To provide an efficient process for the final disposal of radioactive wastes, some nuclear sites are currently building suitable, temporary stores for such material. This paper describes the practical construction programme recently completed at a UK power reactor site under decommissioning. This site has a number of half height ISO containers filled with solid radioactive material that needed a temporary storage area before being consigned for final disposal. As a result, the site, Hunterston A Decommissioning Site, needed to construct some temporary radiation shield walls to contain the half height ISO containers (HHISO) and safeguard staff and public during the storage period. The chosen location of the temporary store was the Charge Machine Maintenance Building (CMMB), which was surplus to requirements during the decommissioning programme, providing a weatherproof environment. Following an in-depth study of the different forms of construction available, the commercially available, hollow, interlocking polyethylene block system was adopted. Because of its modular form, it has the advantage that it can to be dismantled and re-used at other locations, if required. Being hollow, the block could be filled with a variety of materials, such as water, sand, lead or iron shot, depending on the radioactive shielding needs. An important aspect of the modular plastic block was that it could be more easily installed, decontaminated and decommissioned than the cheaper concrete block system, which produces copious quantities of waste for disposal. This paper describes the choice of interlocking block shielding after comparisons with more conventional forms of construction, the features of the HHISO store design, the short duration building programme and the on-site experiences of the construction period.

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