Document: NRC Regulatory Guide
Document ID: 5cdd8024-5f0a-4a1b-8e14-1026125c5667
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Pressurized Water Reactor Radioactive Gas Storage Tank Failure (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0833/ML083300020.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.24
CFR Part: 
CFR Title: 

Content:
principally the noble gases krypton and xenon, the particulate daughters of some of the krypton and xenon isotopes, and trace quantities of the halogens. With the exception of krypton-85, the longest half-life of the principal noble gas radionuclides present in reactor effluents is 5.27 days (xenon-133). Thus, storage of these gases for a period of 60 days will essentially eliminate by decay all of the radionuclides except krypton-85. The probability of a gas decay tank rupturing is low. However, the probability of an accidental release resulting from such things as operator error or malfunction of a valve or the overpressure relief system is considered to be sufficiently high that the calculated offsite whole body exposures that might result from a single failure during normal operation should be substantially below the guidelines of 10 CFR Part 100. In considering the probability and consequences of such a single failure occurring, it is recognized that greater volumes of radioactive gases will be generated by the larger plants presently being constructed than the volumes generated by most presently operating plants. This increased quantity of radioactive gas will necessitate a substantial increase in the number or size of gas storage tanks used. Considering the potential which exists for an inadvertent release and the high noble gas content of the tanks together with the fact that such gas decay tanks are normally located outside the reactor containment, every reasonable effort should be made to reduce the probability of such an accidental release. Thus, there is a need for a strong quality assurance program, as required by Appendix B to 10 CFR Part 50, to “provide control over activities affecting the quality of the identified structures, systems, and components, to an extent consistent with their importance to safety… The program shall take into account the need for special controls, processes, test equipment, tools, and skills to attain the required