RE: volcano?

[James Weldy <jweldy@cnwra.swri.edu>]

Some information on the threat of volcanism at Yucca Mountain:



The repository does sit on the edge of an inactive volcanic field in Crater

Flat. The probability of volcanism is an issue of great debate between

geologists at the DOE, NRC, and the state, but generally is believed to fall

between 10^-8 and 10^-7 per year. An unlikely event, to be sure, but

something that needs to be considered in the DOE license application,

considering the long time period of operation for the repository. The

recently released 10 CFR Part 63 requires an analysis of all events with a

probability greater than 10^-8 per year that could significantly affect

repository performance. When comparing the consequences of the event to the

15 mrem/year standard, the rule indicates that the risk of the event

(probability times consequences) be used to determine whether the repository

meets the standard.



Due to the anticipated robustness of the waste package and drip shield,

current calculations indicate that volcanism leads to the largest risk

(again, probability times consequence) from the repository in the 10,000

year regulatory time frame (the DOE results in TSPA-SR and the more recent

Supplemental Science and Performance Analyses documents used to be available

at www.ymp.gov, but appear to have been taken down temporarily). The DOE

estimate of peak risk from volcanism is between 0.1 and 1 mrem/yr, compared

to the 15 mrem/yr standard. Both DOE and NRC staffs are currently looking

into how ascending magma will react to intersecting the open drift

repository system and whether this could lead to more waste being affected

than just the waste packages within the cross-sectional area of the

ascending conduit.



The bottom line is that volcanism is something that based on regulations

needs to be considered in the performance assessment of the repository, is

being analyzed by DOE and NRC scientists, and leads to relatively large

doses if it does occur (greater than a rem based on current calculations).

However, it does not appear at this point to result in unacceptable risks to

the public.



James Weldy

Center for Nuclear Waste Regulatory Analyses

Southwest Research Institute

jweldy@swri.edu



************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.