The CAvern REtrievable (CARE) concept was originally developed to provide flexibility in tailoring disposal of vitrified HLW to small volunteer host sites, where high emplacement density leads to significant challenges in terms of the management of radiogenic heat. Including an extended storage period in underground caverns prior to sealing solved the heat issue, but also provided benefits in terms of a slow decision-making process that provided more opportunities to engage stakeholders.
Recently, direct disposal of spent fuel is being considered in Japan and this gives more severe challenges for heat management, even for conventional disposal concepts. Due to great uncertainties in the future of nuclear power in Japan, this may also be associated with a desire to preserve the option of retrieval for extended periods. The basic CARE concept has thus been re-assessed to consider these aspects — and also the need to be able to develop a robust safety case that can be readily communicated to stakeholders, who are more sensitive to nuclear issues than they were in the past.