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:
. (ii) The boron dilution is assumed to occur at the maximum possible rate. (iii) The core burnup and corresponding boron concentration are selected to yield the most limiting combination of moderator temperature coefficient, void coefficient, Doppler coefficient, axial power profile, and radial power distribution. This will usually be the beginning-of-life (BOL) condition. 15.4.6-5 DRAFT Rev. 2 - April 1996 (iv) All fuel assemblies are installed in the core. (v) A conservatively low value is assumed for the reactor coolant volume. (vi) For analyses during refueling, all control rods are withdrawn from the core. (vii) For analyses during power operation, the minimum shutdown margin allowed by the technical specifications (usually 1%) is assumed to exist prior to the initiation of boron dilution. (viii) For each event analyzed, a conservatively high reactivity addition rate is assumed taking into account the effect of increasing boron worth with dilution. (ix) Conservative scram characteristics are assumed, i.e., maximum time delay with the most reactive rod held out of the core. Technical Rationale33 The technical rationale for application of the above acceptance criteria to the analyses of boron dilution events is discussed in the following paragraphs: 1. GDC 10 requires that the reactor core and associated coolant, control, and protection systems be designed with appropriate margin to assure that specified acceptable fuel design limits are not exceeded during any condition of normal operation, including the effects of anticipated operational occurrences. Fuel design limits are established to assure the integrity of fuel cladding as a fission product barrier. In PWRs, boron is added to the reactor coolant in sufficient concentrations to effect reactivity control. PWR conditions of normal operation include startup, power operation, hot standby, shutdown (hot and cold), and refueling modes. Because of the frequency with which boron dilution events are anticipated to