Stichting Laka

Publicatie Laka-bibliotheek:
Underground exploration and testing at Yucca Mountain (1993)

Auteur	NWTRB
Datum	oktober 1993
Classificatie	3.01.4.22/05 (VS - AFVAL - YUCCA MOUNTAIN)
Voorkant

Executive Summary

Underground exploration and testing are major components of the DOE's site-
characterization efforts at Yucca Mountain, Nevada. During the past four years, 
the DOE's plans for exploration and testing in an underground facility have evolved 
substantially, and many improvements have been made. The DOE's current program 
involves extensive tunneling throughout the geologic block at Yucca Mountain with 
the goal of gaining visual access to the complex geology at the site. It is especially 
important to thoroughly understand the character and extent of the faults that cross 
the site, as well as the site's hydrogeology and geochemistry. Once tunnels have been 
excavated, scientists also will be able to initiate important tests, which are necessary 
to assess how the natural and engineered barriers will perform under conditions 
similar to those in a potential repository for hot spent fuel and high-level waste. 
Data gathered during these tests will be used to evaluate site suitability, to predict 
long-term performance of the entire repository system, and to support a license 
application - should the site prove suitable.

In this report, the Board reviews the status of the underground exploration and 
testing program. In addition to a number of detailed recommendations, the Board 
makes three general recommendations, which are reviewed below. The Board 
would like to emphasize that all recommendations can and should be implemented 
without slowing the momentum of important site-characterization activities now 
under way at Yucca Mountain.

The Board concurs with the overall objectives established by the DOE for 
underground exploration and testing at Yucca Mountain and supports many of the 
changes that have been made to the design of the facility. However, the Board 
remains concerned that, because of past delays in initiating underground exploration 
and attempts to comply with overly optimistic schedules, the DOE is making 
important technical decisions about the design and approach to excavation of the 
exploratory facility without sufficient analysis. Schedules have been compressed, 
and until recently the DOE had planned for multiple excavation operations from a 
single portal and simultaneous testing activities, which the Board believes would 
have extended, rather than shortened, program schedules and increased costs. The 
Board supports the DOE's recent decision to modify this approach by eliminating 
competing activities during excavation of the initial underground loop. Once this 
portal-to-portal loop has been completed, tunneling off the loop to fault zones, in 
the core test area, and in the Calico Hills can begin, and important testing initiated.

The Board believes, however, that the Yucca Mountain project lacks an overall 
strategy for exploration and testing. To better achieve the objectives of the 
underground exploration and testing program, the Board recommends that the DOE 
develop a comprehensive strategy that integrates exploration and testing priorities 
with the design and excavation approach for the exploratory facility.

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