2-D Evaluation of Bred Tritium Using Neutron Imaging Plate

Abstract

Tritium breeding performance of a fusion blanket is a key parameter for the self-sufficient fueling of a fusion reactor and thus planned to validate the performance in a neutronics experiment. Measuring the two-dimensional (2D) distribution of bred tritium is challenging via conventional methods such as -ray counting from an irradiated lithium sample by a liquid scintillation counter and a single-crystal diamond detector with a thin 6 LiF film because they are point detectors which require many measurements. In present study, 2D distribution of the low quantity produced tritium was evaluated with a neutron imaging plate with a Gd convertor by estimating the loss of neutrons via a capture reaction by Li. Deuterium-deuterium fusion neutrons were generated using a compact fusion device at an average neutron production rate of 1.5×10 5 n/s by applying high voltages. A neutron image with "shadows" projected by thermal neutron capture reactions of 6 Li(n,) and 10 B(n,) was successfully obtained. The experimentally evaluated values were confirmed to be consistent with the total number of capture reactions calculated using a neutron transport code. The results suggest that the approach could be a facile method for two-dimensional evaluation of bred tritium.

Evaluation of 3D printed buckyball-shaped cathodes of titanium and stainless-steel for IEC fusion system

“…3 IEC has been studied intensively during the last three decades, and its current, compact design provides a smallscale neutron source for diverse applications worldwide. [4][5][6][7][8][9][10][11][12][13] The ideal configuration of an IEC device is a spherical grid cathode surrounded by a spherical anode. A potential difference of tens of kV is applied between the electrodes to establish a potential well for trapping ions and beginning discharge.…”

Evaluation of tritium production rate in a blanket mock-up using a compact fusion neutron source

“…Both the cathode and anodes were coated with Ti to increase the neutron yield [24]. The neutron yield was monitored by GE Reuter Stokes 3 He gas-filled detector, which was shielded by Pb foil (2 mm thickness) to minimize miscounts by bremsstrahlung x-rays during discharge in a high voltage condition [12]. The counter was calibrated with a spontaneous fission neutron source of 252 Cf (1.08 × 10 4 Bq with a neutron production rate of 1.25 × 10 3 n s −1 ) placed at the center of the cathode in the device for monitoring the number of source neutron (s.n.…”

“…The downward sloping peaks below 0.75 MeV were detected whether with the 6 LiF film or without (figures 7(a) and (b)). These peaks were mainly caused by the energy deposition by 12 C, originating from 12 C(n, n ) 12 C elastic scattering of fast neutrons in the diamond. The intensity of 12 C peak per unit irradiation time at position A was the highest among the five positions, which was consistent with the highest fast neutron flux at position A (figure 5).…”

“…These peaks were mainly caused by the energy deposition by 12 C, originating from 12 C(n, n ) 12 C elastic scattering of fast neutrons in the diamond. The intensity of 12 C peak per unit irradiation time at position A was the highest among the five positions, which was consistent with the highest fast neutron flux at position A (figure 5). In the PHITS calculations, contributions of neutrons, electrons, and photon were negligibly small.…”

“…The use of the compact source allows a neutron irradiation test in a flexible arrangement of source/target geometry without expensive facilities, such as fission research reactors and accelerators. As its neutron yield is significantly low compared with accelerator-based neutron sources, detectors with ultra-high sensitivity are required [11,12]. One direct method for measuring bred tritium is to count β-rays of irradiated Li 2 CO 3 diagnostic pellets using a liquid scintillation counter (LSC), which evaluates TPR with uncertainties of 4%-10% at the 1σ level [4][5][6][13][14][15].…”