VARIATION IN RADIATION DOSE RATES FROM RADIONUCLIDES DISCHARGED BY THE SPENT NUCLEAR FUEL REPROCESSING PLANT IN ROKKASHO UNDER DIFFERENT YEARLY WEATHER CONDITIONS.

The radiation dose rate from radionuclides released by the spent nuclear fuel reprocessing plant in Rokkasho, Japan, was assessed for a year specified in the safety review during which the weather conditions were not significantly different from those of the other 10 y. However, the actual year-by-year variation in annual radiation dose rate was not examined. A model system for evaluating the dose rate from the radionuclides released into the atmosphere was constructed. In this study, the radiation dose rate in the weather conditions of 24 weather bins was estimated for a standard year by the model. The annual maximum dose rate from 1959 to 2012 was estimated using a simplified method that integrated the dose rates of each weather bin in the standard year by estimating the annual frequency of the bin in the target year. We obtained ~1.3 as the maximum/minimum ratio of the annual maximum dose rate.

RELATIONSHIP BETWEEN SOIL-SOIL-SOLUTION DISTRIBUTION COEFFICIENTS OF 125I AND 127I IN PASTURE SOIL.

We measured the depth profiles of soil-soil-solution distribution coefficients (Kd) of native 127I (127I-Kd) and exogenous 125I- (125I-Kd) in soils from a pasture near the spent nuclear fuel reprocessing plant in Rokkasho, Japan, and investigated their relationships to depth profiles of the concentration in soil of 127I and organic C and Kd of organic C (C-Kd). The depth profiles of 125I-Kd and 127I-Kd were similar. The relatively low 127I concentrations and low values of both 127I-Kd and 125I-Kd indicate that some of the I deposited on the soil surface have been transported to depths greater than 10 cm. On the other hand, high 127I-Kd/125I-Kd ratios in the uppermost 10 cm of soil indicate that some of the 127I bound to that soil could not be exchanged with exogenous 125I. Although a previous study has shown a power function relationship between 125I-Kd and C-Kd, our data show that the relationships of both 125I-Kd and 127I-Kd to C-Kd are exponential functions. The reason for these conflicting results is unknown. Nonetheless, our data clearly show Kd values for both 125I- and 127I to be dependent on C-Kd. In addition, the dependence of both 127I-Kd and 125I-Kd on C-Kd suggests that organic material in the soil has a role in the transport of I down the soil profile.

SPECIATION OF IODINE IN SOIL SOLUTION IN FOREST AND GRASSLAND SOILS IN ROKKASHO, JAPAN.

The behaviour of I in soil depends on its chemical form in soil solution. Stable I (127I) in the soil solution under actual soil conditions was investigated as a natural analogue of long-lived radioiodine (129I). Soil samples were collected at 5-cm depth intervals down to 20 cm from forests and grasslands in Rokkasho, where the Japanese first commercial nuclear fuel reprocessing plant is located, and the soil solution was extracted by centrifugation. Almost half of total I in the soil solution was iodide, and the other half was dissolved organic I (DOI), with iodate under the detection limit. The proportion of DOI in total I at 0-5 cm depth was larger than the proportions at 5-20 cm depth. The concentration of DOI was positively correlated with that of DOC in the soil solution, suggesting that the behaviour of DOI in the surface soil is affected by labile organic matter dynamics.

Estimation of 85Kr dispersion from the spent nuclear fuel reprocessing plant in Rokkasho, Japan, using an atmospheric dispersion model.

The spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Limited (JNFL) located in Rokkasho, Japan, discharged small amounts of (85)Kr into the atmosphere during final tests of the plant with actual spent fuel from 31 March 2006 to October 2008. During this period, the gamma-ray dose rates due to discharged (85)Kr were higher than the background rates measured at the Institute for Environmental Sciences and at seven monitoring stations of the Aomori prefectural government and JNFL. The dispersion of (85)Kr was simulated by means of the fifth-generation Penn State/NCAR Mesoscale Model and the CG-MATHEW/ADPIC models (ver. 5.0) with a vertical terrain-following height coordinate. Although the simulated gamma-ray dose rates due to discharged (85)Kr agreed fairly well with measured rates, the agreement between the estimated monthly mean (85)Kr concentrations and the observed concentrations was poor. Improvement of the vertical flow of air may lead to better estimation of (85)Kr dispersion.

Changes in the chemical form of exogenous iodine in forest soils and their extracts.

Information about the chemical form of exogenous iodine in soil is important for predicting the mobility and behaviour of radioiodine in the terrestrial environment. In this study, soil samples collected at various depths in a pine forest in Rokkasho, Japan, were spiked with stable iodine (as iodide or iodate); after incubation of the spiked soils for 1 or 14 d, the chemical forms of iodine were investigated in both the soils and their water extracts. In surface soil and its extracts, inorganic iodine was found to have been transformed to organically bound forms after incubation for 14 d, resulting in a decrease in the amount of water-extractable iodine in the soil. In contrast, in subsurface soil, which had low organic matter content, the predominant chemical form of iodine after incubation did not differ from that in the spiked soil, and the amount of water-extractable iodine did not decrease noticeably.

Characterization of several amino acid transports and glutamine metabolism in MOLT4 human T4 leukemia cells.

The transport system responsible for glutamine, alanine and glutamate in MOLT4 human T4 leukemia cell line were characterized. Kinetic studies of sodium-dependent glutamine and alanine transport exhibited a single saturable high-affinity carrier with a Michaelis constant of 152 +/- 26 microm and 203 +/- 36 microm and a maximal transport velocity of 960 +/- 165 and 1096 +/- 208 nmol/10(9)cells/min, respectively. Glutamate uptake was less than one-tenth of glutamine and alanine, and linearly increased with glutamate concentration which was mediated by diffusion. 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), known as anion channel blockers, inhibited the sodium-dependent glutamine and alanine transport by 40% at 10 microm. Cellular contents of these amino acids in MOLT4 cells revealed glutamate to be the highest among them despite low glutamate influx. A glutamine metabolism study using whole cells indicated this high conversion rate from glutamine to glutamate, but no conversion to another amino acid. Based on these results, the high glutamate concentration in MOLT4 was speculated to be synthesized from transported glutamine by active glutaminase.

222Rn concentrations in greenhouses in Aomori Prefecture, Japan.

Greenhouses are possible places with high 222Rn concentrations, since soil, the source of 222Rn, is directly exposed inside them. To examine this point, 222Rn concentrations in 28 greenhouses at five locations in Aomori Prefecture were measured for approximately 1 year with passive Rn detectors. For 1 week, measurements of 222Rn concentration and working level were also carried out with active detectors to get equilibrium factors and the ratio of 222Rn concentration in working time to non-working time in selected greenhouses. The geometric mean of annual 222Rn concentrations in greenhouses was 13 Bq m-3, and the same as that in dwellings and lower than that in indoor workplaces in the prefecture. However, variation of the 222Rn concentrations was far larger than in other environments, and ranged from the lowest level in outdoor workplaces to the highest level in indoor workplaces. Significant seasonal variation was also observed in 222Rn concentrations. The mean effective dose from 222Rn and its progenies was estimated to be 0.047 mSv year-1 for a farmer working in a greenhouse.

Radon concentration in indoor occupational environments in Aomori Prefecture, Japan.

The (222)Rn concentrations in indoor workplaces were measured in Aomori Prefecture, Japan, and the results are reported here. This survey was part of a program to measure background natural radiation dose rate in the prefecture where the first Japanese nuclear fuel cycling facilities are now under construction. The survey of the (222)Rn concentrations in indoor workplaces was carried out at 107 locations from 1996 to 1998. The (222)Rn concentrations were measured for approximately one year at each site with passive Rn detectors, which used a polycarbonate film for counting alpha-rays and could separate concentrations of (222)Rn from (220)Rn. Weeklong measurements of (222)Rn concentration and working level were carried out with active detectors to get the ratio of (222)Rn concentration during working hours to non-working hours as well as equilibrium factors in selected locations. Diurnal variation of (222)Rn concentration depended on building structure, air-conditioning, time of day and day of the week (week days or weekend). The (222)Rn concentration during working hours was generally lower than that in non-working hours. Although the annual average (222)Rn concentration in indoor occupational environments was higher than that in dwellings, radiation dose for Aomori Prefecture residents from Rn in the former was 14% of the total indoor dose by Rn because of the lower concentration in working hours and lower occupancy factor.

Rice uptake and distributions of radioactive 137Cs, stable 133Cs and K from soil.

The distributions of radionuclides in plant components as to radionuclide transfer to animals are important for understanding the dynamics of radionuclides in an agricultural field. Most of the non-edible parts in these components are returned to the soil as organic fertilizer where they may again be utilized in the soil-plant pathway and/or are mixed with feed for livestock. Rice plants were grown in an experimental field and separated at harvest into different components, including polished rice, rice bran, hull, leaves, stem and root, and then the distributions of radioactive 137Cs, stable 133Cs and K in these components were determined. The distribution of 137Cs in polished rice and rice bran was similar to that of 133Cs, while that of K was different. The concentration ratios of 133Cs/K in leaf blade positions increased with aging, which means that the translocation rate of 133Cs in rice plants was slower than that of K. At harvest the distribution of dry weight in polished rice to entire rice plants was 34%, and the distributions of 133Cs in the polished rice and the non-edible parts were 7 and 93%, respectively, whereas those of K in the polished rice and the non-edible parts were 2 and 98%, respectively. Findings suggest that the transfer and distribution of 133Cs, not of K, provide better information on the long-term fate of 137Cs in an agricultural environment.

Free water 3H concentration in diet samples collected from 1969 to 1988 in Akita, Japan.

Fallout 3H concentrations in diet samples collected from 1969 to 1988 in Akita Prefecture are reported. Since the data for samples from the 1960's and 1970's are important to understand the long-term movement of 3H in the environment, we searched for old diet samples. Recently, diet samples collected in Akita Prefecture during 1969-1982 were found and subjected to 3H analysis. The samples were originally gathered for nutrition survey programs and had been stored in a refrigerated warehouse at -20 degrees C until we located them. The free water 3H concentrations in the samples were measured and are reported here. The present results are combined with already published data; together they show 3H concentrations exponentially decrease from 1969 to 1988 with an apparent half time of 5.9 y. Levels of diet free water 3H concentrations are also similar to measured and estimated precipitation 3H concentrations in Akita City.

Tritium concentrations in pine needle, litter and soil samples.

Samples of pine needle, litter and soil samples collected in/around Akita City and Rokkasho Village in 1989 were analyzed for both free water 3H (FWT) and organically-bound 3H (OBT). The FWT concentrations decrease in the order, litter or soil > pine needle. FWT concentrations in soil depend on the moisture content, and tend to increase with decreasing soil moisture content. This relationship is consistent with the observation that FWT in the soil increases with oxidation of atmospheric tritiated hydrogen gas (HT) and decreases with rainwater dilution. The OBT concentrations increase in the order pine needle < litter < soil at most of the sampling locations. This suggests that historically high soil 3H concentrations may be reflected as high OBT concentrations in soils of the present.

Organically-bound 3H concentration in rice around atomic energy facilities.

Rice samples collected around atomic energy facilities in the Tokai area were analyzed for organically-bound 3H (OBT). Measurement results were compared with those for samples from control areas in Japan and the People's Republic of China. OBT concentrations of rice in the Tokai area were found to be 4 times higher than the control area as maximum. Although this relatively high 3H concentration shows the effect of 3H release from the facilities into the environment, the concentration level is comparable with those in the rice sample from a northern interior region of China. The OBT concentration of rice sample from the general environment in interior China was 4.5 times higher than the control area in Japan. The radiation dose from the increasing 3H level is negligible in comparison with that from natural radiation.

Atmospheric mercury concentrations in the basin of the amazon, Brazil.

A wide regional mercury pollution in Amazon, Brazil is closely associated with goldmining that has been carried out in the basin of tributaries of the Amazon since the eighteenth century. Possible involvement has been discussed on atmospheric circulation in distributing the volatile pollutant. We developed a portable air sampler for the collection of mercury compounds and determined atmospheric mercury concentrations at several sites in Brazil including the basin of the Amazon tributaries. The mean concentration of total mercury was between 9.1 and 14.0 ng/m(3) in the basin of the Uatumã River located in the tropical rain forest far from goldmining sites and from urbanized area. These mercury levels exceeded the background level previously reported in rural area and, furthermore, were higher than concentrations observed in Rio de Janeiro and in Manaus that were compatible with the reference values for urban area. Mercury concentrations were also determined in gold refineries in the basin of the Tapajos River, and detected at a significant but not a health deteriorating level. Although only preliminary data were available, the present observations were in favor of the hypothesis that mercury is distributed widely by long distant transport by the atmospheric circulation after released at gold mining sites.

In vitro activity of the hairpin ribozyme derived from the negative strand of arabis mosaic virus satellite RNA.

The negative strand of the satellite RNA of tobacco ringspot virus [(-)sTRSV] is a self-cleaving RNA, of which self-cleaving domain is called the hairpin ribozyme. The negative strand of the satellite RNA of arabis mosaic virus [(-)sArMV] has been suggested to have a hairpin ribozyme-like secondary structure, and we have previously shown that this hairpin domain of (-)sArMV has ribozyme activity. Here we report characterization of the cleavage reaction of the (-)sArMV hairpin ribozyme. Mutagenesis analyses in a trans-acting system revealed, surprisingly, that the wild-type ribozyme was less active than almost all the other mutant ribozymes tested. In a cis-acting system (self-cleaving reaction), however, the reaction of the RNA containing the wild-type sequence proceeds highly efficiently. This result suggests that the inefficient cleavage of the wild-type substrate in trans-acting system may be due to low efficiency at the substrate-binding step but not at the chemical cleavage step in the reaction. We also constructed a chimeric ribozyme between the catalytic hairpin domain from (-)sArMV and the substrate-binding site from (-)sTRSV. This chimeric ribozyme had the highest activity among the trans-acting hairpin ribozymes tested.

Binding of amino acid pyrolysates and aflatoxins to autoclaved cells of Enterococcus faecalis FK-23.

There was significant binding in autoclaved cells of Enterococcus faecalis FK-23 toward Trp-P1 and Trp-P2. Although the binding ability towards aflatoxins B1, B2, G1, and G2 was less compared with the significant binding toward Trp-P1 and Trp-P2, higher percentage binding toward these aflatoxins was observed when the amount of the cell preparation was increased.

Tritium concentrations of blood samples collected throughout Japan.

Tritium concentrations were measured for blood samples collected from 20 cities throughout Japan during 1989-1990. The mean 3H concentration was found to be 1.4 +/- 0.4 Bq L-1 and 1.0 +/- 0.4 Bq L-1 (combustion water) for free water 3H and organically-bound 3H, respectively, excluding the abnormally high data of one city. The organically-bound 3H contents clearly depended on the latitudes of sampling locations, although the free water 3H concentrations showed no correlation with the latitudes. Organically-bound 3H is considered to be more suitable than free water 3H as an indicator of long time 3H exposure to human.

Hairpin ribozyme-mediated cleavage of the full-length beta-glucuronidase (GUS) mRNA.

We designed three hairpin ribozymes to cleave Escherichia coli beta-glucuronidase (GUS) mRNA and tested those activities in vitro. One of the ribozymes was designed to form 9 base pairs in total with the target GUS mRNA, and the other two ribozymes had longer substrate binding sites. All ribozymes cleaved the model substrate (100 bases long) at the predicted target site. Two ribozymes containing longer substrate binding sites cleaved the substrate much more efficiently than the other ribozyme containing shorter substrate binding site. Also, the ribozymes with long substrate binding sites had high activity against the full-length GUS mRNA (1.9 kilobases) and maintained the activity even at a low temperature, 26 degrees C, a general growth condition of plant cells. Effects of the substrate binding site length of the ribozyme on cleavage activity are discussed.