Thorium—Energy for the Future pp 205-213 | Cite as

# Radiological Impact Assessment for Near Surface Disposal of Thorium Waste

## Abstract

Thorium (^{232}Th) itself is not fissile and so is not directly usable in a thermal neutron reactor. However, it is fertile and upon absorbing a neutron will transmute to uranium-233 (^{233}U), which is a fissile fuel material. The thorium fuel fabrication may lead to a low-level waste comprising of ^{232}Th. This waste may be disposed of in the Near Surface Disposal Facility (NSDF). The very low probability event of leaching of the waste may lead to contamination of the groundwater system. This paper deals with the estimation of the radiological impact of thorium waste disposal in NSDF through groundwater drinking pathway using the Multiple Area Source Model (MASOM).

## Keywords

Radiological impact Decay chain Dose Groundwater NSDF## Nomenclature

*B*is the width of the NSDF (m)

*C*is the concentration of radionuclides in pore water (Bq m

^{−3})*C*_{i}is the radionuclide concentration in the groundwater for instantaneous release of unit radioactivity (Bq m

^{−3})*C*_{1}is the concentration of parent radionuclide in the groundwater (Bq m

^{−3})*C*_{n}is the concentration of the

*n*th progeny in the groundwater (Bq m^{−3})*D*is the annual effective dose through groundwater drinking pathway (Sv y

^{−1})*DF*_{ing}is the ingestion dose coefficient of the radionuclide (Sv Bq

^{−1})*D*_{w}is the drinking water consumption rate (L day

^{−1})*D*_{x}is the dispersion coefficient in

*x*-direction (m^{2}s^{−1})*D*_{y}is the dispersion coefficient in

*y*-direction (m^{2}s^{−1})*H*is the depth of the trench (m)

*H*_{a}is the thickness of the aquifer (m)

*K*_{d}is the distribution coefficient of the radionuclide for the aquifer material (m

^{3}kg^{−1})*K*_{ds}is the distribution coefficient of the radionuclide for the waste material (m

^{3}kg^{−1})*K*_{L}is the leach rate coefficient of the radionuclide from the NSDF (s

^{−1})*L*is the length of the NSDF (m)

*λ*is the radioactive decay constant of the radionuclide (s

^{−1})*λ*_{1}is the radioactive decay constant of the parent radionuclide (s

^{−1})*λ*_{n}is the radioactive decay constant for

*n*th progeny (s^{−1})*M*is the inventory of the radionuclide (Bq)

- \( \nu \)
is the infiltration velocity (m s

^{−1})*Q*is the disposal rate of the radionuclide into the NSDF (Bq s

^{−1})*ρ*is the bulk density of the aquifer material (kg m

^{−3})*ρ*_{s}is the bulk density of the waste material (kg m

^{−3})*R*_{d}is the retardation factor in the aquifer

*R*_{ds}is the retardation factor in the waste material

- ψ(
*t*) is the radioactivity release rate from the NSDF at any time

*t*after disposal (Bq s^{−1})*T*is the period of dumping (s)

*θ*is the porosity of the aquifer material

*θ*_{S}is the porosity of the waste material in the trench

*u*is the groundwater velocity (m s

^{−1})*x*is the down-flow distance (m)

*y*is the cross-flow distance (m)

## Notes

### Acknowledgements

The authors would like to thank Dr. K. S. Pradeepkumar and Dr. R. B. Oza of Bhabha Atomic Research Centre, Mumbai, India, for their help and support during the study.

## References

- 1.IAEA,
*Thorium fuel cycle—potential benefits and challenges*(Tecdoc 145, International Atomic Energy Agency, Vienna, 2005)Google Scholar - 2.R.K. Sinha, A. Kakodkar, Design and development of AHWR—the Indian thorium fueled innovative reactor. Nucl. Eng. Des.
**236**, 7–8, 683 (2006)Google Scholar - 3.F. Sunny, S.T. Manikandan, R.N. Nair, V.D. Puranik, A multiple area source model to evaluate the groundwater quality at radioactive waste disposal sites. Environ. Geochem.
**8**, 154–157 (2005)Google Scholar - 4.R.N. Nair, T.M. Krishnamoorthy, SLBM-A
*Fortran Code for Shallow Land Burial Low Level Radioactive Waste*. Rep. No. BARC/1997/E/030 (BARC, Mumbai, India, 1997)Google Scholar - 5.R.N. Nair, T.M. Krishnamoorthy, Near field and far field radionuclides from shallow and land burial facility. Nucl. Technol.
**114**, 235 (1996)CrossRefGoogle Scholar - 6.R.B. Codell, K.T. Key, G.A. Whelan,
*Collection of mathematical models for dispersion in surface water and groundwater*(U.S. Nuclear Regulatory Commission, USA, 1982)Google Scholar - 7.D.H. Lester, G. Jansen, H.C. Burkholder,
*Migration of radionuclide chains through adsorbing medium*(Battelle, Pacific Northwest Laboratories, Richland, Washington, 1974)Google Scholar - 8.IAEA,
*Generic Models for Use in Assessing the Impact of Discharges of Radioactive Substances to the Environment*. Safety Reports Series No. 19 (International Atomic Energy Agency, Vienna, 2001)Google Scholar - 9.M.I. Sheppard, D.H. Thibault, Default soil solid/liquid partition coefficients, KdS, for four major soil types: a compendium. Health Phys.
**59**, 471–482 (1990)Google Scholar - 10.IAEA,
*Derivation of Activity Limits for the Disposal of Radioactive Waste in Near Surface Disposal Facilities*(IAEA-TECDOC-1380, International Atomic Energy Agency, Vienna, 2003)Google Scholar - 11.IAEA,
*International Basic Safety Standards for Protection Against Ionizing Radiation and for Safety of Radiation Sources*. Safety Series No. 115 (International Atomic Energy Agency, Vienna, 1996)Google Scholar - 12.B.K. Tewary, et al.,
*Groundwater Modeling for Banduhurang Opencast Uranium Mine and Proposed Tailing Pond Area of UCIL*. BRNS Project Report GAP/006/EMG/DAE/BRNS/05-06 (CIMFR, Dhanbad, India, 2008)Google Scholar - 13.R.N. Nair, V.N. Sastry, Safety assessment methodologies for near surface radioactive waste disposal facilities. Rad. Prot. Env.
**24**(3), 544–563 (2001)Google Scholar