LONG-TERM STABILITY AND FIRE RESISTANCE OF NEUTRON SHIELDING MATERIALS, TNTM RESIN VYAL-B AND KOBESH EPR RESIN

Transnuclear, Ltd. designs transport and storage casks for the Asian market, using technological resources of neutron shielding materials of both TN International and Kobe Steel, Ltd. A series of tests were performed for two types of neutron shielding materials, TNTM resin Vyal-B and kobesh EPR resin, considering cask design approval in Japan. TNTM resin Vyal-B is vinylester resin based and was developed by TN International. And kobesh EPR is Ethylene-Propylene-Rubber based and was developed by Kobe steel, Ltd. These materials were heated under 140°C, 160°C, and 170°C, up to 10000hours to evaluate thermal properties under transport and long-term storage conditions by means of Arrhenius equation. The hydrogen content and density of these neutron shielding materials have been stable under test conditions and it is confirmed that these shielding materials have high stability at such elevated temperatures as 160°C for transport and long-term storage conditions for more than 60 years. The fire resistance tests were performed at 800°C/30minutes for these materials in order to know their behavior under fire accident, using partial models simulating actual cask. After removal from the fire, these neutron shielding materials were instantaneously self-extinguished and most material remains in its previous shape. The remaining weight of these materials after the fire resistance test were more than 90% for TNTM resin Vyal-B, and more than 75% for kobesh EPR respectively. It is confirmed that TNTM resin Vyal-B and kobesh EPR have excellent fire resistant properties.