A well-type phoswich detector for nuclear explosion monitoring

In this work, a well-type phoswich detector with three scintillation layers has been designed and tested for measuring atmospheric xenon radioisotopes in order to monitor nuclear explosions. The detector was made by optically coupling three concentric cylindrical scintillation layers (BC-400, CsI(Tl) and BGO) to a single photomultiplier tube. Beta-gamma coincidence technique was used to detect beta particles and gamma rays. Other important features of this detector are its Compton suppression capability and simple, compact and cost effective design. Our calculations and measurements with the well-type phoswich detector show that the minimum detectable concentrations are close to or below 1 mBq/m³ for the four xenon radioisotopes.     

A review of the developments of radioxenon detectors for nuclear explosion monitoring

Journal of Radioanalytical and Nuclear Chemistry - Developments in radioxenon monitoring since the implementation of the International Monitoring System are reviewed with emphasis on the most...     

A fluorescent probe for monitoring nitric oxide production using a novel detection concept

A fluorescent probe using a novel 'spin exchange' concept was developed for monitoring nitric oxide (NO) production. The probe is composed of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) labeled with acridine and N-dithiocarboxysarcosine (DTCS)-Fe(II) complex. When the non-fluorescent acridine-TEMPO was incubated with DTCS-Fe(II) complex in buffer solution, the nitroxide radical in the acridine-TEMPO interacted with the Fe(II) through a redox interaction. This interaction recovered the fluorescence based on the acridine moiety. The addition of an NO-releasing reagent caused a fluorescent decrease of the probe due to the irreversible binding of NO to the Fe(II), and the amount of the fluorescent decrease strictly corresponded to that of released NO. Using this probe, less than 100 nM of NO can be detected. This probe system is not only useful for monitoring direct production of NO in an aqueous solution, but is also interesting as a basic concept by which to construct new types of NO fluorescent probes.     

The atmospheric monitoring in a protected area

A multi-annual research program was carried out to study the environmental quality of Castelporziano Presidential Estate (Rome, Italy). Within this program, in the field of air quality, a methodological approach was defined and applied, even by means of proper Environmental Indicators for the identification of anthropogenic contribution and the quantification of degradation. By means of mobile laboratories, macro and micro-pollutant concentrations were assessed in order to define Indexes of Atmosphere Quality and Diffuse Contamination, by relating them to possible short or long-range emission sources. Wet and dry atmospheric depositions were collected and analysed for the determination of heavy metal and acid species fluxes. Critical Load and relative Exceedance maps were elaborated, for the purpose of better underline the areas characterized by a higher environmental vulnerability.     

Design of aerosol sampler to remove radon and thoron progeny interference from aerosol samples for nuclear explosion monitoring

A Nuclear Explosion Monitoring Inertial Impactor (NEMII) system was developed to physically separate naturally occurring radionuclides from those produced in nuclear weapons explosions. Studies show that aerosols containing natural activity have an aerodynamic diameter in the range of 0.1–1.0 μm. It has been established that atmospheric nuclear explosions produce radioactive aerosols with aerodynamic diameters <0.1 μm and surface explosion produce a bimodal distribution of radioactive particles with aerodynamic diameters both >1.0 μm and <0.1 μm. A high volume (66 m³ h⁻¹) impactor was designed to separate the particles into three size distributions: aerosols with aerodynamic diameters >1.0 μm, between 0.1 and 1.0 μm, and smaller than 0.1 μm. Calculations based on previous work for high-volume impactors were completed to obtain the impactor geometry that yields the desired cutoff values. The components of the aerosol impactor were manufactured or obtained and then assembled. In addition, a submicrometer aerosol generation system was assembled to benchmark the NEMII system against a commercial Micro-Orifice Uniform-Deposit Impactor (MOUDI). The MOUDI was also used to verify the naturally occurring radioactivity distribution using ²¹²Pb gamma spectra.     

Application of a xenon arc lamp as a light source for evaporative light scattering detection

The standard tungsten-halogen light source used in a commercial evaporative light scattering detector (ELSD) was replaced with a 180 W xenon arc lamp. The xenon arc lamp possesses a broader spectrum in the UV region than the halogen source. The influence of the UV transmittance of five selected solvents was studied with a size-exclusion chromatography column. This solvent parameter was not observed to influence the ELSD response between the two light source settings. With the solvents studied, better sensitivity was obtained with the xenon arc lamp than the halogen lamp. This high-energy source was applied to ceramide III analysis with an octadecyl-grafted silica column and methanol:tetrahydrofuran 97:3 as the mobile phase, and the sensitivity of the quantification of ceramide III increased 16-fold for injected amounts of 14∼140 ng. The molecular species in a sample of naturally occurring ceramides was analyzed using two C18 columns at 40 °C and gradient elution from 100% acetonitrile to 100% isopropanol in 30 min. The increased ELSD sensitivity achieved when using the xenon arc lamp allowed both the minor and major ceramide species to be observed, in contrast to the results achieved when the halogen lamp was used, where the increased photomultiplier voltage needed to observed the signals from the minor species caused the signals from the major ceramide species to occur above the detector response window.     

Screening of potential sites for undeclared nuclear facilities in environmental monitoring for nuclear proliferation

The sensitivity of environmental sampling and analysis for the estimated atmospheric concentrations of radionuclides in effluents from clandestine nuclear facilities may require many sampling sites and exorbitant costs to monitor such large areas. An assessment has been made of the key factors necessary to support the operation of a nuclear facility, e.g., the existence of a nearby transportation network, main electrical power supply, and population centers. Screening, the subject of this paper, evaluates how cartographic data and satellite imagery can be used to identify areas most capable of supporting undeclared nuclear operations. As a result, large geographical areas can be eliminated from environmental monitoring and sampling. This leads to reduced costs, a reduction in the number of sampling sites required, and a reduction in the overall level of effort required to accomplish effective environmental monitoring. The screening methodology and techniques are described and examples given.     

Analysis and processing of samples for a carbon-14 monitoring program at a radioactive waste storage site

A monitoring program was undertaken to determine the levels of airborne radioactive 14CO2 in an operating waste management area, and it its vicinity. As a part of this program, alkaline microporous pellets, recently developed, were used to sample the 14CO2 in air near waste storage structures and near the waste management area. These pellets were never fully characterized for their ability to capture high levels of 14CO2, and the processing and analysis needed to be improved to provide data on recoveries and consistencies, for an eventual method validation, with independent calibrations and standards. The sample analysis scheme also had to accommodate 14CO2 levels varying from near the natural background (250 Bq kg-1 C), to potentially three to four orders of magnitude above this value, near the wastes. The porous alkaline solid pellets were used for the passive capture of airborne 14CO2 over a period of weeks, to a few months. The pellets were processed to release the captured CO2 (14CO2 and 12CO2) into a NaOH solution, which was subsequently analyzed by liquid scintillation. Processing of the pellets yielded a 14C recovery of 96.0 +/- 4.2% and a lower, but consistent total carbon recovery, i.e., 85.9 +/- 2.7 and 86.9 +/- 2.6%, for procedural blanks and standards, respectively. The detection limits for the pellet sampling and processing was sufficient to reach environmental levels. For the higher levels of 14CO2 and for 'spot' sampling, we also used air samples, pumped into a NaOH solution to trap the 14CO2. These NaOH solutions were counted directly for 14C, also by liquid scintillation. The method limits of this latter technique, although much higher than for pellet samples, also achieved the performance objective for detecting airborne 14CO2. Both sampling and processing techniques, when used together, provided sufficient flexibility to be used for low (environmental) levels and high levels, near the wastes.     

In vivo incorporation of radioactive 36Cl, a method for monitoring chloro compounds in biological material

A new method for fast and easy monitoring of the presence, isolation, and separation of natural chloro compounds in plants is described. The method relies on the in vivo incorporation of radioactive 36Cl and new enhancement methods in autoradiographic technology. The method allows the time of exposure to be limited to 4 days and is thus suitable for routine purposes.     

Gamma-spectrometric measurement procedure for a clearance concept of radioactively contaminated mercury from nuclear facilities

Journal of Radioanalytical and Nuclear Chemistry - Radioactive mercury waste constitutes a significant challenge, as no approved disposal concept yet exists for such waste in Germany. This work...     

Processing of data from a global atmospheric radioactivity monitoring network for CTBT verification purposes

Summary Finland has the operational capability to take airborne gamma-ray measurements in emergency situations. The original purpose of airborne radiation mapping in Finland was to identify hazardous areas containing radioactive fall-out after a nuclear accident or use of nuclear weapons. Regular exercises are held annually to keep the operational functionality at a high level. The achieved capability has been well demonstrated in international INEX-2-FIN 1997 and Barents Rescue 2001 exercises. The knowledge and competence achieved can easily be applied in international radiation monitoring campaigns designed to expose undeclared nuclear materials or other clandestine nuclear activities. The essential improvements in the detection system are linked to the ability to locate point-like radiation sources rather than large areas of fall-out. This paper describes the aerial gamma-ray measurement method and its usability for the detection of nuclear material production chains and trails of fission or activation products. The ability of airborne detection systems in revealing the use of undeclared nuclear materials has been tested. Various scenarios for exposing clandestine nuclear material production, enrichment and nuclear waste trails have been considered. Based on detection capability calculations and testing in practice, it was found that the detection of one un-shielded significant quantity of natural uranium (10 tons of yellow cake in storage barrels) is possible through the daughter products, using one single 6&quot;&apos;4&quot; NaI detector on the airplane. The developed fixed wing gamma measurement technique is now able to detect significant amounts of nuclear material conveniently and cost-effectively. Large areas can be screened to identify suspicious sub-areas for more detailed ground-based inspection.     

Development of a micro-fluidic manifold for copper monitoring utilising chemiluminescence detection

The progressive development of a micro-fluidic manifold for the chemiluminescent detection of copper in water samples, based on the measurement of light emitted from the Cu(ii) catalysed oxidation of 1,10-phenanthroline by hydrogen peroxide, is reported. Micro-fluidic manifolds were designed and manufactured from polymethylmethacrylate (PMMA) using three micro-fabrication techniques, namely hot embossing, laser ablation and direct micro-milling. The final laser ablated design incorporated a reagent mixing channel of dimensions 7.3 cm in length and 250 x 250 microm in width and depth (triangular cross section), and a detection channel of 2.1 cm in length and 250 x 250 microm in width and depth (total approx. volume of between 16 to 22 microL). Optimised reagents conditions were found to be 0.07 mM 1,10-phenanthroline, containing 0.10 M cetyltrimethylammonium bromide and 0.075 M sodium hydroxide (reagent 1 delivered at 0.025 mL min(-1)) and 5% hydrogen peroxide (reagent 2 delivered at 0.025 mL min(-1)). The sample stream was mixed with reagent 1 in the mixing channel and subsequently mixed with reagent 2 at the start of the detection channel. The laser ablated manifold was found to give a linear response (R(2) = 0.998) over the concentration ranges 0-150 microg L(-1) and be reproducible (% RSD = 3.4 for five repeat injections of a 75 microg L(-1) std). Detection limits for Cu(ii) were found to be 20 microg L(-1). Selectivity was investigated using a copper selective mini-chelating column, which showed common cations found in drinking waters did not cause interference with the detection of Cu(ii). Finally the optimised system was successfully used for trace Cu(ii) determinations in a standard reference freshwater sample (SRM 1640).     

Development of a detection tablet for a portable NO2 monitoring system.

We have already developed a HCHO monitoring system which is called FP-30. In this experiment, we have developed a NO(2) detection tablet which can be used by the monitoring system. The detection tablet for the NO(2) was constructed with the sensing paper: porous cellulose paper that contains silica gel as an adsorbent, N-1-naphthylethylenediamine dihydrochloride (NED), and glycerin. The NO(2) in sample gas was blown over and adsorbed on the surface of the sensing paper. Then the NO(2) reacted with NED, producing a yellow compound. The coloring reaction took place on the surface of the sensing paper. The degree of color change of paper from white to yellow was monitored as a function of the intensity of the reflected light (lambda = 475 nm) of an LED. The detection limit was 0.01 ppm when the sampling time was 30 min, and the flow rate of sample gas was 250 ml/min. This sensing paper process was not interfered with by acetaldehyde, acetone, alcohols, hydrocarbons, carbon monoxide or carbon dioxide. The NO(2) concentrations in the rooms of a house or school were monitored using this monitoring system and the standard chemiluminescence method. The concentrations of NO(2) monitored by both methods were within 18% of the average. This highly sensitive, selective, and handy NO(2) gas monitoring system will be widely applicable and convenient for users who are not specialists in this field.     

Conductivity detection for monitoring mixing reactions in microfluidic devices

A conductivity detector was coupled to poly(dimethylsiloxane)-glass capillary electrophoresis microchips to monitor microfluidic flow. Electroosmotic flow was investigated with both conductivity detection (CD) and the current monitoring method. No significant variation was observed between these methods, but CD showed a lower relative standard deviation. Gradient mixing experiments were employed to investigate the relationship between the electrolyte conductivity and the electrolyte concentration. A good linear response of conductivity to concentration was obtained for solutions whose difference in concentrations were less than 27 mM. The new system holds great promise for precision mixing in microfluidic devices using electrically driven flows.     

A method for the machine detection of near equivalence of major substructures in a molecule

The use of the concept of near equivalence of substructures in a computer program concerned with organic synthesis requires a concrete definition of «nearness» and an efficient method for implementing the concept. Such a method has been devised and its use is described and examples are given.     

Optimation of fluorine detection for biological and geological applications with a nuclear microprobe

A review of the nuclear reactions used to determine fluorine is presented. In order to optimize the detection of fluorine in biological or in geological samples, a comparison of the performances obtained with the three nuclear reactions¹⁹F(p, ₀)¹⁶O,¹⁹F(p, )¹⁶O,¹⁹F(p, p')¹⁹F was made. The last reaction was chosen for its sensitivity. The homogeneity of biological and geological standard samples, the linearity of the calibration curves, and the stability of fluorine under the beam were tested.     

A simple and reliable monitoring system for 3H and 14C in radioactive airborne effluent

Summary A simple and reliable sampling system for ³H and ¹⁴C in airborne release from nuclear facilities was designed. The sampling system can collect ³H and ¹⁴C simultaneously with a condensation technique using a commercially available cold trap equipment and a CO₂ absorption technique using an organic alkali monoethanolamine solution, respectively. In situ performance tests for the effluent from a reprocessing plant showed that the system has high and stable efficiencies for collecting ³H and ¹⁴C for a one-week batch sampling at a sampling flow rate of 0.4 l ^. min^-1. These collection techniques also provided a simple procedure of following sample preparation for activity measurements by liquid scintillation counting. The detectable concentrations of the proposed monitoring method were 3.0 Bq ^. m^-3 for ³H and 1.6 Bq ^. m^-3 for ¹⁴C, respectively. The sensitivity would be on an acceptable level for routine monitoring of airborne release at nuclear facilities.