US EPA

5077218 

Journal Article 

Development of Pa-231 AMS measurements to improve radiological dose assessment from uranium mining and milling 

Medley, P; Tims, SG; Froehlich, MB; Fifield, LK; Bollhoefer, A; Wallner, A; Pavetich, S 

2019 

1 

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
ISSN: 0168-583X 

ELSEVIER SCIENCE BV 

AMSTERDAM 

438 

66-69 

10.1016/j.nimb.2018.07.030 

WOS:000453491500013 

Limited information exists on the movement and partitioning of U-235 series radionuclides following their release to the environment from activities associated with the nuclear fuel cycle. Only three isotopes in the series, U-235, Pa-231 and Ac-227, have half-lives greater than a month. The extent to which the radiologically-significant isotopes of the U-235 series differentiate and fractionate in the environment, and then accumulate in biota, is largely controlled by the chemical properties of these three elements and by their biological uptake. This is particularly the case for biota with life cycles in the order of years. There is therefore potential for changes in the radiation dose received by humans and the environment during, for example, the operational and post-remediation phases of uranium mining practices, particularly where mine sites revert to traditional land uses such as hunting, fishing and camping.Natural activity concentrations of U-235 are 20 times lower than for U-235. In an environmental context, however, the radiation dose that arises from subsequent members of the U-235 decay chain will be determined by their abundance distribution and can exceed that from the U-235 series. The half-lives of the protactinium isotopes allow only Pa-231 to accumulate independently of its parent radionuclide along the transport pathways and/or through preferential uptake by biota. In particular, Pa-231 could make a disproportionately high contribution to the dose if it is preferentially transported and/or taken up.The AMS technique is capable of assessing accumulation of Pa-231 in natural environmental samples. We report on a new, safer radiochemical extraction method to prepare the Pa-233 isotopic tracer (one that does not use hydrofluoric acid), and on the development of Pa-231 AMS measurements at the Australian National University. 

AMS; Pa-231; Protactinium; Uranium mining; HF-free 

14th International Conference on Accelerator Mass Spectrometry (AMS) 

Ottawa, CANADA