A soft-type neutron-shielding resin has been developed by improving an existing hard-type neutronshielding material using the epoxy-based resin as an additional shielding material. A flexible heat-resistant neutron-shielding material has been developed, which consists of a new polymer-based resin with boron. The neutron shielding performance of the developed flexible heat-resistant resin with the 252 Cf neutron source is almost the same as that of polyethylene. The outgases of H, H 2 , NH 4 , H 2 O, CO, O 2 , C 4 H 10 , and CO 2 from the developed resin have been measured at high temperature (up to 250 C) by thermal desorption spectroscopy methods. The soft-type resin and the newly developed heat-resistant resin will be applied to prevent the effects of neutron streaming and to control the movement of a vibrated pipe as the seal material around the plumbing in the future fast reactor and innovative fission reactor.