抄録
The application of PIC (Polymer-Impregnated Concrete) to the container for conditioning and disposal of low and intermediate level radioactive wastes have been investigated, because the PIC has excellent characteristics such as high mechanical strength, high water impermeability, good corrosion resistance, good durability and so on. It is necessary to evaluate the resistance to gammarays considering the PIC-container for radioactive wastes.
The radiation-resistance of PIC with test piece was evaluated by irradiation of gamma-rays. All the test pieces had JIS mortar size of 4×4×16cm. JIS mortar and concrete were used as specimens. The maximum aggregate size of concrete was 10mm. The specimens impregnated by MMA (methylmethacrylate) monomer and solution of 10% of PSt (polystyrene) in MMA monomer (MMA·PSt) were polymerized by irradiating for 5hr at the dose rate of 1MR (1×106 Roentgen)/hr. PIC specimens were exposed up to maximum 1000MR to 60Co gamma-rays in air and under water which simulate shallow land disposal and deep sea dumping conditions, respectively.
The lowering of strength of the PTC exposed to gamma-rays under water was larger than that of the PIC in air. The improving effect of the added PSt on the radiation-resistance was observed. It was observed that the 50MR-irradiated MMA·PSt-PIC under water, which had the residual compressive strength of 85%, was resistant to gamma-rays. When this residual strength was regardedas a limit of radiation-resistance in air, the limit of MMA and MMA·PSt-PIC were approximately 25MR and 150MR, respectively. The lowering of strength was mainly due to the deterioration of MMA polymer in PIC.
The total exposure dose for PIC-container was estimated by assuming the conditions about the packaged radioactive wastes, dose rate, container and so on. The total exposure dose on PIC- container for 100 years became roughly 1.25MR. Therefore, it is estimated that the PIC-containers for conditioning and disposal of low and intermediate level radioactive wastes have a sufficient resistance to radiation arising from wastes.
