Plutonium and Americium Alpha Radiolysis of Nitric Acid Solutions

Abstract

The yield of HNO, as a function of absorbed dose and HNO concentration, from the α-radiolysis of aerated HNO solutions containing plutonium or americium has been investigated. There are significant differences in the yields measured from solutions of the two different radionuclides. For 0.1 mol dm HNO solutions, the radiolytic yield of HNO produced by americium α-decay is below the detection limit, whereas for plutonium α-decay the yield is considerably greater than that found previously for γ-radiolysis. The differences between the solutions of the two radionuclides are a consequence of redox reactions involving plutonium and the products of aqueous HNO radiolysis, in particular HO and HNO and its precursors. This radiation chemical behavior is HNO concentration dependent with the differences between plutonium and americium α-radiolysis decreasing with increasing HNO concentration. This change may be interpreted as a combination of α-radiolysis direct effects and acidity influencing the plutonium oxidation state distribution, which in turn affects the radiation chemistry of the system.

New insight on the simultaneous H2and HNO2production in concentrated HNO3aqueous solutions under alpha radiation

“…Looking at the previously reported G(HNO 2 ), our results are closest to the ones obtained for a radiolysis using plutonium nitrate in HNO 3 , 47 and rather inconsistent with measurements using helions. 92 For the a radiolysis investigations, there is a long standing debate over the use of external helions versus internal a particle emitters.…”

“…However, fewer studies have been dedicated to the a radiolysis of these solutions, and the majority of these investigations were performed in the radiolysis of HNO 3 in the presence of radionuclides ( 243 Am, 241 Am, 244 Cm, 210 Po, 240 Pu, 238 Pu). 3,4,[38][39][40][41][42][43][44][45][46][47][48][49][50][51] The formation of radiolytic products (H 2 , O 2 , H 2 O 2 , NO 3 c and NO 2 À / HNO 2 ) is generally evaluated using direct methods such as spectrophotometry, gas chromatography, ion chromatography or mass spectrometry 40 or indirect methods such as the classical or modied Shinn 52,53 or Ghormley method. 54 For the gas detection, all measurements are performed by sampling the headspace at the end of irradiations or at different residence times and replacing the sampled gas by laboratory air.…”

Pulse radiolysis study on the reactivity of NO3˙ radical toward uranous(iv), hydrazinium nitrate and hydroxyl ammonium nitrate at room temperature and at 45 °C

“…The radiolytic behavior of HNO 3 solutions [44][45][46]6,[47][48][49][50][51][52][53] has been fully characterized, and the nitrate radicals (NO 3 • ) formation mechanism has been elucidated. 54,55,52,56 The nitrate radicals (NO 3 • ) are used in most investigations as a probe to monitor the radiation-induced changes in HNO 3 solutions, 57,46,49,58,54,50,55,59,56 as they are known to be key radiolytic intermediates and drivers of chemical changes through the formation of secondary radiolytic products or through the oxidation of important metal ions.…”

Challenges to deployment of twenty-first century nuclear reactor systems

“…Commercial nuclear fuel reprocessing is carried out in nitric acid solutions but the extreme radioactivity leads to unexpected chemical effects, which can be explained by better understanding of the interactions of radiation with nitric acid. [26,27]. Seventy years after their discovery, the complexity and subtlety of the transuranium elements is still being revealed, partly due to the technical challenges of working with these radioactive materials, and partly due to the complexity of their physics and chemistry [28,29].…”