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:
ium alloy composition, manufacturing process, and in-reactor corrosion alter the postquench characteristics of the fuel cladding material. Rulemaking pursuant to 10 CFR 50.46 is planned to implement a performance-based test program that will dictate postquench performance requirements and provide an acceptable means to establish specific limits for new cladding materials. Future cladding alloys must comply with the postquench performance requirements specified by the new rule and provide the empirical database to support any limits assigned to the new alloy. ii. Violent Expulsion of Fuel. In severe RIAs, such as rod ejection in a PWR or rod drop in a BWR, the large and rapid deposition of energy in the fuel can result in melting, fragmentation, and dispersal of fuel. The mechanical action associated with fuel dispersal can be sufficient to destroy the cladding and the rod-bundle geometry of the fuel and produce pressure pulses in the primary system. (See Appendix B for criteria.) iii. Generalized Cladding Melting. Generalized (i.e., nonlocal) melting of the cladding could result in the loss of rod-bundle fuel geometry. Criteria for cladding embrittlement in item 1.C.i above are more stringent than melting criteria. Therefore, additional specific criteria are not used. However, this may not always be the case for newer alloys or reactor types. iv. Fuel Rod Ballooning. To meet the requirements of 10 CFR 50.46 as it relates to ECCS performance during accidents, the analysis of the core flow distribution must account for burst strain and flow blockage caused by ballooning (swelling) of the cladding. RG 1.157 describes acceptable models, correlations, data, and methods that can be used to meet the requirements for a realistic calculation of ECCS performance during a LOCA. Alternatively, Appendix K to 10 CFR Part 50 outlines the acceptable features of a conservative evaluation model to consider burst 4.2-12 Revision 3 - March 2007 strain and flow blockage. Burst strain