ML20035C302
| ML20035C302 | |
| Person / Time | |
|---|---|
| Issue date: | 03/30/1993 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Grimes B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20035C303 | List: |
| References | |
| AEOD-E93-02, AEOD-E93-2, NUDOCS 9304070026 | |
| Download: ML20035C302 (2) | |
Text
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NUCLEAR REGULATORY COMMISSION a
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WASHINGTON, D. C. 20555 hy
- ....j MAR 3 01993 MEMORANDUM FOR:
Brian X. Grimes, Director Division of Operating Reactor Support Office of Nuclear Reactor Regulation FROM:
Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
SUBJECT:
LOSS-0F-OFFSITE-POWER DUE TO PLANT-CENTERED EVENTS Our Engineering Evaluation report on loss-of-offsite-power (LOOP) at nuclear power plants due to plant-centered events is enclosed for your information and We initiated this study as a follow up of the March 20, 1990, event at.
use.
Vogtle which resulted in loss of all ac power when a truck backed into the support column for an offsite power feed to the reserve transformer.
The study covers plant-centered events (events caused by failure or malfunction of equipment or systems inside the plant) involving LOOP at the medium voltage (between 2 kV and 15 kV) Class IE buses.
The study included both total and partial LOOP events.
This enabled a wider evaluation of the subject and a comparison between the total and partial LOOP events.
About 30 percent of the plant-centered LOOP events resulted in total LOOP.
The study identified a total of 86 events between 1985 and 1989.
The study analyzed these events from the points of view of LOOP under power and shutdown operation, root-cause analysis, and corrective measures to reduce the plant-centered LOOP events.
Many of these events involved multiple equipment.
malfunctions or failures, especially during power operation.
Analysis of the 86 events indicated that 48 percent of these events were caused by personnel errors, 28 percent by equipment malfunctions or failures, 14 percent by design deficiencies, and the remaining 10 percerit by inadequate maintenance practices.
Analysis of the events caused 'y personnel errors indicated that most of these events could have been avoided by better personnel awareness.
Furthermore, the duration of the event could have been reduced by preplanning for quick restoration of offsite power especially during plant shutdown conditions.
The findings of this report may be of special interest in station blackout and shutdown risk evaluations and in the review of technical specification submittals.
Specifically, some of the findings of this study are significantly different from previous findings reported in other studies on LOOP.
For example, report NUREG-1032, June 1988, " Evaluation of Station Blackout Accidents at Nuclear Power Plants," identified that between 1968 and 1985 there were 46 plant-centered total LOOP events with a median restoration time of 18 minutes.
Many of the conclusions of NUREG-1109, " Regulatory /
Backfit Analysis for the Resolution of Unresolved Safety Issue A-44, Station 1
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Brian K. Grimes -
Blackout," are based on NUREG-1032.
Our study indicates that between 1985 and 1989, there were 26 plant-centered total LOOP events with a median. LOOP duration of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 8 minutes.
The plant-centered LOOP events identified in this study were compared with LOOP events evaluated in the Accident Sequence Precursor program as a means'to assess risk significance.
Twelve events had been evaluated with conditional core damage probabilities in the E-5 to E-4 range.
Thus, plant-centered. LOOP events are' considered risk significant and precursors to accidents.
If you need additional information regarding the report, please contact Earl Brown of my staff at 301-492-4491, or Subinoy Mazumdar-at 301-504-2917.
Original signed trf Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated Distribution:
PDR LSpessard CGrimes, NRR Central File KBrockman CBerlinger, NRR ROAB R/F SRubin JRichardson, NRR DSP R/F
.JJohnson SMazumdar, NRR EBrown KRaglin, TTC Plewis, INP0 JRosenthal RSavio, ACRS DQueener, NOAC EJordan MTaylor, ED0-VChexal, EPRI Dross GMarcus, NRR TNovak WMinners, NRR VBenaroya AChaffee, NRR PBaranowsky FCongel, NRR l
l
- See previous concurrence:
l ROAB ROAB C:R0AB DSP S
SMazumdar:mmk EBrown JRosenthal V
roya Novak 12/17/92*
12/17/92*
2/03/93*
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