ML20135B194
| ML20135B194 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 01/30/1997 |
| From: | Wermiel D OREGON, STATE OF |
| To: | Bless A OREGON, STATE OF |
| References | |
| NUDOCS 9702280123 | |
| Download: ML20135B194 (2) | |
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p-G January 30,1997 DEPARTMENT OF GEOLOGY AND
,,, Jy}AL M
Adam Bless
'o
' RIES Oregon Department of Energy
~~
625 Marion Street NE Salem,OR 97310 ADhENISTRAUVE OFFICE
SUBJECT:
Response to Portland General Electric Re: Ash Fall at the Trojan Site This is in response to your letter of January 8,1997 (attached) in regards to Portland General Electric's (PGE) position regarding potential for ash fall at the Trojan site. We appreciate the opportur.ity to provide these comments which are intended to add information and clarification in regards to the request by PGE to move their spent nuclear fuel into dry storage casks at the Trojan site, and the potential to have the air flow cooling vents clogged by an ash fall event from the Mt. St. Helens volcano.
Tne Attachment III to VPN-085-96 includes Question 8-8 (b) regarding the effects of the potential for ash accumulation at the T.ojan site from an eruption of Mt. St. Helens. In the response to this question, PGE makes several comments that need clarification. The first of these is that PGE indicates that, because of the removal of much of the summit and north flank of the volcano during the eruption of May 18,1980, there is little ash material available.
It should be clariEed that the total volume of ash material available during an eruption is not completely controlled by the volume of materialin the summit and flank of the volcano. I refer you and PGE to the repott. Seismic and Volcanic Hmrd Evaluation of the Mt. St. Helens Area. Washington. Relative to the Troian Nuclear Site. Oregon.
DOGAMI Open File Report 0-81-9, by John Beaulieu. Starting on page 61 of the report, there is a comprehensive discussion of ash fall volumes associated with eruptions of y[#[f Mount St. Helens and controlling factors such as the open conduit within the volcano.
The report points out there is a history oflarge and small volumes of ash from numerous eruptions of the volcano and that, although the chance is quite small, there is potential that a significant volume of ash fall from an eruption of Mt. St. Helens may not be completely ruled out. Nowhere is the shape of the summit linked with the potential size of future ash a
falls.
A second point in need of clarification is PGE's statement that because of the shape cf the existing crater eruption products would be largely directed to the north. In the DOGAMI Open File Report Report OF 0-81-9 cited above, it is pointed out on page 63 that maximum credible ash fall at Trojan from Mt. St. Helens is a function of volume d Suite 965 9702280123 970130 800 NE Oregon Street # 28 PDR ADOCK 05000344 Portland, OR 97222
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i ash erupted and direction of transport which includes wind direction as a controlling factor. The report indicates that winds flow from Mt. St. Helens toward Trojan a minor portion of the time and that the five largest ash falls in the last 4,500 years oflife of the volcano follow the statistically favored wind direction to the north and east of the volcano.
However, there remaire a very small chance for ash fall from an eruption of Mt. St. Helens to impact the Trojan Site. In earlier analyses, PGE has properly noted that even if ash were to begin to accumulate at the site, removal would certainly be a response exercised by staff.
In conclusion, PGE indicates that there is a low probability of significant ash fall impacting the Trojan site which might clog the cooling vents, and we have no disagreement with this statement. However, the above cited reference should be utilized to provide clarity to the question of potential for ash fall to impact the Trojan site.
Please contact me with questions or comments in regards to this matter.
Sincerely, i
h Dan. E. Wermiel Geologist c: John Beaulieu i