ML19351D066
| ML19351D066 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 09/29/1980 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Magnuson W SENATE |
| Shared Package | |
| ML19351D067 | List: |
| References | |
| NUDOCS 8010080669 | |
| Download: ML19351D066 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION C
WASHINGTON, D. C. 20555 a
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Docket No. 50-344 SEP 2 9 EO I
The Honorable Warren G. Magnuson United States Senate Washington, D. C.
20510
Dear Senator Magnuson:
This is in response to your letter of August 8,1980 regarding Carol A. Snow's letter to you of July 29, 1980, which expressed concerns about Mount St. Helens and the Trojan Nuclear Plant.
Those same concerns were raised recently by a member of the public who filed a formal request, under 10 CFR 2.206 of the NRC's regulations, that the NRC issue a show cause order and require the Trojan Plant to be shut down because of the activity of Mount St. Helens.
After an evaluation, it was determined that there was no need to shut down the Trojan Plant and that request was denied in a decision issued by the Acting Director of the Office'of Nuclear Reactor Regulation on August 13, 1980 (DD-80-26).
In response to Ms. Snow's concerns, I am enclosing a technical report which discusses in detail the possible impact of volcanic activity at Mount St. Helens on the safety of Trojan.
The report is in the form of an affidavit which was filed with the Atomic Safety and Licensing Board in the Trojan spent fuel pool proceedi ng.
Although this report was filed prior to the recent volcanic activity, it is with few exceptions considered an accurate assessment today.
Exceptions to the report include (1) the underestimation of the volume of debris associated with a potential mudflow, (2) exclusion of a discussion of volcano-induced earthquakes, and (3) the statement that historic data indica'tes that the volcano has been substantially more active in the 19th century than the 20th century.
Notwithstanding the above exceptions, the report's conclusion that the Trojan site is suitable from a volcanic hazards point of view remains accurate.
The recent massive eruption of May 18, 1980 exceeded that envisioned by the Nuclear Regulatory Comicsion and by our advisors, the U. S. Geological Survey.
Nevertheless, the effects of the recent volcanism (mudflows, earthquakes and ashfall) at the Trojan site have been minimal.
Mudflows in the Toutle, Kalama, and Lewis River valleys have not compromised the safety of the Trojan plant.
Volcanic-induced earthquakes have been small and have neither been felt nor recorded instrumentally at the site.
Ashfall :t the Trojan plant resulting from the May 25, 1980 eruption hu been slight (not exceeding 1/8 of an inch) and fell at the site in the form of a muddy rain or mist.
The only other indication of ash occurred on April 29, '980 when a thin coating i
of the ash was noted at the Trojan site.
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b Senator Magnuson 1 According to University of Washington seismologists, the volcanic-f nduced earthquakes mentioned previously have not exceeded Richter Magnitude 5.1'and have been concentrated -in an area roughly coincidental with the volcano crater which is 35 miles northeast of the Trojan plant. None of the larger events (Magnitude 5.0 and above) have occurred closer than 35 miles to the plant.
' For the most part, the volcanic earthquakes have occurred at shallow depths and have. consequently been felt only in the immediate vicinity of the seismic event.
However, there have been unconfirmed reports of volcanic-related earth-quakes (originating at Mount St. Helens) being felt in the Longview-Kelso, Washington area, roughly five miles north of the Trojan plant. Apparently, those feeling the tremors were located in areas where soil overlies bedrock.
The plant is designed to safely withstand seismic levels of 0.259 peak ground acceleration.
This corresponds to earthquake levels many times greater than i
those generated by the volcano-induced earthquakes.
The potential impact of volcanic activity on the safety of the Trojan facility was investigated thoroughly by government geologists (Atomic Energy Concission and the U. S. Geological Survey) before the plant was allowed to be constructed where it is.
This investigation and reassessment of volcanic-related ha:urds has continued as attested by the enclosed affidavit.
We have been in constaat contact with numerous state, governmental agencies, and university scientists since initiation of earthquake activity and subsequent volcanic activity in the vicinity of Mount St. Helens on March 20, 1980.
This surveillance and accumulation of information will continue as long as the volcano remains active.
As to evacuation'under severe ashfall conditions, this can cause transportation problems somewhat similar to those prcduced by road icing or heavy snowfall.
The first protective action to be taken following a radiological emergency at a nuclear facility is to alert the public to take shelter and await further instructions.
Seeking shelter in homes is an effective protective measure under most circumstances.
A decision to evacuate is based on an assessment of the potential injury to the public from the accident and must be balanced against the risk to the public from the evacuation itself and against-the conditions that prevail at the time.
Seeking shelter would have to be given greater weight under ashfall conditions, depending on its severity.
Therefore, _if an accident occurred in combination with transportation difficulties due to severe volcanic ashfall, effective protecting measures can still be implemented, albeit with greater difficulty.
The probability of these two events occurring simultaneously is, haaever, extremely low.
Our conclusion, based upon an evaluation of volcanic phenomena pricr to con-struction, coupled with an assessment of the effects of the activity ~ beginr'ng March 20, 1980, is that the Trojan site remains suitable from a volcanic r
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hazards viewpoint. Nevertheless, we will continue to monitor, accumulate, and assess information related to the renewed activity at Mount St. Helens as it might_ apply to the safety of the Trojan Nuclear Plant.
Sincerely,
'(signe6)7. A.Rehm -
illiam J. Dircks Executive Director for Operations j
Enclosures:
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Affidavit of R. B. McMullen 2.
Letter, Carol A. Snow to Senator Magnuson, dated July 29,1980
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