United States Nuclear Regulatory Commission - Protecting People and the Environment

Health Physics Questions and Answers - Question 22

Question 22: Alarm setpoints for many radiation monitors are based on 10 CFR 20 Appendix B concentrations. Will these new changes require numerous ODCM changes, setpoint change requests, and procedure changes?

Answer: Separate answers are provided for reactor and materials licensees because these answers are somewhat different.

Reactor Licensees: Alarm setpoints for airborne effluent monitors are not likely to change. These monitors are typically set up to detect an effluent concentration which would yield a whole body dose rate of 500 mrem/y or a thyroid dose rate of 1500 mrem/y (or fraction thereof) in an unrestricted area on an instantaneous basis, as required by the Technical Specifications. Since other limiting conditions are also contained in Technical Specifications to restrict annual doses to the public to much smaller values than those implied above, and since short-term operational flexibility is necessary, it is unlikely that changes would need to be made in the alarm setpoints for airborne effluent monitors.

Alarm setpoints for waterborne effluent monitors are likely to require change, since they are based on 10 CFR 20 Appendix B concentrations, as required by the Technical Specifications. Because Appendix B concentration values differ for many radionuclides between the revised and old versions of Part 20, liquid effluent monitor alarm setpoints may have to be changed.

For reactors, the extent of staff involvement and licensee efforts in adjusting and documenting alarm setpoints will depend on whether the licensee has implemented NRR Generic Letter 89-01.

(References: 10 CFR 20 Appendix B, Reactor Technical Specifications, NRR Generic Letter 89-01)

Materials Licensees: Area monitor alarm setpoints for most materials licensees that are currently required to conduct continuous air monitoring will in all likelihood require change. This is especially true for those facilities that handle significant quantities of source and special nuclear material since the new DACs for these types of material are lower or more restrictive than the old MPCs. It should be noted that for commonly occurring thorium-232 (Th-232) and uranium 238 (U-238) in the oxide (insoluble) form, the DACs are lower than the MPCs by factors of 30 and 5, respectively.

Similarly, alarm setpoints for both airborne and waterborne releases for most materials licensees would have to be modified. It should also be noted that for airborne releases, the allowable concentrations for insoluble Th-232 and U-238 have been reduced by factors of about 170 and 80, respectively. For waterborne releases, the allowable release concentrations for soluble Th-232 and U-238 have been reduced by factors of about 70 and 130, respectively. For these reasons, it is anticipated that numerous procedural changes will have to be made for licensees handling significant quantities of source and special nuclear material.

Page Last Reviewed/Updated Friday, November 24, 2017