Long-term Behavior of Elastomer Seals and Polymers for Neutron Shielding

The long time-frame of the necessary safe enclosure of radioactive waste in containers gains internationally an increasing attention. Extended storage periods as well as an usually necessary subsequent transportation after storage have to be evaluated.In Germany, the concept of dry interim storage in dual purpose metal casks before disposal is being pursued for spent nuclear fuel (SNF) and high level waste (HLW) management. The initially planned and established dry interim storage license duration of up to 40 years will be too short and its extension will become necessary since there is no repository available in due time.The main safety relevant components are the thick-walled dual purpose metal casks. These casks consist e.g. of a monolithic cask body with integrated neutron shielding components (polymers, e.g. polyethylene) and a monitored double lid barrier system equipped with metal and elastomer seals. The metal seals of this bolted closure system guarantee the required leak-tightness, whereas the elastomer seals allow leakage rate measurement of the metal seals.At BAM we focus on the long-term performance of the sealing system and neutron shielding materials as their application conditions are considered as rather demanding.Therefore, BAM began to investigate the overall function and long-term behavior of elastomer and metal seals and also the irradiation influence on neutron shielding materials.Recently a new project was initiated to expand our investigations to obtain more and in some context better applicable data.This paper describes the approach of our new research project with the aim of further closure of existing knowledge gaps and presents an overview of investigations concerning the low temperature behavior of elastomer seals, of running long-term tests on elastomer seals at different temperatures under static conditions and the influence of gamma irradiation on neutron shielding materials.