ML17054B784
| ML17054B784 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 07/24/1985 |
| From: | Vassallo D Office of Nuclear Reactor Regulation |
| To: | Hooten B NIAGARA MOHAWK POWER CORP. |
| Shared Package | |
| ML17054B785 | List: |
| References | |
| NUDOCS 8508070359 | |
| Download: ML17054B784 (8) | |
Text
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~ 0 July 24, 1985 Docket No. 50-220 Mr. B.
G. Hooten Executive Director, Nuclear Operations Niagara Mohawk Power Corporation 300 Erie Boulevard West
- Syracuse, New York 13202 Dear Mr. Hooten
SUBJECT:
SAFETY EVALUATION, CORE SPRAY EFFECTIVENESS IN STEAM ENVIRONMENT Re:
Nine Mile Point Nuclear Station, Unit No.
1 We have completed our review of your submittal dated September 13, 1983 regarding the effectiveness
'of core spray in a steam environment.
The major conclusions and findings of the evaluation are summarized in Enclosure 1.
Our Safety Evaluation is enclosed (Enclosure 2).
During the course of our review we have discovered that the Bases section of the Nine Mile Point 1 Technical Specification on operability of the core spray system (TS 3.4) makes reference to a required system flowrate which is less than the core spray flowrate assumed in the subject analysis regarding core spray effectiveness.
The Technical Specification Bases as presently written reflect the original Core Spray system design requirement that the system provide 3400 gpm at a vessel pressure of less than 125 psia.
Your current analysis takes credit for the fact that during a large LOCA the vessel will depressurize to a pressure below 30 psia, against which the core spray system will deliver a higher flowrate (i.e.,
5020 gpm).
The surveillance test procedure for core spray operability as presently written verifies that core spray pump performance characteristics over the full range of pressures and flowrates have not degraded.
This range includes both pressure vs. flow points (i.e.
125 psia vs.
3400 gpm and 30 psia vs.
5020 gpm).
The surveillance test procedure properly ensures that the system will provide the required flowrate.
A change in procedure is not needed.
- However, we believe the Technical Specification bases as presently written are ambiguous, inaccurate and misleading.
In a telecon on April 2, 1985, we have discussed clarification of the Technical Specification Bases with the lead licensing engineer of Niagara Mohawk Power Corporation.
Accordingly, we are enclosing the revised Bases page for the Technical Specification.
The Bases change has been discu'ssed with your staff and has been found mutually acceptable.
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Mr. B. G. Hooten The material contained in Enclosure 2 (Safety Evaluation) is considered to be proprietary and therefore is withheld from public disclosure per 10 CFR 2.790.
Enclosure 3 is a non-proprietary version of the Safety Evaluation and is being made publicly available.
Sincerely, Original signed by/
Domenic B. Vassallo, Chief Operating Reactor Branch ¹2
'ivision of Licensing
Enclosures:
1.
Conclusions and Findings 2.
Safety Evaluation (Proprietary) 3.
Safety Evaluation (Non-Proprietary) 4.
Technical Specification pages 54 and 55 cc w/enclosures 1,
3 and 4
See next page DISTRIBUTION w/enclosure 1 thru 4
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3 and 4
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Mr. B. A. Hooten
'iagara Mohawk Power Corporation Nine Mile Point Nuclear Station, Unit No.
1 CC:
Troy B. Conner, Jr., Esquire Conner
& Wetterhahn Suite 1050 1747 Pennsylvania
- Avenue, N.
W.
Washington,,D.
C.
20006 Frank R. Church, Supervisor Town of Scriba R. D.
5'2
- Oswego, New York 13126 Niagara Mohawk Power Corporation ATTN:
Mr. Thomas Perkins Plant Superintendent Nine Mile Point Nuclear Station Post Office Box 32
- Lycoming, New York 13093 Resident Inspector U. S. Nuclear Regulatory Commission Post Office Box 126
- Lycoming, New York 13093
- John W. Keib, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard Hest
- Syracuse, New York 13202 Thomas A. Murley Regional Administrator Reaion I Office U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 Mr. Jay Dunkleberger Divisi on of Pol icy Analys i s and Planning New York State Eneray Office Agency Building 2 Empire State Plaza
- Albany, New York 12223
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ENCLOSURE I Evaluation Findin s
1.
The minimum bundle flowrate predicted in the licensee's analysis was arrived at using the General Electric desiqn methodology for determining core sprav distribution.
We have reviewed the licensee's analysis and find it acceptable.
2.
In order to demonstrate acceptable consequences for certain small break loss-of-coolant accident scenarios the licensee has re-analyzed the small break cases with a modified evaluation methodology.
This was done because of uncertainties in core spray distribution at elevated reactor system pressure.
The results of the analysis show that when credit is taken for steam cooling, spray distribution becomes unimportant with respect to core cooling.
The staff has reviewed the methodology and the analyses as part of its review of the Oyster Creek Cycle 10 reload core analysis and found them acceptable.
3.
The licensee has determined the minimum required bundle spray flowrate needed to achieve Appendix K heat transfer coefficients with a method supported by spray cooling test results.
We accept this determination because it is well supported by test data.
4.
We have reviewed the uncertaintv factor applied in the determ~nation of minimum bundle spray flowrate and find it acceptable based on comparisons of test results with calculated results.
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