Document: NUREG-0800
Document ID: 711747d3-335d-42bb-b30d-17cc0f6162ed
Document Type: srp
Title: SEISMIC INSTRUMENTATION
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340571.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.4
CFR Part: 
CFR Title: 

Content:
the control room, so that a signal is given when the preset threshold level (OBE acceleration level) resulting from the earthquake is exceeded. Also both audio and visual signals should be provided to the control room opera- tors in the event of an earthquake. In addition, the triaxial time history accelerograph located in the con- tainment foundation or in the free field should be connected to the control room, so that peak acceleration level experienced in the basement of the reactor containment structure or in the free field is indicated to the con- trol room operator. The response spectrum recorder in the reactor contain- ment foundation or in the free field is also connected to the control room 3.7.4-3 Rev. 1 - July 1981 to indicate if the design response spectra values for discrete frequencies are exceeded during an earthquake. 4. Comparison of Measured and Predicted Responses In the event of an earthquake, the control room operator should be Immedi- ately informed through the event indicators. If the instrumentation shows that the peak acceleration or the response spectra experienced at the foundation of the containment building or in the free field exceed the OBE acceleration level or response spectra, the plant should be shut down (Ref. 3) pending permission to resume operations. To help predict the capa- bility of the plant for resuming operations, field inspection of safety- related items should be implemented and the measured responses from both the peak-recording and strong motion accelerographs should be compared with those assumed in the design. The procedures for comparison of measured and predicted responses are acceptable if a commitment is made to provide detailed comparisons, as outlined below, between measured seismic responses of Category I struc- tures and equipment with calculated responses determined from dynamic analysis. First, the time history records are digitized and corrected for time signal variations and baseline variations. The time