Abstract
The Supercontainer (SC) is a reference concept, adopted by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS), for the packaging of high level vitrified radioactive waste (HLW) and spent fuel (SF). The waste package consists of different components all designed to fulfil specific functions. One of these is a carbon steel overpack developed to prevent contact of the waste with the engineered barrier system and the host geological formation during the thermal phase. Another is a concrete buffer and cementitious filler, both developed to provide a high pH environment during at least the thermal phase, which ensures passivation of the overpack and provides radiological shielding during construction and handling of the SC. Finally, the presence of an outer steel envelope serves as a mould for the casting of the outer buffer while providing additional mechanical strength and confinement during transportation and handling of the waste package. As part of the first safety and feasibility case (SFC-1), ONDRAF/NIRAS has to demonstrate that no fundamental flaws exist regarding the feasibility to construct the SC. To this end, ONDRAF/NIRAS established a research programme consisting of desk studies, modelling, theoretical development and experimental testing. The primary objective of the experimental testing programme is to demonstrate the feasibility to construct the SC. This paper describes the test's setup and design and provides a summary of the main observations obtained during an experimental test performed to evaluate the construction feasibility of the SC.
Highlights
In the reference concept of the SC (Figure 1) canisters containing vitrified high level vitrified radioactive waste (HLW) or spent fuel (SF) assemblies are encapsulated in a watertight carbon steel overpack and cast in a concrete matrix surrounded by an outer steel envelope [1, 2, 3]
The presence of an outer steel envelope serves as a mould for the casting of the outer buffer while providing additional mechanical strength and confinement during transportation and handling of the waste package
ONDRAF/NIRAS established a research programme consisting of desk studies, modelling, theoretical development and experimental testing
Summary
In the reference concept of the SC (Figure 1) canisters containing vitrified HLW or SF assemblies are encapsulated in a watertight carbon steel overpack and cast in a concrete matrix surrounded by an outer steel envelope [1, 2, 3]. Stage 1 comprises the installation of the steel envelope and construction of the first concrete buffer. During this construction stage there is no contact with the radioactive waste. The concrete buffers provide structural confinement for the overpack as well as radiological shielding during construction and transportation to the repository. They provide the high alkaline conditions needed to ensure passivation of the carbon steel overpack. The reduced height was necessary to accommodate the overhead space available at the laboratory where the test was performed, which has a maximum working height of 7 m. This limited the height of the test to 3.45 m
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