Development of Alpha-Ray Spectrometric Techniques for the Measurement of Low-Level ²³⁷Np in Environmental Soil and Sediment

Abstract

Low-level 23, Np analysis/Alpha-ray spectrometry/Environmental soil and sediment Abstract An accurate and reliable analytical method has been developed for the measurement of low-level 23, Np in environmental soil and sediment by alpha-ray spectrometry, with emphasis on the purification from other interfering alpha-ray emitting nuclides, especially uranium isotopes. The method consists of leaching of neptunium by aqua regia, separation and purification by TOA (tri-n-octylamine) extraction, LaF, coprecipitation and two steps of anion exchange. 239 Np was used as a chemical yield tracer. The chemical yield of neptunium ranged from 50% to 84%. The minimum detectable activity of " 7 Np was about 0.1 mBq/sample at the counting time of 10 4 minutes.

Fallout 237Np, Pu Isotopes and 241Am in Lake and Sea Sediments from the Coastal Area of the Sea of Japan

“…The analytical method for Np consists of (i) leaching of Np, Pu and Am from the sample by treating it with aqua regia containing a small amount of H 2 0 2 , (ii) solvent extraction of Np by TOA(tri-n-octylamine), (iii) coprecipitation of Np with LaF 3 and (iv) two anion exchanges for separation and purification. Details of the analytical method have been reported elsewhere, together with the precision and accuracy of the method [20]. Plutonium and Am were separated from aqueous phase of TOA extraction of Np based on the method described by Yamato [25], The alpha-ray activity of each source electroplated onto a stainless steel disc was measured by a Si(Au) surface barrier detector coupled with 1 k channel PHA.…”

“…On the other hand, Np introduced into well-oxidized fresh-or sea-water is considered to have soluble pentavalent species such as NpOj [17]. Consequently, the distribution coefficient of Np on particulate materials is much lower than that of Pu(IV) and Am(III) [18,19], Recently, an accurate and reliable analytical method has been developed for extremely low-level 237 Np in environmental samples using alpharay spectrometry [20], In the present work, the depth profile and inventory of environmental 237 Np derived from nuclear weapons tests have been precisely studied together with those of Pu isotopes, 24 'Am and 137 Cs for sediment cores collected from the Mikata Five Lakes and Nyu Bay, Fukui Prefecture, Japan. The "Mikata Five Lakes" consist of five lakes with quite different environmental features in a narrow area of about 25 km 2 .…”

Measurement of 237Np in environmental water samples by accelerator mass spectrometry

“…The Np yield monitor used was 239 Np, which was freshly milked from its parent 243 Am prior to each chemical separation. The method employed was based on that of Yamamoto et al, 1 using several kBq of 243 Am (AEA Technology, Harwell, UK). The yield monitor was prepared in a laboratory designated as a Controlled Area under the UK Ionising Radiations Regulations because of the relatively high activity of the Am stock.…”

“…Neptunium is becoming an increasingly important component of nuclear waste as the nuclear fuel cycle develops. 1 It has an extremely long half-life (2.14 3 10 6 years) and thus has a low specific activity, but because of this longevity and in-growth from its parent 241 Am and grandparent 241 Pu it will be one of the greatest dose-deliverers to humans over time. 2 The low activities present in the environment have meant that it has been of less immediate concern to humans than the other transuranium elements, Pu and Am, and it has therefore been studied to a lesser extent.…”

Measurements of Radioactivity

“…Livens et al (1989) developed the method for the determination of Am in environmental samples (Fig. Yamamoto et al (1989) developed the method for the determination of Np in environmental samples (Fig. Yamamoto et al (1989) developed the method for the determination of Np in environmental samples (Fig.…”