Assessing the radiation contamination of large areas using advanced technologies.

Military, disaster management and in many cases civilian tasks include surveying of a given section of terrain that is likely to be contaminated with radioactive materials. Such a measurement series can form the basis for the complete recultivation and decontamination of large areas. This survey can take place after an emergency situation. This paper will use concrete surveys to illustrate the efficiency of new measurement technologies and developments. All these technologies aim to carry out radiation reconnaissance tasks as quickly and accurately as possible. Different hot spots were found during on-foot radiation reconnaissance. During in-situ measurements, a Bayesian-based isotope identifying algorithm was used and the measured data were validated with results from gamma spectroscopy in the laboratory. A rapid on-site quantitative analysis was also performed by evaluating the samples taken next to the hot spots. In addition to the measurement, the data were generated and stored in a standard N42 format ideal for data exchange. Many issues were solved like how the measurement data are associated with relevant additional information (e.g. time and coordinate), and how the measurement results can be shared with other partner organisations. Another important consideration was the preparation of the team conducting the measurement. The total cost of the survey was significantly reduced by the fact that the measurement was manageable by one technician and one expert. A quality assurance system had to be established to meet all relevant standards and strict documentation requirements. In addition to operating at high background radiation, these measurements presented additional challenges due to the low activity of hidden and mixed radioactive sources.

Mobility of 232Th and 210Po in red mud.

The valorization of industrial by-products such as red mud became a tempting opportunity, but the understanding of the risks involved is required for the safe utilization of these products. One of the risks involved are the elevated levels of radionuclides (in the 100-1300 Bq/kg range for both the 238U and 232 Th decay chains, but usually lower than 1000 Bq/kg, which is the recommended limit for excemption or clearance according to the EU BSS released in 2013) in red mud that can affect human health. There is no satisfactory answer for the utilization of red mud; the main current solution is still almost exclusively disposal into a landfill. For the safe utilization and deposition of red mud, it is important to be able to assess the leaching behaviour of radionuclides. Because there is no commonly accepted measurement protocol for testing the leaching of radionuclides in the EU a combined measurement protocol was made and tested based on heavy metal leaching methods. The leaching features of red mud were studied by methods compliant with the MSZ-21470-50 Hungarian standard, the CEN/TS 14429 standard and the Tessier sequential extraction method for 232Th and 210Po. The leached solutions were taken to radiochemical separation followed by spontaneous deposition for Po and electrodeposition for Th. The 332 ±â€¯33 Bq/kg 232Th content was minimally mobile, 1% became available for distilled water 1% and 6% for Lakanen-Erviö solution; the Tessier extraction showed minimal mobility in the first four steps, while more than 85% remained in the residue. The 210Po measurements had a severe disturbing effect in many cases, probably due to large amounts of iron present in the red mud, from the 310 ±â€¯12 Bq/kg by aqua regia digestion, distilled water mobilized 23%, while Lakanen-Erviö solution mobilized ∼13%. The proposed protocol is suitable for the analysis of Th and Po leaching behaviour.

Radiological survey of the covered and uncovered drilling mud depository.

In petroleum engineering, the produced drilling mud sometimes contains elevated amounts of natural radioactivity. In this study, a remediated Hungarian drilling mud depository was investigated from a radiological perspective. The depository was monitored before and after a clay layer was applied as covering. In this study, the ambient dose equivalent rate H*(10) of the depository has been measured by a Scintillator Probe (6150AD-b Dose Rate Meter). Outdoor radon concentration, radon concentration in soil gas, and in situ field radon exhalation measurements were carried out using a pulse-type ionization chamber (AlphaGUARD radon monitor). Soil gas permeability (k) measurements were carried out using the permeameter (RADON-JOK) in situ device. Geogenic radon potentials were calculated. The radionuclide content of the drilling mud and cover layer sample has been determined with an HPGe gamma-spectrometer. The gamma dose rate was estimated from the measured radionuclide concentrations and the results were compared with the measured ambient dose equivalent rate. Based on the measured results before and after covering, the ambient dose equivalent rates were 76 (67-85) nSv/h before and 86 (83-89) nSv/h after covering, radon exhalation was 9 (6-12) mBq/m2s before and 14 (5-28) mBq/m2s after covering, the outdoor radon concentrations were 11 (9-16) before and 13 (10-22) Bq/m3after covering and the soil gas radon concentrations were 6 (3-8) before and 24 (14-40) kBq/m3 after covering. Soil gas permeability measurements were 1E-11 (7E-12-1E-11) and 1E-12 (5E-13-1E-12) m2 and the calculated geogenic radon potential values were 6 (3-8) and 12 (6-21) before and after the covering. The main radionuclide concentrations of the drilling mud were CU-238 12 (10-15) Bq/kg, CRa-226 31 (18-40) Bq/kg, CTh-232 35 (33-39) Bq/kg and CK-40 502 (356-673) Bq/kg. The same radionuclide concentrations in the clay were CU-238 31 (29-34) Bq/kg, CRa-226 45 (40-51) Bq/kg, CTh-232 58 (55-60) Bq/kg and CK-40 651 (620-671) Bq/kg. According to our results, the drilling mud depository exhibits no radiological risk from any radiological aspects (radon, radon exhalation, gamma dose, etc.); therefore, long term monitoring activity is not necessary from the radiological point of view.

Study of a remediated coal ash depository from a radiological perspective.

Coal-fired power plants play a significant role in the production of electricity. The Ra-226 concentration of coals mined in the Ajka region can reach up to 3000 Bq/kg. This study focuses on the effects of a Hungarian (Ajka) remediated coal ash depository on the environment and the effectiveness of the cover layer. During the remediation, a method patented in Hungary was used, in which the upper layer of the depository, which had settled like concrete, was ploughed and mixed with woodchips before being planted with vegetation. The gamma dose rate H*(10) of the depository and its vicinity was measured using Automess 6150AD-b at 32 points, surface Rn-222 exhalation at 19 points and air radon concentration at 34 points; at 32 points, soil gas radon content was measured with AlphaGUARD and soil permeability with RADON-JOK. The nuclide content of nine samples was determined using an HPGe gamma spectrometer and their Rn-222 exhalation rates were measured using the AlphaGUARD. H*(10) was 290 (130-525) nSv/h at the covered depository; CRa-226 was 1997 Bq/kg, 960 Bq/kg and 104 Bq/kg for the ash, cover layer and background soil respectively. CRn-222 in the soil was 25-161 kBq/m3, and soil gas permeability K was between 6.4E-13 and 1.80E-11 m2. The radon exhalation of the uncovered and covered depository was 259-1100 mBq/m2s. The exhalation and emanation coefficients of the samples were 0.05-0.32 mBq/kgs and 8-22%. The effects of vegetation on the migration of radon were also examined. The results show that the Ajka coal ash depository involves higher radiological risk than that reported by previously published studies on depositories. The applied cover layer halved the field radon exhalation; in addition, the vegetation reduced the convective airflow and, with this, the migration of Rn.