Document: NUREG-0800
Document ID: 97b8d603-4b3f-40a3-9dbb-e89b68e654c6
Document Type: srp
Title: ANTICIPATED TRANSIENTS WITHOUT SCRAM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350327.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.8
CFR Part: 
CFR Title: 

Content:
uly 1981 The reviewer verifies that the emergency procedures for ATWS events describe the-actions to be taken including manually scramming the reactor, prompt actuation of the turbine trip (PWRs), the auxiliary feedwater (PWRs), and the reactor core isolation cooling (BWRs), and the high pressure coolant injection/ spray (BWRs). These actions should also include the prompt initiation of bora- tion by actuation of the High Pressure Safety Injection (PWR)/Standby Liquid Control (BWR) System if methods to scram the reactor cannot secure a fast reactor scram. Actions should also include prompt initiation of the Residual Heat Removal System in the suppression pool cooling mode and the limiting of actuation of the Automatic Depressurization System and the Low Pressure Injection System (BWR). The BWR recirculation pump -trip is acceptable if the same as the Hatch or Monticello designs. IV. EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided and his review supports conclusions of the following type, to be included in the staff's safety evaluation report. "Anticipated transients without scram (ATWS) are events in which the scram system (the reactor protection and reactivity control systems) is postulated to fail to operate as required following anticipated transients such as a loss of feedwater or a turbine trip. The Commission is currently engaged in a rulemaking to determine what additional modifications, if any, should be required to reduce the probability of unacceptable consequences resulting from ATWS events. It is expected that the necessary plant modifi- cations will be installed within one to four years following a Commission decision on anticipated transients without scram. As a prudent course, to further reduce the risk from anticipated tran- sient without scram events during the interim period before completing the plant modifications that the Commission may find to be necessary, we require that a recirculation pump trip be