United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

U.S. Nuclear Regulatory Commission

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


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 Thursday, March 29, 2012