ML20037D231
| ML20037D231 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 05/15/1981 |
| From: | Groce R Maine Yankee |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8105220341 | |
| Download: ML20037D231 (3) | |
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ENGINEERING OFFICE FRAMINGH AM, MASSACHUSETTS 01701 617 872-8100 p'
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May 15, 1981 z= _ ;
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United States Nuclear Regulatory Commission 8
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Attention:
Office of Nuclear Reactor Regulation
References:
(1) License No. DPR-36 (Docket No. 50-309) t
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Ib (2) Maine Yankee letter to USNRC, FMY 81-f,5, Proposed Change No. 64, April 28, 1981.
Subject:
Demonstrate Non-Limiting Nature of Steam Line Rupture.
Dear Sir:
As noted in reference (2) and in telephone communications with the staff, an analysis of the Steam Line Rupture (SLR) Accident for Cycle 6 was not submitted in reference (2).
The analysis is currently in progress and is scheduled to be submitted prior to the startup of Cycle 6.
The SLR Accident is limiting only during the latter portion of the operating cycle. At this stage of the cycle the combination of fuel doppler and moderator reactivity defect is large enough to approach the available CEA scram reactivity (assuming the worst CEA to be stuck out of the core) during the RCS cooldown resulting from the limiting SLR.
The limiting SLR event for Maine Yankea is from Hot Zero Power (HZP). This is due to the lower available CEA worth and the larger steam generator water inventory at low power.
l In order to demonstrate the non-limiting nature of SLP's early in the Cycle 6 operating cycle a bounding evaluation of the HZP SLR was performed.
The evaluation consisted of a review of the reactivity balance of doppler, moderator, and available scram worth (assuming the worst stuck CEA) during an ins tantaneous cooldown from plant HZP operating temperature to 2120F. An ins tantaaeous cooldown to 2120F bo sads the mos'; limiting SLR response including the effects of the steam driven feedwater pump on feedwater addition and worst single f ailure. The objective of this evaluation was to determine the Cycle 6 burnup where a more detailed analysis would be required to demonstrate that the reactor would not return critical following the SLR.
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United States Nuclear Regulatory Commission Page Two May 15, 1981 A review of the Cycle 6 core physics parameters indicates that 4000 MWD /MTU cycle average exposure represents a conservative estimate of cycle length before a detailed SLR analysis would be required. Taule 1 presents a reactivity balance at 4000 MWD /NEU of available scram worth and fuel and modere. tor reactivity for an instantaneous cooldown from hot zero power conditions (5320F) to 2120F.
No credit has been taken for the additional negative reactivity that would be added by safety injection. The result demons trates that the reactor will remain suberitical for this bounding case.
In summary, our evaluation has demonstrated that SLR events early in the operation of Cycle 6 are not limiting.
It has been shown by conservative analysis that a detailed evaluation of the SLR accident for Maine Yankee Cycle 6 will not be required prior to 4000 MWD /MTU cycle average burnup.
We trust that you will find this submittal satisfactory; however, should you desire additional information, feel free to contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY Robert H. Groce Senior Engineer Licensing l
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4 United ' States Nuclear Regulatory Commis'sion Page Three May 15, 1981 Table 1 Reactivity Balance at 4000 MWD /MTU From HZP to 2120F 3.78 %Ap Available CEA Worth
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(including 10% uncertainty and with highest worth CEA Stuck Out of Core) i 0.77 %$p Reactivity Addition due
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to doppler Feedbrek (25% uncertainty applied)
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2.80 %Ap Reactivity Addition due to
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Moderator Temperature Change j
(15% uncertainty applied) i
.21 %AP Net Reactivity
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l
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