Estimation of gross α-β and tritium activities in groundwater samples using LSC-TDCR technique in and around the geothermal region of Eastern India

The present study is an attempt to assess the radiogenic quality of groundwater on the basis of gross α, gross β and tritium (3H or H-3) activities in the Bakreswar-Tantloi geothermal region of Chotanagpur Plateau, West Bengal and Jharkhand, India. The aforesaid parameters in groundwater samples were measured using liquid scintillation counting triple to double coincidence ratio (LSC-TDCR) technique. Groundwater samples collected from Bakreswar-Tantloi geothermal region show gross α activities from below the minimum detectable activity (BMDA) to 0.5 ± 0.05 Bq/L, gross β activities from BMDA to 0.2 ± 0.01 Bq/L and H-3 activities from BMDA to 63.42 Bq/L. The average gross α, gross β and H-3 activities are also within the permissible limits prescribed by the World Health Organization (WHO). Though the annual effective doses in some samples were higher than the reference dose level of 0.1 mSv, the overall result suggests that the groundwater in the Bakreswar-Tantloi geothermal region is radiologically safe considering the radionuclides covered in this study.

Advection-Dispersion Behavior for Simulation of H-3 and Pu-238 Transport in Undisturbed Argillaceous Shale of a Near-Surface Repository

In this study, a column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection-dispersion behavior of tritium (H-3) and plutonium-238 (Pu-238) in highly weathered argillaceous shale. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and to obtain the relevant migration parameters. The results show the following: (1) the internal structure of the highly weathered argillaceous shale exhibited heterogeneity, and the nuclide migration BTC showed characteristics of a "curve peak moving forward" and a "tail curve trailing"; (2) compared with other models, the stream tube mode could better fit the BTCs and obtain the average dispersion coefficient <D>, average distribution coefficient <K_d>, and other parameters; (3) compared to the results of the batch experiment, the distribution coefficient K_d obtained from the column experiment was smaller than that obtained from the batch experiment, which is speculated to be due to the influence of contact time and the contact area between the nuclide and the medium.

A compact, dual-zone vertical tube furnace for the determination of tritium and carbon-14 in decommissioning wastes

A compact dual zone, two work-tube, vertical tube furnace system (Raddec Pyrolyser-Mini) has been designed for the determination of H-3 and C-14 in decommissioning wastes. An optimised methodology was developed following improvements to sample holder and bubbler trap design, sample loading and loading temperature, as well as length and style of heating programmes. A significant efficiency enhancement was obtained through 'hot-loading' of the sample into the furnace at 600 °C before finally ramping to 900 °C. Direct trapping of H-3 and C-14 in a scintillation vial located in a special anti-suck-back bubbler further improved operations, leading to a reduction in analysis time and measurement sensitivity. Co-trapping of the analytes and dual-label liquid scintillation counting also proved effective. Overall, the developed methodology led to a reduced analyte extraction/trapping time of 150 min whilst achieving limits of detection of <1 Bq/g. Validation of the procedure was assessed using a range of spiked matrices relevant to nuclear site decommissioning, reference materials and operationally-exposed materials. The compact size of this thermal extraction system is such that it allows for deployment in fume cupboards, gloveboxes and a mobile laboratory.

Radionuclides in target station coolant in the China Spallation Neutron Source

The China Spallation Neutron Source (CSNS) is the first pulsed neutron source in China for multidisciplinary research. After operation with 80 kW proton beam for 4 months, 3 circuits of target station coolant, light water 1/2/3 were sampled, and radionuclides in coolants were measured. The results showed that, activity concentration of H-3 in coolant can be up to the magnitude of 1.00E+06 Bq/L, and the H-3 amount in light water 1 was the highest and the amount in light water 3 was the lowest, agreeing with the radiation field exposed by coolants. For Be-7, due to the complicated filtering and trapping process, amount of Be-7 in coolant differed from a minimum of 7.15E+01 Bq/L to a maximum of 4.58E+03 Bq/L. Comparison of the results with former measurements and simulated results were conducted. Permitted volumes for coolant discharge were presented. And the work time in the equipment room of cooling system after the beam is shut off is safe. Results in this research could provide reference data and measurement methods for similar accelerator devices.

Radiological characterisation of graphite components in Advanced Gas-cooled Reactor cores

As the Advanced Gas-cooled Reactors approach the end of generation, research and characterisation are required to support the decommissioning strategy. Radiological data for AGR graphite are negligible and the radiological inventory of the AGR core and other graphite components rely on activation modelling. This is the first study of C-14 activity and its release behaviour in AGR core graphite and its associated carbonaceous deposits and provides valuable information that can support decommissioning activities. In combination with corresponding studies on Magnox core graphite, significant understanding is attained on the main C-14 precursors in the graphite and the deposits. In addition, this study reports C-14, H-3 and gamma spectrometry data on AGR graphite fuel sleeves. This is a waste stream that is currently stored in heavily engineered stores at a significant cost. The data indicate that alternative storage and disposal options with a lower environmental and financial impact are worth considering.

Preclinical evaluation of a promising C-11 labeled PET tracer for imaging phosphodiesterase 10A in the brain of living subject

Phosphodiesterase 10A (PDE10A) plays a key role in the regulation of brain striatal signaling. A PET tracer for PDE10A may serve as a tool to evaluate PDE10A expression in vivo in central nervous system disorders with striatal pathology. Here, we further characterized the binding properties of a previously reported radioligand we developed for PDE10A, [(11)C]TZ1964B, in rodents and nonhuman primates (NHPs). The tritiated counterpart [(3)H]TZ1964B was used for in vitro binding characterizations in rat striatum homogenates and in vitro autoradiographic studies in rat brain slices. The carbon-11 labeled [(11)C]TZ1964B was utilized in the ex vivo autoradiography studies for the brain of rats and microPET imaging studies for the brain of NHPs. MicroPET scans of [(11)C]TZ1964B in NHPs were conducted at baseline, as well as with using a selective PDE10A inhibitor MP-10 for either pretreatment or displacement. The in vivo regional target occupancy (Occ) was obtained by pretreating with different doses of MP-10 (0.05-2.00 mg/kg). Both in vitro binding assays and in vitro autoradiographic studies revealed a nanomolar binding affinity of [(3)H]TZ1964B to the rat striatum. The striatal binding of [(3)H]TZ1964B and [(11)C]TZ1964B was either displaced or blocked by MP-10 in rats and NHPs. Autoradiography and microPET imaging confirmed that the specific binding of the radioligand was found in the striatum but not in the cerebellum. Blocking studies also confirmed the suitability of the cerebellum as an appropriate reference region. The binding potentials (BPND) of [(11)C]TZ1964B in the NHP striatum that were calculated using either the Logan reference model (LoganREF, 3.96 ± 0.17) or the simplified reference tissue model (SRTM, 4.64 ± 0.47), with the cerebellum as the reference region, was high and had good reproducibility. The occupancy studies indicated a MP-10 dose of 0.31 ± 0.09 mg/kg (LoganREF)/0.45 ± 0.17mg/kg (SRTM) occupies 50% striatal PDE10A binding sites. Studies in rats and NHPs demonstrated radiolabeled TZ1964B has a high binding affinity and good specificity for PDE10A, as well as favorable in vivo pharmacokinetic properties and binding profiles. Our data suggests that [(11)C]TZ1964B is a promising radioligand for in vivo imaging PDE10A in the brain of living subject.