Challenges in the radiochemical separation of marine samples from the Montebello Islands

Thiruvoth, S; Child, DP; Harrison, JJ; Johansen, MP; Silitonga, A; Vardanega, CR; Wilsher, KL; Wong, HKY

Challenges in the radiochemical separation of marine samples from the Montebello Islands

Date

2018-11-06

Authors

Publisher

South Pacific Environmental Radioactivity Association

Abstract

The Montebello Islands, located off the North Western coast of Western Australia, was used as a nuclear weapons test site by the British government in the 1950s. Three nuclear tests were conducted around the islands. The first in 1952 (W818) detonated in the hull of the HMS Plym anchored in 12 m of water between Alpha and Trimouille Islands, and the second and third tests (MOSAIC G1 and G2) were detonated on 30 m Aluminium towers in May and June 1956, G1 on the Northern Western tip of Trimouille island and G2, the largest test conducted in Australian territory, on Alpha island. The fallout from these tests deposited long-lived anthropogenic radionuclides on nearby islands and ocean surface, host to an array of animals and plants. Marine sand, marine sediment, algae, fish, turtles and turtle eggs, among others, were sampled from the surrounding zones for dose assessment studies, thirty-nine of which were processed for actinide and strontium analysis. Due to the expected presence of discrete radioactive particles in some matrices a three step digestion method was applied to obtain complete dissolution of sample material. To overcome sample heterogeneity, the digest solution was sub-sampled for actinide and Sr-90 analysis by alpha spectrometry and liquid scintillation analysis, for plutonium isotopic analysis by AMS, and for elemental analysis by ICPAES/MS. The radiochemical separation method developed at ANSTO for Am, Pu, Th, U, and Sr for terrestrial soils and sediments (Harrison et al, 2011) was adapted to samples from the marine environment. However, some sample matrices proved to be challenging in achieving acceptable chemical recoveries of strontium due to the high concentrations of native calcium. This current study will discuss the methods used, and challenges overcome, in radiochemical separation for alpha spectrometry and liquid scintillation analysis for a wide range of sample types.

Keywords

Radiochemistry, Separation processes, Aquatic ecosystems, Islands, Australia, Nuclear test sites, Weapons, Western Australia, ANSTO

Citation

Thiruvoth, S., Child, D. P., Harrison, J., Johansen, M. P., Silitonga, A., Vardanega, C., Wilsher, K., & Wong, H. K. (2018). Challenges in the radiochemical separation of marine samples from the Montebello Islands. Paper presented to the SPERA Conference 2018, "Bringing environmental radioactivity research to Western Australia", Perth, Western Australia, 6 - 9 November 2018, (pp. 51).