Behavior of carbon-14 in the Tokai reprocessing plant

; ; ; Omori, Eiichi

JNC TN8410 2001-021, 33 Pages, 2001/09

JNC-TN8410-2001-021.pdf:4.37MB

Carbon-14 released from the nuclear facilities is an important radionuclide for the safety assessment, because it tends to accumulate in environment through food chain and has as a significant impact to personal dose. Carbon-14 has been monitored routinely as one of the main gaseous radionuclides exhausted from the Tokai Reprocessing Plant (TRP) since OCtober of 1991. Furthermore, behavior of carbon-14 in TRP has been investigated through the reprocessing operation and the literature survey. This report describes the result of investigation about the behavior of carbon-14 in TRP as followings. (1)Only a very small amount of carbon-14 in the fuel was liberated into the shear off-gas and most of it was liberated into the dissolver of-gass. Part of the carbon-14 was trapped at the caustic scrubber installed in the of-gas treatment process, and untrapped carbon-14 was released into the environment from the main stack. Amount of carbon-14 released from the main stack was about 4.16.5GBq every ton of uranium reprocessed. (2)Carbon-14 trapped at the caustic scrubbers installed in the dissolver off-gas and in the vessel off-gas treatment process is transferred to the low active waste vessel. Amount of carbon-14 transferred to the low active waste vessel was about 5.4 9.6GBq every ton of uranium reprocessed. (3)The total amount of carbon-14 input to TRP was summed up to about 11.915.5 GBq every ton of uranium reprocessed considering the released amount from the main stack and the trapped amount in the off-gas treatment devices. The amount of nitrogen impurity in the initial fuel was calculated about 1522ppm of uranium metal based on the measured carbon-14. (4)The solution in the low active waste vesselis concentrated at the evaporator.Most of the carbon-14 in the solution was transferred into concentrated solution. (5)Tokai vitrification Demonstration Facility (TVF) started to operate in 1994. Since then, carbon-14 has been measured in the ...

Study about the dissolution behavior of the irradiated fast reactor fuels in CPF

; Koyama, Tomozo; Funasaka, Hideyuki

JNC TN8400 2000-014, 78 Pages, 2000/03

JNC-TN8400-2000-014.pdf:2.13MB

We investigated the factors which affected the dissolution of U and Pu to the nitric acid solution with the fragmentation model, which was based on the results of dissolution experiments for the irradiated fast reactor fuels in the Chemical Processing Facility(CPF). The equation that gave the fuel dissolution rate was estimated with the condition of fabrication (Pu ratio (Pu/(U+Pu))), irradiation (burn-up) and dissolution (nitric acid concentration, solution temperature and U+Pu concentration) by evaluating these effects quantitatively. We also investigated the effects of fuel volume ratio to the solution in the dissolver, burn-up and flouring ratio of the fuel on the f-value (the parameter which shows the diffusion and osmosis of nitric acid to the fuel) in the fragmentation model. It was confirmed that the fuel dissolution rate calculated with this equation had better agreement with the results of dissolution experiments for the irradiated fast reactor fuels in the CPF than that estimated with the surface area model. In addition, the efficiency of this equation was recognized for the dissolution of unirradiated U pellet and high Pu enriched MOX fuel. It was shown that the dissolution rate of the fuel slowed down at the condition of the high U-Pu concentration dissolution by the calculation of the dissolution behavior with this equation. The dissolution of the fuel can be improved by increasing the nitric acid concentration and temperature, but from the viewpoint of lowering the corrosion of the dissolver materials, it is desirable that the f-value is increased by optimizing the condition of shearing and stirring for the improvement of dissolution.

None

Kurosawa, Ryuhei*

PNC TJ1615 96-001, 5 Pages, 1996/03

PNC-TJ1615-96-001.pdf:0.3MB

no abstracts in English

Analysis of spectra with wavelength fluctuation using neural network

Oba, Masaki

no journal, , 

Training data with a slightly shifted wavelength was created and trained, and the analysis performance were investigated using the similarly wavelength-shifted data as the test data. As a result, when learning with training data without wavelength shift and analyzing test data with wavelength shift, there is a large difference of about 50% between the true value and the analysis value of the content of each element. It was confirmed that the difference between the true value and the analysis value was improved to about 20% when training was performed using training data with a wavelength shift.