Types, Hazards, and Categories of Contained Sources

 

Types of Contained Sources

Contained sources are available in a variety of forms but most typically are:

  • Plated sources in which the radioactivity is electrochemically plated or dried onto a surface,
  • Sources in which the radioactivity is epoxied onto a surface, embedded, or otherwise fixed into a matrix,
  • Sources in which the radioactivity is contained within a capsule in some manner, (typically welded into a capsule), but either has not been evaluated or is not robust enough to meet the federal or state definition of a “registered sealed source” (see the next bullet),
  • Registered sealed sources in which the radioactivity is encapsulated and in which the source design has been evaluated and tested to demonstrate that the source design is robust enough to contain the activity under nearly all conditions. The conditions for testing are established by federal and state radioactive materials licensing authorities. The term "registered sealed source” is reserved for any source for which a Sealed Source & Device Registry Certificate has been issued by a federal and state radioactive materials licensing authority.

 

Contained Sources Types

Types of contained sources.

 

How Are Contained Sources Used?

Most contained sources are used:

  • To calibrate radiation-detection instrumentation or check that instrumentation is functioning properly;
  • To irradiate materials;
  • For experiments in student science labs; and
  • In analytical equipment such as gas chromatographs, static eliminators, density gauges, and liquid scintillation counters

 

Contained Source Hazards

Because the radioactivity is encapsulated or plated onto a surface, contained sources do not present a significant contamination hazard under normal circumstances. However, they may present a significant external exposure hazard, depending on the properties of the radioisotope or the amount of radioactivity present.

In some cases, contained sources can pose a contamination hazard when not used in accordance with established protocols or when damaged.

 

Characteristics of the Radioisotopes Most Commonly Used in Our Contained Sources

Contained Source Isotopes

 

Princeton University’s Categories of Contained Sources

Since contained sources come in a variety of configurations and amount of radioactivity and hazards, Princeton University has established a classification scheme with four categories (A, B, C, and D), each with specific requirements governing their use.  Every contained source used at Princeton University has been assigned to one of the following categories:

Category-A

These sources contain very small amounts of radioactivity, defined in NJDEP regulations as “exempt quantities.”  Examples of such sources are the 0.01 µCi Sr-90 sources used for cloud chamber experiments in the Physics Departments instructional labs and the 1 µCi Cs-137 plastic disk sources often used as instrument check sources.

Contained Source Cat A

Catagory A: Plastic Disk

Using Category-A Sources

Category-  A sources contain such small amounts of radioactivity that they don’t present a significant radiation hazard, and they’re regulated differently than other radioactive sources. For instance, you are not required to have a radioactive materials license from NJDEP to purchase an “exempt quantity” source, and you do not need to obtain a Princeton University radioactive materials authorization to purchase or possess Category-A sources. However, EHS does expect that you will take the following steps:

  • Keep track of Category-A sources, especially in instructional labs, to be sure that the sources aren’t misplaced or “borrowed.”
  • Dispose of Category-A sources as radioactive waste. Contact EHS about how to dispose of Category-A sources.
  • Cloud Chamber Sources:  Radioactive sources used in cloud chamber experiments typically are rods or needles plated on the tips with very small amounts of Sr-90 (for beta activity) or Po-210 or Pb-210 (for alpha activity). Although the amount of radioactivity on each needle is low, it is important to handle the source by holding the cork rather than by touching the needle end of the source.

Cloud Chamber Source

Catagory A: Cloud Chamber Source

Category-B

These sources contain radioactivity in excess of exempt quantity sources (see Category-A) but contain a sufficiently small amount of activity that leak testing is not required. Category-B sources do not meet the criteria for registered sealed sources (see Category-D).

Contained Source Cat B

Category B

Category-C

These sources contain activity in excess of exempt quantity sources (see Category-A) and contain sufficient activity that leak testing is required. Category-C sources do not meet the criteria for registered sealed sources (see Category-D).

Contained Source Cat C

Category C

Category-D

Category-D sources meet the US Nuclear Regulatory Commission criteria for registered sealed sources. These are sources designed, constructed, and rigorously tested such that leakage and source damage is extremely unlikely. However, these sources generally contain sufficient radioactivity that leak testing is required.

Contained Source Cat D

Category D

 

Go to: Rules and Procedures For Using Category-B, C, and D Sources »
Back to: Contained Sources main page »

Staff

Stephen Elwood
Radiation Safety Officer
609-258-6271

Colt Greer
Sr. Program Manager for Radiation Safety

Chelsea McDonnell
Health and Safety Technician
609-258-6255