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JAEA Reports

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; ; ; Iguchi, Yukihiro; Matsui, Yuji;

JNC TN3410 2000-014, 43 Pages, 2000/09

JNC-TN3410-2000-014.pdf:2.37MB

None

JAEA Reports

Detailed investigation on the environmental effects from the liquid effluent of JNC reprocessing plant (IV); (April, 1996March, 2000)

; Shinohara, Kunihiko; ; ; ; Isozaki, Tokuju; ; *

JNC TN8440 2000-003, 93 Pages, 2000/08

JNC-TN8440-2000-003.pdf:2.2MB

The investigation on the radioactivity concentration for gross beta, $^{3}$ H and $^{137}$ Cs in seawater collected around the discharge point had been performed in order to grasp the change of the activity level of the coastal seawater offshore the JNC Tokai Works from the low level liquid effluent of the reprocessing plant. After the investigation on the radioactivity in seawater during the hot examination, the detailed investigation on the environmental effects from the liquid effluent of JNC reprocessing plant has been performed since July 1978 on the basis of the request from Ibaraki prefecture as the full-scale operation of the reprocessing plant. Consequently, no increase of the radioactive concentration due to the discharged effluent has been observed. And also, as the result of the consideration to the investigation on the environmental effect from the liquid effluent throughout 22 years since 1978, no change of the radioactive concentration level in seawater was recognized.

JAEA Reports

Effective diffusion coefficients of HTO, Cs, I and C in compacted Ca-bentonite

Mihara, Morihiro; ; Ueta, Shinzo*; *

JNC TN8430 99-011, 27 Pages, 1999/11

JNC-TN8430-99-011.pdf:2.25MB

In radioactive waste disposal, compacted Na-bentonite has been proposed for a buffer material. However, Na-bentonite would change to Ca-bentonite in the long term period. The change of Na-bentonite to Ca-bentonite might cause the change in the data concerning with nuclides migration properties such as permeability, sorption and diffusion. In this study, effective diffusion coefficients of HTO, Cs, I and C in compacted Ca-bentonite which was changed from Na-bentonite, Kunigel V1, were obtained and were compared to published those of Kunigel V1. In addition, effective diffusion coefficients for compacted Ca-bentonite with syncetic sea system water, SW, were obtained in order to investigate effect of solution composition. The magnitude of effective diffusion coefficients in Ca-bentonite are arranged in smaller order as CsHTOIC. It is estimated that their effective diffusion coefficients are same those of Na-bentonite. About effect of solution composition, effective diffusion coefficients of HTO in 1.8g/cm $^{3}$ dry density with SW were almost same values with distilled system water, DW. However, effective diffusion coefficients of HTO in lower density were smaller than values with DW. Regarding as effective diffusion coefficients of Cs in 1.8g/cm $^{3}$ dry density, the effect of SW could not be observed as well as HTO. However, effective diffusion coefficients of I and C existing as an anion in pore water of bentonite increased by the reduction in the ion exclusion.

JAEA Reports

Hydrochemical Investigation and Status of Geochemical Modeling of Groundwater Evolution at the Kamaishi In-situ Tests Site, Japan

Sasamoto, Hiroshi; Yui, Mikazu; Arthur, R. C,*

JNC TN8400 99-033, 153 Pages, 1999/07

JNC-TN8400-99-033.pdf:58.41MB

The results of hydrochemical investigations of groundwaters in the Kurihashi granodiorite at JNC's Kamaishi in-situ tests site indicate that these solutions are: (1)meteoric in origin, (2)chemically reducing (at depths greater than a few hundreds meters), (3)relatively young [residence times in the Kurihashi granodiorite generally less than about 40 years, but groundwaters older than several thousand years BP (before present) are also indicated by preliminary carbon-14 dating of samples obtained from the KH-1 borehole], (4)Ca-HCO $_{3}$ type solutions near the surface, changing to Na-HCO $_{3}$ type groundwaters with increasing depth. The evolution of groundwater compositions in the Kurihashi granodiorite is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the "real" groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, AI, carbonate and sulfate) in the Kurihashi granodiorite if the following assumptions are adopted: (1)CO $_{2}$ concentration in the gas phase contacting pore solutions in the overlying soil zone = 10 $^{-2}$ bar, (2)minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), microcline (K) and pyrite (Eh and sulfate). Discussions with international experts suggest a systematic approach utilizing reaction-path models of irreversible water-rock interactions in open systems may be needed to more realistically model groundwater evolution at the Kamaishi test site. Detailed information characterizing certain site properties (e.g., fracture mineralogy) may be required to adequately constrain such models, however.