Document: NUREG-0800
Document ID: 41b2cf88-b6dc-4005-939a-cf3fb1a561d2
Document Type: srp
Title: INADVERTENT DECREASE IN BORON CONCENTRATION IN THE REACTOR
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0703/ML070380222.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.6
CFR Part: 
CFR Title: 

Content:
l specifications. 1. The SAR describes moderator dilution transients reviewed by the staff for the occurrences leading to the initiating events. The sequence of events, from initiation to a stabilized condition, is reviewed for: A. The extent that normally operating plant instrumentation and controls are assumed to function. Alarms that alert operators to the unplanned boron dilution are of particular importance. B. The extent that the plant and reactor protection systems are required to function. C. The credit taken for normally operating plant systems. D. The operation of required engineered safety systems. E. The extent of required operator actions. F. The appropriate margin for malfunctions (e.g., stuck rods) is accounted for. 2. The reviewer confirms that analyses are included for a boron dilution incident during each of the following plant initial conditions: refueling, startup, power operation (automatic control and manual modes), hot standby, hot shutdown, and cold shutdown. Refueling condition analyses should consider when the reactor vessel head is removed and the coolant is drained to the elevation of the hot leg piping. For each reviewed incident, the applicant must consider all causes and justify the cause selected for analysis as allowing the operator the least time to take corrective action. 3. The staff reviews the timing of initiation of protection, engineered safety, and other systems needed to limit the consequences of each boron dilution incident to acceptable 15.4.6-8 Revision 2 - March 2007 levels. The reviewer compares the predicted variations of system parameters to various trip and system initiation setpoints. The reviewer also evaluates automatic initiation, actuation delays, possible bypass modes, interlocks, and the feasibility of manual operation where the SAR states that operator action is needed or expected. 4. When necessary, the reviewer evaluates the effects of single active failures of systems and components that may affect the