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Presently, a criticality safety evaluation methodology for the final geological disposal of Swiss spent nuclear fuel is under development at the Paul Scherrer Institute in collaboration with the Swiss National Technical Competence Centre in the field of deep geological disposal of radioactive waste. This method in essence pursues a best estimate plus uncertainty approach and includes burnup credit. Burnup credit is applied by means of a computational scheme called BUCSS-R (Burnup Credit System for the Swiss Reactors–Repository case) which is complemented by the quantification of uncertainties from various sources. BUCSS-R consists in depletion, decay and criticality calculations with CASMO5, SERPENT2 and MCNP6, respectively, determining the keff eigenvalues of the disposal canister loaded with the Swiss spent nuclear fuel assemblies. However, the depletion calculation in the first and the criticality calculation in the third step, in particular, are subject to uncertainties in the nuclear data input. In previous studies, the effects of these nuclear data-related uncertainties on obtained keff values, stemming from each of the two steps, have been quantified independently. Both contributions to the overall uncertainty in the calculated keff values have, therefore, been considered as fully correlated leading to an overly conservative estimation of total uncertainties. This study presents a consistent approach eliminating the need to assume and take into account unrealistically strong correlations in the keff results. The nuclear data uncertainty quantification for both depletion and criticality calculation is now performed at once using one and the same set of perturbation factors for uncertainty propagation through the corresponding calculation steps of the evaluation method. The present results reveal the overestimation of nuclear data-related uncertainties by the previous approach, in particular for spent nuclear fuel with a high burn-up, and underline the importance of consistent nuclear data uncertainty quantification methods. However, only canister loadings with UO2 fuel assemblies are considered, not offering insights into potentially different trends in nuclear data-related uncertainties for mixed oxide fuel assemblies.

The introduction at CERN of new extremely energetic particle accelerators, such as the high-luminosity large hadron collider (HL-LHC) or the proposed future circular collider (FCC), will increase the energy stored in the circulating particle beams by almost a factor of two (from 360 to 680 MJ) and of more than 20 (up to 8500 MJ), respectively. In this scenario, it is paramount to assess the dynamic thermomechanical response of materials presently used, or being developed for future use, in beam intercepting devices (such as collimators, targets, dumps, absorbers, spoilers, windows, etc.) exposed to potentially destructive events caused by the impact of energetic particle beams. For this reason, a new HiRadMat experiment, named “MultiMat”, was carried out in October 2017, with the goal of assessing the behaviour of samples exposed to high-intensity, high-energy proton pulses, made of a broad range of materials relevant for collimators and beam intercepting devices, thin-film coatings and advanced equipment. This paper describes the experiment and its main results, collected online thanks to an extensive acquisition system and after the irradiation by non-destructive examination, as well as the numerical simulations performed to benchmark experimental data and extend materials constitutive models., peer-reviewed

The two beam dumps of the Large Hadron Collider (LHC), made up mostly of low-density graphite, are responsible for absorbing the high-energy particle beams when ejected from the accelerator. In the frame-work of the project to improve the luminosity in the LHC, the beam intensity will be increased by a factor of around two in the coming years. The dominant load on the dump assembly is the energy deposited in the material by the 7 TeV proton beam. Thermomechanical simulations have to be performed to ensure the safe operation of the dump through assessing the integrity in the future. To date, the particle beam contains an average energy of 370 MJ, which is sent to the dump in a sweep movement within around 80 µs. Based on the large dimensions of the dump core and considering the highly dynamic nature of this load, an explicit code like LS-Dyna® was deemed to be best suited for these studies. This paper presents the methodology proposed to model the discrete time structure of the load, caused by the interaction between the particle beam and the dump. Results of the application of this technique, to determine the temperature, stresses and wave propagation on the downstream wall of this device, are described here. In addition to the methodology of the load application, the results of standard quasi-static material tests on the low-density graphite material in the beam dump are presented, to assess the general nature of the material behavior. These experiments will be the basis for a dynamic test campaign to construct a comprehensive material model, as the graphite used in this device has never been fully characterized under such loading conditions.

3D Carbon/Carbon (3D CC) is a well‐known industrial composite material for high‐temperature applications. One of its main advantages resides in its ability to maintain good material characteristics at elevated temperatures (higher than 2700°C), which makes it potentially interesting for beam interaction applications where high strength at high temperature is required. The ability of beam intercepting devices to withstand direct impacts of high‐energy proton beams is essential for the operation of the Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN). Following successful beam impact tests at CERN, as well as positive vacuum acceptance and metrology tests, several collimators and beam extraction absorbers are currently being equipped with 3D CC composite, as part of the LHC Injector Upgrade (LIU) and High Luminosity LHC (HL‐LHC) projects.

The development of intensity-modulated radiotherapy treatments delivering large amounts of monitor units (MUs) recently raised concern about higher risks for secondary malignancies. In this study, optimised combinations of several variance reduction techniques (VRTs) have been implemented in order to achieve a high precision in Monte Carlo (MC) radiation transport simulations and the calculation of in- and out-of-field photon and neutron dose-equivalent distributions in an anthropomorphic phantom using MCNPX, v.2.7. The computer model included a Varian Clinac 2100C treatment head and a high-resolution head phantom. By means of the applied VRTs, a relative uncertainty for the photon dose-equivalent distribution of1 % in-field and 15 % in average over the rest of the phantom could be obtained. Neutron dose equivalent, caused by photonuclear reactions in the linear accelerator components at photon energies of approximately8 MeV, has been calculated. Relative uncertainty, calculated for each voxel, could be kept below 5 % in average over all voxels of the phantom. Thus, a very detailed neutron dose distribution could be obtained. The achieved precision now allows a far better estimation of both photon and especially neutron doses out-of-field, where neutrons can become the predominant component of secondary radiation.