ML19269E239

Responds to Re 790313 Orders Shutting Down Five Nuclear Power Plants Pending Review of Analysis Techniques Used in Seismic Design of safety-related Piping.Maps of Northeastern Us Earthquake Zones Encl

ML19269E239
Person / Time
Site:	Beaver Valley, Surry, Maine Yankee, FitzPatrick
Issue date:	05/17/1979
From:	Harold Denton Office of Nuclear Reactor Regulation
To:	Lewis P AFFILIATION NOT ASSIGNED
Shared Package
ML19269E240	List: ML19269E239 ML19269E242
References
NUDOCS 7906270080
Download: ML19269E239 (3)

Text

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NUCLEAR REGULATORY COMMISSION j w. T'.,.j W ASHIN G T oN, 0. C. 20555 wd o,p% f a

EY 17 :s79 Mr. Phillips F. Lewis, President Sun Savings & Loan Association 561 Congress Street Portland, ME 04104

Dear Mr. Lewis:

This is in response to your letter regarding the orders by the Nuclear Regulatory Commission on March 13, 1979, to shut down five nuclear power plants in the eastern United States because of questions about the ability of their piping systems to withstand earthquakes.

Shortly before those orders were issued, it b'ecame apparent to NPC staff that analysis techniques which had been used in the seismic design of safety-related piping for these five plants were not in accord with proven and generally accepted engineering practice.

The result could be overstressing of piping and supports for earthquakes which could reasonably be expected to occur during the lifetimes of these plants.

The eastern United States is generally believed to be a region of low seismicity, when compared to the western part of the country, but is not without significant historical seismic activity.

Attached is a map showing tht location and intensity of earthquakes that have occurred in your region.

Some of the piping systems involved could, if failure occurred, cause loss of coolant to the nuclear reactor.

In addition, systems needed to shut the plant down safely in that event could also 'ue affected.

Thus, an earthquake of not extremely low likelihood would have the potential for causing an accident and for preventing operation of safety systems designed to cope with tb. accident.

Our objective is to review the situation in an expedited and disciplined manner so that these plants can be returned to operation with assurance that this will not constitute a threat to the public health and safety.

Sincerely,

/ Ad

~

Harold R. Denton, Director Office of Nuclear Reactor Regulation

Enclosures:

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