Characteristics of alanine dosimeter under low dose-rate and long time irradiation. Residual life estimation of organic materials used in the radiation environment

Incremental measurement technique of accumulated dose is required to evaluate radiation damage and to estimate residual-life of apparatus and materials used in radiation environment in nuclear power facilities. Alanine/ESR dosimetry is well-known as a reliable dosimetry method and has suitable properties to apply to this field, such as wide useful dose range, long-term stability, and non-destructive readout. In this work, feasibility of accumulated dose measurement under simulated condition was studied by irradiation up to 0.1 and 1 kGy at dose rates of 0.45 and 1.97 Gy/h and at elevated temperatures in the range of 25degC to 80degC. Long-term stability of dose response after irradiation was also studied at elevated temperatures during irradiation and storage. Dose response of alanine dosimeter increases linearly up to 1 kGy at irradiation temperatures below 60degC, even when dosimeter was irradiated at a dose rate of 0.45 Gy/h and for irradiation time up to about 2000h. Alanine dosimetry allows us to measure accumulated dose without any correction at the above dose rate and temperature range. Dose response depends on irradiation temperature, and linear dependence with a temperature coefficient of +0.1%/degC was found for a dose of 0.1 kGy at dose rates of 0.45 and 1.97 Gy/h, although non-linear relation was found for dose of 1 kGy at a dose rate of 0.45 Gy/h which is long irradiation time of about 2000h. Change in dose response after the end of irradiation is independent of dose rates, although it increases with dose and with temperatures during storage especially at above 60degC. (author)