ML20136C418

Responds to Encl to President.Investigations Have Been Conducted on ECCS & Re TMI-2 Incident to Determine If Any Mods Should Be Made in NRC Requirements

ML20136C418
Person / Time
Site:	Three Mile Island
Issue date:	08/01/1979
From:	Harold Denton Office of Nuclear Reactor Regulation
To:	Hale M AFFILIATION NOT ASSIGNED
References
NUDOCS 7909240264
Download: ML20136C418 (4)

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i Mr. Michael Hale -

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Route 2, Box 242A '

l Reynoldsville, PA 15851 ,

Dear Mr. Hale:

I

! Your letter to the President has been referred to me for reply. In your

! letter you quote an article which discusses the early scale model test on i the perfomance of emergency core cooling systems. I have been unable to obtain a copy of the article, but your letter infers that the Nuclear Regulatory Commission (NRC) and its predessor, the Atomic Energy Commission j (AEC) have not investigated the possibility that emergency core cooling systems could not .perfom this intended function. That conclusion is not correct.

I

! Since the late 1960's the AEC and then the NRC conducted research into i loss-of-coolant accidents. Part of 'the research was in the area of scale model tests. The earliest models were quite small when compared with I

nuclear power reactors. The* volume of some of the earliest models was less

! than one ten thousandth of the volume of the reactor coolant system for a I

nuclear power plant. The results of some of the early tests had to be I

discounted because some of the effects which controlled the behavior of the I model's perfomance would not be controlling for the nuclear power plant.

[ The research in loss-of-coolant accidents is still continuing. The most j recent "model" is called the Loss of Fluid Test (LOFT) facility. The LOFT

! facility uses a' nuclear core to generate heat (previous models used electric l l heaters) and its total power is about one per cent of the latest nuclear '

power plants, but it can duplicate the local heat output of a nuclear power j pl ant. The most recent test at LOFT indicates that the emergency. core l cooling systems perfom nuch better than required.

This brings us to the Three Mile Island accident. The Three Mile Island 1 ' reactor .did not suffer a b'reak in one of the cooling pipes, the kind of l accident studied in the model tests. Instead, a valve on the reactor's pressurizer stuck open after a pre,ssure surge from a loss of feedwater 79092N 024 f

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Mr. Michael Hale .

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. event.: The loss'of coolant 'through the valve plus other errors contributed to the severity of the accident. 'We have taker) steps to reduc.e. the pro-bability of this accident and we are currently investigating the whole .

accident to detemine if ;any changes should be made to our requirements.

TNEnksyoufoh.yourexpress._. ion of. interest. ' &

.- Sincerely, .

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', -Original Signed by H. R. Danton s

,. ~. .- Harold R. Denton, Director

- 1, - 0'ffice of Nuclear Reactor Reguletion I -

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