Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA

Study on novel neutron irradiation without beam shaping assembly in Boron Neutron Capture Therapy

Boron Neutron Capture Therapy (BNCT) is performed using high-intensity neutron sources; however, the energy of the primary neutrons is too high for direct patient irradiation. Thus, neutron moderation is mandatory and is performed using a device known as a Beam Shaping Assembly (BSA). Due to the differences in flux and energy spectra between neutron sources, each facility needs a dedicated BSA design, whether it is based on a nuclear reactor or, more recently, on an accelerator. Since moderation involves the loss of neutrons, typically by a factor of 1000, it is necessary to generate a very high flux before neutrons pass through the BSA. We propose a novel approach that eliminates the necessity of a BSA, BSA-free, by generating neutrons suitable in flux and energy for direct patient irradiation through the [Formula: see text]Sc(p,n)[Formula: see text]Ti reaction using near-threshold protons. Our findings demonstrate that all IAEA quality factors for BNCT can be met with existing proton accelerators. Additionally, figures of merit studied provide similar results compared to real BNCT facilities. This breakthrough opens up new avenues in BNCT, among others, the control of the neutron penetration within the human body by small changing in the proton energy. Also, it is expected simplified accelerator-based facilities in terms of manufacturing and maintenance and operation. This work is a study based on experimental data and Monte Carlo simulations. Technical challenges and safety are addressed in Discussion section. This novel proposal is under evaluation as patent.

Preparation and quality control of a new porphyrin complex labeled with 45Ti for PET imaging

This study aims to produce and quality control of a new porphyrin complex labeled with ⁴⁵Ti for PET imaging, so at the first step, the cross-section of ⁴⁵Sc(p,n)⁴⁵Ti was investigated by TALYS-1.6 and the optimal target thickness and theoretical yield were calculated by SRIM code. The purified ⁴⁵Ti was labeled with the anticancer agent of tetrakis (pentafluorophenyl) porphyrin (TFPP). The radiochemical purity and the percentage of labeling were evaluated by radiation layer chromatography then the division coefficient of [⁴⁵Ti]-TFPP was calculated. The dual coincidence imaging system was used for imaging 1 and 2 h after injection [⁴⁵Ti]-TFPP to rats. Immediately after imaging, the mean percent injected dose per gram and specific activity of different tissues including blood, heart, lungs, stomach, liver, bone, kidney, spleen, intestine, muscle, feces, and skin were measured. The yield of ⁴⁵Ti production was measured 468 MBq/μAh and the labeling rate was observed more than 98%. The highest activity was observed in the liver (%ID/g = 2.27%, 1 h) and spleen (2.2%, 1 h), respectively, because of the high lipophilic of ⁴⁵Ti-TFPP. SPECT images showed a significant uptake of radiopharmaceuticals in the abdomen. The labeling rate of ⁴⁵Ti-TFPP was high and this compound has the potential for clinical application in different ways than PSMA, it can be joined with photodynamic therapy (Severin et al., 2015).

DEVELOPMENT OF A HIGH-EFFICIENCY PROTON RECOIL TELESCOPE FOR D-T NEUTRON FLUENCE MEASUREMENT

A high-efficiency proton recoil telescope was developed to determine neutron fluences in neutron fields using the 3H(d,n)4He reaction. A 2-mm thick plastic scintillation detector was employed as a radiator to increase the detection efficiency and compensate for the energy loss of the recoil proton within. Two silicon detectors were employed as the ΔE and E detectors. The distance between the radiator and the E detector was varied between 50 and 150 mm. The telescope had detection efficiencies of 3.5 × 10-3 and 7.1 × 10-4 cm2 for distances of 50 and 100 mm, respectively, which were high enough to determine the neutron fluence in 14.8-MeV neutron fields, with a few thousand cm-2 s-1 fluence rate, within a few hours.

Development of portable long counter with two different moderator materials

A portable, light-weight long counter (LC) with small dimensions was developed. This LC consists of a (3)He thermal neutron counter, a cylindrical moderator and outer shields. It was designed to have an almost flat response in a neutron energy range of 0.4 eV to 5 MeV. The portable LC has a radius of 11 cm and a length of 39 cm. Its weight was successfully reduced to 15 kg. Polystyrene was employed instead of polyethylene for the front part of the moderator in order to increase the sensitivity to low-energy neutrons. The response function calculated using the MCNP code was consistent with the results of experiments using monoenergetic neutron calibration fields.

Photon dose mixed in monoenergetic neutron calibration fields using 7Li(p,n)7Be reaction

The ambient dose equivalents H*(10) of photons mixed in the 144, 250 and 565 keV monoenergetic neutron fields were evaluated using measurements from an NaI(Tl) detector and calculations done using the MCNP-ANT code. It was found that H*(10) of the photons produced in the target assembly dominates the dose, particularly near the target. The H*(10) of the photons produced in other materials in the field increases with the increase in distance from the target and could not be neglected at a large distance from the target. The ratios of the H*(10) of the mixed photons to that of the monoenergetic neutrons for 144, 250 and 565 keV neutron fields, were evaluated to be below 5.5, 6.9 and 1.5 %, respectively. The ratios were calculated at calibration points between 100 and 500 cm from the target.

Response function of a superheated drop neutron monitor with lead shell in the thermal to 400-MeV energy range

Superheated drop detectors are currently used for personal and environmental dosimetry and their characteristics such as response to neutrons and temperature dependency are well known. A new bubble counter based on the superheated drop technology has been developed by Framework Scientific. However, the response of this detector with the lead shell is not clear especially above several tens of MeV. In this study, the response has been measured with quasi-monoenergetic and monoenergetic neutron sources with and without a lead shell. The experimental results were compared with the results of the Monte Carlo calculations using the 'Event Generator Mode' in the PHITS code with the JENDL-HE/2007 data library to clarify the response of this detector with a lead shell in the entire energy range.