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:
ain and less on their power ramp data to verify that PCMI will not occur. Convincing evidence exists that gaseous swelling and fuel thermal expansion is responsible for cladding strains at high burnup levels and perhaps at even moderate burnups. Therefore, PCI or PCMI analyses of cladding strain for AOO transients and accidents should apply approved fuel thermal expansion and gaseous fuel swelling models, as well as irradiated cladding properties. vii. Bursting. To meet the requirements of 10 CFR 50.46, as it relates to ECCS performance evaluation, the ECCS evaluation model should include a calculation of the swelling and rupture of the cladding resulting from the temperature distribution in the cladding and from pressure differences between the inside and outside of the cladding. Regulatory Guide (RG) 1.157 provides guidelines for performing a realistic (i.e., best estimate) model to calculate the degree of cladding swelling and rupture. Alternatively, Appendix K to 10 CFR Part 50 presents the acceptable features of an evaluation model for predicting the degree of swelling and rupture in the Zircaloy cladding. Although fuel suppliers may use different rupture-temperature vs. differential-pressure curves, an acceptable curve should be similar to the one described in NUREG-0630 based on similar data for a specific material. Cladding burst from non-LOCA accidents also needs to be evaluated and addressed in terms of impact on cladding temperatures and radiological consequences. viii. Mechanical Fracturing. A mechanical fracture refers to a defect in a fuel rod caused by an externally applied force such as a hydraulic load or a load derived from core-plate motion. Cladding integrity may be assumed if the applied stress is less than 90 percent of the irradiated yield stress at the appropriate temperature. Other proposed limits must be justified. Results from the seismic and LOCA analysis (see Appendix A to this SRP section) may show that failures by this mechanism will