Document: NUREG-0800
Document ID: d4441736-a9bb-45c2-8d16-d23e8312ab08
Document Type: srp
Title: CHEMICAL AND VOLUME CONTROL SYSTEM MALFUNCTION THAT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070717.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.6
CFR Part: 
CFR Title: 

Content:
RESULTS IN A DECREASE IN BORON CONCENTRATION IN THE REACTOR COOLANT (PWR) REVIEW RESPONSIBILITIES Primary - Reactor Systems Branch (RSB)(SRXB)1 Secondary - None I. AREAS OF REVIEW Unborated water can be added to the reactor coolant system, via the chemical volume and control system (CVCS), to increase core reactivity. This may happen inadvertently, because of operator error or CVCS malfunction, and cause an unwanted increase in reactivity and a decrease in shutdown margin. The operator must stop this unplanned dilution before the shutdown margin is eliminated. Since the sequences of events that may occur depend on plant conditions at the time of the unplanned moderator dilution, the review includes conditions at the time of the unplanned dilution, such as refueling, startup, power operation (automatic control and manual modes), hot standby, and cold shutdown. The review of postulated moderator dilution events considers causes, initiating events, the sequence of events, the analytical model, the values of parameters used in the analytical model, and predicted consequences of the event. The sequence of events described in the applicant's safety analysis report (SAR) is reviewed by both the RSBSRXB . The RSBSRXB reviewer concentrates on the need for the reactor 2 3 4 protection system and the operator action required to secure and maintain the reactor in a safe DRAFT Rev. 2 - April 1996 15.4.6-2 condition. The RSB review of SRP Section 6.3 covers the systems for emergency injection of borated cooling water.5 The analytical methods are reviewed by RSBSRXB to ascertain whether the mathematical 6 modeling and computer codes have been previously accepted by the staff. If a referenced analytical method has not been previously reviewed, the reviewer initiates a generic evaluation of the new analytical model. The predicted results of moderator dilution events are reviewed by RSBSRXB to assure that the 7 consequences meet the acceptance criteria given in subsection II of this