Document: NUREG-0800
Document ID: 7ed30441-8f7a-44a4-b42a-6bbe8c5bbff4
Document Type: srp
Title: UNCONTROLLED CONTROL ROD ASSEMBLY WITHDRAWAL AT POWER
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070712.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.2
CFR Part: 
CFR Title: 

Content:
acceptable fuel design limits are not exceeded for any single malfunction of the reactivity control system such as accidental withdrawal (not ejection or dropout) of control rods. GDC 25 is applicable to this section because, based on accepted criteria, the reviewer evaluates the effects and consequences of an uncontrolled control rod assembly withdrawal at power (i.e., a bank for a PWR; a single rod with current control modes for a BWR). One criterion specifies that the RPS be designed to ensure that acceptable fuel design limits are not exceeded for either a PWR or a BWR during normal operation or AOOs, including in the event of a single malfunction of the RCS. The RPS operates in a timely manner to initiate automatic termination of the AOOs analyzed in this SRP section. SRP Section 15.4.2 as well as SRP Sections 4.2, 4.3 and 4.4 provide guidance for ensuring that specified acceptable fuel design limits are not exceeded as a result of operation or AOOs. Meeting the requirements of GDC 25 provides 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.28 III. REVIEW PROCEDURES 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 covers 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 transientAOO 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 modifications under consideration may change this to group movement).