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:
ntly. 4. An incident of moderate frequency in combination with any single active component failure, or single operator error, shall be considered and is an event for which an estimate of the number of potential fuel failures shall be provided for radiological dose calculations. For such accidents, the number of fuel failures must be assumed for all rods for which the DNBR or CPR falls below those values cited above for cladding integrity 32 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. (iii) The core burnup and corresponding boron concentration are selected to yield the most limiting combination of moderator