Study of the isomeric ratios in photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in ¹⁶⁵Ho(γ, n)^164m,gHo and ¹⁷⁵Lu(γ, n)^174m,gLu photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

The isomeric ratios in photonuclear reactions of natural barium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in ¹³⁰Ba(γ, n)^129m,gBa, ¹³²Ba(γ, n)^131m,gBa and ¹³⁴Ba(γ, n)^133m,gBa photonuclear reactions of natural barium induced by bremsstrahlungs with end-point energies in the giant dipole resonance region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

The isomeric ratios in photonuclear reactions of natural tellurium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in ¹²⁰Te(γ, n)^119m,gTe, ¹²²Te(γ, n)^121m,gTe, ¹²⁸Te(γ, n)^127m,gTe and ¹³⁰Te(γ, n)^129m,gTe photonuclear reactions of natural tellurium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1,332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

The isomeric ratios in photonuclear reactions of natural strontium induced by bremsstrahlungs in the giant dipole resonance region and by 65 MeV bremsstrahlung

We have determined the isomeric ratio of ^85m,gSr in photonuclear reactions of natural strontium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region as well as the isomeric ratios of ^85m,gSr and ^84m,gRb produced at 65 MeV bremsstrahlung. In GDR region the target was irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The target irradiation with 65 MeV bremsstrahlung was performed at the linear electron accelerator of the Pohang Neutron Facility, Pohang, South Korea. The gamma spectra of the samples irradiated in both cases were measured with spectroscopic systems consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

Rare earth elements,thorium and uranium in ores of the North-Latium (Italy)

In geochemistry, the distribution of the Rare Earth Elements (REEs) in earth crust and mantle allows to understand geochemical cycles and origin and age of igneous rocks. In this article REEs (Ce, Dy, Eu, La, Nd, Sm, Tb, and Yb), Th and U in ores of the North-Latium (Bracciano area, Ceriti Mt., Fate Mt., Sabatini Mt., Vulsini Mt., Acqua Rossa basin), have been investigated for evaluating the extraction feasibility for industrial applications. 107 samples were irradiated in the rotating rack of the TRIGA Mark II reactor of the R.C. Casaccia (ENEA) at neutron flux of 2.6 × 10¹² n × cm⁻² × s⁻¹ for 12 h together with primary and secondary standards. The gamma spectrometry measurements were performed after 8 h, 3 and 30 days of decay by means of HPGe detector (FWHM 1.75 keV at 1332.5 keV, peak/Compton ratio 55.1, relative efficiency of 22%) connected to a multi-channel analyzer. The total REE mean content is 105 μg g⁻¹, ranging widely between 2.23 and 410.5 μg g⁻¹ (average coefficient of variation 112%). A similar behavior is found for Th and U: their average levels are 13.5 and 6.0 μg g⁻¹, respectively. A quite good correlation between REEs and Th (and U) is found for Ceriti Mt. (r ² > 0.8) whereas for the other areas the correlation is <0.7. The results obtained evidence the low U content in the investigated locations.     

Channel effect in isomeric ratio of 137m,gCe produced in different nuclear reactions

This work presents the experimental study of the isomeric ratio of ^137mCe–^137gCe produced in ¹³⁸Ce(γ, n) ^137m,gCe photonuclear reaction, in neutron capture reaction ¹³⁶Ce(n, γ) ^137m,gCe and in the two simultaneous reactions ¹³⁸Ce(γ, n) ^137m,gCe and ¹³⁶Ce(n, γ) ^137m,gCe in the mixed photon—neutron field by the activation method. The investigated samples were irradiated at the bremsstrahlung photon flux, in the epithermal and thermal-epithermal neutron beam and in the mixed photon-neutron field constructed at the electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The results were analyzed, discussed and compared with those of other authors to examine the role of the channel effect in nuclear reaction and provide the nuclear data for theoretical model interpretation of nuclear reactions.

     

Fast determination of gold in large mass samples of gold ores by photoexcitation reactions using 10 MeV bremsstrahlung

The determination of gold is based on the photoexcitation reaction ¹⁹⁷Au(γ,γ’)^197mAu with the half-life of 7.73 seconds and energy of emitted gamma-rays of 279 keV. Three 100 ml aliquots of coarsely ground Au-ore (grains <2 mm) corresponding to ca. 150–180 g were irradiated for 20 seconds with bremsstrahlung of maximum energy 10 MeV produced by a microtron at the electron beam current of 30–40 μA, 1–10 times reactivation was applied. After 3 seconds of decay, samples were measured for 20 seconds using scintillation or semiconductor gamma-spectrometry with the detection limits for an ideal sample down to 0.5 μg·g⁻¹ and 0.1–0.2 μg·g⁻¹ of Au, respectively. Content of U and Th undergoing photo-fission increases the detection limits several times.     

Cyclic neutron activation analysis for determination of selenium in food samples using <Superscript>77m</Superscript>Se

Cyclic neutron activation analysis method was conducted for determination of Se in food samples. High accuracy and good precision were proved by analyzing certified reference materials (CRMs) of chicken (GBW10018), rice (GBW10010) and cabbage (GBW10014). The detection limits for the three CRMs reached 0.16, 0.66 and 1.2 ng after 6 cycles at the 161.9 keV γ-peak from ^77mSe, under a neutron flux of 9.0 × 10¹¹ n cm⁻² s⁻¹ and the conditions of 30 s irradiation, 2 s decay, 30 s counting and 2 s waiting, significantly lower than those of conventional neutron activation analysis without any cycles, which were 0.94, 3.6 and 4.3 ng, respectively.     

Absolute intensity of the 140.5 keV gamma-ray of99Mo

The induced activity of the⁹⁹Mo isotope is mostly determined via the 140.5 keV γ-line, which is the strongest gamma-ray of its daughter,^99mTc. Some recent literature, however, indicates a direct feeding of this energy level from the mother isotope as well. Considering the importance of this line in practice as well as the large controversy and scattering in relevant nuclear data available at present, a combined effort was made to remeasure this questionable absolute intensity. A relative method of irradiating a Mo-target with reactor neutrons and repeatedly measuring its (n,γ) induced activity relative to the 181.1 keV and 739.5 keV gamma lines of⁹⁹Mo as internal references was used. The weighted average of different runs yielded γ(⁹⁹Mo, 140.5 keV)=(5.07±0.37)%. As a consequence, when the 140.5 keV gamma line is used, the contribution from the⁹⁹Mo mother isotope should always be taken into account, e.g. in neutron cross-section measurements and neutron activation analysis.     

Determination of selenium in foods by pseudo-cyclic neutron activation and anti-coincidence gamma-ray spectrometry

A pseudo-cyclic instrumental neutron activation analysis method in conjunction with anti-coincidence gamma-ray spectrometry (PC-INAA-AC) has been developed for the determination of ppb levels of Se. The method consists of repetitions of the irradiation-decay-counting cycles of a sample using the rapid transfer cyclic system at the Dalhousie University SLOWPOKE-2 reactor facility. The 162-keV γ-ray of ^77mSe (t _1/2 = 17.4 s) has been found to be highly selective. The precision and detection limits are significantly improved and the total experimental time drastically reduced by this method. Detection limits are between 2 and 9 ng. The accuracy of the method has been evaluated by analyzing a number of nutritional reference materials. The PC-INAA-AC method has been applied for the routine determination of Se to the composites of 135 food samples with values ranging from as low as 1 ng g⁻¹ for tea to 1,045 ng g⁻¹ for organ meats on fresh weight basis.     

Selenium and mercury determination in biological samples using gamma–gamma coincidence and Compton suppression

Biological materials containing trace amounts of mercury and selenium were examined using neutron activation analysis. They were analyzed using Compton suppression and γ–γ coincidence counting. The 279 keV photopeak of activated mercury (²⁰³Hg) was analyzed in order to observe the mercury content in these samples. Selenium, an element found in many biological samples, interferes with the analysis of ²⁰³Hg when activated (⁷⁵Se). Because the selenium interference comes from a cascading emission, Compton suppression was utilized to reduce this interference. In order to fully characterize the selenium content in the samples, γ–γ coincidence was used which reduced the background and eliminated bremsstrahlung interference produced from neutron activated phosphorous through the ³¹P(n, γ)³²P reaction which is a pure beta emitter. As a result, we determined the mercury and selenium concentrations in three standard reference materials, which contain varying ratios of mercury to selenium concentrations. This study also showed that these types of concentrations can be determined from small (<500 mg) sample masses. Further work needs to be done on wet samples that require dehydration, as mercury can be lost through this process.     

Gamma background measurements in the Laboratoire Souterrain de Modane

In situ gamma-ray measurements were taken at six locations in the Modane Underground Laboratory. Count rates for gamma radiation within the energy range of 7–2734 keV varied from 15 to 108 γs⁻¹. The arithmetic mean was 79 γs⁻¹ for measurements taken without a collimator. The metamorphic rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium equal to 12 and 10 Bq kg⁻¹, respectively.     

Determination of iodine concentration in aqueous solutions by proton activation analysis: preliminary results for digested human thyroids

The aim of our studies is to check the possibilities of using proton activation analysis as a competitive method over other analytical techniques applied for iodine determination. It is well known that long-term irradiation of biological samples leads to their decomposition and formation of gaseous radiolysis products, which increase the pressure inside the sample container. In case of using proton beam another problem with liquid samples appears. It is the production of ⁷Be via spallation reactions ¹⁶O(p, spall)⁷Be. The Compton effect from ⁷Be γ-line increases the detection limits for isotopes with low-energy γ-lines. AIC-144 cyclotron at The Niewodniczański Institute of Nuclear Physics Polish Academy of Science can accelerate protons up to energy of 60 MeV which is sufficient for (p,5n) reaction needed to obtain ¹²³I (T _1/2 = 13.27 h, Eγ = 159 keV, I = 83%) from stable ¹²⁷I, thus the Compton effect from ⁷Be was the main factor perturbing the analysis. Separation and removal of ⁷Be is required to improve the detection limit. The paper presents a method and an example of its application to the determination of iodine concentration in digested fragments of human thyroids obtained during surgical treatment of patients with different types of thyroid tumor.     

Fast determination of the tin content in cassiterite ores by photon activation method

Photon activation analysis has been success-fully applied to the fast and non-destructive analysis of tin in cassiterite ores based on the 159.7 keV gamma line of^123mSn produced in the¹²⁴Sn/γ, n/^123mSn reaction. In order to improve the accuracy of analytical results, corrections for self-absorption and pile-up effects were performed. Under typical conditions /15 μA electron beam current, 15 MeV bremsstrahlung energy, 5 min irradiation time and 10 min measurement/ the sensitivity of the analysis is 10 ppm. The proposed method can be used for routine analysis of tin in geological samples.     

Dosage du carbone dans quelques metaux purs par irradiation dans les photons γ

A method is described for the determination of carbon in iron, chromium, nickel, and molybdenum, using the¹²C (γ, n)¹¹C reaction. The samples are irradiated with the bremstrahlung from a 35 MeV electron beam impinging a platinum target. Two apparatuses for the separation of carbon are described. The¹¹C^* activity of the sample is compared with the activities of two graphite standards, counting the positron annihilation gamma rays. The limit of detection is 0.02 μg/g of carbon in high-purity iron.      

Boron in coral skeletons determined by prompt γ-ray analysis

A systematic and non-destructive technique is proposed for the determination of boron in coral samples by neutron-induced prompt γ-ray analysis (PGA) using a thermal neutron guide beam of the JRR-3M reactor. About 50–150 mg samples in sealed FEP film were irradiated and measured for 5000 s in the PGA system at a neutron flux of 2.4 × 10⁷ n cm⁻² s⁻¹. In order to determine B content in coral skeletons, the Doppler-broadened γ-ray peak of 478 keV (¹⁰B) was used together with the correction of interference from the Na-peak of 472 keV. The analytical precision was ~3% for the JCp-1 coral standard. The data (n = 56) obtained by the present method showed a range of B content from 40.7 to 76.9 ppm which is similar to reported values. Boron in corals showed the highest levels in Rukan-sho (Okinawa) with an average B content of 62.5 ppm, whereas corals collected from Mizugama (Okinawa), Cebu (the Philippines) and Khang Khao (Thailand) exhibited B contents of 56.5, 53.0 and 45.7 ppm, respectively. The uptake of boron by living corals may be influenced by seawater pH related to higher seawater B(OH)₄⁻. In this paper we discuss factors controlling the B levels in corals.     

Photo-neutron cross-section of 100Mo

The ¹⁰⁰Mo(γ, n) reaction cross-section was experimentally determined at end point bremsstrahlung energy of 10 and 12.5 MeV using off-line γ-ray spectrometric technique. It was also found that ¹⁰⁰Mo(γ, n) reaction cross-section increases sharply from the end point bremsstrahlung energy of 10 MeV to 12.5 MeV, which may be because of GDR around the energy region of 12–16 MeV. The ¹⁰⁰Mo(γ, n) reaction cross-section as a function of photon energy was calculated theoretically using TALYS 1.2 computer code. The flux-weighted average values of ¹⁰⁰Mo(γ, n) reaction cross-section for bremsstrahlung having end point energy of 10 and 12.5 MeV were also calculated using the experimental and theoretical data of mono-energetic photon. The present experimental ¹⁰⁰Mo(γ, n) reaction cross-sections were compared with the bremsstrahlung flux-weighted average values of experimental and theoretical data and found to be in the lower side for 10 MeV and in the higher side for 12.5 MeV.     

Cross-sections for formation of <Superscript>178m2</Superscript>Hf and <Superscript>179m2</Superscript>Hf through reactions on natural hafnium at neutron energy 14.8 ± 0.2 MeV

The cross sections for formation of metastable state of ¹⁷⁸Hf (^178m2Hf, 574.215 keV, 31 y) and ¹⁷⁹Hf (^179m2Hf, 362.55 keV, 25.05 d) through reactions induced by 14.8 ± 0.2 MeV neutrons on natural hafnium were measured for the first time. The monoenergetic neutron beam was produced via the ³H(d, n)⁴He reaction on ZF-300-II Intense Neutron Generator at Lanzhou University. Induced gamma activities were measured by a gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The neutron fluence were determined by the cross section of ⁹³Nb(n, 2n)^92mNb reaction. The neutron energy in the measurement were by the cross section ratios of ⁹⁰Zr(n, 2n)^89m+gZr and ⁹³Nb(n, 2n)^92mNb reactions.     

Determination of total Sb,Se, Te,and Bi and evaluation of their inorganic species in garlic by hydride-generation–atomic-fluorescence spectrometry

A sensitive and simple analytical method has been developed for determination of Sb(III), Sb(V), Se(IV), Se(VI), Te(IV), Te(VI), and Bi(III) in garlic samples by using hydride-generation–atomic-fluorescence spectrometry (HG–AFS). The method is based on a single extraction of the inorganic species by sonication at room temperature with 1 mol L⁻¹ H₂SO₄ and washing of the solid phase with 0.1% (w/v) EDTA, followed by measurement of the corresponding hydrides generated under two different experimental conditions directly and after a pre-reduction step. The limit of detection of the method was 0.7 ng g⁻¹ for Sb(III), 1.0 ng g⁻¹ for Sb(V), 1.3 ng g⁻¹ for Se(IV), 1.0 ng g⁻¹ for Se(VI), 1.1 ng g⁻¹ for Te(IV), 0.5 ng g⁻¹ for Te(VI), and 0.9 ng g⁻¹ for Bi(III), in all cases expressed in terms of sample dry weight.     

Comparison of alpha-spectrometry and alpha/gamma ratio method for the determination of americium in plutonium bearing fuel materials

Determination of americium is one of the requirements of chemical quality assurance of plutonium bearing fuel materials. Alpha-spectrometry is generally used for the determination of ²⁴¹Am in Pu bearing fuels since the efficiency of semiconductor detector used for alpha-spectrometry is independent of the alpha-particle energy in the 4 to 8 MeV range. However, this method has limitations for Pu samples containing extremely small or very large amounts of ²⁴¹Am. Thus an alternative methodology based on alpha/gamma (α/γ) activity ratio was developed and tested using different samples. The method is based on the determination of total γ-activity (of 60 keV peak) of an aliquot of the solution and the total α-activity present in the aliquot. The method is fast as it does not involve chemical separation of Pu and Am as required in the alpha-spectrometric method. Data obtained on synthetic and real life samples demonstrates the usefulness of the developed alpha/gamma ratio method for the determination of ²⁴¹Am in Pu bearing fuel samples.