Philippine Journal of Science
149 (S1): 65-75, Special Issue on Nuclear S&T
ISSN 0031 – 7683
Date Received: 18 Mar 2019
Dose Rate Analysis of Upgraded Storage Drums
for Disused Sealed Radioactive Sources by a Multivariate
Interpolation Program Developed Using MCNP5
Frederick C. Hila1*, Ronald E. Piquero2, Cheri Anne M. Dingle1,
Alvie A. Astronomo3, Julius Federico M. Jecong1, and Editha A. Marcelo2
1Applied Physics Research Section, Atomic Research Division
2Radiation Protection Services Section, Nuclear Services Division
3Nuclear Reactor Operations Section, Nuclear Services Division
Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI)
Commonwealth Avenue, Diliman, Quezon City 1101
*Corresponding author: fchila@pnri.dost.gov.ph
[Download]
Hila F et al. 2020. Dose Rate Analysis of Upgraded Storage Drums for Disused Sealed Radioactive Sources
by a Multivariate Interpolation Program Developed Using MCNP5. Philipp J Sci 149(S1): 65–75.
https://doi.org/10.56899/149.S1.08
ABSTRACT
The DOST-PNRI maintains a centralized radioactive waste management facility (RWMF) that performs conditioning of disused sealed radioactive sources (DSRS). These radioactive wastes are encapsulated in stainless steel and deposited into storage drums, which are in turn piled within the facility. This work describes the enhancement of the storage drum design using a dual-layer shielding of lead and concrete. This enables the drums to contain a total of three stainless steel encapsulations, therefore minimizing radioactive waste volumes within the facility. For this design, the MCNP5 code was used to verify that the surface contact dose rate limits will not be surpassed, for all drums to be fabricated. Each drum will be designed with a lead thickness that depends on the strength of radioactive waste to be contained. In order to account for different volumes, activities, and radionuclide types of the encapsulated waste as well as the required lead shielding, series of simulations were prepared to create a program in Microsoft Excel that will interpolate results based on these variable parameters. This program was subsequently applied to three existing source capsules. Results were verified with good agreement by PHITS Monte Carlo (MC) models. Using the program, design parameters were also optimized by acquiring the optimum source volume fractions per capsule, activity insertion ratios, and the maximum insertable radioactivity per drum. The degree of dose rate reduction within the old single-layer design and the enhanced dual-layer design was shown by mesh diagram. The interpolation program can be used as a tool for rapid fabrication of enhanced storage drums that can increase the capacity of the facility due to minimization of radioactive waste volumes.