Document: NUREG-0800
Document ID: 67e3fd64-e6a4-4522-b90f-4184c2f5b357
Document Type: srp
Title: FUNCTIONAL DESIGN OF CONTROL ROD DRIVE SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070540139.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.6
CFR Part: 
CFR Title: 

Content:
as rod ejection or rod dropout, has the potential to result in a relatively high rate of positive reactivity insertion which, if large enough, could cause a prompt power excursion. Such a prompt power excursion could cause a fuel element rupture, rapid fragmentation of the fuel cladding, and dispersal of fuel and cladding into the coolant. This type of event is accompanied by the conversion of nuclear energy to mechanical energy, which if 4.6-8 Revision 2 - March 2007 sufficient, could breach the reactor coolant pressure boundary or impair the coolability of the core. Meeting the requirements of GDC 28 for the CRDS enhances plant safety by limiting the effects of postulated reactivity accidents, thereby mitigating the adverse effects which could result in damage to the reactor coolant pressure boundary or impair the capability to cool the core. 7. GDC 29 requires that the protection and reactivity control systems be designed to ensure an extremely high probability of accomplishing their safety functions in the event of anticipated operational occurrences. The design relies on the CRDS to function in conjunction with the protection systems under anticipated operational occurrences, including loss of power to all recirculation pumps, tripping of the turbine generator, isolation of the main condenser, and loss of all offsite power. The CRDS provides an adequate means of inserting sufficient negative reactivity to shut down the reactor and prevent exceeding acceptable fuel design limits during anticipated operational occurrences. Meeting the requirements of GDC 29 for the CRDS prevents occurrence of mechanisms that could result in fuel cladding damage such as severe overheating, excessive cladding strain, or exceeding the thermal margin limits during anticipated operational occurrences. Preventing excessive cladding damage in the event of anticipated transients ensures maintenance of the integrity of the cladding as a fission product barrier. 8. 10 CFR 50.62(c)(3)