Document: NUREG-0800
Document ID: 8b6b2506-1305-4f5c-9cd6-725a1d90c61c
Document Type: srp
Title: CHEMICAL AND VOLUME CONTROL SYSTEM MALFUNCTION THAT RESULTS IN A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350402.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.6
CFR Part: 
CFR Title: 

Content:
e DNBR or CPR falls below those values cited above for cladding integrity unless it can be shown, based on an acceptable fuel damage model (see SRP Section 4.2), that fewer failures occur. There shall be no loss of function of any fission product barrier other than the fuel cladding. 5. If operator action is required to terminate the transient, the following minimum time intervals must be available between the time when an alarm announces an unplanned moderator dilution and the time of loss of shutdown margin: a. During refueling: 30 minutes. b. During startup, cold shutdown, hot standby, and power operation: 15 minutes. The applicant's analysis of moderator dilution events should be performed using an acceptable analytical model. Should unreviewed analytical methods be proposed, these methods must be evaluated by the staff. For new generic methods, the reviewer initiates an evaluation. All of the following plant initial conditions should be considered in the analysis: refueling, startup, power operation (automatic control and manual modes), hot standby, and cold shutdown. The parameters and assumptions used in the analytical model should be suitably conservative. The following values and assumptions are considered acceptable: (i) For analyses during power operation, the initial power level is rated output (licensed core thermal power) plus an allowance of 2% to account for power measurement uncertainty. (ii) The boron dilution is assumed to occur at the maximum possible rate. 15.4.6-3 Rev. 1 - July 1981 (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. (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