Neutron and gamma radiation effects on thermal storage properties of polyethylene wax

Several nuclear reactors use ice condensers to condense steam in the case of a loss of coolant accident. These ice condensers have many problems that could be alleviated by using another material. The effects of low-dose neutron and gamma radiation on the thermal properties of polyethylene wax (PEW) were investigated for this purpose. PEW was irradiated in the Missouri University of Science and Technology Research Reactor (MSTR), the University of Missouri Cyclotron (MUC) and the University of Missouri Research Reactor (MURR) up to doses equivalent to 10 months in a nuclear power reactor's containment structure. The melting temperature and latent heat of fusion were determined using differential scanning calorimetry (DSC). Changes in the molecular bonds was determined using Raman spectroscopy. It was found that there was not a significant change in the thermal properties nor bonding over the investigated doses. This suggests that organic PCMs could be reliable alternatives to ice in nuclear reactor containment applications. The measured melting peak was found to be significantly wider expected by the suppliers' description. The ramifications of wide melting peaks are discussed in the context of reactor accident analysis and further experiments are suggested.