Land Burial Of Radioactive Waste Research Articles

THE USE OF FLY ASH AND ZEOLITE MIXTURE AS BACKFILL MATERIAL IN THE RADIOACTIVE WASTE REPOSITORY

An investigation of the contribution of fly ash in the fly ash-zeolite mixture as the backfill material on the shallow land burial of radioactive waste has been done. The experiment objective is to know the effect of zeolite particle size and fly ash-zeolite weight ratio on physical properties such as permeability (K) and dispersion characteristic such as effective dispersion coefficient (De) in the fly ash-zeolite form as backfill material. The experiment was carried out by the fixed bed method in the column filled by the fly ash-zeolite mixture with a fly ash-to-zeolite weight percent ratio of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 in the water saturated condition flown by uranyl nitrate solution at concentration (Co) of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, data effective dispersion coefficient (De) in the backfill material were determined. The experiment data showed that -400 mesh fly ash and -70+80 mesh zeolite on fly ash-to-zeolite with weight percent ratio of 40/60 with K = 5.00x10-5cm/second and De = 1.11.10-5 cm2/second can be used as backfill material. Keywords: backfill material, fly ash, radioactive waste, zeolite

BENTONITE-QUARTZ SAND AS THE BACKFILL MATERIALS ON THE RADIOACTIVE WASTE REPOSITORY

An investigation of the contribution of quartz sand in the bentonite mixture as the backfill materials on the shallow land burial of radioactive waste has been done. The experiment objective is to determine the effect of quartz sand in a bentonite mixture with bentonite particle sizes of -20+40, -40+60, and -60+80 mesh on the retardation factor and the uranium dispersion in the simulation of uranium migration in the backfill materials. The experiment was carried out by the fixed bed method in the column filled by the bentonite mixture with a bentonite-to-quartz sand weight percent ratio of 0/100, 25/75, 50/50, 75/25, and 100/0 on the water saturated condition flown by uranyl nitrate solution at concentration (Co) of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, retardation factor (R) and dispersivity () were determined. The experiment data showed that the bentonite of -60+80 mesh and the quartz sand of -20+40 mesh on bentonite-to-quartz sand with weight percent ratio of 50/50 gave the highest retardation factor and dispersivity of 18.37 and 0.0363 cm, respectively. Keywords: bentonite, quartz sand, backfill materials, radioactive waste

Model of Analysis of the Groundwater-Protection Level in Shallow Land Burial of Radioactive Waste

A mathematical model of transfer of radionuclides in the aeration zone has been considered. The analytical solution for this model in a generalized form suitable for practical application has been obtained. A procedure enabling one to determine the optimum size of the protection zone and in which the maximum concentration of radionuclides does not exceed the maximum permissible levels for a specific kind of radionuclides has been proposed.

放射性廃棄物浅地中埋設処分による地下水移行経路からの被曝線量の試算

To identify characteristics of radiation dose and important parameters in calculation of the dose from the pathway through groundwater in shallow land burial of radioactive waste, calculation of dose, sensitivity analysis and pathway analysis were carried out under a specific calculation condition. Following results were obtained: (1) For groundwater migration scenario, the pathway of direct drinking of groundwater is an important one. (2) The critical pathway differs with nuclides and changes with time. (3) Doses from use of river or lake water are several orders of magnitude smaller than that from use of groundwater. (4) When the disposal site is located at a coastal area, the critical pathway is ingestion of sea products and the doses are several orders of magnitude smaller than those at an inland area. (5) The groundwater velocity and the distribution coefficient are important parameters in calculation of radionuclide concentration in groundwater.