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Study of the Performance of Sealing Systems for Access Shafts in a High-Level Waste Repository

Published online by Cambridge University Press:  01 January 1992

A. Saotome ,
K. Hara  and
J. Okamoto
A. Saotome
Affiliation:
Power Reactor & Nuclear Fuel Development Corporation, Tokai-mura, Ibaraki, Japan
K. Hara
Affiliation:
Power Reactor & Nuclear Fuel Development Corporation, Tokai-mura, Ibaraki, Japan
J. Okamoto
Affiliation:
Kajima Corporation, Akasaka, Minato-ku, Tokyo, Japan
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Abstract

Shaft sealing in a high-level waste(HLW) disposal system functions to minimize the water flow passage, and retard the radionuclide transport from the repository to the accessible environment. It is important to estimate the radionuclide migration along the sealed shaft from the viewpoint of the design and the performance assessment of the sealing system.

This study presents the results of sensitivity analyses on the radionuclide migration in the vicinity of the access shaft of a repository in order to evaluate the effects of the length of a plug, as well as the number of plugs, and curtain grouts.

In this study, the upward hydraulic gradient of the groundwater flow along shafts was used, based on transient coupled thermo-hydraulic analyses around a repository. Hydraulic conductivities of the backfill material and the disturbed zones around the shaft tunnels were also assumed to be one order and two orders of magnitude higher than that of the host rock, respectively.

The results show that the velocity of the groundwater within the shaft and the disturbed zone is reduced by a factor of one third by installing a few plugs into the shaft filled with backfill material. The curtain grouts have the effect of retarding the radionuclide migration from the repository to the ground surface at a factor of approximately five. A few plug installations have the same effect. The sealing system properly constituted with backfill, plugs, and grouts can provide the same performance as the original host rock.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 294: Symposium V – Scientific Basis for Nuclear Waste Management XVI , 1992 , 475
Copyright
Copyright © Materials Research Society 1993

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References

REFERENCES

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