ML19350B686
| ML19350B686 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 03/18/1981 |
| From: | Mark J Advisory Committee on Reactor Safeguards |
| To: | Hendrie J NRC COMMISSION (OCM) |
| References | |
| ACRS-R-0923, ACRS-R-923, NUDOCS 8103230308 | |
| Download: ML19350B686 (3) | |
Text
t yy p yh UNITED STATES 4
.g NUCLEAR REGULATORY COMMISSION y,,2, g
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 2
.j W ASHNGTON. D. C. 20555 S.,
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4 March 18,1981 NA 80 U8/
5 **k'4kg Honorable Joseph M. Hendrie Chairman U.S. Nuclear Regulatory Commission f
4 Washington, DC 20555
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SUBJECT:
REPORT ON VIRGIL C. SUMMER NUCLEAR STATION UNIT 1 e, J -
Dear Dr. Hendrie:
During its 251st meeting, March 12-14, 1981, the ACRS completed its review of the application of the South Carolina Electric and Gas Company for a license to operate the Virgil C. Summer Nuclear Station Unit 1.
This proj-ect was considered at subcommittee meetings on February 26-27,1981 i n Columbia, South Carolina, and on March 11, 1981 in Washington, D.C.
A tour of the facility was made by members of the Subcomittee on February 26, 1981.
During its review the Committee had the benefit of discussions with repre-sentatives of the Applicant, the NRC Staff, the U.S. Geological Survey, and of the documents listed.
The Committee reported on the construction permit application for this plant in a letter to AEC Chairman Schlesinger dated November 15, 1972.
The Summer plant is located in Fairfield County, South Carolina, about 26 miles northwest of Columbia, South Carolina.
The nearest community with more than 1000 residents is Winnshore, about 15 miles to the northeast.
The plant is adjacent to the Monticello reservoir, >Aich provides cooling water for the main condenser, as well as the ultimate heat sink.
The Summer plant employs a Westinghouse, three-loop, pressurized water, nu-The containment is a cylindrical, carbon-steel-clear steam supply system.
lined, prestres ed concrete structure having a design pressure of 57 psig.
At the construction permit review stage, some of the ACRS consultants were reluctant to accept the position of the Regulatory Staff and its consul-tants that the 1886 Charleston earthquake could be clearly localized in the a somewhat Charleston area with regard to recurrence and recommended that increased seismic design basis be employed.
The ACRS supported the Regula-tory Staff position favoring a safe shutdown earthquake (SSE) acceleration However, in. separate reports to the AEC dated May 13,1971 and of 0.15g.1973, the ACRS c ged initiation of a seismic research program in-May 16, tended to provide a better understanding of the likely causes of earthquakes near Charleston as well as several other areas in the eastern United States.
Considerable research has since been undertaken in the Charleston area, and an improved understanding of the possible causes of earthquakes in the east-ern United States has been developed.
However, there still exists more than one theory with regard to the source of the 1886 Charleston earthquake.
81082302;pg O
L Honorable Joseph M. Hendrie March 18,1981 Since the construction permit stage, a new issue has arisen with regard to the choice of seismic design basis; namely, the potential for a moderate earthquake at the site resulting from reservoir-induced seismicity.
The Applicant has studied seismic activity in the vicinity of the Monticello reservoir since it was filled in 1977, and combined the results of those studies with information about the local geology and hydrology in arriving at the conclusion that a maximum near-field earthquake magnitude of 4.0 should be considered in evaluating plant safety.
The NRC Staff and its consultants have concluded that a near-field magnitude of 4.5 should be used.
However, one member cf the NRC Staff disagrees with the majority Staff position, suggesting that the available information does not rul e out a somewhat larger reservoir-induced earthquake, and that a near-field earthquake having a magnitude of 3.0 to 5.3 should be used for assessing seismic safety.
The ACRS consultants agree that there does not exist a very good basis for choosing a specific near-field event, and generally support the use of a near-field magnitude of about five for evaluation of the plant.
Because it is difficult to judge that the probability of significant exceed-ence of the original SSE is sufficiently small, the ACRS has requested, and the Applicant has provided, information that indicates there is sufficient margin in the original aesign to cope safely with accelerations considerably larger than the SSE of 0.15g, including those which might arise from a near-field, magnitude 5 earthquake.
The Applicant's results to date regarding seismic design margin are reassur-ing.
The ACRS recommends that these studies by the Applicant be extended to include all systems and components whose function is important to the assurance of the continuing removal of shutdown heat.
Such studies need not be completed prior to operation of the Summer plant.
The discussions relative to the seismic issues at the Summer Nuclear Power Station raise certain questions that we believe should be addressed.
These questions, which largely pertain to emergency preparedness, include the ability of certain key systems to function after a major seismic event.
Included among such systems are the emergency alarm features to alert the public to an accident in the plant, meteorological and field radiation mon-itoring networks, communications, and emergency evacuation routes.
As a result of the continuing microseismic activity induced by_ the reservoir, the Applicant has, at NRC request, agreed to continue seismic monitoring for at least the next two years.
We recommend that the NRC Staff assure that the monitoring program is not halted prematurely.
In its review of the Applicant's organization and management, the NRC Staff has identified several areas requiring attention, including the size of the engineering organization and the adequacy of experience with nuclear power reactors within the compay, including hands-on operating experience within
L Honorable Joseph M. Hendrie March 18,1981 the operating organization.
The Applicant has taken steps to obtain the services of outside groups to provide additional technical capability for the short tenn while the needed in-house capability is developed.
Care should be exercised that, as part of this effort, sufficient technical breadth and independence exists among the members of the Nuclear Safety Review Committee for the plant.
We have previously recommended that probabilistic safety analyses be per-formed for all plants in operation or under construction.
We believe that this recommendation is applicable to this unit, but that such studies need not be performed prior to licensing of the plant.
During construction of the essential servic.e water intake structure and pump house, settlement well beyond that predicted was experienced.
While the settlement of the structures appears to have halted, the NRC Staff is still evaluating information addressing the stability of the subsurface materials and foundations of the intake structure and pumphouse.
This matter should be resolved in a manner satisfactory to the NRC Staff.
The ACRS believes that, if due consideration is given to the items mentioned above, and subject to satisfactory completion of construction and preopera-tional testing, there is reasonable assurance that the Virgil C. Summer Nu-clear Station Unit 1 can be operated at power levels up to 2775 MWt without undue risk to the health and safety of the public.
Si ncerely,
J. Carson Mark t
Chairman
References:
1.
South Carolina Electric and Gas Company, " Final Safety Analysis Report, Virgil C. Summer Nuclear Station," Volumes I-XX and Amendments 1-22 2.
U. S. Nuclear Regulatory Commission, " Safety Evaluation Report Related l
to the Operation of Virgil C. Summer Nuclear Station, Unit No.1,"
l USNRC Report NUREG-0717, dated February,1981 3.
Letter from J. Devine, USGS, to R. Jackson, NRC, in response to an NRC request for update on USGS information concerning occurrence of earthquakes similar to the 1886 Charleston event, dated December 30, 1980 4.
Memorandum from A. Murphy, Site Safety Research Branch, NRC, to R.
Jackson, Chief, Geosciences Branch, NRC,
Subject:
Recommendation of Maximum Reservoir-Induced Earthquake at the V. C. Summer Nuclear Station, dated February 6,1980 5.
" Comments from the Palmetto Alliance, Inc., by Michael Lowe on V. C.
Summer Operating License Application Review by the NRC Advisory Com-mittee on Reactor Safeguards," dated February 26, 1981 6.
" Testimony Before the Advisory Committee on Reactor Safeguards Related to the Virgil C. Summer Nuclear Station," Ms. Ruth Thomas, received February 26,_1981