Accelerator-based Boron Neutron Capture Research Articles

Accelerator-based neutron source for boron neutron capture therapy

A beam shaping assembly (BSA), a neutron moderator system, is a key component of an accelerator based boron neutron capture therapy (BNCT) facility. The neutron energy recommended in the IAEA TECDOC-1223 for the BNCT is much lower than the energy of the neutrons produced by accelerator induced nuclear reactions. The neutron energy depends on the energy of the incident particle and nuclear reaction. Therefore, the BSA should be designed considering the neutron energy dependency. Now, several kinds of accelerators and reactions are used and proposed. Here, neutron producing reaction, moderator system, and activations are introduced.

Radiation safety analysis for the A-BNCT facility in Korea

A Proton Accelerator based Boron Neutron Capture Therapy (A-BNCT) facility is under development in Korea. Neutron beams for treatment are produced from a beryllium (Be) target and an 8 mA, 10 MeV proton beam. The purpose of the research is a radiation shielding analysis and an activation analysis for the facility design satisfying the radiation safety requirements as well as obtaining an operating license for the radiation facility according to a domestic nuclear commissioning procedure. The radiation shielding analysis was performed using the MCNPX computational particle transport code. The radiation source terms in the facility were evaluated and utilized in the shielding calculations. The minimum concrete thickness satisfying the designated dose rate of 5 μSv/h for the worker's area and 0.25 μSv/h for the public area were estimated and applied to the design. For an assessment of the radiation safety inside the facility, the dose rates were evaluated at several positions, such as behind the shielding door, around the primary barriers near the radiation sources, and in the penetrations of the ducts. The dose rate distribution was mapped for verification of the radiation safety for the entire facility. An activation analysis was carried out for the concrete walls, air, target assembly, beryllium target, and cooling water using FISPACT-2010 code. Concentrations of the activation products and dose rate induced by the radionuclides after shutdown were evaluated for the purpose of safe operation of the facility. The results were reviewed with the radiation safety regulations in Korea. As a result, it was proved that the final facility design satisfies the safety requirements.

Characterization and modeling of a MoTaVWZr high entropy alloy

As part of a project for developing Accelerator–Based Boron Neutron Capture Therapy (AB-BNCT), for which the generation of neutrons through nuclear reactions like 9Be(d,n) is necessary, a new material that preserves its physical and mechanical properties for a sufficient length of time under irradiation conditions and hydrogen damage is needed. In this work, a high entropy MoTaVWZr alloy (HEA) is considered for this task, because each one of the constituents is already good by itself under extreme irradiation condition. The structure, microstructure, density, Vickers hardness and melting temperature are reported for this HEA. Atomistic modeling results are in agreement with the experimental findings.

Demonstration of a high-intensity neutron source based on a liquid-lithium target for Accelerator based Boron Neutron Capture Therapy

A free surface liquid-lithium jet target is operating routinely at Soreq Applied Research Accelerator Facility (SARAF), bombarded with a ~1.91MeV, ~1.2mA continuous-wave narrow proton beam. The experiments demonstrate the liquid lithium target (LiLiT) capability to constitute an intense source of epithermal neutrons, for Accelerator based Boron Neutron Capture Therapy (BNCT). The target dissipates extremely high ion beam power densities (>3kW/cm2, >0.5MW/cm3) for long periods of time, while maintaining stable conditions and localized residual activity. LiLiT generates ~3×1010n/s, which is more than one order of magnitude larger than conventional 7Li(p,n)-based near threshold neutron sources. A shield and moderator assembly for BNCT, with LiLiT irradiated with protons at 1.91MeV, was designed based on Monte Carlo (MCNP) simulations of BNCT-doses produced in a phantom. According to these simulations it was found that a ~15mA near threshold proton current will apply the therapeutic doses in ~1h treatment duration. According to our present results, such high current beams can be dissipated in a liquid-lithium target, hence the target design is readily applicable for accelerator-based BNCT.

Development of a higher power cooling system for lithium targets

The accelerator based Boron Neutron Capture Therapy beam at the University of Birmingham is based around a solid thick lithium target cooled by heavy water. Significant upgrades to Birmingham's Dynamitron accelerator are planned prior to commencing a clinical trial. These upgrades will result in an increase in maximum achievable beam current to at least 3mA. Various upgrades to the target cooling system to cope with this increased power have been investigated. Tests of a phase change coolant known as “binary ice” have been carried out using an induction heater to provide a comparable power input to the Dynamitron beam. The experimental data shows no improvement over chilled water in the submerged jet system, with both systems exhibiting the same heat input to target temperature relation for a given flow rate. The relationship between the cooling circuit pumping rate and the target temperature in the submerged jet system has also been tested.