Migration of Radionuclide Chains in Subseabed Disposal
- PDF / 295,736 Bytes
- 8 Pages / 420.48 x 639 pts Page_size
- 43 Downloads / 212 Views
Copyright 1982 by Elsevier Science Publishing Company, THE SCIENTIFIC BASIS FOR NUCLEAR
WASTE MANAGEMENT
549
Stephen V. Topp,editor
MIGRATION OF RADIONUCLIDE CHAINS IN SUBSEABED DISPOSAL A. K. RAY AND H. E. NUTTALL* Department of Chemical Engineering,
University of Kentucky, Lexington, KY 40506
ABSTRACT In this study of subseabed disposal, the two dimensional (axial and radial) migration of radionuclide chains released from a canister located in a sedimentary layer bounded at the top by the ocean and at the bottom by an impermeable basalt zone is analyzed to determine the escape rate of radlonuclides into the seawater. Analytical solutions have been derived to represent the transient concentration profiles within the sediment, flux and discharge rates to the water column of each member present in a decay chain. Using the properties of chain members present in actinide decay systems, the effects of half-life, adsorption equilibrium and other relevant parameters are elucidated. INTRODUCTION The burial of radioactive wastes in the subseabed formations has been proposed and is under study [1-3] for the disposal of high-level radioactive Analytical models to predict the transport rate of radionuclides from material. the disposal site through the subseabed to the ocean are needed to assess the performance and to establish the design requirements of these disposal systems. To this purpose, Nuttall et al. [4-6] have analyzed diffusional transport of radioactive ions in ocean sediments. Their previous analyses of two dimensional (axial and radial) unsteady state diffusion in the subseabed treated only single decaying species of radionuclides, and did not address the radioactive decay chain problem. Modeling of the decay chain problem requires the simultaneous description of all precursors to that chain thus leading to a series of partial differential equations which must be solved simultaneously. Moreover, the analysis of their migration is complicated by the differences in adsorption properties and decay rates among chain members. The one dimensional transport problem with chain decay has been investigated by Burkholder et al. [7-8]; however, this is the first study which treats the two dimensional problem and applies the analysis to a specific waste disposal concept (i.e., subseabed). In this study we have developed a two dimensional transport model for the diffusion-controlled migration of radionuclides leaking out of a canister embedded in a sedimentary layer bounded at the top by an ocean and at the bottom by an impermeable basalt zone. A particular radionuclide in the canister is considered to decay in the following chain form I 1 A1 ÷
A2
-
2
A
3 .3.
We have restricted our analysis to three-member chain, to any number of radioactive species in the chain.
but it can be extended
SDepartment University
of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
of New Mexico,
550 THEORETI CAL ANALYS IS Consider the system shown in Figure 1, which consists of a cylindrical can•
ister containing r
Data Loading...
