Document: NUREG-0800
Document ID: 042bc5c0-5de0-44b4-9599-6c131e20eb7a
Document Type: srp
Title: FUNCTIONAL DESIGN OF CONTROL ROD DRIVE SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070413.pdf
Revision Date: 2023-06
Chapter: 4
Section ID: 4.6
CFR Part: 
CFR Title: 

Content:
te limits on the potential amount and rate of reactivity increase to prevent the adverse effects of postulated reactivity accidents. A postulated failure of the control rod system such as rod ejection or rod dropout provides the potential for 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. Such an event is accompanied by the conversion of nuclear energy to mechanical energy which if sufficient could breach the reactor coolant pressure boundary or impair the coolability of the core. Meeting the requirements of General Design Criterion 28 for the control rod drive systems enhances plant safety by limiting the effects of postulated 4.6-7 DRAFT Rev. 2 - April 1996 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. General Design Criterion 29 requires that the protection and reactivity control systems be designed to assure an extremely high probability of accomplishing their safety functions in the event of anticipated operational occurrences. The control rod drive system is relied upon 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 control rod drive system provides an adequate means of inserting sufficient negative reactivity to shutdown the reactor and prevent exceeding acceptable fuel design limits during anticipated operational occurrences. Meeting the requirements of General Design Criteria 29 for the control rod drive systems prevents occurrence of mechanisms that could result in fuel cladding damage such as