Radiation shielding of high-energy neutrons in SAD (original) (raw)
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Radiation Protection Dosimetry, 2005
An irradiation field of high-energy neutrons produced in the forward direction from a thick tungsten target bombarded by 500 MeV protons was arranged at the KENS spallation neutron source facility. In this facility, shielding experiment was performed with an ordinary concrete shield of 4 m thickness assembled in the irradiation room, 2.5 m downstream from the target centre. Activation detectors of bismuth, aluminium, indium and gold were inserted into eight slots inside the shield and attenuations of neutron reaction rates were obtained by measurements of gamma-rays from the activation detectors. A MARS14 Monte Carlo simulation was also performed down to thermal energy, and comparisons between the calculations and measurements show agreements within a factor of 3. This neutron field is useful for studies of shielding, activation and radiation damage of materials for high-energy neutrons, and experimental data are useful to check the accuracies of the transmission and activation calculation codes.
IEEE Transactions on Nuclear Science, 2022
To characterize the dose rate distribution in an experimental hall of a RIKEN accelerator-driven compact neutron source (RANS) based on the 9 Be(p, n) reaction with 7 MeV proton injection, systematical measurements and calculations for neutron and gamma-ray dose rates by GEometry ANd Tracking (GEANT), Particle and Heavy Ion Transport code System (PHITS), and Monte Carlo N-Particle (MCNP) codes were performed. Calculations always underestimated measurements when proton beam loss effect was not considered. Relatively good agreements were observed among the different simulation codes. To explain the underestimations, the additional dominant neutron and gamma-ray sources due to proton beam loss were identified at the position around exit of the drift tube linac (DTL), made of copper, and the beam pipe from quadrupole (Q) magnets to steering (ST) magnets, made of aluminum, from measurements with placing collimators along linac. The beam loss fractions of 2%-3% on copper and 1% on aluminum, respectively, were the most appropriate estimation. In addition, we proposed the possible measures to reduce the measured total dose rate of 3.8 µSv/h at the operator position in the control room, with the addition of a wall at the entrance of experimental hall and extension of borated polyethylene (BPE) at the end of the beam. As a result, the dose rate became 2.5 times lower than the current one.
International Journal of Advanced Nuclear Reactor Design and Technology, 2021
In this paper, the reactor core, irradiating beam tubes, and radiological shields of a 5 MW open pool type Material Testing Reactor (MTR) are simulated in detail by using the MCNPX 2.6 code and its default library (i.e. mostly made of ENDF/B VI and VII). A safety assessment is performed and discussed based on the related health physics issues. Independently, dosimetry parameters are measured by using the Berthold LB 6411 neutron dose rate monitor and Berthold LB 123 Gamma dose rate monitor. Experimental results are used to benchmark the modeling and calculations especially regarding dosimetry, shielding, and health physics problems. Results are fairly appropriate for further calculations to be validated but some aging problems could be raised for a 50 years old research reactor particularly due to secondary gamma rate of the activated components. Then major beam tubes are characterized for high qualified irradiating applications. Moreover, external dose rates are estimated for empty beam tubes whenever radiological shields fail such as large break of beam tubes, hazardous seismic conditions, or any accident that can remove the plugs. Then, results are very important for the safety of the reactor operator to determine and establish emergency zones (i.e. yellow zones) and planning, respectively.
A standard fission neutron irradiation facility
Nuclear Instruments and Methods, 1979
A fission neutron irradiation facility (FISNIF) has been set up at the thermal column of the CIRUS reactor at BARC. The spectrum and the flux have been measured using threshold detectors. The paper describes the setting up of the facility, measurement and application. A concentric cylinder containing UO 2 powder sealed inside surrounds the irradiation point of a pneumatic sample transfer system located in the thermal column of the reactor. Samples are loaded in a standard aluminium capsule with cadmium lining and transported pneumatically. A sample transfer time of 1 s can be achieved in the facility. The spectrum has been fitted to the expression N(E)=(9.25+O.57)×IOT~.E exp(-0.862E)dE, which when integrated gives the value of (1.025+0.063)x 108 n/cm 2 .s for the total flux. Typical applications of the facility for studying activation of iron and sodium in fission neutrons are also discussed.
2015
The Neutral Beam Test Facility (NBTF), also called PRIMA (acronym for Padova Research on ITER Megavolt Accelerator) consists of two separate development test beds currently under construction in Padua (Italy): the ion source test facility, named SPIDER (Source for Production of Ion of Deuterium Extracted from Rf plasma) and the megavolt test facility, called MITICA (acronym for Megavolt ITER Injector & Concept Advancement). Both injectors accelerate negative deuterium and hydrogen ions with a maximum energy of 1 MeV for MITICA and 100 keV for SPIDER, and a maximum beam current of 40 A for both the experiments. Accelerated ions are stopped on a.CuCrZr alloy calorimeter where an intense neutron field is generated following to D-D and D-T reactions. In the present paper, a systematic review of the radiation safety analysis for both injectors is presented. The shielding design is described, including special shielding solutions planned with the aim of allowing personnel access for inspe...
Radiation Measurements, 2009
The European Commission has funded within its 6th Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organizational framework for this project was provided by the European radiation Dosimetry Group EURADOS. Work Package 6 of CONRAD dealt with ''complex mixed radiation fields at workplaces'' and in this context it organised a benchmark exercise, which included both measurements and calculations, in a stray radiation field at a high-energy particle accelerator at GSI, Germany. The aim was to intercompare the response of several types of active detectors and passive dosemeters in a well-characterised workplace field. The Monte Carlo simulations of the radiation field and the experimental determination of the neutron spectra with various Bonner Sphere Spectrometers are discussed in Rollet et al. (2008) and in Wiegel et al. (2008). This paper focuses on the intercomparison of the response of the dosemeters in terms of ambient dose equivalent. The paper describes in detail the detectors employed in the experiment, followed by a discussion of the results. A comparison is also made with the H * (10) values predicted by the Monte Carlo simulations and those measured by the BSS systems.