DEVELOPMENT OF IN-SITU SYSTEMS FOR 13CO2 EXPOSURE AND DETERMINATION OF 13C NET ASSIMILATION RATE OF FRUIT-BEARING SHOOTS AND WHOLE TREE AND CHAMBER FOR PRECISION 13CO2 EXPOSURE OF YOUNG POTTED TREES.

14C is the most important radionuclide for assessing exposure dose around the Rokkasho nuclear fuel reprocessing plant, Aomori Prefecture, Japan. A simplified model with ample margins has been used so far for the assessment of the dose derived from 14C. Realistic dose estimate of 14C using more realistic model is necessary for safety.

METABOLISMS OF 13C IN CATTLE SEMITENDINOSUS MUSCLE AFTER ADMINISTRATION OF 13C LABELED ORCHARD GRASS.

14C released from nuclear facilities is transferred to cattle through their consumption of 14C contaminated grasses. To estimate the concentrations of 14C in their meat, we conducted two sets of experiments. In the first experiment, 230 mg of 13C per day was administered to cattle aged 10 months for 28 days in the form of 13C-labeled grass.

EXPERIMENTAL EVALUATION OF DISTRIBUTION OF 14C PHOTOASSIMILATED INTO CARBOHYDRATES IN DIFFERENT GROWTH STAGES OF FRUIT-BEARING APPLE SHOOTS USING A 13CO2 IN-SITU EXPOSURE SYSTEM.

In this study, we aimed to investigate the photoassimilation process of 14CO2 into agricultural plants through determining the photoassimilated carbohydrate-13C in each part (leaves, current branch and fruit) of the fruit-bearing apple shoots exposed to 13CO2 in different growth stages (early and late fruit development stages). The carbohydrate content was assessed as soluble (ethanol-extracted fraction) and other (HCl-extracted and residual fractions) components. The total (i.

DIRECT ASSIMILATION OF ATMOSPHERIC CARBON BY IMMATURE APPLE FRUITS.

Although fruit development primarily depends on photoassimilation by leaves, immature green fruits can also directly assimilate atmospheric CO2. To elucidate the process of C accumulation due to direct assimilation by fruit, we conducted a 13CO2 exposure experiment in an orchard in late June with immature 'Fuji' apples (Malus domestica). Four fruits from three trees were enclosed in transparent plastic bags and exposed to 13CO2 using an in-situ exposure system.

Seasonal accumulation of photoassimilated carbon relates to growth rate and use for new aboveground organs of young apple trees in following spring.

Deciduous trees accumulate carbon (C) in woody parts during the growth season which is subsequently used for the initial development and growth of newly formed organs in the following season; however, it is unclear which period during the growth season contributes to C accumulation. Three-year-old potted Malus domestica (apple) trees were grown in controlled growth chambers during the growth season and exposed to 13CO2 in an exposure chamber at seven different periods of the growth season, including vegetative and reproductive growth periods. Approximately half of the trees were harvested in late autumn, and the remaining trees were grown in a field in the following year.

In situ experimental exposure of fruit-bearing shoots of apple trees to CO and construction of a dynamic transfer model of carbon.

Evaluating the transfer and metabolism of carbon (C) in apple fruit is key to estimating the potential accumulation of atmospheric C in fruit near and around nuclear facilities. We developed a dynamic compartment model for apple fruit-bearing shoots, assuming that the shoots are a simple unit of source and sink for photoassimilates. Fruit-bearing shoots of Malus domestica "Fuji" at different fruit growth stages were exposed to COin situ, followed by sampling at 72 h after exposure or at harvest.

Estimation of dietary C dose coefficient using C-labelled compound administration analysis.

Carbon-14 released from nuclear facilities has been assessed to contribute significantly to the radiation dose that people are exposed to through the food chain. However, the current dose coefficient for members of public, which is the ratio of the 50-year committed effective dose to ingested 1 Bq C, recommended by the International Commission on Radiological Protection (ICRP) is not based on experimental human metabolic data for C in nutrients and diet. Therefore, to validate the coefficient, we administered C-labelled nutrients consisting of four amino acids, three fatty acids, and one monosaccharide to volunteers as substitutes for C labelled nutrients and measured the C concentration in various excreta samples.

Short-term metabolism of biologically incorporated I ingested by olive flounder (Paralichthys olivaceus).

Iodine-129 with a long half-time of 1.6 × 10 y was discharged into the Pacific Ocean during the final safety tests of the first commercial nuclear fuel reprocessing plant in Japan, at Rokkasho, Aomori Prefecture. Olive flounder (Paralichthys olivaceus) is an important fishery along this coast.

Biokinetics of C in the human body after oral administration of C-labeled glucose as an index for the biokinetics of C.

The retention of C in the human body after oral administration of C-labeled glucose was studied in three healthy volunteer subjects to estimate the 50 year cumulative body burden for C as an index of the committed dose of the radioisotope C. After administration of C-labeled glucose, the volunteers ingested controlled diets with a fixed number of calories for 112 d. Samples of breath and urine were collected up to 112 d after administration.

A dynamic transfer model for the estimation of 14C radioactivity in Japanese radish (Daikon) plants.

A dynamic compartment model was developed to describe C accumulation in the Japanese radish plant, which is an important crop in the area around Japan's first commercial nuclear fuel reprocessing plant in Rokkasho, Aomori, Japan. Photosynthetically fixed carbon is distributed into the leaf and the root compartments, and a part of the carbon accumulated in the leaf compartment is redistributed to the root compartment. The model parameters were estimated by using data obtained from exposure of the plant to CO2.

Development of a dynamic transfer model of (14)C from the atmosphere to rice plants.

A dynamic compartment model was investigated to describe (14)C accumulation in rice plants exposed to atmospheric (14)C with temporally changing concentrations. In the model, rice plants were regarded to consist of three compartments: the ear and the mobile and immobile carbon pools of the shoot. Photosynthetically fixed carbon moves into the ear and the mobile carbon pool, and these two compartments release a part of this carbon into the atmosphere by respiration.

Development of a 1-week cycle menu for an Advanced Life Support System (ALSS) utilizing practical biomass production data from the Closed Ecology Experiment Facilities (CEEF).

Productivities of 29 crops in the Closed Ecology Experiment Facilities (CEEF) were measured. Rice and soybean showed higher productivities than these given by the Advanced Life Support System Modeling and Analysis Project Baseline Values and Assumption Document (BVAD), but productivities of some other crops, such as potato and sweet potato, were lower. The cultivation data were utilized to develop a 1-week cycle menu for Closed Habitation Experiment.