Comparison of Waste Due to Irradiated Steels in the Esfr and Demo

Abstract

For either nuclear fusion or generation IV fission reactors to be viable as a commercial energy source the decommissioning and waste disposal solutions must be considered during the design. A multi-step simulation process combining Monte Carlo Neutron Transport simulations with inventory simulations have been performed to estimate the activation of steels in key reactor components of the European Sodium-cooled fast Reactor (ESFR). Waste classifications based on UK waste disposal regulations have been applied to the key components to estimate the expected masses of low level and intermediate level waste. The use of reduced activation steels, EUROFER and F82H, in reactor components external to the core results in a factor of 10 reduction in the percentage of waste classified as Intermediate Level Waste (ILW). Waste estimates are compared to existing waste estimates for the European Demonstration fusion reactor (DEMO). The ESFR has a lower percentage of ILW per total reactor mass due to irradiated steels compared to DEMO. However, there is no Higher Activity Waste (HAW) associated with DEMO, compared with arisings from the ESFR spent fission fuel.

Nuclear data for fusion: inventory validation successes and future needs

“…The experiment did not identify the origin of the 4 He particles produced, which were measured using silicon detectors, and so the experiment in fact measured the total (n,Xα) cross sections. This explains why the '94' data points continue to increase beyond 16 MeV, in contrast to the evaluated curves from the data libraries-those higher energy cross sections correspond to the sum of at least two 4 He production channels, (n,α) and (n,nα), which is confirmed by the equivalent (n,α) + (n,nα) curve from JEFF-3.3 (ENDF/B-VIII.0 does not contain the (n,nα) channel in the version of the library read by FISPACT-II, potentially indicating a processing issue due to improper adherence to ENDF-6 coding standards [50]). This 1994 [49] experiment is the only one in the EXFOR database with such a complete coverage of the relevant energy range for fusion neutrons, and gives the most confidence to the evaluated libraries.…”

“…The cross section curves for (n,α) reactions, neutron capture followed by α-particle emission (i.e. 4 He, the primary stable isotope of helium), for the JEFF-3.3 [26] and ENDF/B-VIII [29] are a good match to the majority of EXFOR data in the fusion relevant range up to 14 MeV. Note that some recent experimental data from 2019 (the EXFOR points are labelled in the figure with the year of publication) originally appeared to deviate significantly from the general trend of data, but a review of the source data [47] indicated that these data points had been incorrectly inserted into the EXFOR database (and actually correspond to the 54 Fe(n,α) cross section).…”

“…To see the impact of this apparent omission in modern libraries we can compare 4 He production predictions in C under fusion conditions, with and without this additional (n,n ′ 2α) channel. In [59], where a comprehensive response database was created for all elements under EU-DEMO conditions, the predicted He production after 2 years of continuous operation in the first wall of the reactor (corresponding to a flux of 5.04 × 10 14 n cm −2 s −1 ) was 410 atomic parts per million (appm) with the TENDL-2015 [60] nuclear data library.…”

“…In particular, engineers need to design the plant operation, maintenance and decommissioning with accurate knowledge of the neutron-induced activation of the materials being proposed for regions within the vacuum vessel of magnetic confinement fusion tokamaks (and inside the vessel/chamber of any other fusion concept where neutrons are produced), where the neutron exposure will be highest. For example, computational assessments are vital to understand the radioactive waste arisings that can be expected at the end-of-life (EOL) of future fusion reactors, with results of the severity [1,2] and volumes [3,4] of waste being used to drive design refinement [5], consideration of alternative materials [6], and even review of the approach to classification of fusion waste [7]. For example, figure 1(a) illustrates outputs from whole reactor waste assessment predictions for the European Figure 1.…”

Re-examining the role of nuclear fusion in a renewables-based energy mix

“…In fact, more intermediate-level waste (ILW) may be produced by fusion than by fission: the European Sodium-Cooled fission Fast Reactor (SCFR) design has a lower percentage of ILW per total reactor steel mass compared to the EU-DEMO1 design (for a similar power output) [76].…”