Non-Destructive Determination of Silicon in Steel and Steel-Related Samples by INAA Using the 29Si(n,p)29Al reaction

A non-destructive method has been developed for the determination of silicon in steel alloys by reactor fast neutron activation analysis using the ²⁹Si(n,p) ²⁹Al reaction. An iron sample and a comparator of pure metallic silicon powder are irradiated in a cadmium case. In order to obtain the net counting rate of the 1273.4 keV peak from ²⁹Al, background activities are corrected carefully to avoid peaks of 1268.0 keV from ²⁸Al single-escape and 1266.2 keV from ³¹Si. The present method is superior to the method using the ²⁸Si(n,p) ²⁸Al reaction.     

Possibilities of low-level determination of silicon in biological materials by activation analysis

The capabilities of neutron and photon activation analysis (NAA and PAA, respectively) for low-level determination of silicon in biological materials have been examined. Sensitivities of a variety of modes of NAA and PAA with radiochemical separation have been evaluated. Results are presented for silicon in reference materials CSRM 12–2-03 Lucerne, Bowen’s Kale, NIST SRM-1571 Orchard Leaves, and NIST SRM-1515 Apple Leaves. The results were obtained by employing the ²⁹Si(n,p)²⁹Al reaction with fast reactor neutrons and the radiochemical procedure developed for aluminium separation. Possibilities of further improvement of the silicon determination limit down to the μg g^–1 level by employing NAA and PAA with radiochemical separation are outlined.     

Mapping of neutron flux gradient at NIST reactor to optimize neutron activation analysis of53Mn

Determination of⁵³Mn in meteorites by neutron activation analysis requires a thermal neutron flux high enough to ensure adequate production of⁵⁴Mn from⁵³Mn with a sufficiently low fast neutron component to minimize its production through fast neutron reactions. Thermal and fast neutron fluxes were mapped as a function of sample position within the NIST research reactor in order to determine the optimum position for irradiation of⁵³Mn.     

Application of the k0 standardization method in reactor nuetron activation analysis of standard steels and fly ash

The method of k₀ standardization is suitable for routine multi-element determinations by reactor neutron activation. Investigation of NBS steel standards showed the systematic error of the method to be less than 3%. Numerical evaluation of the spectra was found to be fast and convenient. Fourteen elements in the steel samples were determined; for nine, the standard deviation was less than 4%. Thirty seven elements were determined in NBS SRM-1663a Coal Fly Ash; agreement with certified values was again very good.     

Development of a flow-sheet for the radiochemical processing of irradiated sulphate targets for the production of carrier-free 32P

Carrier-free ³²P was produced in KAlpakkam MINI reactor (KAMINI) via ³²S (n, p) ³²P using its small fast flux component. This method has established the flow-sheet for the production of ³²P from sulphate targets such as magnesium sulphate and strontium sulphate which can withstand high temperatures of fast reactors unlike the conventionally used sulphur powder. The chemical processing involved (i) struvite precipitation method for magnesium sulphate and (ii) co-precipitation with ferric hydroxide method for strontium sulphate.     

Fast neutron activation analysis of silicon in aluminum alloys

The silicon content in an aluminum-silicon alloy was measured by nondestructive fast neutron activation analysis with fission spectrum neutrons. A boron nitride irradiation container reduced the flux of thermal and epithermal neutrons at the sample position, enhancing the²⁹Si (n, p)²⁹Al reaction. A detection limit of 0.4% silicon in a 0.5 g alloy sample was obtained.     

The single-comparator method in thermal neutron activation analysis extended for some (n,p) reactions

From experimental studies of the rate of the reactions⁴⁷Ti(n, p)⁴⁷Sc,⁴⁸Ti(n, p)⁴⁸Sc and⁵⁸Ni(n, p)⁵⁸Co in four nuclear reactors, it is concluded that for the irradiation positions of the light water moderated reactors BR2 (Mol, Belgium) and HFR (Petten, Netherlands) a simple empirical relation exists between the fast neutron flux on the one hand and the thermal and epithermal neutron flux on the other. The graphite moderated reactor BR1 (Mol, Belgium) and the heavy water reactor FRJ2 (Jülich, Federal Republic of Germany), however, have relatively much lower fast fluxes and their irradiation facilities do not obey the empirical relation determined.     

Reactor neutrons irradiation effect on the photocatalytic activity of SnO<Subscript>2</Subscript> thin films

SnO₂ thin films synthesized by sol-gel are irradiated with reactor neutrons up to fast neutron fluence of 9.6 × 10¹⁷ neutrons cm^–2 at 40°C. The influence of defects generated by neutrons irradiation, through the properties modification, on the photo-catalytic activity of SnO₂ films is investigated. It is found that the photoactivity of the irradiated films is enhanced after reactor neutrons irradiation. An improvement of 41% is observed for the sample irradiated at a neutron fluence of 9.6 × 10¹⁷ neutrons cm^–2. This is attributed to several parameters modified by the reactor neutron irradiation principally the crystallite size and space charge region which are closely related to the photocatalytic performance.     

Neutron energy spectrum determination and flux measurement using MAXED, GRAVEL, and MCNP for RACE experiments

Stainless steel flux wires were used to determine the neutron energy spectra and total flux during the Reactor Accelerator Coupling Experiments (RACE) at The University of Texas at Austin. A LINAC electron accelerator produced 20 MeV electrons at a power of 1.6 kW, which struck a tungsten-copper target to produce bremsstrahlung radiation and photoneutrons. The neutrons produced in the target were multiplied by the subcritical core of a Triga reactor. The purpose of the RACE experiments is to develop a sub-critical accelerator driven system that would be capable of transmuting actinides from spent fuel. Flux measurements were made with 1.58 mm diameter stainless steel wires placed throughout the core between the fuel rods and cadmium covered and uncovered gold and indium foils above the target. The MAXED and GRAVEL computer codes were used to perform the spectrum unfolding. The composition of the stainless steel wires was determined using neutron activation analysis with comparators prior to the flux measurement. The reactions measured in the stainless steel to determine the flux were ⁵⁰Cr(n,γ)⁵¹Cr, ⁵⁸Ni(n,p)⁵⁸Co, ⁵⁴Fe(n,p)⁵⁴Mn, and ⁵⁸Fe(n,γ)⁵⁹Fe. Flux measurements agreed well with an MCNP simulation of the experiment.     

Poly (phenylmethylsilane) obtained by electrochemical reduction in a divided cell containing a polymeric membrane

The electrochemical synthesis of poly(phenylmethylsilane) was carried out in a divided cell using a polymeric anion-exchange membrane. The solution contained phenylmethydichlorosilane (PhMeSiCl₂), mixed solvent tetrahydrofuran + hexamethylphosphoramide, with tetrabutylammonium perchlorate as support electrolyte. The electrodes were stainless steel as the cathode, stainless steel as the sacrificial anode or platinum as the resistant anode. Poly(phenylmethylsilane) was obtained in yields from 1.5 to 4.5 % from phenylmethyldichlorosilane concentrations equal or higher than 1 M. The number-average molecular mass M_n of poly(phenylmethylsilane) was in the range from 5600 to 9500. A monomodal molecular weight distribution was obtained with a polydipersity Index of 2. The spectra of ¹H, ¹³C, ²⁹Si MMR and IR were determined. From the ²⁹Si NMR analysis, the poly(phenylmethylsilane) showed a clear difference in the tacticity related to the chemical synthesis of the same polymer. The UV spectra showed a strong absorption in a 331 to 335 nm characteristic for the poly(phenylmethylsilane).     

Determination of the fast fission yield of141Pr using neutron activation analysis

A method is described for the determination of the fission yield of¹⁴¹Pr. This method was developed to determine the fast fission yield of¹⁴¹Pr in the Mark III loading (enriched uranium with about 2% zirconium) of the fast fission breeder reactor, EBR-1. The burnup of the fuel sample was determined using the previously reported fission yield of¹³⁷Cs. Praseodymium was separated from uranium, plutonium and other fission products by a combination of precipitation and ion exchange stages. Thereafter,⁵⁵Mn was added to serve as an internal flux monitor and praseodymium determined by neutron activation analysis. A precision of ±2% was obtained. Presented at the 15th Annual Meeting of the American Chemical Society, Miami Beach, Florida (USA), April 1967.     

Cesium-137 in air late after the Chernobyl reactor accident

Summary Cesium-137 in air as high as 88.1 μBq ^. m^-3 was recorded in Thessaloniki, Northern Greece (40°38’N, 22°58’E) on June 3, 1998 very late after the Chernobyl reactor accident following a radiological incident occurred in a steel factory at Acerinox, Spain.     

Estimation of isotopic composition of plutonium from thermal reactors by neutron coincidence counting through isotopic correlation technique

Correlations have been established between %Eff ²⁴⁰Pu and various plutonium isotopes formed in thermal reactors. Based on these correlations, a method has been developed for the estimation of isotopic composition of plutonium obtained from thermal reactors. The method is simple, fast, non-destructive and finds application for the verification of plutonium isotopic composition in the finished products of known plutonium content. The method could be applied in the nuclear fuel fabrication to verify and confirm the fissile content (²³⁹Pu+²⁴¹Pu) specification. It has also been shown that in principle, similar correlations could be established for Pu obtained from different thermal reactor fuels with reactor specific fitting parameters.     

Radiochemical methods in nuclear waste management

Radiochemical techniques play an important role in nuclear waste management studies at the Centre for Analytical Research in the Environment. Current research includes the measurement of atmospheric emissions from a reprocessing plant, modelling of environmental pathways, and evaluation of reactor materials for the prediction of releases from ultimate disposal sites. A radiochemical separation procedure has been developed for¹²⁹I, which has been applied to a study of emissions from the Sellafield nuclear reprocessing plant. Atmospheric emissions, rainfall, grass, milk and wild food are analysed to model the ultimate fate of¹²⁹I. A new procedure has been developed for measuring sub-ppm concentrations of chlorine in archive steel samples as part of programme to produce an inventory of arisings of³⁶Cl from nuclear power stations. The method has been extended to other reactor materials and this paper describes the application of the radiochemical method for Magnox alloys, mild steel and cast iron.     

Synthesis,Characterization and Properties of (Vinyl Triethoxy Silane-grafted PP)/Silica Nanocomposites

A new route has been developed to produce PP/silica nanocomposites starting from porous PP reactor powder and making use of sol-gel chemistry. Silica-like, nano-sized particles were prepared in the pores of the PP reactor powder with a controlled degree of adhesion between PP and silica. Magic-angle spinning (MAS) ²⁹Si NMR spectra showed that the chemical building blocks of the silica-like clusters are of Q³ and Q⁴-type. For (vinyl triethoxy silane (VTES)-grafted PP)/silica nanocomposites, VTES was grafted via solid-state modification (SSM) in porous PP particles. Subsequently, silica particles were prepared by sol-gel technology in the VTES-grafted PP. MAS ²⁹Si NMR and FT-IR spectroscopy showed that the grafted VTES becomes part of the in-situ formed silica particles. The study on the mechanical properties of (VTES-grafted PP)/silica nanocomposites showed that the silica particles improved the impact toughness of PP by a factor of 2, when there is no chemical interaction between the particles and the matrix, while for (VTES-grafted PP)/silica nanocomposites the impact toughness decreased. This indicates that chemical bonding between the filler particles and the PP-matrix results in brittle failure and supports the hypothesis that debonding is necessary for improving the impact toughness of PP with inorganic fillers.     

Verwendung schneller Reaktorneutronen zur raschen und zerst?rungsfreien Spurenanalyse, insbesondere von Sauerstoff

Zusammenfassung Der intensive Fluß schneller Neutronen, wie er von Kernreaktoren geliefert wird, kann für eine rasche und zerstörungsfreie, aktivierungs-analytische Bestimmung einer Vielzahl von Elementen verwendet werden. Bei manchen Elementen läßt sich sogar bei der Aktivierung mit schnellen Reaktorneutronen eine im Vergleich zur Aktivierungsanalyse mit thermischen Neutronen tiefere Erfassungsgrenze erreichen. Werden die Proben in einem schnellen, halbautomatischen Rohrpostsystem zum Reaktorkern befördert, können auch sehr kurzlebige Radionuklide gemessen werden. Besonders Sauerstoff läßt sich über die Kernreaktion ¹⁶O(n, p)¹⁶N sehr empfindlich bestimmen, wobei die hochenergetischen -Quanten des 7,2 sec Stickstoff-16 gemessen werden. Es können so bis zu 10 ppm Sauerstoff in vielen Arten von Analysenproben erfaßt werden. Das halbautomatische Analysensystem, das mit Hilfe einer schnellen Rohrpost die Durchführung rascher und zerstörungsfreier Aktivierungs-analysen im Forschungsreaktor München erlaubt, wird beschrieben. Die Verwendung des Systems zur Sauerstoffanalyse und die damit zusammenhängenden Probleme werden genauer besprochen.

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Summary The intense fast-neutron fluxes, which are available in nuclear reactors, can be used for rapid and non-destructive activation analysis of many elements. Some elements have even superior detection limits for activation with fast reactor neutrons compared to reactor thermal-neutron activation. Short-lived radionuclides can also be measured using a fast pneumatic tube system. Oxygen can be determined by the nuclear reaction ¹⁶O(n, p)¹⁶N initiated by fast reactor neutrons counting the high-energy gamma rays of the 7.4 sec nitrogen-16. The method is suitable for determining as little as 10 ppm of oxygen in many types of analytical samples. The fast transfer system, which is used in the Munich research reactor for rapid and non-destructive activation analysis is described. The use of the transfer-system for oxygen activation analysis and problems associated with oxygen analysis are discussed.

     

TDCR measurements of 3H, 63Ni and 55Fe using Hidex 300SL LSC device

The commercial Hidex LSC system has been used to measure triple to double coincidence ratio (TDCR), experimental counting efficiency (CE) and the absolute activity for radioactive standards of pure beta emitters viz. ³H, ⁶³Ni and ⁵⁵Fe, an electron capture nuclide. Colour and chemical quench measurements of ⁶³Ni and ⁵⁵Fe have been done. An excellent match between TDCR and CE has been obtained for beta emitters, while very large deviations have been observed for ⁵⁵Fe. The deviation between TDCR and experimental efficiency has been found to be nearly uniform. Based on this, an empirical correction factor for TDCR which gives the correct efficiency has been evaluated, to enable efficient application of this commercial instrument for ⁵⁵Fe estimation. These TDCR correction factors were further validated by applying for ⁵⁵Fe activity measurements in ASTM standard steel samples irradiated to a fixed neutron flux in research reactor CIRUS. Finally, ⁵⁵Fe activity in steel sample from APSARA reactor decommissioning waste was successfully estimated using this modified TDCR.     

Recovery of neptunium from highly radioactive waste solutions of PUREX origin using CMPO

The partitioning and recovery of²³⁷Np from three types of simulated high level waste solutions originating from PUREX processing of spent nuclear fuels such as sulfate bearing high level waste (SB-HLW), HLW from a pressurised heavy water reactor (PHWR-HLW) and from a fast breeder reactor (FBR-HLW) have been carried out using a mixture of 0.2M CMPO and 1.2M TBP in dodecane. Quantitative extraction of neptunium was possible by either oxidizing it to the hexavalent state keeping K₂Cr₂O₇ at 0.01M concentration or by reducing it to tetravalent state keeping Fe²⁺ at 0.02M concentration. Stripping of neptunium was carried out using different reagents, such as dilute nitric acid, oxalic acid and sodium carbonate. Almost quantitative recovery of neptunium has been achieved during these studies.     

Reactor production of anhydrous18F ion

The direct production of anhydrous¹³F ion has been achieved through the incorporation of a new approach to hot atom reactions for reactor generated radiopharmaceuticals. Capitalizing on the traditional Li₂CO₃ method for hydrated¹⁸F production, a unique target design and geometry utilizing neutron generated energetic tritions emerging from the surface of a thin LiF embedded stainless steel matrix react with gaseous O₂ to produce¹⁸F as a free recoiling anhydrous species. Approximately 10–15 MBq of reactive anhydrous¹⁸F ion absorbed onto a metallic foil has been produced by this method. Verification of the production of¹⁸F was substantiated through decay measurements using Ge(Li) spectroscopic analysis, and by the synthesis of¹⁸F-fluoromethane gas. Cyclotron gas target chemistry which has been instrumental in the preparation of¹⁸F-2FDG and other metabolic tracers may be reproduced using this technique by the addition of 1% F₂ scavenger gas to a recirculating reactor gas handling system.     

Validation of chemical separation method for the determination of 63Ni using TDCR technique in steel samples of APSARA reactor

Activity Standards of ⁶³Ni was used to benchmark our triple-to-double coincidence ratio (TDCR) primary standardization instrument Hidex 300SL TDCR device under different chemical and colour quench conditions. The results were compared with a secondary standardization instrument Tricarb 2910TR that employs transformed spectral index of external standard to assess the quench level of samples. Excellent agreement was observed (within 3 %) for a wide range of standard activity and quench conditions. The method was subsequently used for validating chemical separation procedure for estimation of ⁶³Ni in neutron activated standard nickel and steel samples. Further the method was applied for estimation of ⁶³Ni from decommissioning waste of a research reactor, APSARA.