The 13th International Conference on Environmental ... - Events

Abstracts
Supercontainer and to provide experimental data to validate modelling calculations obtained using the finite element
program HEAT/MLS. <strong>The</strong> test focused on the early age behaviour of the concrete matrix materials and the practical
aspects of construction. Generally, the results obtained from the half scale test confirm that it is feasible to construct the
Supercontainer with currently available techniques. <strong>The</strong> results also validate scoping calculations obtained earlier with
the finite element model. <strong>The</strong>se findings contribute an important step to demonstrate the feasibility to construct the
Supercontainer and to validate the Belgian Supercontainer concept proposed by ONDRAF/NIRAS for disposal of high
level waste (HLW) in Belgium.
Keywords: Belgian supercontainer concept, high-level radioactive waste, half-scale test, concrete buffer, overpack,
construction feasibility
3) 40175 – Full-Scale Test on Overpack Closure Techniques for HLW Repository Operation - Welding Methods
and UT Systems For Long-Term Structural Integrity of the Weld Joint -
Ario Nakamura, Hidekazu Asano, RWMC (Japan);
Takashi Furukawa, JAPAN POWER ENGINEERING AND INSPECTION CORPORATION (Japan);
Kyosuke Fujisawa, KOBE STEEL, LTD. (Japan); Susumu Kawakami, IHI Corporation (Japan);
Takashi Ito, Mitsubishi Heavy Industries, Ltd. (Japan).
Overpack, a high-level radioactive waste package for Japan’s geological disposal program, is required for preventing sealed
vitrified waste from contact with groundwater for at least 1,000 years. <strong>The</strong> weld joint between the body and lid must also meet this
requirement. Certain welding methods were examined for applicability through full-scale welding tests using various welding depths
up to 190 mm and two different lid structures. Results show that generation of welding flaws must be considered unavoidable.
<strong>The</strong>refore, ultrasonic testing (UT) must be conducted on the assumption that weld flaws will be present. Such UT systems must be
designed for natural defects. Several types of UT must be evaluated for detection and size estimation capability at depths ranging from
the surface to the bottom of the weld joint. Certain UT methods were examined for their ability to detect natural defects that were
created on the surface of and inside a 190-mm thick carbon steel specimen. Probability of detection (POD) of each UT method was
calculated by comparing the results of UT and destructive examination. In consideration of the preferred range of scanning depth for
each UT method, a concept that combines UT methods was proposed as a practical UT system for the overpack weld joint.
KEYWORDS: radioactive waste management, geological disposal, waste package, overpack, final closure weld, structural
integrity, natural defects, UT, POD
4) 40242 – Design Options for HLW Repository Operation Technology, (I) Demonstration and Evaluation of
Remote Handling Technologies
Hitoshi Nakashima, Hidekazu Asano, RWMC (Japan); Hideki Kawamura, Obayashi Corporation (Japan)
<strong>The</strong> long-term safety of a geological repository for high-level radioactive waste(HLW) in Japan is achieved using a
multi-barrier system, with emphasis on an engineered barrier system (EBS) consisting of bentonite-based buffer material
and a steel overpack containing vitrified wastes. Providing a wide variety of technical options for repository operation,
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. <strong>The</strong> 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. <strong>The</strong> 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. <strong>The</strong> large-scale
bentonite block and part of the full-scale Vertical Emplacement equipment are now on view at the Full-scale
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