Plutonium in the coastal seawater around Chinese nuclear power plants: Sources, distribution, and environmental implications.

Coastal surface seawater samples within 30 km around ten Chinese nuclear power plants (NPPs) were systematically investigated. The 239+240Pu activity concentration in the samples varied from 0.226 mBq/m3 to 3.098 mBq/m3, meanwhile the 240Pu/239Pu atom ratios ranged from 0.151 to 0.353. Besides, the Pacific Proving Ground (PPG) close-in fallout and the global fallout were recognized as two primary sources of Pu in these samples. The 239+240Pu activity concentration as well as the PPG contribution showed similar trends as the Kuroshio intrusion path and the coastal currents in the China Seas, illustrating long-range transport and consuming of PPG derived Pu in the coastal China Seas. Moreover, accumulation of PPG sourced Pu in the Beibu Gulf were observed and was attributed to the continuous invasion of the high isotopic Pu that remobilized from the South China Sea (SCS).

New-designed measurement device for radon and thoron activity concentration based on gas direct detection.

A new-designed measurement device for radon and thoron activity concentration is developed based on gas direct measurement to support their in-situ calibration. It consists of a 2000 mm2 Passivated Implanted Planar Silicon (PIPS) detector, a Multi-Channel Analyzer (MCA), a Micro Controller Unit (MCU), and a small electrostatic chamber with a volume of nearly 23 ml. The device records those alpha particles emitted from radon and thoron gas, and the detection efficiency and the crosstalk factor of 218Po/216Po are determined by Monte Carlo simulation. Measurement results have been compared with AlphaGUARD DF2000 in pure radon and thoron environments, respectively. Results show that the measurement results of the devices and the reference monitor agree well with each other, with an average relative deviation of 0.48% for radon gas from about 3300 Bq/m3 to 38 kBq/m3 and -3.25% for thoron gas from about 25 kBq/m3 to 70 kBq/m3. Uncertainty assessment has also been done, and a relative system uncertainty of radon is about 6.8%, while that of thoron is nearly 7.3%.

First study of 237Np in Chinese soils: Source, distribution and mobility in comparison with plutonium isotopes.

In this study, the distribution and migration of 237Np and 239+240Pu in soils in the vicinity (<5 km) of Qinshan and Tianwan Nuclear Power Plants in China were studied, which is the first specific study of global fallout 237Np in Chinese soils. The 237Np and 239+240Pu concentrations in surface soils showed large spatial inhomogeneity. A remarkable 239+240Pu concentration (4.783 mBq/g) was observed in a surface soil near Qinshan NPP and stands for the ever reported highest value in the Chinese soils. The inventories of 239+240Pu in two Qinshan and Tianwan soil cores were estimated to be 128.8 Bq/m2 and 121.0 Bq/m2, respectively; while the 237Np inventories were 0.039 Bq/m2 and 0.035 Bq/m2 at these sites, respectively. The 240Pu/239Pu atomic ratios in these soils indicated that the global fallout is the main source of Pu in these regions. However, the non-isotopic 237Np/239Pu atomic ratio in environmental soil is not a sensitive indicator for source identification. Furthermore, we conducted pilot study on the migration behaviors of 237Np and 239+240Pu in soil core at Qinshan site with the Convection-Dispersion Equation (CDE) model. The obtained apparent dispersion coefficients of 237Np (2.82 ± 2.06 cm2/y) was 5 times higher than that of 239+240Pu (0.57 ± 0.16 cm2/y), proving that 237Np has stronger migration ability than Pu isotopes in the Qinshan soil. Finally, we predicted that with the increase of migration time, both 237Np and 239+240Pu concentration in the soil will gradually become more evenly distributed among different soil layers due to the dominant dispersion effects.

The transfer of fallout plutonium from paddy soil to rice: A field study in Japan.

Reported transfer factor (TF) values of Pu from paddy soil to rice are rather scarce, despite the radiotoxicity of Pu and the irreplaceable role of rice in Asian peoples' diets. Here, we conducted a field study to investigate the transfer of global fallout Pu from paddy soil to rice grain (hulled rice) in Japan. The 240Pu/239Pu atomic ratios in two rice grain samples out of 16 samples were determined and the ratios corresponded well with the global fallout value. The soil-to-rice TFPu in 12 Japanese prefectures ranged from 4.5 × 10-6 to 1.2 × 10-4 with a geometric mean of 3.3 × 10-5. The TFs of rice obtained in this study were compatible to the TFs for the broad heading "cereals" compiled in the IAEA Technical Report Series No. 472. Weak correlations were found between the TF and the investigated soil characteristics such as soil pH and loss on ignition. Regarding the TFs for cerium (Ce) and thorium (Th) which are commonly considered as Pu analogues, we observed no significant correlations between the log(TFPu) and log(TFCe) or log(TFPu) and log(TFTh). On the other hand, interestingly, a significantly positive correlation (r = 0.795, p < 0.001) was observed between log(TFPu) and log(TFU). In view of the observed similarity of TF values for U and Pu from soil to rice, we thought that using the easy-to-measure TFU to estimate TFPu from soil to rice might be suggested although the mechanism was unclear.

Rapid determination of ultra-trace plutonium isotopes (239Pu, 240Pu and 241Pu) in small-volume human urine bioassay using sector-field inductively coupled plasma mass spectrometry.

A rapid method with enhanced 238U decontamination was developed for ultra-trace Pu analysis in small-volume urine bioassays. This method consists of acid digestion, co-precipitation, extraction chromatography and sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) measurement. Parameters that may influence the analytical performance were studied systematically. This method achieved a high 238U decontamination factor (3.8 × 106) and the 242Pu recovery was stable for 20 mL and 100 mL urine bioassays with an average value of 72.7 ±â€¯5.5%. The limits of detection for 239Pu, 240Pu and 241Pu by the method were 0.016 fg mL-1, 0.016 fg mL-1 and 0.019 fg mL-1 for 20 mL urine samples and 0.003 fg mL-1, 0.002 fg mL-1 and 0.003 fg mL-1 for 100 mL urine samples, respectively. Considering the small volume of urine employed in this study, the absolute detection limits of the method were comparable or even better than those measured with thermal ionization mass spectrometry and accelerator mass spectrometry. All procedures for 20 mL and 100 mL urine bioassays were completed in 9.5 h and 11 h, respectively, and analysis of 10 samples could be finished within one day. With the considerably low detection limits of Pu isotopes and high sample throughput, this method would be a promising tool for the quick response to radiological emergencies and for rapid screening of unexpected occupational exposures of workers involved in the future FDNPP reactor decommissioning operations.

The experimental study on the emanation power of a flow-through thoron source made from incandescent gas mantles.

To improve the quality of the calibration of thoron concentration activity measurement, an experimental study on the emanation power of a flow-through thoron source based on incandescent gas mantles was carried out in this paper. The thoron activity concentrations of the outflowed air from the flow-through source were measured using RAD7, and the quantitative relationship between thoron concentrations and flowrates was studied through theoretical analysis, and the thoron emanation powers were obtained from the fitting of the relationship above. Results show that the thoron concentration decreased with the increasing flowrate in the gas path, and the thoron emanation powers of three batches of gas mantles obtained by fitting were 1.33% ± 0.17%, 0.77% ± 0.10% and 0.57% ± 0.07% respectively in low humidity condition. Those results were checked using the gamma spectroscopy method, and were consistent within the error range.

Ultra-trace plutonium determination in small volume seawater by sector field inductively coupled plasma mass spectrometry with application to Fukushima seawater samples.

Long-term monitoring of Pu isotopes in seawater is required for assessing Pu contamination in the marine environment from the Fukushima Dai-ichi Nuclear Power Plant accident. In this study, we established an accurate and precise analytical method based on anion-exchange chromatography and SF-ICP-MS. This method was able to determine Pu isotopes in seawater samples with small volumes (20-60L). The U decontamination factor was 3×10(7)-1×10(8), which provided sufficient removal of interfering U from the seawater samples. The estimated limits of detection for (239)Pu and (240)Pu were 0.11fgmL(-1) and 0.08fgmL(-1), respectively, which corresponded to 0.01mBqm(-3) for (239)Pu and 0.03mBqm(-3) for (240)Pu when a 20L volume of seawater was measured. We achieved good precision (2.9%) and accuracy (0.8%) for measurement of the (240)Pu/(239)Pu atom ratio in the standard Pu solution with a (239)Pu concentration of 11fgmL(-1) and (240)Pu concentration of 2.7fgmL(-1). Seawater reference materials were used for the method validation and both the (239+240)Pu activities and (240)Pu/(239)Pu atom ratios agreed well with the expected values. Surface and bottom seawater samples collected off Fukushima in the western North Pacific since March 2011 were analyzed. Our results suggested that there was no significant variation of the Pu distribution in seawater in the investigated areas compared to the distribution before the accident.

Hsp90 interacts with AMPK and mediates acetyl-CoA carboxylase phosphorylation.

Heat shock protein 90 (Hsp90) serves to stabilise and correctly fold multiple significant client proteins associated with cell proliferation and cell survival. However, little is known about the Hsp90 client proteins that regulate cell metabolism. Here, we describe a unique ability of Hsp90 to regulate the stability and activity of AMP-activated kinase (AMPK), a key sensor of cellular energy status. Hsp90 is found to interact with AMPK and to maintain its AMP-activated kinase activity, which in turn is required for the phosphorylation of its substrate, acetyl-CoA carboxylase (ACC), the key enzyme in fatty acid metabolism. Our binding analysis reveals that both the γ subunit and the α subunit of AMPK bind to Hsp90 with a high affinity. We demonstrate that Hsp90 inhibitors, including geldanamycin (GA) and mycoepoxydiene (MED), can induce the dissociation of AMPK from Hsp90, and cause a significant decrease in phosphorylation of AMPK and ACC. Furthermore, we demonstrate that shRNAs of Hsp90 can efficiently suppress the activation of AMPK. These findings not only establish a novel interaction between Hsp90 and AMPK but also suggest a new mechanism for regulating tumour cell fatty acid metabolism.

Gambogic acid inhibits Hsp90 and deregulates TNF-α/NF-κB in HeLa cells.

Gambogic acid (GB) is an important anti-cancer drug candidate, but the target protein by which it exerts its anti-cancer effects has not been identified. This study is the first to show that GB inhibits heat shock protein 90 (Hsp90) and down-regulates TNF-α/NF-κB in HeLa cells. The effects of GB on Hsp90 were studied by characterizing its physical interactions with Hsp90 upon binding, the noncompetitive inhibition of Hsp90 ATPase activity, and the degradation of Hsp90 client proteins (i.e., Akt, IKK) in HeLa cells. GB seems to bind to the N-terminal ATP-binding domain of Hsp90. Additionally, GB suppresses the activation of TNF-α/NF-κB and decreases XIAP expression levels and the ratio of Bcl-2/Bax, which in turn induces HeLa cell apoptosis. Thus, GB represents a promising therapeutic agent for cancer; it may also be useful as a probe to increase understanding of the biological functions of Hsp90.

Measurement of thoron gas in the environment using a Lucas scintillation cell.

A simple and fast method for measuring the concentration of (220)Rn in the environment was developed based on the AB-5 portable radon measuring device. First, background counts were measured with a Lucas scintillation cell (LSC), then air sampling measurement was started immediately and lasted for 1 min; the (220)Rn concentration could be calculated from the counts before and after sampling as well as the theoretical detection efficiency. Results of theoretical calculations showed that in a pure (220)Rn environment the lower detection limit of the LSC would be some 65  Bq m(-3) (with a confidence level of 70%). The experimental results showed that compared with a RAD7 monitor in pure (220)Rn or mixed (222)Rn/(220)Rn environments the deviations were less than ± 10%. This method can also be used for quantitative measurement of (220)Rn concentration.

Characterization of plutonium in deep-sea sediments of the Sulu and South China Seas.

Anthropogenic Pu isotopes are important geochemical tracers for sediment studies. Their distributions and sources in the water columns as well as the sediments of the North Pacific have been intensively studied; however, information about Pu in the Southeast Asian seas is limited. To study the isotopic composition of Pu, and thus to identify its sources, we collected sediment core samples in the South China Sea and the Sulu Sea during the KH-96-5 Cruise of the R/V Hakuho Maru. We analysed the activities of (239+240)Pu and the atom ratios of (240)Pu/(239)Pu using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS). The (240)Pu/(239)Pu atom ratios in the sediments of both areas (inventory weighted mean: 0.251 for the South China Sea and 0.280 for the Sulu Sea) were higher than the global fallout value (0.178+/-0.019), suggesting the existence of Pu from the Pacific Proving Grounds in the North Pacific. Low inventories of (239+240)Pu in sediments were observed in the South China Sea (3.75 Bq/m(2)) and the Sulu Sea (1.38 Bq/m(2)). Most of the Pu input is still present in the water column. Scavenging and benthic mixing processes were considered to be the main processes controlling the distribution of Pu in the deep-sea sediments of both study areas.

Concentration and characterization of plutonium in soils of Hubei in central China.

To study the Pu concentration and isotope ratio distributions present in China, the (239+240)Pu total activities and (240)Pu/(239)Pu atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBqg(-1) and the (239+240)Pu inventories of 45 and approximately 55 Bqm(-2) agree well with that expected from global fallout. The (240)Pu/(239)Pu atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar (240)Pu/(239)Pu ratio to that of global fallout. The top 10 cm layer of the soil contributes approximately 90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil.