Diffusion Behaviour of Nuclides Considering Pathways in Fractured Crystalline Rocks

Sato, Haruo; ; ; *; *; Yui, Mikazu

PNC TN8410 97-127, 57 Pages, 1997/08

PNC-TN8410-97-127.pdf:1.51MB

Retardation of key nuclides is one of the most important mechanisms to be examined specifically and modelled for the performance assessment of geological disposal of radioactive waste. We have been studing diffusion of nuclides into the pore spaces of the rock matrix, sorption of nuclides on the rock pore surfaces and pore properties to quantify the degree of nuclide retardation in fractured crystalline rock. The work has concentrated on predominant water conducting fracture system in the host granodiorite in the Kamaishi In Situ Test Site, which consists of fracture fillings and altered granodiorite. Through-diffusion experiements to obtain effective and apparent diffusion coefficients (Da and De, respectively) for Na, Cs, HTO, Cl and Se as a function of ionic charge at 22 25C and batch sorption experiments for Cs, Sr, Se, U and Pu were conducted on fracture fillings, altered and intact granodiorite. The experiments only for Se, a redox sensitive element, were done in an N2-atmospheric glove box (O 1 ppm) to keep the chemical species. In situ groundwater (pH8.79.5) sampled from the same place as rock samples was used for the experiments. Porosity and density of cach rock sample were determined by both water saturation method and mercury porosimetry, and pore-size distribution and specific surface area of pores were measured by mercury porosimetry. The porosity is in the order; fracture fillings (5.6%) altered rock (3.2%) intact rock (2.3%). The pore-size distribution of the intact and altered granodiorite is ranging from 10 nm to 0.2 mm, and the fracture fillings have that of 50 nm to 0.2 mm, but a lot of pores were found around 100 nm and 0.2 mm in the fracture fillings. The effective diffusion coefficients for all species (Na, Cs, HTO, Cl, Se0) are in the order of fracture fillings altered rock intact rock in proportion to these porosities. Effective diffusion ...

Neutron total cross sections of Pufrom transmission measurements in the energy range of 1500 keV

H.Derrien*

Journal of Nuclear Science and Technology, 29(8), p.794 - 804, 1992/08

https://doi.org/10.3327/jnst.29.794

no abstracts in English

Experimental studies on water radiolysis by alpha rays from plutonium 239 in solid materials, 1; The Energy spectrum of alpha rays emitted from the solid material powder

Nagaishi, Ryuji; Ito, Tatsuya; DiPrete, D.*; Fellinger, A.*

no journal, , 

In the 1F decommissioning, the retrieval of fuel debris is planned, and then the importance of water radiolysis by alpha-rays becomes increasing in the debris storage more than 10 years after the accident. When alpha-emitting nuclides are contained in insoluble solid materials, the alpha-rays slowdown in the materials, and the energies of alpha-rays escaped from the materials become lower and continuous. The energy spectrum varies with the type and size of materials, and this spectral difference affects the pattern and magnitude of G-value of water radiolysis. Therefore, in order to study the alpha-radiolysis, it is necessary to measure and evaluate the material-dependent spectrum. In this study, we used solid material powders containing plutonium 239 (Pu-239) and measured the alpha-ray spectrum from the powders to estimate the linear energy transfer (LET) of alpha-rays. It was further compared with that when the nuclide is a dissolved species in water.