Document: NRC Regulatory Guide
Document ID: 4d46a966-d280-43da-9b03-8b0abe7b29ce
Document Type: regulatory_guide
Title: Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2120/ML21204A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.183
CFR Part: 
CFR Title: 

Content:
fuel should be assumed to be completely dissolved in the primary coolant and available for release to the secondary system. H-4. The chemical form of radioiodine released to the containment atmosphere should be assumed to be 95-percent cesium iodide, 4.85-percent elemental iodine, and 0.15-percent organic iodide. If containment sprays do not actuate or are terminated before accumulating sump water, or if the containment sump pH is not controlled at values of 7 or greater, the iodine species should be evaluated on an individual case basis. Evaluations of pH should consider the effect of acids created during the control rod ejection accident event (e.g., pyrolysis and radiolysis products). With the exception of elemental and organic iodine and noble gases, fission products should be assumed to be in particulate form. 1 Facilities licensed with, or applying for, alternative repair criteria should use this section in conjunction with the guidance that is being developed in Draft Regulatory Guide DG-1074, “Steam Generator Tube Integrity,” issued December 1998, for acceptable assumptions and methodologies for performing radiological analyses. 2 Calculated values of the combined release (gap activity plus fuel melt) are limited to a value of 1.0. DG-1389, Appendix H, Page H-2 H-5. Iodine releases from the steam generators to the environment should be assumed to be 97-percent elemental iodine and 3-percent organic iodide. Transport from Containment H-6. Assumptions acceptable to the NRC staff related to the transport, reduction, and release of radioactive material in and from the containment are as follows: H-6.1 A reduction in the amount of radioactive material available for leakage from the containment that is due to natural deposition, containment sprays, recirculating filter systems, dual containments, or other engineered safety features may be taken into account. Refer to Appendix A to this guide for guidance on acceptable methods and assumptions for evaluating