ML20029E733
| ML20029E733 | |
| Person / Time | |
|---|---|
| Issue date: | 05/09/1994 |
| From: | Ibrahim A NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Bell M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| NUDOCS 9405200010 | |
| Download: ML20029E733 (6) | |
Text
.
A '
gigTTiM MEMORANDUM FOR:
Mike Bell, Branch Chief Engineering and Geosciences Branch /DWM THRU:
Keith McConnell Geosciences and Geotechnical Engineering Section l
Engineering and Geosciences Branch /DWM FROM:
Abou-Bakr Ibrahim Geosciences and Geotechnical Engineering Section Engineering and Geosciences Branch /DWM
SUBJECT:
TRIP REPORT OF THE MEETING WITH TECHNICAL REVIEW BOARD PANEL TO DISCUSS PROBABILISTIC SEISMIC AND VOLCANIC HAZARDS Attached please find the trip report for the above subject matter.
The meeting was attended by representatives from DOE, NRC, CNWRA, and the State of Nevada.
A copy of the presentations is available in my office for review.
This trip report was written by me with contributions from Steven McDuffie and I
comments from K. McConnell and J. Trapp.
If you have any questions, please contact Bakr Ibrahim at 504-2523.
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i Abou-Bakr Ibrahim Geosciences and Geotechnical Engineering Section Engineering and Geosciences Branch /DWM
Enclosure:
As stated 003047 DISTRIBUTION:w/ enc 1.
Central File DWM r/f JAustin, LLPD JSurmeier, DWM JHolonich, HLUR MFederline, PAHB NMSS r/f ENGB r/f LPDR/PDR ACNW 0FC FENSB'
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NAME AINaYNn/wd YMcConnell DATE 04/ n/94 k51/94 C:\\WMEG\\t18.AKI 0FFICIAL RECORD COPY C = Cover E = Cover & Enclosure N = No Copy 6 J'W /F /
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TRIP REPORT i
SUBJECT:
MEETING WITH THE NUCLEAR WASTE TECHNICAL REVIEW BOARD PANEL ON STRUCTURAL GE0 LOGY AND GE0 ENGINEERING DATE/ PLACE:
March 8-9, 1994, San Francisco, California AUTHORS:
Abou-Bakr Ibrahim and Steve McDuffie PURPOSE OF MEETING: TO DISCUSS PROBABILISTIC SEISMIC AND VOLCANIC HAZARDS ESTIMATION
SUMMARY
OF PRESENTATIONS:
John Whitney, USGS:
He provided an update of the seismic and geophysical investigations at Yucca Mountain. Whitney identified three classifications of faults: A) Those with Quaternary displacements; B) Those with suspected Quaternary displacements; and C) Those with no indications of Quaternary displacements.
He expects a preliminary tectonic model to be completed later j
this year. A trench on the Bow Ridge fault shows 5 events over 200,000 year i
period.
Another trench with 60 meters of exposure near Busted Butte shows 7 meters of offset over 700,000 years. Whitney presented a preliminary map of a natural exposure of the Paintbrush Canyon fault and indicated that based on paleaseismic data: there are 2-5 events in the past 100 Ka, displacement sizes / event ranges from 10-100 cm, recurrence intervals are about 20 Ka'to 100 Ka, and slip rates range from.001 to.02 mm/yr.
Based on new information, he indicated that the slip rate on the Bare Mountain fault is approximately 0.015 mm/yr instead of the 0.19 mm/yr value published in the literature.
Based on a geologic mapping and subsurface investigations at Midway Valley, he indicated that no significant faults with displacement >5 cm have been observed in rock units of 100,000 years or younger, and the observed fractures in Middle Quaternary deposits do not extend into Late Holocene deposits.
Based on a seismic investigation in Midway Valley, he indicated that there is about 1.7-2.0 factor of amplification at Midway Valley.
The Little Skull Mountain earthquake of June,1992, indicated a left lateral fault system parallel to the Rock Valley fault.
He showed the location of the proposed reflection line and expected that data collection will start soon.
Frank Perry, LANL:
He provided an update of volcanism studies at Yucca Mountain.
He indicated that the Lathrop Wells center had 6 or more magma batches in the last 0.1 Ma, while Crater Flat centers had 7 or more magma batches during their span of activity at approximately 1 Ma. Sleeping Butte Centers had 2 or more batches in the last 0.3 Ma years.
He considers Lathrop Wells to be still within its polycyclic activity and the 100,000 year pattern of repeated volcanism indicates that the next eruption in the region will be at Lathrop Wells.
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2 Chris Fridrich, USGS: He proposed a structural model for Yucca Mountain in which the Yucca Mountain region is divided into 10 structural domains.
He suggested that active faults were formed about 12.5 Ma ago, and the chance of a new fault forming at the repository is nil.
Quaternary volcanic eruptions have been confined to a narrow zone that does not include the repository, and the rate of extension may vary episodically along with volcanism.
He believes that the detachment fault hypothesis is not valid for recent tectonics at Yucca Mountain, Allin Cornell, NWTRB Consultant: He favors a probabilistic approach rather than a deterministic one to address the seismic and volcanic hazards at Yucca Mountain. On the issue of when "enough is enough," he suggested that this is a value judgement which should not be made by scientists in isolation.
For the probabilistic seismic hazard estimation, he indicated that the objective of the process is to communicate, coordinate, and describe all the scientific information and identify critical factors for further investigations.
Uncertainties which may include sensitivities should be associated with the hazard estimates.
Researchers should avoid making value judgements.
He believes that volcanism and earthquakes are equivalent problems.
Bob Budnitz, NWTRB Consultant: He presented fragility curves and showed how they are related to seismic hazard analyses.
He provided several examples of how seismic hazard estimates are considered in the design of facilities important to safety. He prefers a probabilistic approach with the use of expert judgment.
He suggests that the Yucca Mountain Project would benefit by following more closely the approach used in licensing nuclear power plants.
Richard Quittmeyer, DOE:
He discussed the first part of the topical report which deals with the methodology to assess seismic and fault displacement hazards.
The approach is based mainly on the probabilistic method, that incorporates: A) frequency of earthquake occurrence; B) variability in seismic hazard inputs; and C) hazard contribution from all significant sources.
The proposed approach of DOE is based on a " Performance Goal-Based Design Process."
Tim Sullivan, DOE:
He gave an overview of PSHA and resta.ted some of Quittmeyer's positions. He restated that the deterministic method is not identified in the topical report.
He indicated that the current design basis of 0.4g will be updated by 6/94.
This presentation concentrated on the preclosure period of performance.
He stated that DOE experts (PI's) will be responsible for determining the adequacy of the data and when "enough is enough."
Kevin Copper mith, Geomatrix: He summarized where PSHA has 'oeen applied in the past (nuclear power plants, non-nuclear facilities, major bridges and highway structures,- dames, and commercial facilities). He elaborated on how the Diablo Canyon Long Term Seismic Program benefited from applying PSHA and how the logic tree for the Hosgri fault zone had been-used.
He also showed how various fault sources contributed to the seismic hazard analysis at the Carqinez site, San Francisco.
in conclusion, he summarized the lessons learned from PSHA in practice.
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Keith McConnell, NRC:
He presented the NRC staff position on seismic and fault displacement hazards. He indicated that both deterministic and probabilistic analyses of seismic and fault displacement hazards should be presented in the License Application.
David Tillson, State of Nevada: He indicated that there is still a lack of knowledge about the structural and tectonic features of the site.
He was concerned about blind faults, distribution of fractures in the repository block, and the structural control. of volcanism.
Steve Wesnouski, UNR: His presentation was titled "How good is PSHA?" He indicated that the seismic hazard estimates should be on the conservative side.
He advised careful examination of the elicitation pre:ess and how the input from the elicitation is used.
Paul Pomeroy, ACNW:
He addressed the same subject as the previous speaker, "How-good is PSHA?" He addressed the important factors that should be considered in the elicitation of experts. He touched on the proposed new Appendix A (Appendix B) to Part 100 for seismic siting criteria for nuclear power plants.
He recommended that an expert elicitation similar to the LLNL be performed for the repository and that this be done before the topical report is submitted.
He advised DOE to resolve issues in advance of any licensing procedure.
He seems to favor a seismic hazard analysis approach similar to the hybrid approach proposed for the new Appendix B.
He also mentioned an NRC legal opinion that only individual expert judgements can be used in licensing, not aggregate opinions.
Keiiti Aki, USC: He provided several comments on the use of PSHA and how they use PSHA in Southern California. He demonstrated how the combination of different investigations such as: geological, GPS, strain measurements, and
. seismological data provided a reliable estimate of the seismic hazard in.
Southern California.
He cautioned about the lack of transparency in the probabilistic approach.
He favors using some type of deterministic evaluation as a sanity check.
Bruce Crowe, LANL:
He presented the DOE perspective on volcanic hazards at Yucca Mountain.
He addressed the major differences between his probability model and that of the Center.
Crowe continues to divide volcanic probabilities into his El, E2, and E3.
He indicated that the volcanic record is too limited for robust statistical calculations. He suggested that future work should include: examination of polycyclic models; geophysical studies; and expert elicitation.
Kevin Coppersmith, Geomatrix:
He presented an overview of the use of expert judgment in PVHA.
He indicated that expert judgment will play a major role in estimating the hazard at Yucca Mountain.
Jeanne Nesbit, DOE:
She discussed the objective of PVHA and its use in programmatic and statutory decisions.
She indicated that the primary focus of DOE to date has been whether the probability of magmatic disruption of the repository is large enough to disqualify the site.
In FY 95, DOE will decide-whether to write a topical report to resolve some of the volcanism issues.
In J
s 4
addressing "Enough is Enough," she indicated that this depends on how much confidence the PI has in his results, and how much the additional data will enhance the results versus cost.
In FY94, DOE expects to finish the work on Lathrop Wells cone, start expert judgment elicitation, and complete the review of the geophysical program dealing with magma identifications.
She identified some of the critical studies needed, such as: subsurface information, 3
sensitivity studies, subsurface effects studies, probability of polycyclic volcanism, and a tectonic model for the Crater Flat volcanic zone.
I Keith McConnell, NRC:
He addressed the criteria for igneous activity and provided some insights on what additional work DOE should be performed in order to adequately address the potentially adverse condition.
Charles Connor, CNWRA: He provided an update on the Center's volcanism probability models addressing the spatial and temporal patterns in vent distribution, the near neighbor nonhomogeneous Poisson model, and the Markov model. He discussed the limitations of the Center models.
He stressed again that homogeneous Poisson models do not adequately describe the spatial distribution of volcanism.
He suggested that the probability of a new volcano forming within the repository assuming the CNWRA models is 1.0E-4 to 3.0E-4 over 10,000 years.
He proposed that more work is needed to examine the effect of structural and tectonic controls on the spatial distribution of volcanism.
Dave Tillson, State of Nevada: He expressed concern about the lack of knowledge of the site and the volcanic system.
Until the processes are understood, an appropriate volcanic hazard assessment can not be made.
Gene Smith, and C-H Ho, UNLV:
They proposed alternative geological models for estimating the volcanic hazard at Yucca Mountain.
Smith went into some detail on the chemistry of the Red and Black Cone centers. He discussed the " hazard zones" that incorporate structures which he believes control volcanism.
He mentioned the importance of understanding how magma reaches the surface, and the importance of structural control.
Ho restated that his estimate of the probability of basaltic volcanic disruption at Yucca Mountain is 2.02E-5 to 6.57E-3 over 10,000 years.
He stressed that we must understand the process of volcanism at small mafic centers before we can have confidence in the statistical models.
Peter Wallmann, Golder Associates:
He discussed sensitivity studies of the l
volcanic hazard at Yucca Mountain.
He suggested that the disruptive probability depends on the E2 conceptual model, and that clustering does not increase disruptive probability.
Mike Sheridan, SUNY, Buffalo: He provided some examples of volcanic hazard forecasting, and he addressed some issues relevant to Yucca Mountain.
He recommended that sensitivity studies on model parameters be performed and that i
expert judgment should be used to evaluate conceptual issues.
He believes that volcanism should be placed in a " global" framework; a local Yucca Mountain forecast should be compared with an entire Basin and Range forecast.
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5 Round Table Discussion:
Carl Stepp outlined the ASCE guideline on Seismic and design consideration for a high-level nuclear waste repository.
He indicated that earthquake design loads are determined using probabilistic-based procedures.
He. concluded by indicating that a combined deterministic and 4
probabilistic seismic hazard analysis has advantages.
George Thompson indicated that dikes can be identified by aeromagnetics if they are of large dimensions.
He stated that extension can be accommodated by either faulting or dike emplacement.
Bruce Crowe and Chuck Conner aired their differences concerning which is the appropriate volcanic model for Yucca Mountain.
Bill Melson, a consultant to the NWTRB, stated that a highly explosive volcano is unlikely at Yucca Mountain.
A. Ibrahim asked if the seismic topical ' report includes any new information.
R. Quittmeyer stated that the forthcoming topical report on seismic hazard methodology will not contain much new material; it is based on past experience.
CONCLUSIONS:
The meeting accomplished its objectives.
It provided the NWTRB with a status report of DOE activities regarding seismic and volcanic investigations.
It appears that some mutual understanding on the probability of volcanic eruption may achievable in the near future.
DOE will use expert judgment elicitation to address the existing differences in the conceptual models proposed by the Center, the State, and DOE.
Nothing new was presented regarding the seismic and fault investigations.
PROBl. EMS: Warner North of the NWTRB was very critical and rather displeased with the lack of progress and specifics of the seismic program, t
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