Document: NUREG-0800
Document ID: baab1f26-b869-4986-9c53-36842ceaa7c3
Document Type: srp
Title: SPECTRUM OF ROD DROP ACCIDENTS (BWR)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070723.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.4.9
CFR Part: 
CFR Title: 

Content:
., pressure or neutron flux) reaches the level for which protective action is required and the onset of negative reactivity insertion, is reviewed under by the Instrumentation & Controls Branch (HICB) as part of its primary review responsibility for SRP Sections 7.2 and 7.3. 11 II. ACCEPTANCE CRITERIA CPBSRXB acceptance criteria are based on meeting the requirements of General Design 12 Criterion 28 (GDC 28) (Ref. 2) as it relates to the effects of postulated reactivity accidents, 13 14 neither resulting in damage to the reactor coolant pressure boundary greater than limited local yielding nor causing sufficient damage to impair significantly the capacity to cool the core. Specific criteria necessary to meet the relevant requirements of GDC 28 are as follows: 1. Reactivity excursions should not result in radially averaged fuel rod enthalpy greater than 280 cal/gm at any axial location in any fuel rod. 15 2. The maximum reactor pressure during any portion of the assumed excursion should be less than the value that will cause stresses to exceed the "Service Limit C" as defined in the ASME Code (Reference 3). 3. The number of fuel rods predicted to reach assumed fuel failure thresholds and associated parameters such as the amount of fuel reaching melting conditions will be an input to a radiological evaluation. The assumed failure thresholds are a radially averaged fuel rod enthalpy greater than 170 cal/gm at any axial location for zero or low power initial conditions, and fuel cladding dryout for rated power initial conditions. Technical Rationale The technical rationale for application of acceptance criteria for rod drop accidents is discussed in the following paragraphs:16 Compliance with GDC 28 requires that reactivity control systems be designed with appropriate limits on the potential amount and rate of reactivity increase. Such a design ensures that the effects of postulated reactivity accidents can neither (1) result in damage to the reactor coolant 15.4.9-3