ML20141H267
| ML20141H267 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/20/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20141H253 | List: |
| References | |
| RTR-REGGD-01.127, RTR-REGGD-1.127 NUDOCS 8601130506 | |
| Download: ML20141H267 (3) | |
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UNITED STATES g
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 48 TO FACILITY OPERATING LICENSE NPF-12 SOUTH CAROLINA ELECTRIC & GAS COMPANY SOUTH CAROLINA PUBLIC SERVICE AUTHORITY VIRGIL C. SUMMER NUCLEAR STATION, UNIT 1 I.
INTRODUCTION I
By letter dated November 24, 1982, as amended by letters dated October 21, 1983, and February 29, 1984, South Carolina Electric & Gas Company requested that license condition 2.C.(5) be amended to change the mor:ltoring and inspection of the service water intake structure from that recomended by Regulatory Guide 1.127 to an inspection interval of every five years maximum.
II.
EVALUATION l
The tunnel portion of the service water intake structure (the portion subject to underwater inspection) is formed of lightly reinforced concrete i
..Ith inside dimensions of 12 ft. (wide) x 15 ft. (high) and total length of 167 ft. The service water intake tunnel at the V. C. Sumer station underwent excessive differential settlement prior to being pet into service.
In the opinion of the NRC staff, the differential settlement was the result i
of inadequate investigation and preparation of the soils underlying the l
structure. The settlement was evidenced by cracks, some as wide as 0.2 inches at the point of maximum opening that broke through the 3 ft. thick roof and in some instances reached approximately 40 ft. in overall length.
The applicant instituted repair procedures using epoxy grout to seal off I
cracks wider than 0.012 inches.
(The provisions of the American Concrete l
Institute (ACI) 318-71 design code strive to assure that concrete cracks do not exceed widths of about 0.012 inches as a measure to protect reinforc-ing steel from degradation due to corrosion.
In critical structures, l
significant cracking of greater widths is usually cause for engineering evaluation and repair where warranted.) An underwater inspection performed by the licensee in 1979 found that two grout holes had not been plugged and p
that some cracks had not been recorded in the initial report to the NRC.
The need for inspection is motivated by two principal concerns. The first is maintenance of sufficient structural integrity to assure function under extreme environmental loading, e.g., earthquakes. The second is to assure l
that silt or debris has not filtered through cracks or otherwise accumulated ll to a degree that could degrade function of the intake structure under design basis events. These are much the same reasons that internal inspection of large water intake and discharge systems are typically performed during each major overhaul of electric generating stations, other large irdustrial complexes and municipal sanitary systems.
In many instances dewatering of i
i opK05000395 6 851220 P
the system has been the desired approach, although inspections utilizing a diver are becoming more comon.
In the nuclear industry, diver inspection has been extended to reactor cavities, torus tubes, spent fue.1 pits, and l
fuel transfer canals, as well as intake and discharge structures.
I By letter dated May 11, 1983, the licensee provided a report of a January 1983 diver's inspection of the essential service water intake structure of the Virgil C. Summer Nuclear Station. The results of this inspection provide a significant data point in assessing the interrelation of measured settlement and the condition of the intake structure.
The 1983 diver inspection report indicates eight new cracks in the intake t
tunnel since the June 1979 diver inspection. All new cracks were less than 0.015 inch wide. Most cracks were vertically oriented and all were L
in the tunnel wall. The diver also reported accumulation of silt on the walls and floor of the intake. Based on its review of the January 1983 inspection report, the staff finds that the condition of the intake tunnel is stabilized, i.e., no further significant cracking or deterioration of the repaired cracks after approximately four years of service.
Monitoring masts are attached to the intake structure to provide indication of settlement or rebound occurrences. The licensee will perform surveil-lance of the monitoring masts semiannually for the life of the facility to, i
ensure that no undetected significant differential movement occurs.
Indications of differential movement greater than one (1) inch would result in more frequent surveys, and an additional diver's inspection.
Under R.G. 1.127, the recommended inspection interval is every two years through 1987 but thereafter the inspection interval may be extended to H
five years if the results of the previous inspections warrant the exten-sion. Based on the stabilized condition of the intake structure and the semiannual surveillance of the monitoring masts, the staff concludes that changing the inspection interval to a five year maximum inspection interval before the time period recommended by R.G. 1.127 is acceptable.
III. ENVIRONMENTAL CONSIDERATION l
This amendment involves a change in the inspection of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may i
be released offsite and that there is no significant increase in individual i
or cumulative occupational radiation exposure. The Commission has pre-i viously issued a proposed finding that this amendment involves no signifi-cant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibilit categorical exclusion set forth in 10 CFR Sec. 51.22(c)(9)y criteria for Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assess-ment need be prepared in connection with the issuance of this amendment.
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1 f t IV.
CONCLUSION The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Register (49 FR 21839) on May 23, 1984, and consulted with the state of South Carolina. No public comments were received, and the state of South Carolina did not have any comments.
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regula-tions :nd the issuance of this amendment will not be inimical to the I
common defense and security or to the health and safety of the public.
Principal Contributor: Jon B. Hopkins, Licensing Branch No. 4, DL Dated: December 20, 1985 i
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