Determination of <Superscript>237</Superscript>Np, <Superscript>93</Superscript>Zr and other long-lived radionuclides in medium and low level radioactive waste samples

The majority of long-lived radionuclides produced in the nuclear fuel cycle can be regarded as “difficult-to-measure” nuclides, hence chemical separation is needed before the nuclear measurement of them. A combined radiochemical procedure that enables the simultaneous determination of some “difficult-to-measure” nuclides in medium and low level radioactive wastes has been developed in our laboratory. Recently, this method has been extended for determination of ²³⁷Np and ⁹³Zr. ²³⁷Np and ⁹³Zr are pre-concentrated by co-precipitation on iron(II) hydroxide and zirconium oxide, separated by extraction chromatography using UTEVA, and measured by inductively coupled plasma mass spectrometry (ICP-MS). As even traces of polyatomic ions and isotopes at m/z 237 or 93 cause considerable interferences during ICP-MS detection, a purification step by extraction chromatography was needed. Analyzing real samples (evaporation concentrates of a nuclear power plant) 66–99% and 31–99% chemical yields were achieved for Np and Zr, respectively.     

A selective separation method for <Superscript>93</Superscript>Zr in radiochemical analysis of low and intermediate level wastes from nuclear power plants

The zirconium isotope ⁹³Zr is a long-lived pure β-particle-emitting radionuclide produced from ²³⁵U fission and from neutron activation of the stable isotope ⁹²Zr and thus occurring as one of the radionuclides found in nuclear reactors. Due to its long half life, ⁹³Zr is one of the radionuclides of interest for the performance of assessment studies of waste storage or disposal. Measurement of ⁹³Zr is difficult owing to its trace level concentration and its low activity in nuclear wastes and further because its certified standards are not frequently available. A radiochemical procedure based on liquid–liquid extraction with 1-(2-thenoyl)-3,3,3-trifluoroacetone in xylene, ion exchange with Dowex resin and selective extraction using TRU resin has to be carried out in order to separate zirconium from the matrix and to analyze it by liquid scintillation spectrometry technique (LSC). To set up the radiochemical separation procedure for ⁹³Zr, a tracer solution of ⁹⁵Zr was used in order to follow the behavior of zirconium during the process by γ-ray spectrometry through measurement of the ⁹⁵Zr. Then, the protocol was applied to low level waste (LLW) and intermediate level waste (ILW) from nuclear power plants. The efficiency detection for ⁶³Ni was used to determination of ⁹³Zr activity in the matrices analyzed. The limit of detection of the 0.05 Bq l⁻¹ was obtained for ⁶³Ni standard solutions by using a sample:cocktail ratio of 3:17 mL for OptiPhase HiSafe 3 cocktail.     

Half-life of <Superscript>97</Superscript>Zr,re-measured

Summary The half-life of ⁹⁷Zr, used for the calculation of thermal/epithermal neutron flux ratio in k₀-NAA, is re-determined using three measurement systems with different pulse processing principles. The result of 16.755±0.013 hours clarifies the discrepancy between two widely used literature values, 16.744±0.011 and 16.90±0.05 hours. Different dead-time correction methods used on various measurement systems are evaluated. Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives).     

Determination of <Superscript>93</Superscript>Zr and <Superscript>237</Superscript>Np in nuclear power plant wastes

A combined radioanalytical method for determination of ⁹³Zr and ²³⁷Np (as well as other actinoids) in radioactive wastes has been developed. Analytes were co-precipitated on iron(II)-hydroxide, separated and purified on UTEVA columns, and detected by inductively coupled plasma mass spectrometry. According to Zr and Np, 65 and 75% yields were achieved, respectively.     

Radiopharmaceutical Studies and Nuclear Medicine; Simultaneous <Superscript>68</Superscript>Ge and <Superscript>88</Superscript>Zr recovery from proton irradiated Ga/Nb capsules (LA-UR #03-2319)

Summary Germanium-68 (270.8 d, EC 100%) is the parent nuclide of ⁶⁸Ga, a β+ emitter important to positron emission tomography (PET). ⁶⁸Ge is obtained by a (p,x) induced nuclear reaction on natural Ga. A typical Ga target assembly consists of liquid Ga contained in a Nb capsule, since Nb is one of the few metals resistant to liquid Ga. Zirconium-88 (83.4 d, via ⁹³Nb(p, α2n)) is one longer-lived radioisotope generated by the proton irradiation of naturally mono-isotopic ⁹³Nb. It decays into ⁸⁸Y, which, in turn, has been considered a useful radiolabel surrogate for ⁹⁰Y in the investigation of radiolabeled compounds for cancer radioimmunotherapy. This paper introduces a wet chemical procedure for the processing of Nb/Ga target capsules and the simultaneous recovery of ⁶⁸Ge and ⁸⁸Zr.     

Production of <Superscript>88,89</Superscript>Zr by proton induced activation of <Superscript>nat</Superscript>Y and separation by SLX and LLX

^natY foil was irradiated by 20 MeV proton to produce no-carrier-added ^88,89Zr. A comparative evaluation on radioanalytical separation methods of ^88,89Zr was carried out from irradiated target matrix by both liquid–liquid (LLX) and solid–liquid (SLX) extraction methods using di-(2-ethylhexyl) phosphoric acid (HDEHP) dissolved in cyclohexane as liquid cation exchanger and Dowex 50W-X8 H⁺ form (20–50 mesh) as solid cation exchanger. Both the methods offer good separation and high yield of nca ^88,89Zr but SLX offers much higher separation factor and better yield.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Further development of accelerator mass spectrometry for the measurement of <Superscript>90</Superscript>Sr at Lawrence Livermore National Laboratory

Based on the encouraging results of our initial efforts to develop a ⁹⁰Sr accelerator mass spectrometry capability, we have undertaken efforts to enhance our system. By changing some key operating parameters and constructing an optimized detector we were able to improve the discrimination of ⁹⁰Sr from the isobaric interference ⁹⁰Zr and reduce our instrumental background by nearly two orders of magnitude. Our current background (4 × 10⁶ atoms, 3 mBq) is comparable to that achievable by decay counting, but is still a factor of ten higher than what is theoretically predicted based on the efficiency of our system. Therefore, future plans include implementation of a time-of-flight system to improve the rejection of ⁹⁰Zr.     

Preparation of <Superscript>166</Superscript>Dy/<Superscript>166</Superscript>Ho-chitosan as an in vivo generator for radiosynovectomy

¹⁶⁶Ho is one of the most effective radionuclides used for radiosynovectomy. One method to deliver this radioisotope to target tissue is via the ¹⁶⁶Dy/¹⁶⁶Ho in vivo generator system. The aim of this work was to prepare ¹⁶⁶Dy/¹⁶⁶Ho-chitosan (¹⁶⁶Dy/¹⁶⁶Ho-CHIT) in vivo generator for radiosynovectomy applications. ¹⁶⁶Dy obtained by the irradiation of natural ¹⁶⁴Dy target. ¹⁶⁶Dy was separated from ¹⁶⁶Ho by extraction chromatographic method (separation yield; 93% and separation factor;1.7). Chitosan labeling was performed in acetic acid with 99.3 ± 0.6% radiochemical purity. Biodistribution studies on intraarticular injected rats demonstrated high retention in the knee joint even 7 days showing no radioactivity leakage from the injection site into other organs as well as any translocation of the daughter nucleus after β^? decay of ¹⁶⁶Dy.     

Porous ZrC-carbon microspheres as potential insoluble target matrices for production of <Superscript>188</Superscript>W/<Superscript>188</Superscript>Re

New microsphere sorbents are reported, which could find application in demanding radiation environments and especially as targets for the production of nuclear medicines by neutron irradiation. An easily-synthesized Zr anionic complex was introduced into quaternary amine-functionalised polystyrene-divinylbenzene-based anion-exchange resins by batch adsorption. Upon carbothermal reduction, the precursors were converted to porous carbon matrices containing particles of ZrC and ZrO₂ polymorphs. The most phase-pure material, ZrAX-1, possessed high surface area, multi-scale porosity and high mechanical strength. Adsorption of Re and W was investigated and its possible deployment as a reusable host for the production of ¹⁸⁸W/¹⁸⁸Re is discussed.     

Study of the <Superscript>241</Superscript>Am(n,2n)<Superscript>240</Superscript>Am reaction cross section in the energy range of <Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> = 8.8−11.1 MeV

The measurement of the cross section of the reaction ²⁴¹Am(n,2n)²⁴⁰Am has been performed at neutron energies from 8.8 to 11.1 MeV, implementing the activation technique. The neutron beam was produced at the TANDEM accelerator of NCSR “Demokritos” by the ²H(d,n)³He reaction, using a deuterium gas target. During the 5-day long irradiation, the neutron beam fluctuations were monitored in 100 seconds intervals by a BF₃ counter connected with a multiscaling unit. The radioactive target consisted of a 37 GBq ²⁴¹Am source enclosed in a Pb container. A natural Au foil, a ²⁷Al foil and a ⁹³Nb foil were used as reference materials for the neutron flux determination. After the end of the irradiation the activity induced at the target and the reference foils, was measured off-line by a 56% HPGe detector.     

Metabolism of <Superscript>14</Superscript>C-labelled and non-labelled sulfadiazine after administration to pigs

The behaviour of sulfadiazine (SDZ) and its metabolites was investigated by administering the ¹⁴C-labelled veterinary drug to fattening pigs. The excretion kinetics were determined after daily collection of manure. Two known metabolites, N-acetylsulfadiazine and 4-hydroxysulfadiazine, and two hitherto unidentified minor metabolites were recovered. Various mass spectrometric techniques such as parent, product ion scans and accurate mass measurement were used. The new compounds were identified as N-formylsulfadiazine (For-SDZ) and N-acetyl-4-hydroxysulfadiazine (Ac-4-OH-SDZ). The identification of SDZ, Ac-SDZ and For-SDZ was confirmed by comparison of the spectroscopic and chromatographic data of the synthesized authentic references. The identification of the hydroxylated compounds 4-OH-SDZ and Ac-4-OH-SDZ was performed by MSⁿ, and accurate mass measurements. Only 4% of the administered radioactivity remained in the pig after ten days and SDZ accounted for 44% of the 96% radioactivity excreted. More than 93% of the labelled compounds were detected and identified in the manure. The key analytical problem, namely a high concentration of matrix in sample extracts, was overcome by advanced measurement techniques and with the use of a suitable internal standard. The mean recoveries for all compounds were ≥96%. Linearity was established over a concentration range of 0.5 to 10,000 μg kg⁻¹ manure with a correlation coefficient ≥0.99. The same experiment was carried out simultaneously with non-labelled SDZ to obtain manure for outdoor soil experiments.     

Determination of <Superscript>3</Superscript>H and <Superscript>14</Superscript>C in the Dry Active Wastes (DAW) generated from the Light Water Reactors (LWR) by a wet oxidation method

³H and ¹⁴C Measurements of the dry active waste (DAW), such as the cotton, paper, and vinyl, generated from a nuclear power plant (NPP) were conducted with wet oxidation using open vessel equipment based on simulation results. The recovery efficiency with the simulated samples was around 93% with a relative standard deviation (RSD) of 1–3%. A liquid scintillation counter (LSC) was used for counting and adjusted to a quenching correction curve. The counting value was evaluated for the minimum detectable activity (MDA), which was found to be about 4 × 10⁻¹ Bq/g for ³H and 2 × 10⁻² for ¹⁴C when approximately 5 g of the samples were measured. The measured DAW samples for the cotton, paper, and vinyl generated from NPP achieved of RSD values of 25, 25, and 60%, respectively, for ³H and 0–50% for ¹⁴C.     

Zirconium silicotungstate matrix as a prospective sorbent material for the preparation of <Superscript>113</Superscript>Sn/<Superscript>113m</Superscript>In generator

The zirconium silicotungstate (ZrSiW) was studied as an effective sorbent material to be used in the ¹¹³Sn/^113mIn generator. The results elucidated that the distribution coefficient of ¹¹³Sn (3700 mL/g) is greater than ^113mIn (275 mL/g) from 0.1 M HCl acid solution to the ZrSiW material. The maximum sorption capacity of Sn (IV) was found to be 33 mg per gram ZrSiW (~?0.3 mmol/g). The elution yield of ^113mIn was found to be >?78?±?6.4% with an acceptable purity of radionuclidic and radiochemical (≥?99.99 and 96.8%, respectively). The rigorous separation of ^113mIn from the ¹²⁵Sb was carried out due to its long half-life (2.758 years) and beta emission that causes tissue damage. Zr, W and Si levels are below the permitted limit in the ^113mIn eluate.     

Sequential separation of <Superscript>99</Superscript>Tc, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe, <Superscript>90</Superscript>Sr and <Superscript>59/63</Superscript>Ni from radioactive wastes

A sequential separation procedure has been developed for the determination of ⁹⁹Tc, ⁹⁴Nb, ⁵⁵Fe, ⁹⁰Sr and ^59/63Ni in various radioactive wastes generated from nuclear power plants. Ion exchange and extraction chromatography were adopted for individual separation of the radionuclides. Precipitation was supplementarily utilized for both purification of the individual radionuclides and preparation of the radionuclide sources for use in a radioactivity measurement. The chromatographic separation behavior of the radionuclides both from the sample matrix metals and from one another was investigated using stable metals, Re (as a surrogate of ⁹⁹Tc), Nb, Fe, Sr and Ni. The validity of the procedure for reliability and applicability was evaluated by measuring the recovery of the metal carriers added to synthetic radioactive waste solutions. The recoveries by the chromatographic separation were in the range of 84.8 to 102.2% with 2s of less than 8.6%, the recoveries by the precipitation being in the range of 84.3 to 97.3% with 2s of less than 10.9%.     

Field measurement of the <Superscript>218</Superscript>Po, <Superscript>214</Superscript>Pb and <Superscript>214</Superscript>Bi concentrations in typical indoor and outdoor environments in Beijing

The activity concentrations of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi [i.e. C(²¹⁸Po), C(²¹⁴Pb), and C(²¹⁴Bi)] and the calculated concentration ratios [i.e. 1:C(²¹⁴Pb)/C(²¹⁸Po):C(²¹⁴Bi)/C(²¹⁸Po)] are necessary for assessing radon and its progenies exposure. In this study, a measurement method of radon progenies concentrations with both high sensitivity and low uncertainty, was developed based on the Kerr method. The field measurement results of radon progeny concentrations and calculated concentration ratios in both typical indoor and outdoor environments in Beijing, China, were reported. The effects of air exchange rate on concentration ratios of radon progenies in indoor environments were discussed.     

Half-life measurement of <Superscript>126</Superscript>Sn isolated from Hanford nuclear defense waste

Summary Long-term risk assessment of residual and disposed nuclear fuel reprocessing waste requires good knowledge of component isotopes with long half-lives. For example, the accuracy of the accepted ¹²⁶Sn half-life of approximately 100,000 years is insufficient for desired risk assessments. From modeling and sampling, ¹²⁶Sn is known to exist in Hanford nuclear waste. Excess portions of waste characterization samples were used to isolate ¹²⁶Sn for measurement of its half-life. Isolation was performed with ion-exchange resins. The resulting ¹²⁶Sn was gamma-assayed with a hyperpure germanium spectrometer for decay photon identification and activity values. An inductively coupled plasma/mass spectrometer was used to measure the atom quantity of the isolated ¹²⁶Sn. The separation chemistry, observed gamma energies, and calculated half-life are presented. The half-life of ¹²⁶Sn estimated in this work is (2.33±0.10) ^. 10⁵ years.     

Measuring <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and decay products of <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th in samples of different nature by a multidetector spectrometer

A coincidence method for measuring ¹³⁷Cs, ⁴⁰K, ²²⁶Ra and ²³²Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of ¹³⁷Cs, ²²⁶Ra and ²³²Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer ones.     

Improvement in precision of extremely low <Superscript>236</Superscript>U/<Superscript>238</Superscript>U isotope ratio determination by using mass spectrometer with narrow dynamic range

The precision in measurement of trace level uranium isotopic ratio, i.e., ²³⁶U/²³⁸U or ²³⁴U/²³⁸U, on single Faraday detector with narrow dynamic range is very hard to achieve. this is mainly due to the narrow dynamic range of a single detector systems. A significant improvement in mass spectrometric determination of ²³⁶U/²³⁸U ratio has been achieved by employing an alternate method using a single Faraday detector of narrow dynamic range. The method makes use of the precise measurements of the ²³⁶U/²³⁴U ratio, ²³⁴U/²³⁵U ratio and ²³⁵U/²³⁸U ratio, which are used to calculate the ²³⁶U/²³⁸U ratio using the equation ²³⁶U/²³⁸U=²³⁶U/²³⁴Uײ³⁴U/²³⁵Uײ³⁵U/²³⁸U. Despite the fact that correlation of the data tends to increase the uncertainty in the result, our results show a significant improvement, i.e., more than 8 times better precision in measuring the ²³⁶U/²³⁸U ratio with this method (σ=3.98×10⁻⁰⁸) as compared to direct measurement of ²³⁶U/²³⁸U (σ=3.104×10⁻⁰⁷). The method widens the applicability of the single collector system with narrow dynamic range and it will potentially be helpful to improve the precision in the case of the static multi-collector system also. The objective of the present study was to compare the results of the same sample analyzed with the present alternate method and the direct method for precision.     

Quantitative analysis of hydrogen peroxide by <Superscript>1</Superscript>H NMR spectroscopy

A technique utilizing ¹H NMR spectroscopy has been developed to measure the concentration of hydrogen peroxide from 10^–3 to 10 M. Hydrogen peroxide produces a peak at around 10–11 ppm, depending upon the interaction between solvent molecules and hydrogen peroxide molecules. The intensity of this peak can be monitored once every 30 s, enabling the measurement of changes in hydrogen peroxide concentration as a function of time. ¹H NMR has several advantages over other techniques: (1) applicability to a broad range of solvents, (2) ability to quantify hydrogen peroxide rapidly, and (3) ability to follow reactions forming and/or consuming hydrogen peroxide as a function of time. As an example, this analytical technique has been used to measure the concentration of hydrogen peroxide as a function of time in a study of hydrogen peroxide decomposition catalyzed by iron(III) tetrakispentafluorophenyl porphyrin.Electronic Supplementary Material Supplementary material is available for this article at