Presence Of Plutonium Research Articles

Passive high explosive neutron inspection (PHENIX): a new method to confirm the presence or absence of high explosives for nuclear treaty verification

Advanced instruments and methods need to be developed now to create a technical basis to support the negotiation of future nuclear arms control treaties. One new capability that is anticipated is the ability to confirm either the declared presence or declared absence of high explosive (HE) material in the presence of special nuclear material (SNM). Towards this goal, Passive HE Neutron Inspection (PHENIX) has been developed and demonstrated as a method for confirming the presence or absence of HE in the presence of plutonium. The method exploits the inherent presence of neutrons associated with the decay of plutonium as an internal probe source for performing prompt gamma-ray neutron activation analysis (PGNAA), searching for the presence of HE as revealed by the emission of characteristic gamma rays following neutron absorption in hydrogen and nitrogen which are building blocks of present-day, military-grade HE. Tests using stoichiometrically-correct hemishells of mock HE with plutonium show that a system can be expected to positively confirm the presence or absence of these signatures, supporting determination of HE presence or absence with Pu, in a few hours. To protect other potentially sensitive gamma-ray signatures from a treaty accountable item, an analog information barrier has been conceptualized and tested which physically prevents the collection of gamma-ray spectral data outside of user selected energy windows strategically chosen to view only narrow spectral regions corresponding to the hydrogen (2223.2 keV) and nitrogen (9807.2 keV, 10,318.2 keV, and 10,829.2 keV) PGNAA signatures.

Confirming the absence of nuclear warheads via passive gamma-ray measurements

Arms-control agreements between the United States and Russia negotiated after the end of the Cold War have imposed limits on the number of deployed strategic nuclear weapons. Verification of these agreements has relied on onsite inspections, sometimes supported by radiation detection techniques to confirm the absence of a nuclear warhead when ambiguities arise. So far, these measurements have sought to detect neutron emissions associated with the presence of plutonium, but they would be inadequate for uranium devices. In an effort to offer instruments that could be used to confirm the absence of both plutonium and uranium weapons, here we propose an inspection system that uses only passive gamma radiation detection techniques. Such a system would be particularly valuable for next-generation arms-control agreements that limit total numbers of weapons and would involve containerized items in storage. We conducted extensive Monte Carlo simulations to support the development of a verification protocol and detection algorithm. We demonstrate the viability of the technique using standard laboratory check sources and MCNP simulations for simplified configurations of special nuclear material.

Swing Reactivity Calculation of Accelerator Driven System Subcritical Reactor 100 MWth

Accelerator driven system (ADS) applied subcritical reactor which can effectively transmute plutonium, minor actinide, and thorium as nuclear waste. In order to lower the amount of nuclear wastes sent to the geological repository, an optimized scattered reloading scheme for ADS is proposed to maximize the discharge burnup and lower the burnup reactivity loss. Accelerator Driven System ( ADS) system lead store duce of the amount of the Pu and Th, so it’s not only can create the addition of energy source, but also high safety reactor. The fuel used in this reactor is obtained from LWR’s spent fuel and thorium - based fuel. The use of thorium-based fuel can lower k-eff of the core and generates U-233, which is a nuclear fuel for critical reactor. Neutron obtained from spallation reaction of Pb-Bi target is placed in the center of the core. This ADS design produces subcritical k-eff during the operation of the reactor and can decrease the amount of fission products of LWR’s spent fuel and produce U-233. The objective of the calculation are criticality as a function of burn up (swing reactivity) in the subcritical assembly fuel. this ADS fuel is originated from UO2 PWR spent fuel with enrichment of 3,4 % and burn up level 64 GWD or 100 MWt for 1825 days calculation of accelerator driven system subcritical reactor 100MWth has been performed. This research d one by using Origen2.1, SRAC2006 and MCNP6 Code. Based on the results swing reactivity of the calculation by using Origen2.1 Code, indicates that Kinf whose value be low subcritical condition (k-eff<1) is Kinf resulted fromTh-232 with percentage from 10% to 5%(as U-238 substitution).the calculation by using SRAC2006 Code indicates that at the beginning of life (BOL), the k-eff of ADS design with 50 cm thickness is 0.9821491 and at the end of life (EOL) k-eff is 0.9396284 and the calculation by using MCNP6 Code. At beginning of life (BOL), the k-eff of ADS design is 0.9847 and the end of life (EOL) is 0.9823.The presence of plutonium and mayor actinides makes k-eff get slightly lower. Arrangement at this ADS model is performed to produce subcritical condition, in which an increase in fuel volume cause k-eff>I.

On the presence of plutonium in Madagascar following the SNAP-9A satellite failure

This study examined the 238Pu and 239+240Pu activity concentration and the 240Pu/239Pu atomic ratio in peat bogs sampled in 2012 from marshlands in central Madagascar. The purpose was to investigate the presence of plutonium isotopes, 238, 239, 240Pu, from the 1964 satellite failure carrying a SNAP-9A radiothermal generator. With an average 238Pu/239+240Pu activity ratio of 0.165 ± 0.02 (decay corrected to 1964), the peat bogs in Madagascar exhibit similar values as the ones found in the southeastern African continent, except they are one order of magnitude higher than expected (0.025) from global fallout in the Southern Hemisphere. The 240Pu/239Pu atomic ratio showed a distinct decrease for layers dating back to the mid-1960s (down to 0.069 compared with an anticipated ratio of 0.17 for global fallout), indicating that the SNAP-9A failure also resulted in an elevated deposition of 239Pu. The obtained results demonstrate that further Pu analysis in Madagascar and in southeastern continental Africa is necessary to fully account for the regional Pu deposition from the SNAP-9A event.

Analysis Of Doppler Reactivity Coefficient On The Typical Pwr-1000 Reactor With Mox Fuel

&lt;p&gt;Doppler coefficient is defined as a relation between fuel temperature changes and reactivity changes in the nuclear reactor core. Doppler reactivity coefficient needs to be known because of its relation to the safety of reactor operation. This study is intended to determine the safety level of the typical PWR-1000 core by calculating the Doppler reactivity coefficient in the core with UO&lt;sub&gt;2&lt;/sub&gt; and MOX fuels. The typical PWR-1000 core is similar to the PWR AP1000 core designed by Westinghouse but without Integrated Fuel Burnable Absorber (IFBA) and Pyrex. Inside the core, there are UO&lt;sub&gt;2&lt;/sub&gt; fuel elements with 3.40 % and 4.45 % enrichment, and MOX fuel elements with 0.2 % enrichment. By its own way, the presence of Plutonium in the MOX fuel will contribute to the change in core reactivity. The calculation was conducted using MCNPX code with the ENDF/B- VII nuclear data. The reactivity change was investigated at various temperatures. The calculation results show that the core reactivity coefficient of both UO&lt;sub&gt;2&lt;/sub&gt; and MOX fuel are negative, so that the reactor is operated safely.&lt;/p&gt;

Structural Investigation of (U0.7Pu0.3)O2-x Mixed Oxides.

Uranium-plutonium mixed oxide containing 30% of plutonium is a candidate fuel for several fast neutron and accelerator driven reactor systems. In this work, a detailed structural investigation on sol-gel synthesized stoichiometric U0.7Pu0.3O2.00 and substoichiometric U0.7Pu0.3O2-x, using X-ray diffraction (XRD), oxygen 17 magic angle spinning nuclear magnetic resonance ((17)O MAS NMR) and X-ray absorption spectroscopy is described. As observed by XRD, the stoichiometric U0.7Pu0.3O2.00 is monophasic with a lattice parameter in good agreement with Vegard's law, while the substoichiometric U0.7Pu0.3O2-x material is biphasic. Solid solution ideality in terms of a random distribution of metal atoms is proven for U0.7Pu0.3O2.00 with (17)O MAS NMR. X-ray absorption near-edge structure (XANES) spectroscopy shows the presence of plutonium(III) in U0.7Pu0.3O2-x. Extended X-ray absorption fine-structure (EXAFS) spectroscopy indicates a similar local structure around both cations, and comparison with XRD indicates a close similarity between uranium and plutonium local structures and the long-range ordering.

Further evaluations of the toxicity of irradiated advanced heavy water reactor fuels.

The neutron economy and online refueling capability of heavy water moderated reactors enable them to use many different fuel types, such as low enriched uranium, plutonium mixed with uranium, or plutonium and/or U mixed with thorium, in addition to their traditional natural uranium fuel. However, the toxicity and radiological protection methods for fuels other than natural uranium are not well established. A previous paper by the current authors compared the composition and toxicity of irradiated natural uranium to that of three potential advanced heavy water fuels not containing plutonium, and this work uses the same method to compare irradiated natural uranium to three other fuels that do contain plutonium in their initial composition. All three of the new fuels are assumed to incorporate plutonium isotopes characteristic of those that would be recovered from light water reactor fuel via reprocessing. The first fuel investigated is a homogeneous thorium-plutonium fuel designed for a once-through fuel cycle without reprocessing. The second fuel is a heterogeneous thorium-plutonium-U bundle, with graded enrichments of U in different parts of a single fuel assembly. This fuel is assumed to be part of a recycling scenario in which U from previously irradiated fuel is recovered. The third fuel is one in which plutonium and Am are mixed with natural uranium. Each of these fuels, because of the presence of plutonium in the initial composition, is determined to be considerably more radiotoxic than is standard natural uranium. Canadian nuclear safety regulations require that techniques be available for the measurement of 1 mSv of committed effective dose after exposure to irradiated fuel. For natural uranium fuel, the isotope Pu is a significant contributor to the committed effective dose after exposure, and thermal ionization mass spectrometry is sensitive enough that the amount of Pu excreted in urine is sufficient to estimate internal doses, from all isotopes, as low as 1 mSv. In addition, if this method is extended so that Pu is also measured, then the combined amount of Pu and Pu is sufficiently high in the thorium-plutonium fuel that a committed effective dose of 1 mSv would be measurable. However, the fraction of Pu and Pu in the other two fuels is sufficiently low that a 1 mSv dose would remain below the detection limit using this technique. Thus new methods, such as fecal measurements of Pu (or other alpha emitters), will be required to measure exposure to these new fuels.

Optimization of an analytical method for reducing the volume of radioactive waste generated during determination of uranium in presence of plutonium

A new method for uranium (U) determination in presence of plutonium (Pu) in the range of 0.7–2.4 mg per aliquot is optimized in a low volume potentiometric cell (4 mL) and waste volume is decreased by six times. U determination in presence Pu at higher dynamic range is optimized by a complexometric titration by employing 2,6 pyridine di-carboxylic acid and ethylene diamine tetra acetic acid as the masking agent. In this method Pu introduced a bias of 6 % irrespective of U–Pu concentration ratio with a precision of 0.4 %.

Non-invasive material discrimination using spectral x-ray radiography

Current radiographic methods are limited in their ability to determine the presence of nuclear materials in containers or composite objects. A central problem is the inability to distinguish the attenuation pattern of high-density metals from those with a greater thickness of a less dense material. Here, we show that spectrally sensitive detectors can be used to discriminate plutonium from multiple layers of other materials using a single-view radiograph. An inverse algorithm with adaptive regularization is used. The algorithm can determine the presence of plutonium in simulated radiographs with a mass resolution per unit area of at least 0.07 g cm−2.

Features of Hybrid Core Calculations at BFS-62-3A Experiments

Different uranium-plutonium fuel compositions are considered for sodium fast reactors of the next generation. Considerable discrepancies in axial and radial neutron spectra for hybrid reactor systems compared to uranium oxide fuel cores increase uncertainties in the key calculated neutronic characteristics of hybrid systems. The calculation results of a BFS-62-3A critical assembly considered as a full-scale model of BN-600 hybrid core with steel reflector specify quite different spectra in local areas. In such systems the MCNP5 calculations demonstrate a noticeable sensitivity of the key neutronic characteristics (effective multiplication factor keff, spectral indices) to nuclear data libraries and extra steel such as dowels placed in the core. Uncertainties in the location of stainless steel dowels and in their quantity cause uncertainties in the fuel-to-steel mass ratio in the core. For 235U, 238U, and 239Pu, the calculated radial fission rate distributions against the reconstructed ones are analyzed. A comparative analysis of spectral indices, neutron spectra, and radial fission rate distributions is performed using nuclear data libraries generated from ENDF/B-VII.0, JEFF-3.1.1, JENDL-3.3, and BROND-3 for Fe and Cr isotopes. When performing analysis of the fission-rate sensitivity to the presence of plutonium in fuel, 239Pu is replaced by 235U in local areas containing plutonium. For radial fission rate distributions, peak discrepancies may be due to possible underestimation of some features of experimental data processing and reconstruction methods (Westcott factors, temperature dependence, local core features). A more-sophisticated impact analysis of spatially different neutron spectra on neutron characteristics of the core is also required. To confirm the results of BFS-62-3A analysis, radial fission-rate distributions are calculated for BFS-62-4 with UO2 blanket instead of steel reflector.

Development of a method for the estimation of low amount of plutonium in 200 L waste drums in presence of high amount of β γ activity due to 137Cs and 60Co

The waste drum monitoring system based on HPGe detector was used to study its performance for the estimation of low amounts of plutonium in presence of high activity of 137Cs and 60Co. The counting was carried out by keeping amount of plutonium constant at 100 mg level and varying the count rate for the γ rays of 137Cs and 60Co. Present study has shown that the estimation of low amount of 239Pu in a waste drum can be carried out using 129 keV γ ray in the presence of 137Cs up to an activity level of 16 mCi and in the presence of 60Co up to an activity level of 8 mCi.

Chemical Compatibility at High Temperature between the Carbide Fuel UC or (U,Pu)C and SiC Cladding for the Gas cooled Fast Reactor

AbstractThe chemical compatibility at high temperature between the fuel kernel (U,Pu)C and SiC cladding, the reference materials for the GFR reactor, is studied. For that purpose, a thermodynamic database on the U-Pu-C-Si system was developed with the Calphad method to calculate the phase diagrams. Differential thermal analysis experiments were performed to measure phase transition temperatures in Si-U and C-Si-U systems. According to the calculated isopleth section between the hyperstoichiometric uranium carbide UC1.02 and SiC, the materials shall not react below 2056 K, the temperature at which a liquid phase shall form. These calculations are in good agreement with two chemical compatibility tests performed at 1873 K and 2073 K between the materials. Calculations were also performed to study the chemical interaction between the mixed carbide (U,Pu)C1.04 and SiC. The presence of plutonium in the fuel kernel lowers the liquid formation temperature of 167 K.

A robust biamperometric titration methodology for the determination of uranium by Ti(III) reduction in the presence of plutonium

A biamperometric method is described for the determination of uranium in plutonium bearing nuclear fuel materials. Ti(III) is used for reducing U(VI) to U(IV) in 6 to 9 M H 2 SO 4 medium, followed by destruction of the excess reductant by HNO 3 . Plutonium is also reduced to Pu(III), but is selectively oxidized to Pu(IV) by the HNO 2 produced in situ during the destruction of the excess Ti(III) by HNO 3 . The U(IV) is determined by titration with standard K 2 Cr 2 O 7 . Accuracy and precision of the method have been evaluated using different amounts of uranium ranging from 5 microgram to 20 milligram. The method has been applied to U determination in uranium oxides, uranium carbides, (U, Pu)O 2 , (U, Th)O 2 , (U, Pu)C and U-Al alloy. The method has also been employed for the determination of U present at very low levels (< 0.2%) in PuO 2 .

Characterisation of hot particles remaining in soils from Palomares (Spain) using a nuclear microprobe

More than 40 years ago, an aircraft accident took place in Palomares (Spain) which involved the destruction of two nuclear weapons. A portion of the remaining transuranic contamination in the affected soils is present in the form of small high activity concentration particles (10–100 μm), also called “hot particles”, which contain plutonium and uranium. Several hot particles have been isolated and identified from the superficial soils recently collected in the zone affected by the accident. The isolation was carried out by screening the soil using gamma-ray spectrometry, through discrimination of the high activity concentrations of 241Am in the samples which indicates the presence of plutonium. The hot particles, composed of several elements with very high atomic number, could be easily identified by scanning electron microscopy (SEM) in backscattering electron image (BSE) mode. Moreover, their morphology and size were also studied using SEM in secondary electron (SE) mode. In this work, the hot particles have been investigated with the nuclear microprobe of the National Accelerator Centre (CNA) in Seville. Compositional analysis, mapping and depth distribution of different elements have been performed by a simultaneous combination of Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS). Uranium and plutonium have been identified in the PIXE spectra as the main components of the particles, whereas the concentration of Americium is two orders of magnitude smaller. In addition, an estimation of the particles density has been obtained by comparison of the RBS results with the particles thickness directly determined by SEM.

A γ-ray integrated prototype system for the measurement of plutonium component attributes

A γ-ray integrated measurement prototype system named HAM-1 has been built up by integrating the technologies of γ-ray detection，spectral analysis and information barrier，which can be used for potential nuclear disarmament verification of plutonium components through the measurement of attributes such as the presence of plutonium，the weapon-grade plutonium and its age. A basic starting point for the development of HAM-1 was to prevent any possible leakage of sensitive weapon design information in the process of measurement. Two embedded ARM controllers were selected as the CPUs of HAM-1 according to the design requirements of information barriers. A code dedicated to HAM-1 has been developed for analyzing the high-resolution γ-ray spectra to accurately determine the attributes. The all-round process of HAM-1 from the spectra sampling to data processing and result display was automatic, during which the sensitive weapon design information was protected from leakage.

Rapid identification and analysis of airborne plutonium using a combination of alpha spectroscopy and inductively coupled plasma mass spectrometry.

Recent wildland fires near two U.S. nuclear facilities point to a need to rapidly identify the presence of airborne plutonium during incidents involving the potential release of radioactive materials. Laboratory turn-around times also need to be shortened for critical samples collected in the earliest stages of radiological emergencies. This note discusses preliminary investigations designed to address both these problems. The methods under review are same day high-resolution alpha spectroscopy to screen air filter samples for the presence of plutonium and inductively coupled plasma mass spectrometry to perform sensitive plutonium analyses. Thus far, using modified alpha spectroscopy techniques, it has been possible to reliably identify the approximately 5.2 MeV emission of 239Pu on surrogate samples (air filters artificially spiked with plutonium after collection) even though the primary alpha-particle emissions of plutonium are, as expected, superimposed against a natural alpha radiation background dominated by short-lived radon and thoron progeny (approximately 6-9 MeV). Several processing methods were tested to prepare samples for analysis and shorten laboratory turn-around time. The most promising technique was acid-leaching of air filter samples using a commercial open-vessel microwave digestion system. Samples prepared in this way were analyzed by both alpha spectroscopy (as a thin-layer iron hydroxide co-precipitate) and inductively coupled plasma mass spectrometry. The detection levels achieved for 239Pu--approximately 1 mBq m(-3) for alpha spectroscopy screening, and, < 0.1 mBq m(-3) for inductively coupled plasma mass spectrometry analysis--are consistent with derived emergency response levels based on EPA's Protective Action Guides, and samples can be evaluated in 36 to 72 h. Further, if samples can be returned to a fixed-laboratory and processed immediately, results from mass spectrometry could be available in as little as 24 h. When fully implemented, these techniques have the potential to provide useful information and improved operational flexibility to emergency planners and first-responders during radiological emergencies.

Identification and characterization of radioactive ‘hot’ particles in Chernobyl fallout-contaminated soils: the application of two novel approaches

The Chernobyl accident in 1986 resulted in the widespread identification of the post-accident presence of radioactive (or ‘hot’) particles across large areas of Eastern and Central Europe. Such particles arise from direct deposition and also from condensation and interactions on particle surfaces during and following the deposition of soluble fallout. Identification of the presence and nature of hot particles is necessary in order to determine the long-term ecological impact of radioactive fallout. This paper describes several techniques for the identification and characterization of hot particles in soil samples from Belarus. In addition to new results from the use of gamma spectrometry, we include two novel instrumentation approaches that have been developed and applied to Chernobyl fallout-contaminated soils. The first, ‘differential’ autoradiography, utilizes a photographic film sandwich to characterize the nature of the ionizing radiation emitted from samples. In this paper we show that differential autoradiography can not only identify hot particle presence in soil, but can also determine the dominant radionuclide in that particle. The second approach, sector field ICP-MS (ICP-SFMS), can provide rapid, high-precision determination of the actinides, including the transuranic actinides, that characteristically occur in hot particles originating from weapons fallout or fuel matrices. Here, ICP-SFMS is shown to yield sufficiently low detection limits for plutonium isotopes (with the exception of 238Pu) to enable us to confirm negligible presence of plutonium in areas outside the Chernobyl exclusion zone, but with high levels of fission-product contamination.

Application of normal pulse voltammetry to on-line monitoring of actinide concentrations in molten salt electrolyte

The applicability of electroanalytical methods – square wave voltammetry (SWV) and normal pulse voltammetry (NPV) – to on-line monitoring of actinide concentrations in molten chlorides was investigated for use in pyrometallurgical processes. For SWV curves for plutonium, the concentration dependence of the peak current was not linear at high concentration. However, the limiting currents for uranium and plutonium determined by NPV were proportional to their concentrations up to about 1.7 wt%. The fission product elements do not seem to affect the accuracy in determination of actinide concentrations because the limiting currents for uranium and plutonium were not influenced by the addition of gadolinium. It was found to be difficult to determine neptunium concentration in the presence of plutonium due to the overlap of the output current waves. From those results, NPV was considered more promising although the optimization of applied potential waveform is necessary for use at higher concentrations.

Chromatographic extraction of plutonium and inorganic impurity analysis using ICP-MS and ICP-AES

The purpose of this study was to assess the feasibility of ICP-MS and ICP-AES for the quantitation of 45 target analytes in solutions containing plutonium, and solutions where the plutonium had been removed using anion exchange. The selectivity of the anion exchange resin was also evaluated. High purity plutonium solutions, including a spiked solution were dissolved in triplicate and analyzed by both ICP-MS and ICP-AES, before and after removal of the plutonium matrix. The presence of plutonium appeared to have little effect on recoveries for the ICP-MS technique, whereas twenty-six out of thirty six elements were outside the preferred recovery range of 80–120% for the emission technique. Once the plutonium was removed using a strong anion exchange resin, only 6 elements fell outside the quantitative recovery acceptance window for ICP-AES. Of the target analytes studied, only Ag, Th, Tl, and U appeared to be adsorbed onto the column. These elements are readily determined directly in the plutonium solution by ICP-MS. Elements that must be determined in the extracted sample by ICP-AES are Fe, K, P, and Si. Interelement correction factors were established for the ICP-AES technique and method detection limits were determined for both techniques.

Determination of uranium and thorium in geological materials using extraction chromatography

A procedure has been developed for the determination of uranium and thorium in geological samples using extraction chromatography. Following sample preparation, uranium and thorium are pre-concentrated by precipitation with iron(III) hydroxide and then separated using UTEVA resin. The separated uranium and thorium are electrodeposited onto stainless-steel discs and then measured by alpha spectrometry. The procedure was evaluated using uraninite ore, coral and granite reference materials. The uranium and thorium concentrations and the 234U/238U and 230Th/234U activity ratio values determined for the reference materials were in good agreement with the certified values. The presence of plutonium was found to interfere with the separation, but the inclusion of a reduction step using iron(II) sulfamate eliminated the problem. Chemical recoveries for the procedure are similar to those for an anion-exchange procedure, but the extraction-chromatography procedure provides a more rapid separation using less reagents.