Document: NRC Regulatory Guide
Document ID: 61b22006-634a-415a-a204-22e515d96707
Document Type: regulatory_guide
Title: Pressurized-Water Reactor Control Rod Ejection and Boiling-Water Reactor Control Rod Drop Accidents + HISTORY - HISTORY 11/2016 – DG-1327 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1612/ML16124A200.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.236
CFR Part: 
CFR Title: 

Content:
nium), or a pellet central annulus. This guidance is not applicable to mixed oxide (MOX) fuel rod designs. 1.2 The high temperature cladding failure threshold described in Section 3.1 is applicable to reactor startup, zero power, and low power operations (i.e., < 5% rated power) and covers the entire initial reactor coolant temperature range (i.e., room temperature to operating temperatures). For all other operating conditions up to full power (i.e., Mode 1), fuel cladding failure is presumed if local heat flux exceeds thermal design limits (e.g., departure from nucleate boiling and critical power ratios). 1.3 As described in Section 3.2, separate PCMI cladding failure thresholds are provided for different initial reactor coolant temperatures and different cladding thermal annealing treatments. The high temperature PCMI cladding failure threshold curves are applicable to reactor coolant temperatures at or above 500 ˚F. Below 500 ˚F, the low temperature PCMI cladding failure threshold curves are applicable. The fully recrystallized annealed (RXA) PCMI cladding failure threshold curves are applicable to cladding which has undergone thermal treatment to remove all residual stresses and is in an RXA state. For all other stages of thermal treatments, the stress relief annealed (SRA) PCMI cladding failure threshold curves are applicable. 2. Analytical Methods and Assumptions The following analytical inputs, assumptions, and methods are considered acceptable for evaluating the postulated CRE and CRD accidents. 2.1 Methods and models 2.1.1 Accident analyses should be performed using NRC approved analytical models and application methodologies that account for calculational uncertainties. The analytical models and computer codes used should be documented and justified, and the conservatism of the models and codes should be evaluated both by comparison with experiment and with DG 1327, Page 8 more sophisticated spatial kinetics codes. In particular, the importance of two-