Calibrating and testing tissue equivalent proportional counters with 37Ar

A method for testing and calibrating tissue equivalent proportional counters with37Ar is described.37Ar is produced by exposure of argon in its normal isotope composition to thermal neutrons. It is shown that - up to volume ratios of 0.01 of argon to the tissue equivalent gas - there is no appreciable effect of the argon admixture on the function of the proportional counter. Conventional calibration methods with characteristic x-rays or with -particles require modifications of the detectors, and they test only small sub-volumes in the counters. In contrast, argon permits calibrations and tests of the resolution that are representative for the entire counter volume and that do not require changes in detector construction. The method is equally applicable to multi-element proportional counters; it is here exemplified by its application to a long cylindrical counter of simplified design that is part of such a multi-element configuration

Comparison of effective dose and lifetime risk of cancer Incidence of CT attenuation correction acquisitions and radiopharmaceutical administration for myocardial perfusion imaging

Objective: To measure the organ dose and calculate effective dose from CT attenuation correction (CTAC) acquisitions from four commonly used gamma camera single photon emission CT/CT systems. Methods: CTAC dosimetry data was collected using thermoluminescent dosemeters on GE Healthcare's Infinia™ Hawkeye™ (GE Healthcare, Buckinghamshire, UK) four- and single-slice systems, Siemens Symbia™ T6 (Siemens Healthcare, Erlangen, Germany) and the Philips Precedence (Philips Healthcare, Amsterdam, Netherlands). Organ and effective dose from the administration of 99mTc-tetrofosmin and 99mTc-sestamibi were calculated using International Commission of Radiological Protection reports 80 and 106. Using these data, the lifetime biological risk was calculated. Results: The Siemens Symbia gave the lowest CTAC dose (1.8mSv) followed by the GE Infinia Hawkeye single- slice (1.9mSv), GE Infinia Hawkeye four-slice (2.5mSv) and Philips Precedence v. 3.0. Doses were significantly lower than the calculated doses from radiopharmaceutical administration (11 and 14mSv for 99mTc-tetrofosmin and 99mTc-sestamibi, respectively). Overall lifetime biological risks were lower, which suggests that using CTAC data posed minimal risk to the patient. Comparison of data for breast tissue demonstrated a higher risk than that from the radiopharmaceutical administration. Conclusion: CTAC doses were confirmed to be much lower than those from radiopharmaceutical administration. The localized nature of the CTAC exposure compared to the radiopharmaceutical biological distribution indicated dose and risk to the breast to be higher. Advances in knowledge: This research proved that CTAC is a comparatively low-dose acquisition. However, it has been shown that there is increased risk for breast tissue especially in the younger patients. As per legislation, justification is required and CTAC should only be used in situations that demonstrate sufficient net benefit

Plutonium from Above-Ground Nuclear Tests in Milk Teeth: Investigation of Placental Transfer in Children Born between 1951 and 1995 in Switzerland

BACKGROUND: Occupational risks, the present nuclear threat, and the potential danger associated with nuclear power have raised concerns regarding the metabolism of plutonium in pregnant women. OBJECTIVE: We measured plutonium levels in the milk teeth of children born between 1951 and 1995 to assess the potential risk that plutonium incorporated by pregnant women might pose to the radiosensitive tissues of the fetus through placenta transfer. METHODS: We used milk teeth, whose enamel is formed during pregnancy, to investigate the transfer of plutonium from the mother's blood plasma to the fetus. We measured plutonium using sensitive sector field inductively coupled plasma mass spectrometry techniques. We compared our results with those of a previous study on strontium-90 ((90)Sr) released into the atmosphere after nuclear bomb tests. RESULTS: Results show that plutonium activity peaks in the milk teeth of children born about 10 years before the highest recorded levels of plutonium fallout. By contrast, (90)Sr, which is known to cross the placenta barrier, manifests differently in milk teeth, in accordance with (90)Sr fallout deposition as a function of time. CONCLUSIONS: These findings demonstrate that plutonium found in milk teeth is caused by fallout that was inhaled around the time the milk teeth were shed and not from any accumulation during pregnancy through placenta transfer. Thus, plutonium may not represent a radiologic risk for the radiosensitive tissues of the fetus

The presence and dosimetry of radon and thoron in a historical, underground metalliferous mine

A combination of long term passive, and short term active radon-222, radon-220 and respective progeny measurements were conducted in both traverse and longitudinal axes of a historical metalliferous underground mine in North Queensland, Australia. While the passive monitor results provided average radon and thoron air concentrations over periods of 70–90 days, active measurements over a four day period provided significantly more detail into the dynamics of radon and progeny concentrations in the naturally ventilated mine environment. Passive monitor concentrations for radon and thoron ranged between 60 and 390 Bq m−3 (mean: 140 ± 55 Bq m−3) and 140 and 2600 Bq m−3 (mean: 1070 ± 510 Bq m−3) respectively, with passive thoron progeny monitors providing a mean concentration of 9 ± 5 Bq m−3EEC. Active measurement mean concentrations for radon, thoron, radon progeny and thoron progeny in the centre of the mine drive were 130 ± 90 Bq m−3, 300 ± 100 Bq m−3, 20 ± 20 Bq m−3EEC and 10 ± 10 Bq m−3EEC respectively.It was identified that thoron passive detector placement is critical in establishing reliable monitoring data, and is the reason for the discrepancy between the active and passive thoron results in this study. Site specific progeny measurements are required for the accurate estimation of dose to persons entering the mine. Based on short term active measurements and passive thoron progeny monitor results, the dose contribution from thoron and progeny in the mine was observed to contribute up to 80% of the total radon/thoron inhalation dose, and therefore should not be underestimated in monitoring programs under similar conditions

An extended dose-response model for microbial responses to ionizing radiation

© 2017 Siasou, Johnson and Willey. An understanding of the environmental toxicology of ionizing radiation (IR) is needed because nuclear power production is expanding and there is increasing pressure to build nuclear waste repositories. The effects of IR in the environment have long been investigated but there have been fewer studies involving environmental microbiology than its importance to key ecosystems services demands. Here, we highlight some unique aspects of the relationship between microbes and IR and use them to suggest an extended dose-response model. At high doses, IR causes DNA damage and oxidative stress but some microbes have a remarkable capacity for DNA repair and are tolerant of oxidative stress. Not only is significant radioresistance increasingly being reported for microbes, but some microbes are even radiotrophic. The stressful radiative environment of the early Earth might help explain the existence of these traits, which challenge the assumptions of current dose response models for IR. We suggest that a perspective that takes into account these traits plus both dose and dose rate can be used to model an "effects landscape" that might provide insights for the environmental toxicology of IR to microbes. This might help to predict the effects of IR on key ecosystem processes and also be useful in understanding the environmental toxicology of IR in general

Considerations in relation to off-site emergency procedures and response for nuclear accidents

The operation of nuclear facilities has, fortunately, not led to many accidents with off-site consequences. However, it is well-recognised that should a large release of radioactivity occur, the effects in the surrounding area and population will be significant. These effects can be mitigated by developing emergency preparedness and response plans prior to the operation of the nuclear facility that can be exercised regularly and implemented if an accident occurs. This review paper details the various stages of a nuclear accident and the corresponding aspects of an emergency preparedness plan that are relevant to these stages, both from a UK and international perspective. The paper also details how certain aspects of emergency preparedness have been affected by the accident at Fukushima Dai-ichi and as a point of comparison how emergency management plans were implemented following the accidents at Three Mile Island 2 and Chernobyl. In addition, the UK’s economic costing model for nuclear accidents COCO-2, and the UK’s Level-3 Probabilistic Safety Assessment code “PACE” are introduced. Finally, the factors that affect the economic impact of a nuclear accident, especially from a UK standpoint, are described

Primjena bioeseja i alfa-spektrometrije za neizravno praćenje španjolskih radnika izloženih obogaćenom uraniju

Workers at risk of exposure to uranium compounds should be monitored and their internal exposure quantified in terms of committed effective dose E(50) in mSv. In vitro bioassay methods can quantify uranium in urine and faeces at low activity levels. Alpha spectrometry (AS) is the most common method used for monitoring alpha-emitting radionuclides in internal dosimetry services. It provides isotopic information and low minimum detectable activity (MDA) values (≤0.50 mBq per sample). This study reports the results of a five-year monitoring of workers exposed to uranium at a Spanish Juzbado facility, which produces nuclear fuel elements enriched with up to 5 % of 235U. Monitoring included about 100 workers per year, most of whom had worked at the facility for more than 10 years before the individual monitoring programme was established. We analysed nearly 550 samples of more than 200 workers over five years. The obtained results indicate that workers were adequately protected from uranium exposure through inhalation and had an acceptably low chronic intake at the facility.Radnici koji su izloženi riziku od izloženosti spojevima s uranijem trebaju se pratiti i njihova unutrašnja izloženost mjeriti pomoću očekivane efektivne doze E(50) izražene u mSv. Uranij se može kvantificirati u mokraći čak i pri vrlo niskim razinama aktivnosti pomoću bioesejnih metoda in vitro. Najčešća metoda koja se rabi u internoj dozimetriji za praćenje/nadziranje razina radionuklida koji emitiraju alfa-čestice jest alfa-spektrometrija. Njome se identificiraju izotopi i može otkriti nisku minimalnu aktivnost (engl. minimum detectable activity, MDA) (≤0.50 mBq po uzorku). Ovdje donosimo rezultate petogodišnjega praćenja radnika izloženih uraniju u španjolskoj tvornici sastojaka za nuklearno gorivo Juzbado, u kojoj se sastojci obogaćuju izotopom 235U do udjela od 5 %. Pratilo se oko 100 radnika na godinu, a većina njih je radila u tvornici više od deset godina prije nego što je uveden program praćenja. Ukupno je u pet godina analizirano gotovo 550 uzoraka mokraće oko 200 radnika. Dobiveni rezultati upućuju na to da su radnici dobro zaštićeni od izloženosti uraniju udisanjem te da je kronični unos uranija u tvornici na prihvatljivo niskoj razini

Reducing dose for digital cranial radiography : The increased source to the image-receptor distance approach

This investigation proposes that an increased source to the image-receptor distance (SID) technique can be used to optimize occipital frontal and lateral cranial radiographs acquired with direct digital radiography. Although cranial radiography is not performed on a routine basis, it should nonetheless be optimized to keep the dose to the patient as low as reasonably achievable, particularly because it can form part of the facial bone and sinus series. Dose measurements were acquired at various SIDs, and image quality was assessed using visual grading analysis. Statistically significant reductions in the effective dose between 19.2% and 23.9% were obtained when the SID was increased from the standard 100 to 150 cm (P ≤.05), and visual grading analysis scores indicate that image quality remained diagnostically acceptable for both projections. This investigation concludes that increasing the SID effectively optimizes occipital frontal and lateral skull radiographs. Radiology departments must be advised of the benefits of this technique with the goal of introducing an updated reference SID of 150 cm into clinical practice.Peer reviewe