ML19276G059
| ML19276G059 | |
| Person / Time | |
|---|---|
| Issue date: | 04/03/1979 |
| From: | Vollmer R Office of Nuclear Reactor Regulation |
| To: | Stello V Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-B-23, REF-GTECI-FU, TASK-B-23, TASK-OR TAC-10968, NUDOCS 7905150179 | |
| Download: ML19276G059 (3) | |
Text
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APR 3 1979 MEMORANDUM FOR:
V. Stello, Director, Division of Operati Reactors FROM:
R. Vollmer, Assistant Director for Systems and Projects, Division of Operating Reactors S"3 JECT:
EXPANSION OF SCOPE FOR 00R GENERIC ISSUE B-23,
" DEGRADED GRID VOLTAGE" The purpose of this memo is to obtain your approval of our proposal to expand the subject generic issue to accommodate the causes of degraded voltage that were identified by the Arkansas Abnormal Occurrence.
Enclosed is a memorandum to the D0R Project Management Branch Chiefs for your concurrence and a feedback memorandum to DSS for your signature.
D0R Generic Issue Number B-23 is the staff's program for implementing requirements for the protection of safety equipment from damage due to a sustained degraded voltage on the electric grid.
These require-ments were developed as a result of the Millstone Unit 2 event of July 5,1976.
Since that time it has come to our attention that the voltage on the safety buses can become degraded by mechanisms other than a degradation of the offsite electric grid.
During the September 16, 1978 event at the Arkansas Nuclear One (ANO) station, a shared startup transformer was overloaded due to the automatic transfer of excessive electrical loads onto it.
Second, analysis subsequent to the September 16, 1978 event indicated that the dedicated startup transformer for Unit i lacked " sufficient capacity and capability" to provide electric power of acceptable quality for the starting of safety equipment.
In both of these situations deficiencies in the station's electric power distribution system produced the same result - - degraded voltage on the ESF buses, even though the offsite electric grid was normal.
All prompt remedial actions for the Arkansas station have been taken.
A telephone survey of other stations has been made to ascertain if any other facility might be vulnerable to the same potential problems.
In addition, IE Ir. formation Notice No 79-04 informed all licensees of the events at ANO.
7905150177
. To provide appropriate and complete resolution of the two concerns arising from the Arkansas event, we propose the following two general courses of action. For operating reactors, we propose that D0R Generic Issue No. B-23 be expanded to review licensee's analysis to confirm the adequacy of their electric system designs.
The attached memo to PM Branch Chiefs addresses this matter.
For reactors under construc-tion and future applicants, we propose that our coordination with the Division of Systems Safety be formalized via a feedback memo, describing the operating experience at ANO and the remedial actions taken by DOR.
The bases for the abcVe proposed courses of action are as follows:
(1) the end results of both the Millstone concern and the Arkansas concerns are t,.a same - - degraded voltage on the safety buses, (2) the calculational analyses needed to be provided by the licensees for both situations are not greatly different, (3) the type of expertise needed within the NRC to review the licensees' analyses is the same, a substantial manpower savings is available if the same staff members review both sets of analyses - both in terms of the general learning curve regarding the nature of the potential problem and regarding the differences in plant specific electrical designs, (4) the Abnormal Occurrence Report we submitted to the Commissioners stated that our intent was to expand B-23, and (5) LlR resporse to Commissioner Kennedy's specific question regarding generic concerns arising from the Arkansas event stated our intent to expand the scope and effort on the B-23 program, k'e estimate the total NRC manpower commitment involved to be 2 man-years.
This would include the efforts of D0R Project Managers, DDR Technical Reviewers, and Lawrence Livermore Laboratory (under an existing technical assistance contract with DOR).
We propose also that the title of the B-23 program be revised from " Degraded Grid Voltage" to
" Adequacy of the Station Electric Distribution System Voltage" to reflect the expanded scope.
Subject to your concurrence, we will send the attached memo to the operating reactors branch chiefs.
This memo will transmit a sample generic letter to licensees, provide background information and request the submittal of appropriate voltage drop analyses to demonstrate the adequacy of their electric system design.
Also provided with the
6 3-generic letters is our guidance on the analysis necessary to reveal the types of potential voltage deficiencies surfaced by the Arkansas event. Our proposed feedback memo to DSS on this subject is attached for your signature.
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[ t-R. Vollmer, Assistant Director for Systems and Projects Division of Operating Reactors
Contact:
E. Wenzinger X-28077 cc:
R. Vollmer B. Grimes D. Eisenhut A. Schwencer D. Ziemann T. Ippolito R. Reid G. Lainas W. Russell J. T. Beard S. Rhow S. Hanauer F. Rosa G. Vissing L. Engl e E. Wenzinger D. Vassallo S. Sheppa rd