Document: NUREG-0800
Document ID: 3ea2f0ac-4d7e-464a-b1c4-390c3970f642
Document Type: srp
Title: provides specific thermal-hydraulic criteria.  The available radioactive fission product
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070740002.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.4
CFR Part: 
CFR Title: 

Content:
n 4.3), (2) the fuel linear heat generation rate (LHGR) - see SRP Section 4.4, and (3) the potential for cladding collapse. NUREG-0085 and RG 1.126 discuss densification magnitudes for power spike and LHGR analyses. To be acceptable, densification models should follow the guidelines of RG 1.126. Models for cladding- collapse times should also be reviewed. The memorandums on Evaluation of Westinghouse Report, WCAP-8377, January 14, 1975 and on CEPAN-Method of Analyzing Creep Collapse of Oval Cladding, February 5, 1976, provide previous review examples. 4.2-17 Revision 3 - March 2007 iii. Fuel Rod Bowing. The memorandum on Request for Revised Rod Bowing Topical Reports, May 30, 1978, includes guidance for the analysis of fuel rod bowing. The memorandum on Revised Interim Safety Evaluation Report on the Effects of Fuel Rod Bowing in Thermal Margin Calculations for Light Water Reactors, February 16, 1977, presents interim methods that may be used. At this writing, the causes of fuel rod bowing are not well understood and mechanistic analyses of rod bowing have not been approved. iv. Cladding Collapse. Approved analytical models/methods are used to demonstrate that cladding collapse is not possible within the fuel lifetime. A change in cladding or fuel material (additives or significant changes in fabrication) and/or a reduction in the as-fabricated fuel cladding gap can impact the approved analytical model/methods used for this analysis. A change in fuel material can impact fuel densification and a change in cladding material can impact cladding creep, both of which can impact cladding collapse. If any of these parameters change, they must be evaluated in terms of their impact on the approved analytical models and methods for evaluating cladding collapse. v. Structural Deformation. Appendix A discusses the acceptance criteria. vi. Rupture and Flow Blockage (Ballooning). The ECCS evaluation model includes Zircaloy rupture and flow blockage models, which should be