Document: NUREG-0800
Document ID: 855b2438-2ddf-48e9-8762-e39097109e12
Document Type: srp
Title: FUEL SYSTEM DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340660.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.2
CFR Part: 
CFR Title: 

Content:
addition to its effect on fuel temperatures (discussed above), densification affects (1) core Although needed in fuel performance codes, this model is reviewed as described in SRP Section 4.4. 4.2-10 Rev. 2 - July 1981 power distributions (power spiking, see SRP Section 4.3), (2) the fuel linear heat generation rate (LHGR, see SRP Section 4.4), and (3) the potential for cladding collapse. Densification magnitudes for power spike and LHGR analyses are discussed in Reference 21 and in Regulatory Guide 1.126 (Ref. 22). To be acceptable, densification models should follow the guide- lines of Regulatory Guide 1.126. Models for cladding-collapse times must also be reviewed, and previous review examples are given in References 23 and 24. (c) Fuel Rod Bowing: Guidance for the analysis of fuel rod bowing is given in Reference 25. Interim methods that may be used prior to compliance with this guidance are given in Reference 26. At this writing, the causes of fuel rod bowing are not well understood and mechanistic analyses of rod bowing are not being approved. (d) Structural Deformation: Acceptance Criteria are discussed in Appendix A, "Evaluation of Fuel Assembly Structural Response to Externally Applied Forces." (e) Rupture and Flow Blockage (Ballooning): Zircaloy rupture and flow blockage models are part of the ECCS evaluation model and should be reviewed by CPB. The models are empirical and should be compared with relevant data. Examples of such data and previous reviews are contained in References 10, 12, and 13. (f) Fuel Rod Pressure: The thermal performance code for calculating temperatures discussed in paragraph (a) above should be used to calculate fuel rod pressures in conformance with fuel damage criteria of Subsection II.A.1, paragraph (f). The reviewer should ensure that conservatisms that were incorporated for calculating temperatures do not introduce nonconservatisms with regard to fuel rod pressures. (g) Metal/Water Reaction Rate: To meet the requirements of