Radiation changes in hardened Portland cement paste under the influence of gamma radiation

The possibility of using materials in radiation protection shields when designing new and extending the service life of existing nuclear energy facilities requires knowledge or the ability to predict their radiation changes. The studies were carried out due to the lack of data sufficient to predict radiation changes in hardened Portland cement paste (HPCP) and concrete under the influence of gamma radiation when used as radiation shield materials for nuclear energy facilities. The research is based on published data on the effect of gamma radiation on concrete at irradiation temperatures of 20–30 °C and on HPCP at 70–375 °C. The author carried out computational and analytical studies to assess and establish the possibility of predicting radiation changes in HPCP under the influence of gamma radiation. The studies were conducted using the previously developed and tested method of analytical determination of radiation changes in concretes according to data on changes in their components. The formulas used in this method made it possible to determine (restore) the radiation changes of the HPCP from experimental data on radiation changes in concretes and aggregates. According to the available results of concrete irradiation, changes in linear dimensions and strength during compression of HPCP under the action of only gamma radiation were calculated (restored). The dependences of radiation changes in HPCP on the magnitude of the absorbed dose in the range from 3.8×10⁴ to 4.7×10⁸ Gy after irradiation at 20–30 °C were established. According to the available data on the irradiation of HPCP with gamma radiation at temperatures from 70 °C to 375 °C, the effect of the irradiation temperature on radiation changes in the HPCP was revealed. Mathematical expressions that approximate the established dependencies are selected. On the basis of the obtained mathematical expressions, radiation changes in the linear dimensions and strength of HPCP for compression, caused only by the action of gamma radiation, after irradiation to the values of absorbed doses from 3×10⁴ Gy to 1×10¹⁰ Gy were calculated. The calculations of radiation-thermal changes in the linear dimensions and strength of HPCP under the action of gamma radiation and heating after irradiation to the values of absorbed doses from 3×10⁴ Gy to 1×10¹⁰ Gy and the accompanying heating at temperatures from 20 °C to 500 °C were estimated.