ML20046B317
| ML20046B317 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/26/1993 |
| From: | Opeka J NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20046B318 | List: |
| References | |
| B14376, NUDOCS 9308040063 | |
| Download: ML20046B317 (4) | |
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L J ZC3%C[72, (203) 665-5000 July 26,1993 Docket No. 50-245 s14376 Re:
10CFR50.90 U.S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, DC 20555 Gentlemen:
14111 stone Nuclear Power Station, Unit No. 1 i
l Proposed Revision to Technical Specifications
_ Increased Stroke Time fodsolation Valves Pursuant to 10CFR50.90, Northeast Nuclear Energy Company (NNECO) hereby proposes to amend its Operating License DPR-21 by incorporating the attached change into the liillstone Unit No.1 Technical Specifications.
illustrates the marked-up page of the current technical specifications for informational purposes, and Attachment 2.provides the retyped page.
Description of the Proposed Chanae The proposed change would increase the maximum stroke time for reactor water cleanup (RWCU) system isolation valves CU-2, 3, 5, and 28 from 18 secords to 20 seconds in Table 3.7.1.
This increase in stroke time allowance would provide a more appropriate closure limit which would aid in trending of valve performance and correcting identified valve degradation prior to exceeding the maximum stroke time allowed by the techaical specifications.
This change is bounded by current accident analyses assumptions.
Historically, RWCU system isolation valves CV-2, 3,
5, and 28 have closed within the 18-second time period; however, the margin for meeting the 18-second closure limit has always been narrow.
Trending of stroke times for these valves from 1984 to date provides illustration that this narrow margin is not indicatin of valve degradation, but rather represents a random variation in the average closure time for the valves.
There has been no significant or consistent increase in closure time for these valves except for RWCU valves CU-2 and 3.
Their actuators were replaced during the 1989 refueling outage.
Subsequently, these valves have closed in a consistent and acceptable manner, but still within a narrow margin of the-18-second_ stroke time limit.
Safety Assessment In support of this change, it should be noted that loss-of-coolant accident (LOCA) calculations assume that as long as all containment isolation valves
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U.S. Nuclear Regulatory Commission B14376/Page 2 l
July 26, 1993 (CIVs) close within 60 seconds, calculated release rates will not increase.
All reactor building environmental profiles have been developed utilizing the 20-second maximum closure time of these CIVs.
Therefore, the environmental profiles of temperature, pressure, humidity, and radiation are unaffected by this change.
The 2-second increase in CIV response time would remain l
conservatively within the bounds of the 60-second closure limit assumed in the calculations for radiological consequences from a LOCA, and at the closure time assumed for the environmental and radiological consequences for an RWCU system line break outside containment.
j Sionificant Hazards Consideration In accordance with 10CFR50.92, NNECO has reviewed the proposed change described abave and has concluded that it does not involve a significant hazards consideration (SHC) because the change would not:
1.
Involve a significar,t increase in the probability or consequences of an accident previously evaluated.
The proposed increase in the allowable closure time for RWCU system isolation valves CU-2, 3, 5, and 28 from 18 to 20 seconds would have no impact on the core cooling aspect of a LOCA.
With respect to the radiological consequence of a LOCA, the proposed valve closure time of 20 seconds is well within the 60-second closure limit assumed in the associated LOCA analysis.
The proposed increase in closure time to 20 i
seconds is consistent with the Updated Final Safety Analysis Report analysis of RWCU line break in the reactor building which assumes a 20-second closure limit. The analysis results are used in calculating harsh environment impact in the reactor building and in calcula ing the off-site dose of an RWCU line break.
The environmental profiles for the reactor building are not affected by this change.
Therefore, this proposed change has no affect on the initiation, probability, or consequences of any previously evaluated accident scenarios.
2.
Create the possibility of a new or different kind of accident from any previously analyzed.
The 20-second closure time for RWCU system isolaticn valves CV-2, 3, 5, and 28 has been previously analyzed and found to be consistent with design basis accident assumptions. The proposed increase in closure tine to 20 seconds is consistent with the Updated Final Safei.y Analysis Report analysis of RWCU line break in the reactor building which assumes 1 20-second closure limit.
The analysis results are used in calculating harsh environment impact in the reactor br11 ding and in calculating the l
off-site dose of an RWCU line break.
The environmental profiles for the reactor building are not affected by this change. As such, the potential for an unanalyzed accident is not created.
No new failure modes are introduced.
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U.S. Nuclear Regulatory Commission i
B14376/Page 3 J
July 26, 1993 3.
Involve a significant reduction in a margin of safety.
i Increased maximum allowable isolation times for RWCU valves do not diminish the ability to isolate the containment.
The proposed change i
does not affect the consequences of any accidents previously analyzed, and no safety limits :for the protective boundaries are ' impacted.
Therefore, the proposed change does not reduce the margin of safety.
j j
The Commission has provided guidance concerning the application of standards in 10CFR50.92 by providing certain examples (51FR7751, March 6, 1986) of amendments that are considered not-likely to invrive an - SHC.
The change i
proposed herein is not enveloped by a specific example, but this does not alter.the conclusion that the proposed amendment 'does not involve a l
significant' hazards consideration.
There are two accident scenarios. which could be impacted by the proposed change:
LOCA (inside the drywell) and RWCU l
line break outside the drywell.
The proposed increase in the~ maximum allowable stroke time for RWCU system isolation valves CU-2, 3, 5, and 28 from
- 18. seconds. to 20 seconds remains within the bounds of the 60-second closure limit assumed in LOCA calculations, as well as the '20-second closure time calculated as the limit for radiological and environmental consequences for an RWCU system'line break outside' containment. This increase in allowable stroke time is intended to provide more operating-margin so.that valve-degradation can be detected and corrected prior to exceeding ' technical specification i
limits.
J; Environmental Consideration NNEC0 has reviewed the proposed license amendment against the criteria of 10CFR51.22 for environmental considerations.
The proposed change does not increase the types and amounts of effluents that may be released off site, nor significantly increase individual or cumulative occupational radiation exposures.
Based on the foregoing, NNECO concludes that the proposed changes meet the criteria delineated in 10CFR51.22(c)(9) for a categorical exclusion from the requirements for an environmental ' impact statement.
The change described above is beneficial for long-term trending purposes and I
has no immediate impact on operation of the plant.
As such, no specific schedule for approval and issuance is requested.
However, we request that i
this. proposed change become effective 60 days after issuance in order to allow adequate time for implementation.
l The Millstone Unit No.1 Nuclear Review Board has reviewed and approved the attached proposed revision to the technical specifications and has concurred j
with the above determinations.
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U.S. Nuclear Regulatory Commission B14376/Page 4 July 26, 1993 In accordance with 10CFR50.91(b), NNECO is providing the State of Connecticut with a copy of this proposed amendment.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY I
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J. F. Opekh O
Executivb'Vice President cc:
T. T. Martin, Region I Administrator J. W. Andersen, NRC Acting Project Manager, Millstone Unit No.1 P. D. Swetland, Senior Resident Inspector, Millstone Unit Nos.1, 2, and 3 Mr. Kevin McCarthy, Director Radiation Control Unit Department of Environmental Protection Hartford, CT 06116 Subscribed and sworn to before me thisd?8 day of 9//A
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'NotaryfPublic Date Connission Expirest3h r^
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