Etsuko Furuta

USEFULNESS OF FLOATING RADIOLUMINOGRAPHY TO TRITIATED SAMPLES

Abstract A new technique of radioluminography for 3 H is shown, where by a spacer is inserted between the imaging plate and the radioactive sample in order to avoid radioactive contamination of the plate for repeated use. Also, elevation of the detection efficiency has been realized by improvement in the evacuation to minimize the absorption of 3 H β-rays. The technique has been studied systematically for space distance (1 spacer thickness) and for air pressure. By evacuation, the detection sensitivity can be elevated to more than 15 times. This technique is highly suitable for microplate and filter samples.

Comparisons between radioactive and non-radioactive gas lantern mantles

Gas lantern mantles containing radioactive thorium have been used for more than 100 years. Although thorium was once believed to be indispensable for giving a bright light, non-radioactive mantles are now available. From the radioactivities of the daughter nuclides, we estimated the levels of radioactivity of 232Th and 228Th in 11 mantles. The mantles contained various levels of radioactivity from background levels to 1410 +/- 140 Bq. Our finding that radioactive and non-radioactive mantles are equally bright suggests that there is no advantage in using radioactive mantles. A remaining problem is that gas lantern mantles are sold without any information about radioactivity.

A new tritiated water measurement method with plastic scintillator pellets

ABSTRACT A new tritiated water measurement method with plastic scintillator pellets (PS-pellets) by using a conventional liquid scintillation counter was developed. The PS-pellets used were 3 mm in both diameter and length. A low potassium glass vial was filled full with the pellets, and tritiated water was applied to the vial from 5 to 100 μl. Then, the sample solution was scattered in the interstices of the pellets in a vial. This method needs no liquid scintillator, so no liquid organic waste fluid is generated. The counting efficiency with the pellets was approximately 48 % when a 5 μl solution was used, which was higher than that of conventional measurement using liquid scintillator. The relationship between count rate and activity showed good linearity. The pellets were able to be used repeatedly, so few solid wastes are generated with this method. The PS-pellets are useful for tritiated water measurement; however, it is necessary to develop a new device which can be applied to a larger volume and measure low level concentration like an environmental application.

A plastic scintillation counter prototype

A new prototype device for beta-ray measurement, a plastic scintillation counter, was assembled as an alternative device to liquid scintillation counters. This device uses plastic scintillation sheets (PS sheets) as a sample applicator without the use of a liquid scintillator. The performance was evaluated using tritium labeled compounds, and good linearity was observed between the activity and net count rate. The calculated detection limit of the device was 0.01 Bq mL(-1) after 10 h measurement for 2 mL sample.

Measurement of tritium with high efficiency by using liquid scintillation counter with plastic scintillator.

The detection efficiencies of tritium samples by using liquid scintillation counter with hydrophilic plastic scintillator (PS) was approximately 48% when the sample of 20 μL was held between 2 PS sheets treated by plasma. The activity and count rates showed a good relationship between 400 Bq to 410 KBq mL(-1). The calculated detection limit of 2 min measurement by the PS was 13 Bq mL(-1) when a confidence was 95%. The plasma method for PS produces no radioactive waste.

NORM as consumer products: issue of their being

The objects of this study are only radioactive consumer products added NORM (NRCP). In Japanese current markets, many NRCP are sold claiming some effects like hormesis. The existence of NRCP in the living environments here may raise the radiation exposure dose of the user. The activity concentrations in many kinds of NRCP have been determined by gamma-ray spectrometry and the radiation exposure doses from NRCP were calculated in the case of normal use and misuse. The results show that there are some inhalation risks in the cases of NRCP misuse. Furthermore, many kinds of NRCP and ores were analysed by prompt gamma-ray activation analysis method and the results show the added radioactive materials in NRCP are monazite. The three principles of the radioprotection should be applied for users of NRCP. The Japanese NORM guideline of 2009 mentions requirements for optimisation (ALARA) and dose criteria, without justification. Justification is most important for an effective use of radioactive ores that are added in NRCP.

Measurement of tritium with plastic scintillator surface improvement with plasma treatment

Abstract Tritium is usually measured by using a liquid scintillation counter. However, liquid scintillator used for measurement will be radioactive waste fluid. To solve this issue, we have developed the method of measuring tritium samples with plasma-treated plastic scintillator sheets instead of liquid scintillator (Plasma method). With the Plasma method of 2-min plasma treatment, we had obtained measurement efficiency of 48 ± 2 % for 2 min measurement of tritium except for tritiated water. On the other hand, it needed almost 6 hours to obtain constant measurement efficiency. We tried putting silica gel beads into vials to remove H2O molecules from PS sheet surface quickly. The silica gel beads worked well and we got constant measurement efficiency within 1-3 hours. Also, we tried using other kinds of PS treated with plasma to obtain higher measurement efficiencies of tritium samples.

A new wiping device for detecting removable contamination.

AbstractA new wiping device for detecting removable contamination was developed. A cylindrical plastic scintillator (PS) is applied to a roller device. A wiping material wraps around the cylindrical PS roller, and then the roller is used for wiping to detect removable contamination (PS method). After contamination on the floor is wiped off using the roller, the wrapped PS is removed from the roller and placed in a glass vial for use in a liquid scintillation counter (LSC). The vial is measured by LSC without liquid scintillation cocktail. When the PS method was used by wrapping with NUC-Wipe™, the wiping efficiencies, except for the measurement efficiencies, were almost 15% for 3H and 40% for 14C. Also a repositionable tape (Double Stick Tape™) could be used for wiping material. The device has three main advantages: 1) Though the wiping efficiency is not very high when using the PS method, the variability observed is lower than that for hand wiping; 2) even when it is contaminated with nuclides whose maximum beta ray energies (Emax) are very close, for example 14C (Emax; 156 keV) and 35S (Emax; 167 keV), the contaminated radioisotopes are identified with their spectra by using PS; and 3) the PS method is environmentally friendly, as post-processing time is vastly shortened because it does not use a liquid scintillator. Some issues that were previously considered unavoidable in the wiping method were improved using a plastic scintillator as a roller.

Monitoring of 3H surface contamination by noncontact radioluminography.

A phosphor screen imaging technique has been developed to detect 3H contamination on floor surfaces. A 3H imaging plate is elevated a maximum of 0.1 cm above the surface being monitored. This technique prevents the imaging plate from being cross-contaminated. Unlike the traditional smear test, this technique can be used to monitor fixed contamination.

Measurement of tritium with plastic scintillators in large vials of a low background liquid scintillation counter: an organic waste-less method

The tritium compounds, tritiated water as a volatile compound and 3H-methionine as a non-volatile compound, were measured with two types of plastic scintillators (PSs) using a low background liquid scintillation counter (LSC). It is advantage that minimal organic waste is generated when a plastic scintillator is used for LSC measurement. The effect of large vials on counting efficiency, plasma effects with three types of plasma devices for PS-sheets, the effect of UV-light on PS-pellets, the relationship between the activity and the count rate, and the detection limits of tritium were studied with respect to the development of large-scale measurement systems.