The International journal of applied radiation and isotopes最新文献

Nuclear techniques have been used to determine the solids weight fraction (W) and ash content of (fine) coal in slurries independent of voidage. The basis of the techniques is the correlation between W and the hydrogen concentration (w/w) of the slurry. At constant ash content, W is determined by combining neutron moderation and γ-ray transmission (density) measurements. With varying ash content, both W and ash content of coal are determined by combining the above measurements with either of two well-established techniques for the determination of ash content of dry coal, namely x-ray backscatter compensated by iron K x-ray excitation, and low energy γ-ray transmission.

Radioisotope source and detector were incorporated into three probes which were immersed directly into coal slurry in a 200 L drum. Measurements were made on coal slurries with W in the range 5–22 wt%. ash in coal 20.7–30 wt%, and voidage 0–4 vol.%. The r.m.s. difference between W determined by probe measurements and W obtained from assay of slurry samples was 0.54 wt%, a factor of five better than that obtained from the γ-ray transmission (density) measurement alone. The r.m.s. difference for ash content, based on the x-ray backscatter method combined with neutron and γ-ray (density) count rates, was 0.78 wt% ash.

The first part of this paper is concerned with the reusability of CaF₂:Tm (TLD-300) ribbon without thermal treatment between read-out and irradiation. It has been checked up to a dose level of about 200 mGy and the results show that it is possible to reuse this material without annealing in the used dose range. In the second part of the paper a fractional method of TL readings is outlined. The peak separation is checked at different linear testing rates and with different reading times for each peak. The separation technique is then checked in a dose accumulation experiment.

A system for control of radiochemical processes has been designed and constructed. Control passes through a single 8-bit port (6522 VIA) to up to 64 on-off sensors and 64 on-off switches. The outputs are latched; they are switched one at a time.

Oxygen-15 labeled 1-butanol and 2-butanol were prepared by the reaction of O₂−¹⁵O with tri-n-butylborane and tri-sec-butylborane in tetrahydrofuran. The reaction products were isolated and identified via reversed-phase high performance column chromatography and gas chromatography. Radiochemical yields of 50% (EOB) were obtained. The use of ¹⁵O-labeled butanol is suggested for cerebral blood flow measurements in conjunction with PET.

The general purpose Monte Carlo code MORSE and nuclear data derived from ENDF/B-IV are used to model an iron ore analyser which detects thermal neutron capture γ rays from ⁵⁶Fe. Measurements on an actual system have been simulated. Calculated detector count rates agree, after normalisation, with measured values to within the accuracy of the calculations (∼5% at 1σ). Practical use of the model is dependent upon improving the efficiency of the calculations.

The use of dual energy γ-ray transmission techniques to determine the concentration of a higher atomic number (Z) component in a lower Z matrix is investigated. Examples discussed are the determination of lead in lead-zinc ore, iron in high-grade iron ore, uranium in solution, and ash in coal. These examples are considered in relation to the main application fields of on-stream analysis of mineral slurries and solutions, on-line analysis on conveyors, and scanning of borecores.

A method for reducing errors in analysis by compensating for variations in concentration of some of the wanted or matrix components is proposed. This method depends on choice of one γ-ray energy in the photoelectric absorption region and the other in the pair production region. Calculations show that this method reduces errors in the determination of ash in coal caused by variation in concentration of iron in the ash. However, sensitivity to ash is poor, so this application is suitable only when γ-ray path lengths in the coal are large.

Preliminary results are presented of the combination of dual energy γ-ray transmission and pair production techniques to give an estimate of iron concentration in coal. This can be used to give an approximate estimate of sulphur in pyrites in coal, assuming that iron is present only as pyrites.

A diagrammatic lay-out of the facility for the on-line radioiodine (¹²³Xe) by CsCl irradiation on the LNP JINR synchrocyclotron is presented. The problems in designing the target, collection systems and radioxenon transport are considered. The described experimental arrangement is a model for future ¹²³I production on the “F”-facility (JINR high-current accelerator).

In order to have a methylmercury compound of much higher specific activity than was obtainable from commercial suppliers of the compound, a procedure for the methylation of radioactive mercuric chloride with no addition of non-radioactive mercury has been developed. Methylation is accomplished by reacting the mercuric chloride with tetramethyl tin. Extractions into and out of benzene twice produces a methylmercury compound which is finally dissolved in a dilute sodium carbonate solution suitable for biological experiments. The entire procedure to produce a batch of the compound may be accomplished within a single day.

A comparison of the calculated absolute full-energy peak efficiencies of CdTe and NaI detectors, i.e. the ratio of the number of counts under the full-energy peak (FEP) to the number of photons at the same energy emitted by the source, is made for six different detectors and three source sizes. The CdTe and NaI detectors are assumed to be of equal volume. The calculations are performed in the photon energy region 15-2000 keV using water, muscle and blood as source media.

Absolute full-energy peak efficiencies, i.e. the ratio of the number of counts under the full-energy peak (FEP) to the number of photons at the same energy emitted by the source, are calculated for three true coaxial Ge(Li) detectors of differing size in the photon energy region 0.1–3.0 MeV. The detector volumes are 28.9, 82.1 and 144.9 cm³. Three different source-to-detector geometries are considered, namely a point source, a needle-shaped source and an extended volume source. The attenuation effects in the sources, the aluminium windows of the detectors and the p-cores of the detectors are taken into account. Three different media are considered in the extended sources.