Characterization of Radiation Fields in Biological Shields of Nuclear Power Plants for Assessing Concrete Degradation*

Abstract

Abstract. Life extensions of nuclear power plants to 60 and potentially 80 years of operation have renewed interest in long-term material degradation. One material being considered is concrete, with a particular focus on radiation-induced effects. Based on the projected neutron fluence values (E > 0.1 MeV) in the concrete biological shields of the US pressurized water reactor fleet and the available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database and a reliable determination of relevant neutron fluence energy cutoff value are necessary to ensure reliable risk assessment for extended operation of nuclear power plants.

Review of the Current State of Knowledge on the Effects of Radiation on Concrete

“…It is, therefore, of interest to investigate neutron-induced atom displacements in aggregates. Remec et al (2016b) showed that, for the neutron spectra in the biological shield of two-loop and three-loop (the number of reactor cooling circuits) PWRs, neutrons with energies above 0.1 MeV contribute more than 95% of all atom displacements in several widespread aggregate minerals, while neutrons with energies above 1 MeV cause only about 20 to 25% of the total atom displacements, as shown in Fig. 1 (Remec et al 2016a).…”

“…As previously discussed, (Remec et al 2016b;Rosseel et al 2014;Rosseel et al 2015b), the onset of radiationinduced concrete degradation has been correlated to neutron fluence and gamma ray dose based on data assembled by Hilsdorf et al (1978). Obtaining accurate estimates of the bounding fluence and dose values for the US NPP fleet at the projected extended service is clearly important.…”

“…As previously noted, a review of existing data on irradiated concrete reveals that neutron fluence is predominately used to characterize the radiation environment (Hilsdorf et al 1978;Field et al 2015), but there is little consistency in the neutron energy cutoff applied for the neutron fluence (Remec et al 2016b). However, in the CBS of pressurized water reactors (PWRs), the neutron fluence for a cutoff energy of E >0.1 MeV is about 8-15 times higher than the neutron fluence at E >1 MeV (and the neutron fluence for E >0 eV can be 20-40 times higher) .…”

Characterization of Radiation Fields for Assessing Concrete Degradation in Biological Shields of NPPs

“…The values listed in Table 1, obtained in a transport analysis of a two-loop and three-loop PWR [5,8] Another observation related to Fig. 3 is that the data points at the high fluence end are dominated by the data reported for the fluence energy cutoff of 1 MeV.…”