Shutdown Dose Rate Evaluation Around the High-Power Beam Dump for 5 MeV and 9 MeV Deuteron Beam Operations in the Linear IFMIF Prototype Accelerator (LIPAc)

Status and future developments of the Linear IFMIF Prototype Accelerator (LIPAc)

Shutdown dose rate (SDDR) analysis requires (a) a neutron transport calculation to estimate neutron flux fields, (b) an activation calculation to compute radionuclide inventories and associated photon sources, and (c) a photon transport calculation to estimate final SDDR. In some applications, accurate full-scale Monte Carlo (MC) SDDR simulations are needed for very large systems with massive amounts of shielding materials. However, these simulations are impractical because calculation of space- and energy-dependent neutron fluxes throughout the structural materials is needed to estimate distribution of radioisotopes causing the SDDR. Biasing the neutron MC calculation using an importance function is not simple because it is difficult to explicitly express the response function, which depends on subsequent computational steps. Typical SDDR calculations do not consider how uncertainties in MC neutron calculation impact SDDR uncertainty, even though MC neutron calculation uncertainties usually dominate SDDR uncertainty.The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) hybrid MC/deterministic method was developed to speed SDDR MC neutron transport calculation using a deterministically calculated importance function representing the neutron importance to the final SDDR. Undersampling is usually inevitable in large-problem SDDR simulations because it is very difficult for the MC method to simulate particles in all space and energy elements of the neutron calculation. MS-CADIS can assess the degree of undersampling in SDDR calculations by determining the fraction of the SDDR response in the space and energy elements that did not have any scores in the MC neutron calculation. It can also provide estimates for upper and lower limits of SDDR statistical uncertainties resulting from uncertainties in MC neutron calculation.MS-CADIS was applied to the ITER SDDR benchmark problem that resembles the configuration and geometrical arrangement of an upper port plug in ITER. Without using the hybrid MC/deterministic methods to speed MC neutron calculations, SDDR calculations were significantly undersampled for all tallies, even when MC neutron calculation computational time was 32 CPU-days. However, all SDDR tally results with MC neutron calculations of only 2 CPU-days converged with the standard Forward-Weighted CADIS (FW-CADIS) method and the MS-CADIS method. Compared to the standard FW-CADIS approach, MS-CADIS decreased the undersampling in the calculated SDDR by factors between 0.9% and 0.3% for computational times between 4 and 32 CPU-days, and it increased the computational efficiency of the SDDR neutron MC calculation by factors between 43% and 69%.

Neutronic effects of the ITER Upper Port environment update in C-model

Shutdown dose rate calculation for fission reactors: An application of the MS-CADIS method to OPAL

The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) hybrid Monte Carlo (MC)/deterministic radiation transport method was proposed to speed up the shutdown dose rate (SDDR) neutron MC calculation using an importance function that represents the neutron importance to the final SDDR. In this work, the MS-CADIS method was applied to the ITER SDDR benchmark problem. The MS-CADIS method was also used to calculate the SDDR uncertainty resulting from uncertainties in the MC neutron calculation and to determine the degree of undersampling in SDDR calculations because of the limited ability of the MC method to tally detailed spatial and energy distributions. The analysis that used the ITER benchmark problem compared the efficiency of the MS-CADIS method to the traditional approach of using global MC variance reduction techniques for speeding up SDDR neutron MC calculation. Compared to the standard Forward-Weighted-CADIS (FW-CADIS) method, the MS-CADIS method increased the efficiency of the SDDR neutron MC calculation by 69%. The MS-CADIS method also increased the fraction of nonzero scoring mesh tally elements in the space-energy regions of high importance to the final SDDR.

EPICS based low-level radio frequency control system in LIPAc

The Linear International Fusion Materials Irradiation Facility Prototype Accelerator (LIPAc) is under commissioning in Rokkasho Fusion Institute in Japan and aims to accelerate 125 mA D+ at 9 MeV in Continuous Wave mode for validating the IFMIF accelerator design. To ensure a fine characterization and tuning of the machine many beam diagnostics are installed spanning from injector to the beam dump. The beam operations in 1.0 ms pulsed D+ at 5 MeV were successfully completed with a low power beam dump in 2019. Despite the challenges posed by the pandemic, the crucial transition to a new LINAC configuration was also finalized to enable operation in 1.0 ms — CW D+ at 5 MeV with the high-power beam dump. The 1st beam operation of the configuration was carried out in 2021. The experiences and challenges encountered during these beam campaigns are described in this paper.

Activation of the IFMIF prototype accelerator and beam dump by deuterons and protons

Shut-down dose rate analysis for the activated target assembly in IFMIF-DONES during maintenance

In the framework of the IFMIF/EVEDA project, the cryomodule of the Linear IFMIF Prototype Accelerator (LIPAc) will be assembled then tested at Rokkasho in 2019. Eight Series Power Couplers (PC) operating at 175 MHz were manufactured under a CEA contract, in order to equip this Cryomodule. They were all successfully RF conditioned up to 100 kW CW in TW and SW configurations. All the high RF power tests were performed under CIEMAT responsibility in BTESA Company premises, according to the CEA requirements. In order to fix difficulties encountered during the fab process, manufacturing and quality control have been analyzed in depth. Thanks to the corrective actions implemented, every PC reached the performances targeted for qualification. This paper will give details about this manufacturing phase and provide an overview of the obtained RF test results.

Detailed Characterization of MEBT Quadrupoles for the Linear IFMIF Prototype Accelerator (LIPAc)

Shutdown dose calculations for the IFMIF-DONES lithium loop cell using variance reduction techniques

Beam diagnostics of an ECR ion source on LIPAc injector for prototype IFMIF beam accelerator

Linear IFMIF Prototype Accelerator (LIPAC) is the prototype accelerator of the Engineering Validation and Engineering Design Activities (EVEDA) phase of the International Fusion Materials Irradiation Facility (IFMIF) project. The EVEDA phase is a first IFMIF step devoted to the construction of prototypes of the main units. The deuteron beam of LIPAC (125 mA, 9 MeV) is stopped by a conical copper beam stop, giving rise to neutron and photon sources that must be shielded to comply with dose requirements. A reliable characterization of these secondary sources is a mandatory task.The built-in-semi-analytical nuclear models used by advanced Monte Carlo transport codes as Monte Carlo N-Particle eXtended (MCNPX) or Particle and Heavy Ion Transport code System (PHITS) have been demonstrated as unreliable for describing deuteron interactions and secondary particle production at these low energies. The use of reliable external nuclear data is consequently necessary in the design of the LIPAC shielding. In particular, the TENDL-2010 library has been compared with recently published experimental data demonstrating its reliability for deuteron interaction on copper at 9 MeV. The Monte Carlo Universidad Nacional de Educación a Distancia (MCUNED) code has been developed to make use of external nuclear data, and its use with the TENDL-2010 library has proven very satisfactory for LIPAC radioprotection analysis.The impact on radioprotection tasks in LIPAC when the unreliable nuclear models mentioned above are used is discussed.

Gamma-ray and neutron area monitoring system of linear IFMIF prototype accelerator building