial number)
  • Follow-up action is taken when contamination is found.

When to Report Contamination

  • Skin contamination, regardless of the level of contamination, must always be immediately reported to EHS.
  • Uncontained spills (e.g., spills outside of contained areas on the workbench or hood) in excess of 10 µCi must be promptly reported to EHS.
  • Widespread contamination in any amount should be promptly reported to EHS. Contamination is considered to be widespread if it is found in several locations which are not normally expected to be contaminated (e.g., on floors and handles, in non-radioisotope areas, etc.).

Purchase, Repair and Calibration of Survey Meters

Call EHS for recommendations and information about purchasing a radiation survey meter. After a new meter arrives, call EHS to register the meter. Every survey meter must have a check source attached to it. Check sources are available from EHS.

EHS performs a periodic electronic calibration of laboratory survey meters. Meters must be calibrated at least annually.

Call EHS whenever a survey meter is not functioning properly or needs to be repaired for any reason. EHS maintains repair and calibration records for each survey meter and can offer limited diagnostic and repair services.

Table 5.1

Survey Instrumentation Guide

Radioisotope Acceptable Survey Method Comments
H-3 LSC There are no other acceptable survey methods
C-14 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm
P-32 G-M or LSC G-M detects low levels of contamination
P-33 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm
S-35 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm.
Cr-51 NaI, g, or LSC  
Zn-65 G-M or g  
I-125 NaI, g, or LSC  
U-238 G-M or LSC  

Table Key:
G-M = Survey meter with a Geiger-Muller detector
LSC = liquid scintillation counting
NaI = survey meter with a thin crystal sodium iodide detector
g = gamma counter

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Section 6: Dose Limits & Personal Monitoring

Annual Radiation Dose Limits

Each worker who is monitored for external or internal radiation exposure at the University is notified about the doses he or she receives. For example, a worker who is notified that he or she received a whole body dose of 50 millirems (mrem) and a shallow skin dose of 150 mrem during a quarter will note that this constitutes 1% and 0.3%, respectively, of the appropriate annual limits. (See the table below for a listing of the dose limits established by the state of New Jersey).

The University has established investigational levels at doses considerably less than the dose limits. When a worker accumulates during any part of a year a dose at or above the investigational level, Environmental Health & Safety (EHS) will investigate to determine causes of the dose and to recommend practices to minimize radiation exposure in the future.

Further information about radiation exposure from radioactive materials taken up internally is provided in Appendix B in the listings of Annual Limits of Intake (ALI), the amount of a specific radioisotope taken internally which will produce a whole body dose of 5000 millirems. For example, Appendix B states that the ALI for H-3 is 80 mCi. If a worker is notified that he or she has had an intake of 80 mCi of H-3 with a resulting dose of 5 mrem, then the table below indicates this dose to be 0.1% of the annual radiation dose limit.


NJ Limit (mrem/yr)

University Investigation Level (mrem)

Whole Body

Includes dose from external and internal sources
Lens of Eye
Extremities include the arm below the elbow or leg below the knee
Embryo & Fetus
500 for entire pregnancy
Applies only when a Declaration of Pregnancy has been submitted
Occupational exposure of a minor
10% of the limits above
Applies to anyone under age 18
Member of the General Public

The ALARA Principle

Although the University must keep doses of students, staff and visitors below the relevant state dose limits, the University is further required by state regulation to keep doses As Low As Reasonably Achievable (ALARA). This means that the University must work to keep doses as far below the dose limits as can readily be achieved. Consequently, the University has established investigational dose levels and will investigate any dose exceeding these levels in an effort to address causes of unnecessary radiation exposure.

External Monitoring

Required Monitoring

Monitoring of external radiation exposure is required for the following persons:

  • Any person using an x-ray diffractometer
  • Persons using radioactive materials in the following amounts and types of use:

* Monitoring is not required for operations that only involve aliquoting from a stock vial and do not involve any other manipulation of radioactive materials.

  • Declared pregnant workers who work in labs using gamma emitters or high-energy beta emitters (>250 keV)
  • Other persons may be issued monitors at the discretion of the Radiation Safety Officer (RSO).
Optional Monitoring

External monitoring can be requested by any person working in a laboratory in which gamma emitters or energetic beta emitters are used, even if that person does not meet the criteria for required monitoring. In such a case, EHS meets with the worker initially to discuss any concerns the worker has and will then initiate radiation monitoring for the next year. After providing dosimetry for a year, EHS meets with the worker again to review doses for the past year and to discuss whether monitoring should be continued.

Monitoring is not generally provided for persons working in laboratories in which only alpha emitters or low energy beta emitters (< 250 keV) are used.

How to Request a Monitor Badge

Use the Radiation Monitoring Service Request Form to submit a request to EHS to request radiation monitoring services. 

The Rules of Monitor Badge Wear
  • Wear badges so the name label faces toward the source of radiation.
  • Wear the ring badge under gloves to avoid contaminating the badge (but be careful not to throw out the ring badge with the gloves when discarding the gloves as radioactive waste.)
  • Store badges in low radiation background areas.
  • Do not expose badges to elevated temperatures (e.g., don’t store badges on hot sunny surfaces or near radiators).
  • Notify EHS immediately if you suspect you may have received an unusual exposure.
  • Do not wear your badges when you receive medical x-rays or are exposed to other medical sources of radiation.
  • If your badges become contaminated, damaged or lost, call EHS immediately to request replacements.
  • Badges are generally exchanged once a quarter, although badges for declared pregnant workers are exchanged once a month.
  • Turn in your old badges to your badge exchange contact promptly at the end of the wear period, after you receive your new set of badges.
How to Find Out Monitoring Results

Monitoring reports are received by EHS approximately six weeks after the end of a monitoring period and forwarded to each Authorized User shortly thereafter. An individual can request his/her radiation exposure history any time by contacting EHS.

Internal Monitoring

Radioactive materials can be taken up internally when volatile or other airborne radioactive materials are inhaled and when radioactive materials are absorbed through skin or ingested. Internal uptakes may occur when lab personnel unknowingly handle contaminated objects, when permeation occurs through highly contaminated gloves, or when spills occur. To determine the dose resulting from an intake, bioassays must be performed. For the radioisotopes commonly used at Princeton University, bioassays usually involve urinalysis or external thyroid counting.

When are Bioassays Required?

EHS may request bioassays when widespread contamination has occurred in a laboratory, and when skin contamination has occurred. A worker can request a precautionary bioassay at any time. A bioassay is required under the following circumstances:

When a person uses H-3 exceeding the amounts listed below (which are the amounts a person handles at any one time or the cumulative activity handled by that person during one month):

Nature of Use Form Activity
In an open room HTO* and other forms, including nucleotide precursors 100 mCi
  H-3 gas in a sealed vessel 100 Ci
In a chemical fume hood HTO* and other forms, including nucleotide precursors 1 Ci
  H-3 gas in a sealed vessel 1000 Ci

* HTO is tritiated water

When a person uses I-125 exceeding the amounts listed below (which are the amounts a person handles at any one time or the cumulative activity handled by that person during any three month period):

Nature of Use Form Activity
In an open room As NaI or other volatile form 1 mCi
  Bound to a non-volatile agent 10 mCi
In a chemical fume hood As NaI or other volatile form 10 mCi
  Bound to a non-volatile agent 100 mCi
How to Arrange for a Bioassay

Thyroid counting is performed at the EHS office and requires no more than ten minutes. Contact EHS to schedule an appointment. Supplies and instructions for urine bioassays are provided by EHS.

Declared Pregnant Worker Program

NJDEP’s Fetal Dose Regulations

The two most important aspects of the NJDEP’s fetal dose regulations are:

  • The fetal dose regulations apply only to a woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.
  • The dose to the fetus resulting from occupational exposure of a declared pregnant woman may not exceed 500 mrem for the entire pregnancy.
How to Submit a Declaration of Pregnancy

Any radiation worker who is pregnant or believes that she may be pregnant should contact EHS. All inquiries will be kept in confidence. EHS will take the following steps:

  1. Provide an opportunity to submit a Declaration of Pregnancy. A Declaration of Pregnancy form is included in Appendix E or may be obtained from EHS. If a written declaration of pregnancy is not submitted to EHS, then the worker’s dose continues to be controlled under the normal dose limits for radiation workers.
  2. Provide information concerning the risk of fetal radiation exposure.
  3. Evaluate the worker’s dose history and exposure potential. For the type of radiation work performed at Princeton University, it is rarely necessary to recommend reassignment or changes to job duties.
  4. Make recommendations for reducing radiation exposure.
  5. Monitor the worker’s radiation dose with regard to the worker and fetal dose limits.

Research Involving Radiation Work at Other Institutions or Companies

Any Princeton University employee or student who plans to do radiation work at other institutions must notify EHS before visiting the other institution. The radiation exposure of visitors from Princeton University will be monitored by the host institution, using badges supplied by that institution. However, Princeton is required to keep track of the total radiation exposure received by its employees and students. EHS will contact the host institution and request radiation exposure records.

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Section 7: Waste Disposal

The Radioactive Waste Management Program

Several factors determine the route by which radioactive wastes are disposed. These factors include: half-life, radionuclide, chemical constituents, physical form (liquid or solid), dose rate, and other physical characteristics (is the source sealed and encapsulated or open?).

  • Most solid wastes that contain isotopes with half-lives not exceeding 120 days are handled through the centralized Decay-in-Storage (DIS) Program for ultimate disposal as non-radioactive medical waste.
  • Solid radioactive wastes contaminated with radionuclides with half-lives greater than 120 days are disposed of through a contracted radioactive waste disposal services broker as part of the Off-Site Radioactive Waste Disposal Program managed by EHS.
  • Certain liquid wastes are disposed of through the Sanitary Sewer Disposal Program.
  • All liquid scintillation wastes are disposed of through a contracted radioactive waste disposal services broker as part of the Off-Site Radioactive Waste Disposal Program.
  • Special wastes that include animal or other biological waste, hazardous chemical wastes such as phenol, sealed sources, certain uranium and thorium compounds, radium, or transuranic isotopes are disposed of through special arrangements. Contact EHS to make disposal arrangements.

Mixed Wastes

Mixed wastes are radioactive wastes that also contain hazardous waste components regulated under RCRA (the federal Resource Conservation and Recovery Act) regulations. Currently there are limited options for the disposal of mixed wastes, and the options which do exist are often costly. In the laboratory setting the type of mixed wastes most likely to be generated include:

  • contaminated lead
  • certain organic solvents such as chloroform, phenol, toluene and xylene.

EHS is available to help determine whether specific wastes meet the definition of mixed wastes. Whenever feasible, contact EHS before generating mixed wastes to allow time to determine disposal options or to establish procedures that may prevent a mixed waste from being generated. The flow charts at the end of this section will allow a user to determine the basic disposal route for any waste form and will either refer the user to detailed disposal procedures or to EHS for further help.

Waste Disposal Procedures

The flow charts at the end of this section will allow a user to determine the basic disposal route for any waste form and will either refer the user to detailed disposal procedures or to EHS for further help.

Summary of Radioactive Waste Disposal Procedures

Step 1: Is this animal or other biological waste?

  • Yes - call EHS for procedures
  • No - go to Step 2

Step 2: Is this mixed waste?

  • Yes - call EHS for procedures
  • No - go to Step 3

Step 3: Is this liquid scintillation counting waste?

  • Yes - go to the liquid scintillation waste procedures
  • No - go to Step 4

Step 4: Is the waste liquid?

  • Yes - go to the liquid waste disposal chart
  • No - go to Step 5

Step 5: Is the waste solid?

  • Yes - go to the solid waste disposal chart

Liquid Scintillation Counting Wastes

  • The use of toluene-, xylene- and pseudocumene-based solutions is prohibited.
  • LSC solutions must have a flashpoint of 140º F. or greater. Acceptable LSC solutions include:
    • BCS
    • CytoScint ES
    • Formula 989
    • BCS-NA
    • Ecolite
    • Scintiverse BD
    • BetaMax ES
    • Ecolume
    • Universol ES
    • Bio-Safe II
    • Econo-Safe
    • Fisher’s ScintiSafe solutions
    • Bio-Safe NA
    • Ecoscint
  • All LSC wastes, regardless of the isotope, are disposed of through an off-site disposal program.

LSC Waste Disposal Procedures

  1. Obtain a lined 5-gallon pail from the department waste contact or from EHS.
  2. To minimize costs, certain isotopes should be segregated from other isotopes. EHS will provide separate instructions for segregating LSC wastes.
  3. Place tightly closed vials in the lined pail.
  4. Do not place gloves or anything except vials in the pail.
  5. Make an entry on the waste card each time wastes are placed in the pail.
  6. When the pail is full, securely twist closed and seal the liner, using tape, string or twist ties.
  7. Contact EHS to remove full waste pails.
  8. Contact the department waste contact or EHS for supplies. Call EHS with any questions.

Liquid Waste Disposal Procedures

A flow chart for liquid radioactive waste disposal

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Section 8: Transporting & Shipping Radioactive Materials

Transfers within the University

Whenever radioactive material is moved from a laboratory to any other facility, even to adjacent buildings, package it and move it in a way that will avoid spilling the material and unnecessary exposure to anyone. Take the following steps:

  1. Contact Environmental Health & Safety (EHS) in advance, if the material is being moved along or across any public street. Under some circumstances, the transportation of radioactive materials across campus must comply with U. S. Department of Transportation (USDOT) regulations. Normally it will be easy to comply with USDOT requirements. EHS will advise you on how to comply.
  2. Surround any container of radioactive liquid with sufficient absorbent material to absorb at least twice the volume of liquid. Use materials such as vermiculite, paper towels, or absorbent padding.
  3. Provide adequate shielding.
  4. Label the inner container of radioactive materials with a Radioactive Materials label. Label the outer package with the names and addresses of the labs that the package is coming from and going to.

Transfers between Princeton University and Other Institutions

Do not ship or transport radioactive materials to another institution without contacting EHS in advance. In order to transfer and ship radioactive materials properly, take the following steps:

  1. Contact EHS well in advance of the planned shipment date, using the Hazardous Materials Shipping Request Form. EHS will contact the other institution to obtain a copy of its license and to make arrangements with the other institution for receipt of the package and will advise the Authorized User and lab personnel about packaging and shipping requirements.
  2. Plan to use a commercial carrier such as a Federal Express to ship radioactive materials. Do not use a private vehicle to transport radioactive materials because the transportation regulations are complex. Any person transporting hazardous materials must receive specialized training, be insured for transporting the hazard, and may require a commercial driver's license.

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Section 9: Radiation Producing Machines

A radiation-producing machine is defined to be either any machine primarily intended to produce radiation, such as:

  • x-ray diffraction or x-ray fluorescence units
  • electron microscopes
  • medical x-ray equipment
  • x-ray radiography units
  • cabinet x-ray systems
  • particle accelerators

or any electrical equipment which is not primarily intended to produce radiation but produces radiation greater than 0.5 mrem/hour at any readily accessible point five centimeters from its surface. Any electronic tube operating at a potential above 5 kV should be considered as a possible source of x-rays even though it may not have been designed for that purpose. Such equipment may include:

  • electron beam evaporator
  • high voltage rectifiers
  • high power amplifying tubes (e.g. klystrons and magnetrons) used to produce microwave fields
  • discharge tubes in which the gas pressure may be varied while studying electrical discharge.

Consult with Environmental Health & Safety (EHS) if there are questions concerning the radiation-producing potential of any equipment.

The possession and use of these radiation-producing machines is regulated by the New Jersey Department of Environmental Protection (NJDEP).

Acquiring Radiation-Producing Machines

Purchasing Machines

Any proposed purchase and installation of a radiation-producing machine must be reviewed and approved in advance by the Radiation Safety Officer. EHS will register the new machine with NJDEP.

Loans or Other Transfers of Machines

EHS must be notified in advance when any radiation-producing machine is planned to be acquired as a loan, transfer or a gift from another institution or from any individual or department at the University. EHS will register a new machine or will update any previously registered machine’s registration with the NJDEP.

Precautions and Guidelines for Analytical X-Ray Equipment

  • Call EHS for radiation surveys and monitoring of any newly installed or relocated machines and especially when the machine has been modified for special experiments.
  • A survey meter with a low-energy NaI detector, rather than a G-M detector, is the most appropriate detector to survey for the low-energy x-rays associated with x-ray diffraction work.
  • Under normal operating conditions, always turn off the machine's high voltage before opening the enclosure (for enclosed beam systems) or before taking any action which could expose the primary beam path (for open beam systems).
  • Each day before using the machine, open and close the shutter a few times to check that the shutter is functioning properly.
  • Never assume that the unit was left in a safe working condition by the previous user. Check the shielding and interlock status before turning the unit on.
  • Do not bypass any safety device or interlock without the approval of the person responsible for the machine. When any portion of the safety devices are disabled, post a conspicuous sign stating the date, your name and listing what has been disabled. Return the machine to its unmodified state with all interlocks and safety devices operational as soon as possible.
  • Do not work near the open, unshielded beam. However, if it is necessary to work near the unshielded beam (e.g., during system alignment):
    • Reduce the beam current and high voltage to the lowest possible settings to reduce exposure rates.
    • Keep hands and body as far as possible from the beam by using appropriate alignment tools.
    • You are in a potentially hazardous situation. Think before each step.
  • Know what you are doing and where to expect problems. Be aware of the dangers. Do not work in a hurry or allow yourself to become distracted.
  • In the event of a known or possible exposure to the beam, notify EHS immediately (see Section 1, Radiation Spill & Incident Procedures).

Precautions and Guidelines for Electron Microscopes

  • Call EHS for radiation surveys and monitoring of any newly installed or relocated microscope, when the machine has been modified for special experiments, and following any service work in which the column has been opened.
  • Uranium, often as uranyl acetate, may be used as a stain in some electron microscope procedures. Uranium is regulated somewhat differently than other radioactive materials and can be purchased directly by the user from a vendor. However, once uranium compounds are brought onto the Princeton University campus, the compounds fall within the scope of the University’s NJDEP radioactive material license. Some degree of inventory control is required and waste materials must be disposed of as radioactive waste. Contact EHS when uranium compounds are acquired.

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Appendix A:  Contamination Surveys

Types of Contamination

  • Removable contamination can be readily removed using proper decontamination procedures. Removable contamination in any amount may present both an external and internal hazard because it can be picked up on skin and possibly ingested.
  • Fixed contamination cannot be readily decontaminated. Fixed contamination generally does not present a significant hazard unless the material comes loose or is present in such large amounts that it presents an external radiation hazard.

Types of Surveys

  • Meter surveys, using Geiger detectors or scintillation probes, can identify gross contamination (total contamination consisting of both fixed and removable contamination) but will detect only certain isotopes.
  • Wipe surveys, using “wipes” counted on a liquid scintillation counter or a gamma counter, can identify removable contamination only but will detect most isotopes used at Princeton. Wipe tests are the most versatile and most sensitive method of detecting low-level contamination in the laboratory.

Survey Instrumentation

  • The portable Geiger-Muller (G-M) survey meter is best used for P-32, a high energy beta emitter, and other high energy beta and gamma emitters, such as Co-60, Zn-65, Cs-137, and U-238. A G-M meter can also be used to identify areas heavily contaminated with lower energy betas, such as C-14 or S-35, for which the G-M meter has a relatively low efficiency. G-M meters should not be used to survey for I-125 contamination, since G-M meters will detect I-125 only when there are very high levels of contamination.
  • The portable thin crystal NaI scintillation survey meter is used to locate I-125 contamination and to conduct surveys around low-energy x-ray sources such as x-ray diffractometers and electron microscopes.
  • The liquid scintillation counter, used for counting wipe tests, is not portable but is the most versatile counting instrument because it has a high counting efficiency for a wide range of radionuclides.
  • Gamma counters are not portable and are used to count wipe tests for photon emitters, such as Cr-51 or I-125.

How to Perform a Meter Survey

  1. Check the survey meter’s battery by turning the meter knob to the battery test position. If the battery is adequately charged, the meter needle will swing to the battery test position on the meter face. Replace the batteries if the batteries are low.
  2. Perform an operational check the first time you use the meter each day or when you suspect it may have been misused or damaged. Look at the calibration sticker on the side of the meter and note what the expected reading for the operational check source should be. Turn the meter on and turn the meter’s multiplier switch to a setting that will measure the check source and will provide a mid-scale reading but will not cause the needle to swing beyond the full scale. For a Ludlum G-M survey meter the multiplier knob should generally be set to the X1 position. Place the probe firmly against the check source on the side of the meter and note the meter response. If the observed meter response differs from the expected response by more than 20%, the meter should be considered nonfunctional and should be taken out of service.
  3. Take the meter to an area away from sources of radiation and note the meter background reading. Typically, the background for a G-M meter with a pancake survey probe should be less than 100 counts per minute (cpm) while the background reading for a meter with a NaI scintillation crystal should be less than 300 cpm. If the meter’s background reading is substantially greater than expected, confirm that there are no unexpected sources of radiation or radioactive materials in the vicinity, and then call Environmental Health & Safety (EHS) to report a contaminated meter.
  4. Do not cover the probe surface with parafilm or other protective covering. Parafilm and similar materials will shield the low energy betas from C-14, P-33 and S-35 and will prevent the meter from detecting contamination.
  5. Slowly move the probe about 1 centimeter above the area of interest.
  6. If an item or area with a sustained count rate more than three times background is found, the item or area should be considered to be contaminated.
  7. Immediately label the area or item and promptly decontaminate it. Decontamination procedures are provided in Section 1. If an area cannot be decontaminated, the contaminated area should be marked and labeled to indicate the isotope, date and level of contamination.
  8. Sometimes, especially in the presence of other radioactive materials, the meter survey may be equivocal. When the meter survey indicates that low level contamination may be present, a wipe survey should be performed to confirm or disprove the presence of contamination.
  9. Document the survey results whenever contamination is discovered or if 250 µCi or more have been handled. Record survey results in the laboratory survey log. This is a University requirement.

How to Perform a Wipe Test

  1. Wipe surveys must be performed when H-3 is used and is the survey method of choice to detect the presence of low levels of removable C-14, P-33 and S-35 contamination. Wipe surveys should also be performed to confirm the presence of contamination when a meter survey suggests that low level contamination may be present.
  2. Using a piece of filter paper (about 1” in diameter), Q-tip or other swab, wipe the area being surveyed. If the area is very large, subdivide it into smaller areas and use several wipes to better pinpoint the location of contamination. For some surfaces, including skin and clothing, the wipe media should be moistened with water or other appropriate solvent.
  3. Prepare the sample for counting as suggested in the counter’s operating manual. Analyze the wipe samples in a liquid scintillation counter for H-3 and other beta emitters and preferably in a gamma counter for Cr-51 and I-125.
  4. Sample activity is determined by dividing the sample count by the counter’s efficiency for the isotope in question. The counter’s operating manual should provide information about efficiencies and activity determination.
  5. Call EHS with questions about liquid scintillation and gamma counter use.

Form401- Survey Log.pdf Use this log to record your laboratory contamination surveys.

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Appendix B: Radioisotope Fact Sheets

Radioisotope Fact Sheets: Click here for fact sheets for various radioisotopes used at Princeton University.

Appendix C: Decay Calculator

Appendix D:  Staff

See the Staff sidebar at the top of this page.

Appendix E: Declaration of Pregnancy Form

Click here for the Declaration of Pregnancy Form.

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Colt Greer
Assistant Director and RSO

Chelsea McDonnell
Health and Safety Technician