ML19338C533

Responds to VT Agency of Environ Conservation Re Js Miller on Radioactive Leakage.No Potential for Outleakage of Contaminated Coolant in Primary Sys Operating at Below Atmospheric Pressure

ML19338C533
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	08/06/1980
From:	Houston R Office of Nuclear Reactor Regulation
To:	Whittaker B VERMONT, STATE OF
Shared Package
ML19338C534	List: ML19338C533 ML19338C539
References
NUDOCS 8008180094
Download: ML19338C533 (2)

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'BGrimes WPasedag L. Knesel - 278 Mr. Brendan J. Whittaker, Secretary Agency of Environmental Conservation State of Vemont Montpelier, Vemont 05602 l

Dear Mr. Whittaker:

This letter is in response to a letter of June 22, 1980 from Mr. J. Sam Miller, regarding possible contamination of the secondary cooling system at Vemont Yankee. Mr. Miller mquested that the mply to his letter (copy enclosed for your reference) be addressed to_you.

Mr. Miller is concerned 'abodttthe potential of leakage of radioactivity contaminated water to the environment at Vemont Yankee. His concern arises from tie THI-2 accident, whem primary coolant was spilled in the auxiliary building. Corrective measures have been taken to prevent a recurmnce of the THI-2 events. However, the corrective measures which are being done as a follow-up to the TMI accident are not directly applicable to Vemont Yankee, since they apply to pressurized water reactors (PWRs), which is an entirely l

different system from Vemont Yankee,.a boiling water reactor (BUR).

In a BWR, the primary coolant nomally leaves the reactor in the fom of ' steam at a pressum of 1000 psi and temperature of 545 F, passes through the turbine, 0

then is condensed and returned to the reactor.

(By contrast, in a PWR, the primary coolant nomally does not leave the primary containment.)

Regarding accidents that could lead to contamination of the secondary ' cooling system, _let us first examine the pathways by which primary coolant can be transferred to the secondary system. During nomal operation, the primary system steam travels down the steam lines and through the turbines to the condenser, where it arrives at a pressure approximately 13 psi below atmos-pheric pressum and a temperatum of somewhat over 1000F. Sinne there is a

- nominal positive pressure in the secondary system (for the purpose of pumping the water through the system), it is apparent that any leakage in the con-denser would be from the higher pressure system, i.e., the secondary system, e-

.to the lower pressure system, i.e., the primary coolant system. Themfom, there is no potential ~ for. out-leakage of any contaminated coolant in those a

portjons of the primary system operating at pressures below atmospheric pressure.

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= Mr. Brendan J. Whittaker AUG There have been no accidents in the nu Mar power industry which led to the transfer of radioactivity from the primais to the secondary system of a boiling water plant such as Vermont Yaniec.

nce, there are no effects of such accidents to discuss.

Minor leaks from the secondary system into the prim ' s., : "

cccur occasionally but always in the direction indicated above, i.e., secondary.

laaking into the primary system. These are, in some cases, detected by c:. rett..

-ing of the flows in the system to detect the unwanted source of water in c.

v system. Leaks too small to. detect by this method are usually found by noti..,

the appearance of radioactivity in the primary system which could not haw originated from the nuclear process. This occurs when the impurities in the secondary system water pass through the reactor and become activated by the neutrons inside the reactor. These activated impurities then evidence them-

'selves as'new forms of radioactivity in the primary system, which. is monitored continuously.

In this matter, small leaks can be detected in a few hours, and are repaired as the need arises.

We hope that this discussion of Mr. Miller's. concern will be helpful to you.

Sincerely, W

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R. Wayne Houston, Chief Accident Evaluation Branch Division of Systems Integration Office of Nuclear Reactor Regulation cc: Vemont Yankee Decommissioning Alliance 127 Main Street Brattleboro, Vermont 05301 0

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