Document: NUREG-0800
Document ID: b4cff877-ab63-46c3-8140-32e309d767a2
Document Type: srp
Title: EMERGENCY DIESEL ENGINE STARTING SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070571.pdf
Revision Date: 2023-06
Chapter: 9
Section ID: 9.5.6
CFR Part: 
CFR Title: 

Content:
, otherwise the 39 starting air dew point should be controlled to at least 5.5 C (10 F) less than the 40 lowest expected ambient temperature. Plants that have emergency ac sources in excess of minimum redundancy requirements for loss-of-offsite-power conditions may use one of the existing emergency sources as an alternate 9.5.6-5 DRAFT Rev. 3 - April 1996 ac (AAC) power source for the purposes of coping with a station blackout, provided it meets the applicable criteria for an AAC source. For a plant relying on an emergency diesel engine as an AAC power source, the design of the starting system for that engine is acceptable if it meets 10 CFR Part 50.63, "Loss of All Alternating Current Power," paragraph (a)(2), and Regulatory Guide 1.155, Position C.3. 41 Technical Rationale:42 The technical rationale for application of the above acceptance criteria to the emergency diesel engine starting system is discussed in the following paragraphs. 1. GDC 2 requires that SSC important to safety be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform the safety function. Regulatory Guide 1.117 provides the methods acceptable to the staff for tornado design classification of structures, systems and components important to safety. The safety function of the EDESS is to start the emergency diesel engine following a loss of offsite power or as required by the plant protection circuitry. The reliable starting of the emergency diesel engine is necessary to ensure the prompt restoration of ac power to safety related components that are necessary to maintain the integrity of the reactor coolant pressure boundary, to safely shutdown the reactor and maintain it in a safe shutdown condition, and to prevent or mitigate the consequences of accidents. Compliance with the requirements of GDC 2 ensures that emergency ac power will be available to safety- related components in the