ML20024B534
| ML20024B534 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/08/1979 |
| From: | Labelle D BABCOCK & WILCOX CO. |
| To: | Womack E BABCOCK & WILCOX CO. |
| References | |
| TASK-03, TASK-06, TASK-07, TASK-3, TASK-6, TASK-7, TASK-GB GPU-0293, GPU-293, NUDOCS 8307090093 | |
| Download: ML20024B534 (1) | |
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THE BABCOCK & WILCOX COMPANY POWER GENERATION GROUP p w m,,,,,,,
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E. A. Womack. Manager, Plant Design cc:
J. D. Carlton i
B. A. Karrasch
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m ses.s D. W. I.aBelle. Manater. Safecy Analysis File No.
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May 8. 1979 utsG Drv Out g su. in.. e....
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F A key issue that we must combat in the market place will be OTSG dry out in 1-2 minutes following loss of feedwater. In the past, i
safety Analysis had not been concerned with this issue in that time appeared j
available for operator action to provide auxiliary feedwater (if not auto-core.
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initiated) prior to loss of sufficient RCS inventory to uncover the k-This was not censidered, however, based on plant operating data, to be a high frequency occurrence nor that pressuriser relief valve challenge and f
failure would be as frequent. In the wake of the THI-2 accident, this E
component of our safety philosophy is no longer appropriate.
7r It is my conclusion that B&W must enforce as a new safety criteria that both operating and futura plants must have a turbine trip initiated p
i by LOFW indication and an AFW design which will assure flow sufficient for decay heat removal to the OTSG's within 40 seconds following a loss of main (J
feedwater. This criteria must go well beyond " reasonable" assurance to The AFW systest need not be a totally
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. "very highly reliable" assurance.
safety grade design, but should approach these design principles if reliability
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p goel is to be achiaeed It is also very important that the turbine trip and AFW system be actuated by a highly reliable and appropriate safety grade signaI. Such a signal has not been identified yet, although OTSG low level is being used for AFV actuation in current plant designs. OTSG 1evel is inappropriate according to IDFW analysis performed for Midland 1, 2 since AFW cannot be i,
actuated prior to repressurizing to pressurizer relief valves.
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I presume that the issues I have raised will be appropriately addressed in the hardware chargeout being made at this time by the operating plants or will become an objective of long term planning with regard to operating and future plants. Please advise if there is a need for Safety Analysis to take any immediate action in establishing a design basis for these changes.
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