Document: NUREG-0800
Document ID: f018d9c1-daa9-44c5-b7e9-907bec814455
Document Type: srp
Title: TURBINE BYPASS SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0703/ML070380209.pdf
Revision Date: 2023-06
Chapter: 10
Section ID: 10.4.4
CFR Part: 
CFR Title: 

Content:
REVIEW RESPONSIBILITIES Primary - Organization responsible for the review of power conversion systems Secondary - None I. AREAS OF REVIEW The turbine bypass system (TBS) provides operational flexibility so that the plant may accept certain load changes without disturbing the nuclear steam supply system. The TBS is designed to discharge a stated percentage of rated main steam flow directly to the main condensers, bypassing the turbine. This steam bypass enables the plant to take step load reductions up to the TBS capacity without the reactor or turbine tripping. The system is also used during startup and shutdown to control reactor pressure for a boiling water reactor (BWR) and steam generator pressure for a pressurized water reactor (PWR). The TBS is not required for safe shutdown, as the relief and safety valves are operated under emergency conditions. The system is not required to function as a heat sink for the prevention or mitigation of postulated accidents. Failure of the TBS during a load reduction or turbine trip would result in the actuation of the relief valves and possibly the safety valves. For a BWR without a main steam isolation valve leakage control system (MSIVLCS), the TBS potentially serves an accident mitigation function. A TBS, along with the main steam system and condenser, can mitigate the effects of MSIV leakage during a LOCA by the holdup and plateout of fission products. A TBS in such a BWR must be capable of maintaining its integrity after a safe shutdown earthquake (SSE). 10.4.4-2 Revision 3 - March 2007 The specific areas of review are as follows: 1. Review of the system from the branch connection at the main steam system to the main condensers. 2. Review of the TBS to determine that a failure of the system or system components will not have an adverse effect on essential equipment. 3. Review of the TBS functional requirements for both normal and abnormal operating conditions, and with respect to the following: (a) capability to isolate