ASME Message

Abstracts
which can allow EBS construction under various repository conditions, is valuable for the volunteering approach to siting
a HLW repository in Japan. In order to confirm technological applicability of candidate techniques and to evaluate
compatibility in an operation system, full-scale tests of various remote-handling and-emplacement techniques for the
EBS were conducted. The test results are summarized in the technical menu which is hierarchical structured database.
Since the long-term performance of EBS is significantly influenced by remote handling and emplacement techniques for
EBS, consistency of the operation technology must be evaluated from the view point of system standing. In this program,
evaluation methodology was studied and several indexes, representing requirements for the repository operation and
management, were identified. Indices include current technical availability, long-term safety of the resultant EBS,
operational safety, engineering reliability, retrievability, etc., with expert assessment complementing a more quantitative
evaluation.
5) 40251 – Design Options for HLW Repository Operation Technology, (II) Bentonite Block Forming and
Vertical Emplacement/JGC
Hajime Takao, Tatsuhiro Takegahara, JGC Corporation (Japan);
Hitoshi Nakashima, Hidekazu Asano, RWMC (Japan)
RWMC and JGC have been running an all-round R&D program for the period of 2000-2010 to develop the concept
of Vertical Emplacement for disposal of vitrified waste. The conceptual design of its basic equipment was worked out in
2000, followed by forming the large-scale bentonite block in 2001-2004. Study has also been conducted on a mechanism
to convey and position the large-scale block using a vacuum suction device. Subsequent to these developments, various
technologies necessary for designing the Vertical Emplacement equipment have been reviewed, which would enhance
engineering feasibility and reliability.
Full-scale demonstration program under a joint research program with JAEA (Japan Atomic Energy Agency)
started in 2008 with the twin objectives i) supporting of public relations and ii) technical verification. The large-scale
bentonite block and part of the full-scale Vertical Emplacement equipment are now on view at the Full-scale
demonstration facility in Horonobe, Hokkaido, Japan.
6) 40268 – Design Options for HLW Repository Operation Technology, (III) Transportation and Horizontal
Emplacement of Pre-Fabricated EBS Module (PEM)
Susumu Kawakami, IHI Corporation (Japan); Hitoshi Nakashima, Hidekazu Asano, RWMC (Japan)
As one of the repository operation technologies for high-level radioactive waste?(HLW), the pre-fabricated
engineered barrier system (EBS) module (PEM) was carried out the examination of handling and emplacement technique
for EBS. The PEM technology was examined to confirm technological applicability. The PEM is concept of the
integration of EBS as the module in the surface facilities, and transporting the module underground facilities. This
concept is the one of the candidate concepts of horizontal emplacement techniques for EBS in Japan. Therefore, PEM is
the same level large size and heavy weight as EBS, and it is necessary to examine the applicability of handling and
emplacement techniques. Full-scale level tests were performed to confirm the applicability of these techniques with the
air bearing/air jack devices. In the tests, we prepared the testing devices of full-scale level size/weight and confirmed the
applicability of these technologies as an elemental technology on the condition of considering the environment of an
underground tunnel. The air bearing test that produced the surface-roughness of the tunnel environment was carried out
the evaluation concerning the transportation performance of the air bearing. And, the air jack test was carried out the
holding and emplacement of PEM. The repository operation technology with the air bearing/jack device was confirmed
to execute the examination, and to apply to handling and emplacement technique for PEM.
7) 40236 – Design Options for HLW Repository Operation Technology, (IV) Shotclay Technique for Seamless
Construction of EBS
Ichizo Kobayashi, Soh Fujisawa, Makoto Nakajima, Masaru Toida, Kajima Corporation (Japan);
Hitoshi Nakashima, Hidekazu Asano, RWMC (Japan)
In Japan, the construction method of the buffer material has been investigated focusing on the block emplacement
and in-situ compaction methods. Under the current concept of geological disposal of radioactive waste, since it has been
important that the barrier satisfies the dry density requirement as a mass, no enough attention has been paid to the
distribution of density and the gaps between blocks which were caused by the conventional methods. This is based on the
assumption that bentonite swells from the permeation of groundwater and that the density eventually becomes
homogeneous. However, it is not clear whether the high density bentonite does in fact swell until the density is
homogeneous. The effects of density distribution and the gaps in long-term high impermeability of a
bentonite-engineered barrier may be not small. Therefore, the option of the construction method for a
bentonite-engineered barrier that does not have such uncertainty concerning the implementation of a disposal concept
should be prepared. In order to remove such uncertainty, the high-density spray method for bentonite, termed the
shotclay method, was developed as a method for constructing a uniform bentonite-engineered barrier without gaps even
in a narrow space. The shotclay method is used to construct compacted soil at high density by spraying material
preconditioned with water. Using this method, the dry density of 1.6 Mg /m3, which was considered impossible with the
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