ML20058C302
| ML20058C302 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/23/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058C301 | List: |
| References | |
| NUDOCS 9011010145 | |
| Download: ML20058C302 (7) | |
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UNITED STATES y\\ fri e
NUCLEAR REGULATORY COMMISSION f
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W ASHING TON, D. C. 205$$
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 34 TO FACILITY OPERATING LICENSE NO. NPF-73 DUQUESNE LIGHT COMPANY OHI0 EDIS0N COMPANY THE CLEVELAND ELECTRIC ILLUMINATING COMPANY THE TOLED0 EDISON COMPANY BEAVER VALLEY POWER STATION, UNIT'NO. 2 DOCKET NO. 50-412
1.0 INTRODUCTION
By letter dated October 1,1990 (Ref.1) Duquesne Light Company (DLC) submitted applications for license amendments.for a change in the surveillance requirements of Technical Specification (TS) 4.6.1.6.1 for Units 1 and 2 at the Beaver Valley Power Station (BVPS-1 and BVPS-2). The applications requested approval of the proposed amendments in time to support restart of BVPS-2 from the second refueling outage. A telephone conference call with the-staff and DLC representatives was held on October 5,-1990. During this phone call, the staff was informed that the equivalence between the liner and i
channel material in terms of welding quality and ultimate elongation had not l
yet been established for BVPS-2.
Because the proposed amendments would be i
applicable for the long term., the staff concluded that there was insuff141ent t
information then available and the staff review could not be completed within the time frame requested.,However, the staff suggested that an amendment for BVPS-2 for a limited time period might be possib.e. DLC then applied on October 9, 1990 (Ref. 2) for an emergency TS change for Unit 2 only for a limited period of time. This Safety Evaluation relates to the October 9, 1990, application for Unit 2 only to support DLC's planned Type A test and unit restart schedule.
2.0 BACKGROUND
AND DISCUSSION The containment building at BVPS-2 has a continuously welded carbon steel liner
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which acts as a leak tight membrane. The cylindrical portion of the liner is j
5/8 inch thick, the hemispherical done is 1/2 inch thick and the flat floor liner covering the concrete mat is 1/4 inch thick. Thefloorlinerplateis covered with approximately 2 feet of reinforced concrete. At the intersection of the containment liner and the concrete floor, a 1/2 inch joint is provided which is filled with a 1/2 inch thick premolded joint filler. The top of the joint is sealed with an elastic sealant adhesive. All welded seams are covered i
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7 with continuously welded test channels, called leak-chase channels, which were installed to facilitate leak testing of welds during liner erection. Test ports that were provided for leak testing were "-b
' with vent plugs after the completion of the testing. These plugs wei emain in place during subsequent Type A leak rate testing. The desigt...J construction of the BVPS-2 containment building is similar to BVPS-1 and Virginia Electric and power Company's Surry and North Anna containment buildings.
The test channels in BVPS-2 are larger than those in BVPS-1 but are installed in a similar manner.
The BVPS-2 TS 4.6.1.6.1 requires, among other things, that the structural integrity of the containment liner plate and concrete shall be determined by visual inspection of accessible containment liner test channels arior to each Type A contairment leakage rate test. The TS further requires t1at any containment liner test channel, which is found to be damaged to the extent that channel integrity is impaired or which is discovered with a vent plug removed, shall be removed and a protective coating shall be applied to the liner in that area.
The proposed license amer.cment, if epproved, would allow DLC to restart the plent after performing the Type A containment leakage rate test without removing the test channels. The proposed change involves revision of TS 4.6.1.6.1 by including an alternative to the current surveillance requirement. DLC has proposed that the alternative surveillance requirement be applicable only for the interval that would include the Type A testing to be conducted in October 1990 up to the next Type A leakage rate (Ref. 2).
3.0 EVALVATION Eecause of the missing vent plugs, the curront prescriptive wording of TS 4.6.1.6.lb would require extensive cutting and grinding to remove approximately 1500 feet of test channel.
The proposed alternative wording does not contain specific details on the required actions if a test channel is found to be damaged or is discovered with a missing plug. The proposed alternative require-ment specifies that the structural integrity of the exposed accessible interior t
l and exterior surfaces of the containment vessel, including the liner plate, shall be determined by performing a visual inspection of these surfaces prior to the Type A leakage rate test to verify no apparent changes in appearance or other abnormal degradation and appropriate corrective measures will be taken should the visual examination uncover any evidence of damage that affects the containment integrity.
To support the proposed alternative surveillance requirement, the DLC appli-cation included a Stone & Webster (S&W) Report titled, " Containment Liner Test Channels at BVpS Unit No. 2."
According to this report, the test channels are capable of withstanding all loads that might be imposed on them during normal, test, and upset conditions without impairing, in any way, the performance of the containment liner itself. The material of the channels is ASTM Grade C with ultimate elongat*0n of 24%, and the liner material is ASTM-A537 Grade B l
quenched and tempered with ultimate elongation of 22%.
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Thus, the materials are equivalent. A detailed comparision of welding process and the examination of welds has not been reviewed by the staff; however, they are expected to be equivalent as well.
DLC has also referred to the NRC staff's 1989 determination of the accept-ability of the conteinment test channels as the pressure boundary for VEPCO's Surry plant (Ref. 3).
The main thrust of the staff's position as stated in Ref. 3 was that the leak chase channels can be lef t in place provided it can t
be demonstrated that (a) the channel welds are qualitatively (b)quivalent to o e
better then those for the primary containment liner welds, the channels would maintain their integrity when subjected to the loading conditions of a postulated design basis accident as well as during normal operation, and (c) the inspection and reporting of tests as required in 10 CFR Part 50, Appendix J has been imslemented.
Based on VEPCO's compliance with the above conditions, the staff Ted concluded that the channels would maintain their i
structural integrity at all times at the Surry plant (Ref. 3).
In performing its review of this application, the staff asked DLC to completa the following actions:
(a) visual ins trapped in the test channels, and (c) pections, (b) chemical analyses of water corrosion rate prediction. DLC has i
completed the above actions and reported the results in Ref. ?, Attachment 1 which are briefly described below.
Borescopic inspections into the test channels with the mi: sing vent plugs were attempted by DLC with mixed results. Some of these inspections wcre successful while others were not.
Entry into the test channel for the vent connection 90A was successful. An area of liner metal approximately 3/8 inch in diameter was visible with indications of minor corrosion along with traces of moisture.
Entry into the test channel for vent connection 90C was also successful revealing minor corrosion in a visible area of liner metal epproximately 3/8 inch in i
diameter, but with no trace of moisture in this case.
In some cases, samples of debris which appeared to be sand and/or sandblasting material were collected from the vent connection tubing. DLC did not continue further borescopic inspections since previous inspection failed to provide adequate information to assess the condition of the liner or weld.
Since the missing vent plugs may permit moisture to enter the test channels and cause corrosion of the liner metal, DLC sampled the water accumulated inside several test channels to evaluate the extent to which corrosion may have occurred. The results of the chemical analysis of the samples of water revealed a pH value of 10.1 and 11.4 with sodium (Na) in the range of 19 to 44 ppm.
Assuming, therefore, that the primary corrosive chemical present was NaOH, DLC has estimated a total expected corrosion of 86 mils (for 40 years life plus 3 years of preservice) using a corrosion rate of 2 mils per year. This estimate of corrosion is bounded by the S&W evaluation of 88 mils total bliowance (Ref. 2, Attachment 1).
DLC has thus determined, and the staff agrees, that there is sufficient margin in the containment liner thickness to accommodate a total, worst-case corrosion of 88 mils over the 40 year life of the plant.
DLC has further stated that any test channel subsequently identified as holding free standing water will be e
i l evaluated further to determine the corrosive properties of the sample of water and to assure that the containment liner remains capable of performing its design function for the life of the plant.
Based on the above corrosion rate prediction, the containment vessel is quite safe up to the next Type A leakage i
rate test.
The proposed alternative surveillance requirement (TS 4.6.1.6.lb) specifies that the exposed accessible interior and exterior surfaces of the containment vessel and the liner will be inspected to verify that no apparent changes in appearance or other abnormal degradation have occurred. DLC has committed to continue visual inspections of all the exposed accessible test channels and the associated vent plugs and to make repairs, where necessary, to the liner in accordance with the ASHE Boiler and Pressure Vessel Code. DLC will replace, after completing the Type A leakage rate test, any missing vent plugs or will otherwise seal the test connections. This will preclude possible reoxygenation of the test channels and the introduction of fluids which might lower the pH.
This will assure not exceeding the corrosion rate assumed in the S&W report.
Finally, DLC has committed to continue to verify the structural integrity of the containment vessel by inspections and tests as required by 10 CFR Part 50, Appendix J, to ensure that the containment structure will remain capable of performing its intended function.
BasedonareviewofDLCsubmittals(Refs.1and2)andthephonecall,the staff finds that the proposed license amendment to allow an alternate surveil-lance requirement 4.6.1.6.1b does not affect the structural integrity or the leak tightness of the containment vessel as discussed above. Therefore, the I
staff accepts DLC's request for the proposed TS change for a limited interval of time, starting with the Type A testing to be conducted in October 1990, up to the next Type A test.
- t. 0 EMERGENCY CIRCUMSTANCES The first indication of missing test channel plugs was noticed by the licensee about September 17, 1990, while conducting the required inspections prior to i
proceeding with the Type A test. The NRC staff was* informed that day by telephone that DLC was evaluating the circumstances to determine a course of action. From their evaluation, DLC determined that the amount of test channel that would need to be removed to comply with the TSs was large, and in some cases, not assessible. Therefore DLC concluded that it would be prudent from a
both the radiological and technical serspective to justify leaving the test channels in place and to request a c1ange to the TSs.
An application for license amendment was submitted to the NRC staff on October 1, 1990.
DLC requested that the proposed change be approved in time to support transition into Mode 4 which, at that time, was scheduled for October 24, 1990, and the Type A test was scheduled for about October 12, 1990. On October 5, 1990, a telephonic conference was held between the NRC staff and DLC to discuss the issue.
Based on information obtained in that conference, the staff deter-mined that it would be unable to support DLC's request for permanent change to the TSs in time to support the scheduled mode transition. The staff agreed to continue its efforts to process the application, but requested that DLC prepare an additional application requesting changes, that if approved, would provide
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the sought-after relief for a limited time. That application was submitted to the NRC on October 9,1990, with the request that it be treated as an emergency.
The Type A test is now scheduled to be conducted on October 23, 1990. Thus, there is insufficient time to provide notice pursuant to 10 CFR 50.91(a).
The NRC staff does not believe that DLC has abused the emergency provisions in this instance.
Accordingly, the staff has determined that emergency circum-stances exist warranting 3rompt approval, in that failure to act will cause the plant to delay startup, tie situation could not have been avoided, and the -
amendment as discussed in Section 5.0 does not involve a significant hazards consideration.
5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The f. omission has made a final determination that the amendment involves no.
signSficant hazards consideration.
Under the Commission's regulations in 10 CFR 50.92(c), this means that the operation of the facility in accordance with the proposed amendment would not (1) involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
The staff has evaluated the proposed changes against the above standards as required by 10 CFR 50.91(a) and has concluded that:
A.
Thechangedoesnotinvolveasignificantincreaseintheprobability(1))
orconsequencesofanaccidentpreviouslyevaluated(10CFR50.92(c) because the alternate surveillance method provides assurance that the structural integrity and leaktightness of the containment continues to be maintained, t
B.
The change does not create the possibility of a new or different kind of accident from any accident previously evaluated (10 CFR 50.92(c)(2))
l because neither plant configuration nor the manner by which the facility i
is operated is affected.
C.
The change does not involve a significant reduction in a margin of safety (10 CFR 50.92(c)(3)) because the same structural integrity and leaktightness of the containment assumed in the original design will still be assured. Plugging or sealing the test channels provides an additional and redundant barrier to the containment liner welds, and the alternative surveillance will assure that abnormal degradation has not l
occurred.
6.0 STATE CONSULTATION
In accordance with the Comission's regulations in 10 CFR 50.91(b), the repre-sentative of the Commonwealth of pennsylvania was consulted. The representative had no comments with regard to this action, i
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7.0 ENVIRONMENTAL CONSIDERATION
This amendrent changes a surveillance requirerent. We have determined that
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the amendrent involves no significant increase in the amounts, and no signifi-1 cant change in the types, of any effluents that may be released offsite and i
radiation exposure.gnificant increase in individual or cumulative occupa,tional that there is no si l
The staff has made a final determination that this amendment involves no significant hazards consideration. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in10CFF51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
8.0 CONCLUSION
We have concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities willbeconductedincompliancewithtieCommission'sregulations,and(3)the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: October 23, 1990 Principal Contributors:
Raman Pichumani Albert W. De Agazio O
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9.0 REFERENCES
1.
Letter dated October 1,1990 from J. D. Sieber, DLC, to NRC,
Subject:
Beaver Valley Power Station, Unit Nos. I and 2, Proposed OperatingLicenseChangeRequestNo.181/45(TACNos.77638and77639),
2.
Letter dated October 9,1990 from J. D. Sieber. DLC, to NRC,
Subject:
Beaver Valley Power Station, Unit No. 2, Proposed Operating License Change Request No. 46 (TAC No. 77726).
3.
Letter dated March 6, 1989 from Bart C. Buckley, NRC, to W. R. Cartwright,-
Subject:
Surry Units 1 and 2 - Containnent Liner Weld Leak. Chase L
Channels (TACNos.67573and67574).
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