A Versatile Methodology for Reactor Pressure Vessel Aging Assessments

A Detailed Analysis of the H.B. Robinson-2 Reactor Pressure Vessel Dosimetry Benchmark

“…To help the reader better understand the following results, Figure 3 shows the activation cross sections for the six types of dosimeters considered, processed at 600K using the NJOY2016 code [18] with ENDF files taken from the JEFF-3.3 data library [19]. Figure 3 shows that all dosimeters are sensitive to fast neutrons (i.e., those with energies above 1 MeV), making them highly relevant for assessing the reliability of vessel aging assessments (given that fast neutrons are the primary contributors to radiation damage [6]). Finally, it is interesting to note that 58 Ni(n,p), 54 Fe(n,p), 46 Ti(n,p) and 63 Cu(n,α) represent reactions with a strong energy threshold.…”

“…In this second approach, the fission neutron source term averaged over the 9th cycle of the HBR-2 reactor was computed using VACS. A detailed description of this methodology can be found in [6], and in this section we only recall the main principles of the calculation scheme. In addition, this section details the few approximations not present in the methodology as described in [6] that had to be made in order to carry out the analysis of the HBR-2 benchmark.…”

“…Processed energycontinuous cross sections (ACE format) Then, the pin-scale fission neutron emission distributions calculated by following the above methodology are used to compute the cycle-averaged fission neutron distribution within the reactor, according to Equation (6).…”

“…In this context, efforts have been made at the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) to develop a versatile, best-estimate calculation scheme for the analysis of RPV embrittlement under neutron irradiation [6], named VACS (vessel aging calculation scheme). The methodology relies on a two-step approach, coupling deterministic and Monte Carlo calculations.…”

“…The first step estimates the full-core fission neutron source term and the second step considers the transport of neutrons from the core to the RPV, using the fission neutron distribution determined in the previous step. Throughout the construction of the methodology, several studies were conducted to minimize the inherent methodological biases [6][7][8][9] and to pave the way towards the quantification of the global uncertainty in its predictions [9,10]. In order to validate the numerical predictions using experimental dosimeter data from ex-core locations, a detailed analysis of the H.B.…”