Nuclear Irradiation effect on Polymers for Electrical Systems
NIPES is a EU cascade Project funded in the framework of OFFERR and done in collaboration between University of Bologna and UJV (Czech Republic).
Abstract
In the framework of the desired extension current nuclear power plants (NPPs) life, all the pieces of equipment inside the plants should be tested and their reliability verified.
Among others, low voltage cables play a very important role in guaranteeing adequate operating life of the NPPs. Early failure of cables important to safety could lead to unexpected power loss, lack of communication and, in the worst case, to a nuclear accident. Proper functionality of cables is ensured by the insulating polymer layer next to the conductor. This material degrades throughout the application life of the cable due to the enhanced environmental stresses i.e., radiation, heat, moisture, and chemical sprays in nuclear environments.
The NIPES project aims at investigating the effect of radiation and heat on typical polymeric materials used inside NPPs e.g., XLPE (cross-linked polyethylene), PVC (polyvinyl chloride) and EPDM (Ethylene-Propylene Diene Monomer).
Inside the project, flat sheets will be aged inside an irradiation chamber under accelerated conditions to simulate degradation on the materials equivalent to real environment.
Aged materials will be characterized with both conventional destructive testing techniques (e.g., tensile tests) and non-destructive (ND) ones e.g., dielectric spectroscopy and electrical conductivity. The correlation among techniques will open the possibility to monitor and assess cable health trough NDTs and plan the maintenance or substitution of the related equipment. Finally, a phenomenological life model will be built based on the experimental results obtained. This would allow the estimation of the life of the electrical equipment under service and accelerated aging conditions.
