Document: NUREG-0800
Document ID: 061b3f99-1bfd-4e65-be97-7e9affac9aef
Document Type: srp
Title: UNCONTROLLED CONTROL ROD ASSEMBLY WITHDRAWAL AT POWER
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600414.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.2
CFR Part: 
CFR Title: 

Content:
GDC 25 provides reasonable assurance that a single malfunction of the reactivity control system, together with AOOs caused by the initiating event of an uncontrolled control rod assembly withdrawal at power, will not cause specified acceptable fuel design limits to be exceeded. III. REVIEW PROCEDURES The reviewer will select material from the procedures described below, as may be appropriate for a particular case. These review procedures are based on the identified SRP acceptance criteria. For deviations from these acceptance criteria, the staff should review the applicant’s evaluation of how the proposed alternatives provide an acceptable method of complying with the relevant NRC requirements identified in Subsection II. 1. The review process and the areas examined differ somewhat, depending on whether a BWR or PWR is being reviewed. For both systems, the review considers the entire power range from low to full power and the allowed extreme range of reactor conditions during the operating (fuel) cycle, including rod configurations, power distribution, and associated reactivity feedback components. The continuous withdrawal of normal configurations of rods should be assumed for the initial conditions in the AOO calculation. For a PWR, this is one or two control banks; for a BWR with current modes of control, it is a single control rod (future addresses under consideration may change this to group movement). The review considers a full range of rod or bank withdrawals, up to maximum rod or bank worths and rates of reactivity addition. The exact analysis of the AOO would ideally involve a three-dimensional, coupled neutron kinetics, thermal-hydraulics calculation. However, acceptable results may be obtained with suitable approximate calculations. The problem examined and the approximations used differ for a PWR and a BWR. 2. For a BWR, past analyses and reviews have shown that at maximum rod worths and rates of reactivity addition, the reactor power increases slowly