ML20054G119
| ML20054G119 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 06/15/1982 |
| From: | Caruso R Office of Nuclear Reactor Regulation |
| To: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| References | |
| TASK-09-04, TASK-9-4, TASK-RR LSO5-82-06-041, LSO5-82-6-41, NUDOCS 8206210130 | |
| Download: ML20054G119 (5) | |
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1 June 15, 1982 Docket flo.50-029 LS05-82 041 fir. James A. Kay Senior Engineer - Licensing Yankee Atomic Electric Company 1671 Worcester Road Framingham, Massachusetts 01701
Dear Mr. Kay:
SUBJECT:
SEP TOPIC IX-4, BORON ADDITI0fi SYSTEM (YAtlKEE)
Enclosed is a copy of our final evaluation of Topic IX-4, " Boron Addition System" for the Yankee fluclear Power Station. This assessment compares your facility as described in a letter from J. A. Kay to D. M. Crutchfield dated August 31,1981, "SEP Topic 4
Cocpletion (Topics XV-12, II-4.F and IX-4)," with the criteria currently used by the regulatory staff for licensing new facilities.
We now consider this evaluation to be final.
This evaluation will be a basic input to the integrated safety assess-ment for your facility.
Sincerely, Ralph Caruso, Project flanager Operating Reactors Branch rio. 5 Division of Licensing SCg osu 'dg (u)
Enclosure:
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Mr. James A. Kay cc Mr. James E. Tribble, President Yankee Atomic Electric Company 25 Research Drive
-Westborough, Massachusetts 01581 Chairman Board of Selectmen Town of Rowe Rowe, Massachusetts 01367 Energy Facilities Siting Council 14th Floor One Ashburton Place Boston, Massachusetts 02108 U. S. Environmental Protection Agency Region 1 Office i
ATTH:
Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Yankee Rowe Nuclear Power Station c/o U.S. NRC Post Office Box 28 Monroe Bridge,* Massachusetts 01350 Ronald C. Haynes, Regional Administrator Nuclear Regulatory Commissicn, Region I 631 Park Avenue
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4 SYSTEMATIC EVALUATION PROGRAM TOPIC IX-4 YANKEE TOPIC IX-4, BORON ADDITION SYSTEM I.
INTRODUCTION Following a LOCA, boric acid solution is injected into the' reactor core from the accumulators and the safety injection tank.
After the injection phase High or Low Pressure Safety Injection pump suction is switched to recirculate break flow from the containment building vapor container back into the reactor vessel.
A portion of the coolant is converted to steam by the decay heat of the fuel.
Because steam flowing out of the break has few impurities, the boric acid concentration of the remaining coolant is increased.
Unless a dilution flow is provided to reduce the boric acid concen-tration, it is possible to eventually precipitate solid boric acid which could clog coolant passages.
I II.
REVIEW CRITERIA The plant design was reviewed with regard to Appendix A,10 CFR Part 50, General Design Criteria - 35, " Emergency Core Cooling,"
which requires that a system to supply abundant emergency core cooling shall be provided.
In addition, the plant design was reviewed with regard to 10 CFR 50.46, " Acceptance Criteria for Light Water Nuclear Power Reactors," and Appendix K to 10 CFR Part 50, "ECCS Evaluation Models," which set forth the requirements to maintain coolable core geometry and to provide long-term core cooling; the basis for the boron precipitation reviews.
III.
RELATED SAFETY TOPICS Topic VI-7.A.3 reviews the ECCS actuation system with respect to the testing for operation and design performance of each component of the system.
Topic VI-7.B reviews the procedures for ESF switchover from injection to recirculation node.
IV.
REVIEW GUIDELINES There are no unique SRP sections that deal with this issue.
The primary criterion used for review of this system was discussed in a memo dated January 21, 1976 entitled, " Concentration of Boric Acid in Rea, tor Vessel During Long Term Cooling - Method for Reviewing Appendix K Submittals."
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. V.
EVALUATION The guidelines for this review are contained in Reference 1, which is a memo describing the methods used to review boric acid buildup during post-LOCA long-term cooling.
There is no SRP section covering this topic.
The concern stems from the long term cooling requirements of 10 CFR 50.46.
To prevent the buildup of boron in the core during the long-term recirculation mode, Yankee Nuclear Power Station utilizes simul-taneous cold and hot leg injection with the HPSI and LPSI pumps.
This method works for both cold and hot leg large break LOCAs.
For small break LOCAs, boron precipitation is a reduced concern since decay heat is removed by the steam generators as well as by boiling, and decreased boiling causes less boron concentration; however, simultaneous cold and hot leg injection is a viable pro-cedure for small break LOCAs as well.
1 r:bmitted evaluation of the boron addition system for Yankee hm aar Power Station (Ref. 2) utilizes an analysis presented in Reference 3 and modified in Reference 4.
The minimum time to reach boron saturation was 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> following a double-ended cold leg break without diluting flow.
With a flushing flow of 25 gpm in the hot leg, boron concentration is kept below the saturation concentration.
Expected flushing rates will be much larger.
The hot leg injection path is available through two (2) parallel motor operated valves to provide redundancy.
VI.
CONCLUSION The Yankee Nuclear Power St'ation method of preventing boron precipi-tation is to utilize simultaneous cold leg and hot leg injection c.
with the HPSI an~d LPSI pumps.
This will provide sufficient dilution flow for both hot and cold leg breaks.
Based on our review and using staff criteria referenced earlier, we conclude that the Yankee Nuclear Power Station method for prevention of boron precipitation is acceptable.
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REFERENCES 1.
Memorandum for T. M. Novak, Chief, Reactor Systems Branch, from K. I.
Parczewski, Reactor Safety Branch, January 21, 1976.
2.
Letter from J. A. Kay, Yankee Atomic Electric Company, to D. Crutchfield, 3
NRC dated August 31, 1981.
3.
Letter from D. E. Vandenburg, YAEC0, to R. A. Purple, NRC dated July
{
8, 1975.
1.
Letter from W. P. Johnson, YAEC0, to Office of Nuclear Reactor Regulation, NRC, dated June 6,1978.
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