ML20138C760
| ML20138C760 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/16/1985 |
| From: | Opeka J, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | Charemagne Grimes Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-43, REF-GTECI-ES, TASK-A-43, TASK-OR B11823, NUDOCS 8510230031 | |
| Download: ML20138C760 (4) | |
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(203) 665-5000 October 16,1985 Docket No. 50-245 Bil823 Director of Nuclear Reactor Regulation Attn:
Mr. Christopher I. Grimes, Chief Systematic Evaluation Program Branch U. S. Nuclear Regulatory Commission Wasington, D. C. 20535
References:
(1)
- 3. F. Opeka letter to C. I. Grimes, dated May 17,1985.
(2)
H. L. Thompson letter to 3. F. Opeka, dated July 31,1985.
Gentlemen:
Millstone Nuclear Power Station, Unit No.1 Integrated Safety Assessment Program In Reference (1), Northeast Nuclear Energy Company (NNECO) provided a proposed scope for the Integrated Safety Assessment Program (ISAP) review of Millstone Unit No.1. In Reference (2), the Staff formally issued the results of the ISAP screening review process, establishing the scope of ISAP for Millstone Unit No. I and initiating issue-specific evaluations. Reference (1) also indicated that for each issue or topic included in ISAP, NNECO would provide a discussion of the safety objective and an evaluation of the plant design with respect to the issue being addressed to identify specific items to be considered in the integrated assessment. In accordance with this commitment, the review for the following ISAP topic is attached.
o ISAP Topic 1.47 " Containment Emergency Sump Performance" If you have any questions concerning the attached review, please contact us.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY S A.O cuk J. F. Opeka Senior Vice President 8510230031 851016 PDR ADOCK 05 25 P
g By: C. F. Sears Vice President cc:
- 3. A. Zwolinski joo/
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h ISAP TOPIC 1,47 CONTAINMENT EMERGENCY SUMP PERFORMANCE
ISAP Topic No.1.47 Containment Emergency Sump Performance I.
Introduction Unresolved Safety Issue A-43,
" Containment Emergency Sump Performance," safety concerns deal with post-accident conditions which could degrade long term recirculation capability. These safety concerns deal with potentialloss of NPSH margin due to:
air ingestion to the pumps; and o
suction strainer blockage resultind froin LOCA generated insulation o
debris being transported to the torus and being drawn onto the suction strainers.
The purpose of this topic is to provide the status of USI A-43 for Millstone Unit No.1.
II.
Review CriteriT 1.
Unresolved Safety Issue A-43, " Containment Emergency Sump Performance."
III.
Related Topics / Interfaces None.
IV.
Evaluation By letter dated July 7,1982 (Reference 1), NNECO was re_ quested to provide the NRC with the status of and progress towards completion of the Unresolved Safety Issues (USIs) at Millstone Unit No.1.
Although not specifically applicable to Millstone Unit No.1, Reference 2 requested licensees to confirm the applicability of the NRC Staff generic positions ar.d conclusions developed on individual USI.
On October 13, 1982 (Reference 3), NNECO presented its positions on each USI applicabic to Millstone Unit No. 1; USI A-43, " Containment Emergency Sump Performance," was addressed in this submittal.
Subsequently, on July 24, 1985, in the NRC's Draf t Safety Evaluation Report (Reference 4), the NRC concluded that for Millstone Unit No.1, air ingestion in the post-LOCA period does not appear likely, if design conditions are maintained.
This conclusion was based on full scale experiments of BWR-type suction strainers which demonstrated that for typical submergences and flow rates, the debris strainers act as effective vortex suppressors and that air ingestion levels are nearly zero (Reference 5).
Reference 4 further concludes that blowdown and transport of insulation debris to the torus region will be impeded by the Millstone Unit No. I plant design and layout and states:
1 I.
J "The breaks of principle concern are within the drywell. Direct blowdown to the torus will be impeded by baffles at the inlet to the torus downcomers, followed by transport to the suction strainers which is a function of the bulk fluid velocity in the torus, which is generally low. Furthermore, in Millstone 1, the insulation employed is a mix of reflective metallic and
" blanket" type. Due to the elevation of the intakes (relative to the torus bottom) metallic debris will not likely be drawn to the 4
intakes."
V.
Conclusions The NRC concluded in Reference 4 that there is reasonable assurance that Millstone Unit No. I can be operated without endangering public health and safety, pending ultimate resolution of this generic issue. Based on the above NNECO concludes that this issue no longer has any safety significance for Millstone Unit No.1, and has, therefore, been resolved.
VI.
References 1.
G. Lainas letter to W. G. Counsil, dated July 7,1982.
j 2.
D. M. Crutchfield letter to 3. A. Kay, dated August 17,1982 (Docket No. 50-29).
3.
W. G. Counsil letter to D. M. Crutchfield, dated October 13,1982.
4.
Draf t NUREG-ll43, Safety Evaluation Report Related to the Full-Term Operating License for Millstone Nuclear Power Station, Unit No.1, Jud 24,1985.
f 5.
NUREG/CR-2772, " Hydraulic Performance of Pump Section Inlets for Emergency Core Cooling Systems in Boiling Water Reactors," Alden Research Laboratories, Sandia National Laboratory, and Worceste Polytechnic Institute, June 1982.
6.
NUREG/CR-3616," Transport and Screen Blockage Characteristics of Reflective Metallic Insulation Materials,"
Alden. Research Laboratory, January 1984.
7.
NUREG-0897, Revision 1, Draf t, " Containment Emergency Sump Performance - Technical Findings Related to USI A-43," U.S. Nuclear i
Regulatory Commission, March 30,1984.
8.
NUREG-0869, Draf t Revision 1, "USI A-43 Regulatory Analysis," U.S.
Nuclear Regulatory Commission, September 1984.
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