ML19352A975
| ML19352A975 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/28/1981 |
| From: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| FYR-81-80, GL-81-19, NUDOCS 8106020465 | |
| Download: ML19352A975 (1) | |
Text
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- YANKEE ATOMIC ELECTRIC COMPANf
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1671 Worcester Kood, FramingF.:., Massothusetts 01701 YKm;e...Q xee
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s-May 28, 1981 f
O TYR-81-80
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United States Nuclear Regulatory Commission i
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Washington, D. C.
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Attention:
Mr. Da rrell G. Eisenhut, Director
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s Division of Licensing
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) YAEC Letter to USNRC dated October 9,1980 (WYR 80-113)
Subject:
Thermal Shock to Reactor Pressure Vessels (Generic Letter 81-19)
Dear Sir:
As discussed in Ref erence (b), Yankee has already evaluated the effect of rapid cooldown transients and has instituted plant system changes to reduce the thermal shocking of the reactor vessel that may result af ter a severe transim t.
The approach used was to establish a conservative vessel f ailure criterion that no transient could result in a crack growth greater than 75 percent of vessel wall. A series of conservative thermal shock analyses were then performed resulting in a curve of pressure-temperature limits.
Using this curve as a limit, all plant transients, including large LOCA, small LOCA and main steamline break were evaluated and compared against the limit.
It was concluded that as long as the safety injection tank temperature was raised to 120 F, no crack propagation greater than 75 percent of vessel wall thickness would occur for any traasient through end-of-lif e (24 EFPY).
Appropriate upper limits on water temperature are also imposed to ensure adequate NPSH for the safety injection pumps.
In addition, plant p~ocedures have been reviewed and modified as necessary as part of our overall evaluation. This review assured that adequate instructions and precautions have been incorporated into the procedures to enable the operator to recognize certain plant conditions and take the appropriate actions to prevent repressurization.
We trust this letter adequately responds to your Generic Letter 81-19.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY J. A. Kay Senior Engineer - Licensing JAK/kab l 78106 02 O&$