CROSS SECTIONS MEASURED BY QUASI-MONOENERGETIC NEUTRONS

CROSS SECTIONS MEASURED BY QUASI-MONOENERGETIC NEUTRONS Abstract 197Au, 209Bi, 59Co, natFe and 169Tm samples were irradiated several times with quasi-monoenergetic neutrons from the p+7Li reaction in the energy range of 18–34 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross sections were extracted using the SAND-II code with the reference cross sections from the IRDFF database. INTRODUCTION The experimentally measured neutron data above 20 MeV are becoming increasingly important in the future energy production. New reactor concepts, fusion and accelerator driven systems (ADS) utilize faster neutron spectrum than conventional reactors and many dedicated facilities are operating or are in construction for the studies of relevant neutron data. This work is a part of the IAEA Coordinated Research Project ‘Testing and Improving the International Reactor Dosimetry and Fusion File (IRDFF)’(1, 2). The IRDFF is a standardized evaluated cross-section library of neutron dosimetry reactions and uncertainty information. Library evaluations are based mainly on comprehensive experimental data, the energy range of the neutron library is extended up to 60 MeV, beyond the traditional limit of 20 MeV and contains additional nuclear activation reactions. The goal of this work was to remeasure the cross sections of (n,x) reactions on 197Au, 209Bi, 59Co, natFe and 169Tm and to reduce the absolute uncertainties of the measurement. As seen for example in Figure 1, the experimental data above 20 MeV are scarce and new measurements are required for good evaluation. Figure 1. View largeDownload slide The cross sections for the reaction 169Tm(n,3n)167Tm extracted from the experimental database EXFOR(3) with the IRDFF evaluation. Figure 1. View largeDownload slide The cross sections for the reaction 169Tm(n,3n)167Tm extracted from the experimental database EXFOR(3) with the IRDFF evaluation. In the past decades, several procedures to gather the knowledge on neutron reactions were standardized. Irradiation with the known neutron spectrum (quasi-monoenergetic neutrons based on the p+7Li reaction) and the subsequent γ-activity measurement is commonly used. We irradiated the samples of the studied material with QM neutrons (with energies of the monoenergetic peak ranging from 17 to 34 MeV) during several campaigns. After several hours of irradiation we recorded the γ-spectra of the irradiated samples with the HPGe detectors and extracted the activities and subsequently the cross sections. EXPERIMENT The neutron irradiations have been performed with the quasi-monoenergetic neutron generator, based on the p+7Li reaction. Protons with energies 20, 22.5, 25, 27.5, 30, 32.5 and 35 MeV were directed at the 2 mm thick lithium foil (enriched foils with 99.9% of 7Li) with 1 cm carbon backing, which fully stopped the protons(4). The irradiations at the proton energies of 25 and 27.5 MeV were repeated with the natural composition lithium foil. During each irradiation, the proton charge deposited on the target/carbon backing was recorded with the time period of 1 s, the beam current in the range of 5 μA was used. The neutrons in the forward direction were simultaneously recorded with the scintillator. After each irradiation, the lithium target was unmounted and measured with the HPGe detector, and the number of produced 7Be isotopes was determined. The irradiated samples were made from high purity metal and were of the disc shape with a 15 mm diameter and a thickness of 0.025–1.5 mm (Tm 0.1 mm, Au 0.05 mm, Fe 0.25 mm, W 0.025 mm, Co 0.25 mm, Bi 1.5 mm). The samples were weighted at an absolute accuracy below 0.5%. New samples were used at each irradiation. In every experimental run the samples were irradiated at distances of 42 mm and 86 mm from the neutron source. The distance of 42 mm was used for short irradiations (5 min) and quick transport of the samples to the HPGe detector with the pneumatic post system (ca. 20 s), this distance was used only for the measurements of the production of 53Fe isotope. The distance of 86 mm was used for long irradiation (8 h). Offline γ-spectroscopy of the samples irradiated with neutrons and the lithium target irradiated with protons was performed with two calibrated HPGe detectors with the efficiency around 50% and the energy resolution 1.8–1.9 keV at 1332 keV. The decay γ spectra were measured during the cooling period from tens of seconds up to tens of days. The number of radioactive isotopes produced by neutrons/protons was determined with the uncertainty of 2–3%. NEUTRON SPECTRA The neutron spectra at the position of the irradiated foils (distance 86 mm from the target front) can be seen in Figure 2. The spectra were calculated by the MCNPX code(5) using the LA150h library(6) at positions 42 mm, 86 mm, and in the forward direction for renormalization. The spectra were then renormalized to the number of the peak neutrons in the forward direction determined experimentally from the produced number of 7Be nuclei in the lithium target and the experimental formula for the ratio of forward directed peak neutrons(7, 8). The neutron spectra used in this work were determined as described in(4), but their lower energy part (below the monenergetic peak) was left unmodified according to our latest studies. The neutron absorption in the carbon backing and further construction materials was taken in account. Figure 2. View largeDownload slide Quasi-monoenergetic neutron spectra produced by proton beams with the energy varying between 20 and 35 MeV on 2 mm 7Li target at the position of 8.6 cm from the lithium target front. The spectra were calculated with the MCNPX code and renormalized to the experimentally measured production of the 7Be in the lithium target. At 25 and 27.5 MeV the irradiations were repeated with the natLi target, both spectra are shown. Figure 2. View largeDownload slide Quasi-monoenergetic neutron spectra produced by proton beams with the energy varying between 20 and 35 MeV on 2 mm 7Li target at the position of 8.6 cm from the lithium target front. The spectra were calculated with the MCNPX code and renormalized to the experimentally measured production of the 7Be in the lithium target. At 25 and 27.5 MeV the irradiations were repeated with the natLi target, both spectra are shown. CROSS-SECTION EXTRACTION AND UNCERTAINTY The experimentally measured radioisotopes were produced in the complex neutron spectrum (monoenergetic peak + continuum, which contributes to the production). Iterative approach based on a modified version of the SAND-II(9) code with the IRDFF v1.05 evaluated data as the input cross sections was used to extract the cross-section curves. The cross-section curves were iteratively adjusted so that their product with the neutron spectra corresponded to the measured reaction rates. The average values of the extracted cross-section curve in the energetic regions covered by the monoenergetic peaks were taken for the experimental cross-section values, Figure 3. Figure 3. View largeDownload slide The extraction procedure with the IRDFF cross-section curve and the modified cross-section curve from the first and the final iteration. The average values from monoenergetic regions are taken as final cross-section values. The final cross-section values for the reaction 209Bi(n,3n)207Bi are shown. Figure 3. View largeDownload slide The extraction procedure with the IRDFF cross-section curve and the modified cross-section curve from the first and the final iteration. The average values from monoenergetic regions are taken as final cross-section values. The final cross-section values for the reaction 209Bi(n,3n)207Bi are shown. The uncertainty of the extracted cross-section values on the energy scale was set to the width of the monoenergetic peak (ca. 1.5 MeV at 34 MeV and 2.5 MeV at 18 MeV). The sensitivity analysis of the extracted values to the input parameters was performed to obtain the uncertainty on the cross-section scale. The limited knowledge of the neutron spectra was determined to be the main source of the uncertainties, while the uncertainties from the irradiation (positioning, beam parameters), γ-spectra measurements (efficiency calibration, peak counting statistics) or input cross sections were of secondary importance (few percentage points). The estimated uncertainties of the input parameters were used to randomly sample each input parameter according to the normal distribution and perform the extraction procedure. The distribution of the extracted cross sections was analyzed and the resulting sigma for each parameter was extracted. The overall uncertainties originating from the extraction procedure were found to lie within 15% and we adopted this uncertainty for all extracted cross sections. The resulting sigma from the extraction procedure was summed in square with the sigma of the measured reaction rate to obtain the cross-section uncertainty. The extracted cross-section values are shown in Figures 4–11. The extracted cross sections from the previous measurements on the same experimental setup(4) are shown where available. Figure 4. View largeDownload slide Measured cross sections for the reaction 197Au(n,2n)196g+m+m2Au with the values from previous work(4). Figure 4. View largeDownload slide Measured cross sections for the reaction 197Au(n,2n)196g+m+m2Au with the values from previous work(4). Figure 5. View largeDownload slide Measured cross sections for the reaction 59Co(n,2n)58g+mCo with the values from previous work(4). Figure 5. View largeDownload slide Measured cross sections for the reaction 59Co(n,2n)58g+mCo with the values from previous work(4). Figure 6. View largeDownload slide Measured cross sections for the reaction 59Co(n,3n)57Co with the values from previous work(4). Figure 6. View largeDownload slide Measured cross sections for the reaction 59Co(n,3n)57Co with the values from previous work(4). Figure 7. View largeDownload slide Measured cross sections for the reaction 59Co(n,p)59Fe with the values from previous work(4). Figure 7. View largeDownload slide Measured cross sections for the reaction 59Co(n,p)59Fe with the values from previous work(4). Figure 8. View largeDownload slide Measured cross sections for the reaction 54Fe(n,2n)53g+mFe. Figure 8. View largeDownload slide Measured cross sections for the reaction 54Fe(n,2n)53g+mFe. Figure 9. View largeDownload slide Measured cross sections for the reaction 59Co(n,α)56Mn. Figure 9. View largeDownload slide Measured cross sections for the reaction 59Co(n,α)56Mn. Figure 10. View largeDownload slide Measured cross sections for the reaction 169Tm(n,2n)168Tm. Figure 10. View largeDownload slide Measured cross sections for the reaction 169Tm(n,2n)168Tm. Figure 11. View largeDownload slide Measured cross sections for the reaction 169Tm(n,3n)167Tm. Figure 11. View largeDownload slide Measured cross sections for the reaction 169Tm(n,3n)167Tm. DISCUSSION The reaction rates determined in this work agree within the experimental accuracy with our previous measurements (available for elements Au, Bi and Co). The neutron spectra that were used in the cross-sections extraction procedure were determined on the basis of the Time-Of-Flight measurements, the 7Be activity induced in the lithium target and the empirical formula for the forwardness of the peak neutrons. The extracted cross sections do not agree within experimental uncertainties with the evaluation and our older measurements. The agreement of the reaction rates and the disagreement trends of the extracted cross sections suggest the problems with the neutron spectra determination. From the spectroscopic point of view, all the studied reactions are good candidates for neutron flux and spectrum monitoring with the exception of the reaction 54Fe(n,2n)53g+mFe. The relatively short decay time of this isotope (8.51 m) and the fact that it has the isomeric state (2.58 m) allowed us to measure the production of this isotope only with the use of the fast pneumatic transport system of the samples from the irradiation position to the HPGe detector. We also noticed the disagreement between the evaluated cross sections and measurements for this reaction. The values presented in this paper are ca. 2 times lower than the other set of measured cross sections(10), while the IRDFF evaluation is in between. CONCLUSION This work provided new experimental data on the (n,2−3n), (n,p) and (n,α) reactions in materials 197Au, 209Bi, 59Co, natFe and 169Tm. The accuracy of the newly measured reaction rates was optimized with the additional measurement of the integral neutron flux based on the 7Be activity of the lithium target and the Time-Of-Flight measurements of the neutron spectra. The disagreement of the extracted cross sections with the evaluation and our older experimental data (although the reaction rates agree) might be the underestimation of the neutron spectra below the monoenergetic peak and the incorrect estimation of the forward directed neutrons. We intensively study both possibilities experimentally and by Monte Carlo simulations. FUNDING This work was supported by Ministry of education, Youth and Sports of the Czech Republic under the project LM2015056 and the International Atomic Energy Agency (IAEA). REFERENCES 1 Capote , R. , Zolotarev , K. I. , Pronyaev , V. G. and Trkov , A. Updating and extending the IRDF-2002 dosimetry library . J. ASTM Intern. (JAI) 9 ( 4 ), JAI104119 ( 2012 ). Google Scholar CrossRef Search ADS 2 Zsolnay , E. M. , Capote , R. , Nolthenius , H. K. and Trkov , A. Technical Report INDC(NDS)-0616, IAEA, Vienna, 2012 ; https://www-nds.iaea.org/IRDFF/ 3 Otuka , N. , Dupont , E. , Semkova , V. , Pritychenko , B. , Blokhin , A.I. , Aikawa , M. , Babykina , S. , Bossant , M. , Chen , G. , Dunaeva , S. , Forrest , R.A. , Fukahori , T. , Furutachi , N. , Ganesan , S. , Ge , Z. , Gritzay , O.O. , Herman , M. , Hlavač , S. and Zhuang , Y. Towards a more complete and accurate experimental nuclear reaction data library (EXFOR): international collaboration between Nuclear Reaction Data Centres (NRDC) . Nucl. Data Sheets 120 , 272 ( 2014 ) http://dx.doi.org/10.1016/j.nds.2014.07.065 . Google Scholar CrossRef Search ADS 4 Majerle , M. , Bém , P. , Novák , J. , Šimečková , E. and Štefánik , M. Au, Bi, Co and Nb cross-section measured by quasimonoenergetic neutrons from p + 7Li reaction in the energy range of 18–36 MeV . Nuc. Phys. A 953 , 139 – 157 ( 2016 ) DOI:10.1016/j.nuclphysa.2016.04.036 . Google Scholar CrossRef Search ADS 5 MCNPX 2.7.0, information is available on https://mcnpx.lanl.gov/ 6 Mashnik , S. G. , Chadwick , M. B. , Young , P. G. , MacFarlane , R. E. and Waters , L. S. Li(p,n) Nuclear Data Library for Incident Proton Energies to 150 MeV, Report LA-UR_00-1067, Los Alamos 2000 . 7 Schery , S. D. , Young , L. E. , Doering , R. R. , Austin , S. M. and Bhowmik , R. K. Activation and angular distribution measurements of 7Li(p, n)7Be(0.0+0.49 MeV) for Ep=25-45 MeV: a technique for absolute neutron yield determination . Nucl. Instrum. Meth. 147 , 399 ( 1977 ) DOI:10.1016/0029-554x(77)90275-0 . EXFOR ID: B0127. Google Scholar CrossRef Search ADS 8 Uwamino , Y. , Soewarsono , T. S. , Sugita , H , Uno , Y , Nakamura , T , Shibata , T , Imamura , M and Shibata , S-I. High-energy p-Li neutron field for activation experiment . Nucl. Instrum. Meth. A 389 , 463 – 473 ( 1997 ) DOI:10.1016/S0168-9002(97)00345-8 . EXFOR ID: E1826. Google Scholar CrossRef Search ADS 9 SAND-II-SNL . : Neutron Flux Spectra Determination by Multiple Foil Activation-iterative Method, RSICC Shielding Routine Collection PSR-345, Oak Ridge 1996 10 Soewarsono , T. S. , Uwamino , Y. and Nakamura , T. JAERI-M Reports, No. 92,027, p. 354 ( 1992 ). © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiation Protection Dosimetry Oxford University Press

CROSS SECTIONS MEASURED BY QUASI-MONOENERGETIC NEUTRONS

Loading next page...
 
/lp/ou_press/cross-sections-measured-by-quasi-monoenergetic-neutrons-bx43ChZ2Kc
Publisher
Oxford University Press
Copyright
© The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
ISSN
0144-8420
eISSN
1742-3406
D.O.I.
10.1093/rpd/ncy031
Publisher site
See Article on Publisher Site

Abstract

Abstract 197Au, 209Bi, 59Co, natFe and 169Tm samples were irradiated several times with quasi-monoenergetic neutrons from the p+7Li reaction in the energy range of 18–34 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross sections were extracted using the SAND-II code with the reference cross sections from the IRDFF database. INTRODUCTION The experimentally measured neutron data above 20 MeV are becoming increasingly important in the future energy production. New reactor concepts, fusion and accelerator driven systems (ADS) utilize faster neutron spectrum than conventional reactors and many dedicated facilities are operating or are in construction for the studies of relevant neutron data. This work is a part of the IAEA Coordinated Research Project ‘Testing and Improving the International Reactor Dosimetry and Fusion File (IRDFF)’(1, 2). The IRDFF is a standardized evaluated cross-section library of neutron dosimetry reactions and uncertainty information. Library evaluations are based mainly on comprehensive experimental data, the energy range of the neutron library is extended up to 60 MeV, beyond the traditional limit of 20 MeV and contains additional nuclear activation reactions. The goal of this work was to remeasure the cross sections of (n,x) reactions on 197Au, 209Bi, 59Co, natFe and 169Tm and to reduce the absolute uncertainties of the measurement. As seen for example in Figure 1, the experimental data above 20 MeV are scarce and new measurements are required for good evaluation. Figure 1. View largeDownload slide The cross sections for the reaction 169Tm(n,3n)167Tm extracted from the experimental database EXFOR(3) with the IRDFF evaluation. Figure 1. View largeDownload slide The cross sections for the reaction 169Tm(n,3n)167Tm extracted from the experimental database EXFOR(3) with the IRDFF evaluation. In the past decades, several procedures to gather the knowledge on neutron reactions were standardized. Irradiation with the known neutron spectrum (quasi-monoenergetic neutrons based on the p+7Li reaction) and the subsequent γ-activity measurement is commonly used. We irradiated the samples of the studied material with QM neutrons (with energies of the monoenergetic peak ranging from 17 to 34 MeV) during several campaigns. After several hours of irradiation we recorded the γ-spectra of the irradiated samples with the HPGe detectors and extracted the activities and subsequently the cross sections. EXPERIMENT The neutron irradiations have been performed with the quasi-monoenergetic neutron generator, based on the p+7Li reaction. Protons with energies 20, 22.5, 25, 27.5, 30, 32.5 and 35 MeV were directed at the 2 mm thick lithium foil (enriched foils with 99.9% of 7Li) with 1 cm carbon backing, which fully stopped the protons(4). The irradiations at the proton energies of 25 and 27.5 MeV were repeated with the natural composition lithium foil. During each irradiation, the proton charge deposited on the target/carbon backing was recorded with the time period of 1 s, the beam current in the range of 5 μA was used. The neutrons in the forward direction were simultaneously recorded with the scintillator. After each irradiation, the lithium target was unmounted and measured with the HPGe detector, and the number of produced 7Be isotopes was determined. The irradiated samples were made from high purity metal and were of the disc shape with a 15 mm diameter and a thickness of 0.025–1.5 mm (Tm 0.1 mm, Au 0.05 mm, Fe 0.25 mm, W 0.025 mm, Co 0.25 mm, Bi 1.5 mm). The samples were weighted at an absolute accuracy below 0.5%. New samples were used at each irradiation. In every experimental run the samples were irradiated at distances of 42 mm and 86 mm from the neutron source. The distance of 42 mm was used for short irradiations (5 min) and quick transport of the samples to the HPGe detector with the pneumatic post system (ca. 20 s), this distance was used only for the measurements of the production of 53Fe isotope. The distance of 86 mm was used for long irradiation (8 h). Offline γ-spectroscopy of the samples irradiated with neutrons and the lithium target irradiated with protons was performed with two calibrated HPGe detectors with the efficiency around 50% and the energy resolution 1.8–1.9 keV at 1332 keV. The decay γ spectra were measured during the cooling period from tens of seconds up to tens of days. The number of radioactive isotopes produced by neutrons/protons was determined with the uncertainty of 2–3%. NEUTRON SPECTRA The neutron spectra at the position of the irradiated foils (distance 86 mm from the target front) can be seen in Figure 2. The spectra were calculated by the MCNPX code(5) using the LA150h library(6) at positions 42 mm, 86 mm, and in the forward direction for renormalization. The spectra were then renormalized to the number of the peak neutrons in the forward direction determined experimentally from the produced number of 7Be nuclei in the lithium target and the experimental formula for the ratio of forward directed peak neutrons(7, 8). The neutron spectra used in this work were determined as described in(4), but their lower energy part (below the monenergetic peak) was left unmodified according to our latest studies. The neutron absorption in the carbon backing and further construction materials was taken in account. Figure 2. View largeDownload slide Quasi-monoenergetic neutron spectra produced by proton beams with the energy varying between 20 and 35 MeV on 2 mm 7Li target at the position of 8.6 cm from the lithium target front. The spectra were calculated with the MCNPX code and renormalized to the experimentally measured production of the 7Be in the lithium target. At 25 and 27.5 MeV the irradiations were repeated with the natLi target, both spectra are shown. Figure 2. View largeDownload slide Quasi-monoenergetic neutron spectra produced by proton beams with the energy varying between 20 and 35 MeV on 2 mm 7Li target at the position of 8.6 cm from the lithium target front. The spectra were calculated with the MCNPX code and renormalized to the experimentally measured production of the 7Be in the lithium target. At 25 and 27.5 MeV the irradiations were repeated with the natLi target, both spectra are shown. CROSS-SECTION EXTRACTION AND UNCERTAINTY The experimentally measured radioisotopes were produced in the complex neutron spectrum (monoenergetic peak + continuum, which contributes to the production). Iterative approach based on a modified version of the SAND-II(9) code with the IRDFF v1.05 evaluated data as the input cross sections was used to extract the cross-section curves. The cross-section curves were iteratively adjusted so that their product with the neutron spectra corresponded to the measured reaction rates. The average values of the extracted cross-section curve in the energetic regions covered by the monoenergetic peaks were taken for the experimental cross-section values, Figure 3. Figure 3. View largeDownload slide The extraction procedure with the IRDFF cross-section curve and the modified cross-section curve from the first and the final iteration. The average values from monoenergetic regions are taken as final cross-section values. The final cross-section values for the reaction 209Bi(n,3n)207Bi are shown. Figure 3. View largeDownload slide The extraction procedure with the IRDFF cross-section curve and the modified cross-section curve from the first and the final iteration. The average values from monoenergetic regions are taken as final cross-section values. The final cross-section values for the reaction 209Bi(n,3n)207Bi are shown. The uncertainty of the extracted cross-section values on the energy scale was set to the width of the monoenergetic peak (ca. 1.5 MeV at 34 MeV and 2.5 MeV at 18 MeV). The sensitivity analysis of the extracted values to the input parameters was performed to obtain the uncertainty on the cross-section scale. The limited knowledge of the neutron spectra was determined to be the main source of the uncertainties, while the uncertainties from the irradiation (positioning, beam parameters), γ-spectra measurements (efficiency calibration, peak counting statistics) or input cross sections were of secondary importance (few percentage points). The estimated uncertainties of the input parameters were used to randomly sample each input parameter according to the normal distribution and perform the extraction procedure. The distribution of the extracted cross sections was analyzed and the resulting sigma for each parameter was extracted. The overall uncertainties originating from the extraction procedure were found to lie within 15% and we adopted this uncertainty for all extracted cross sections. The resulting sigma from the extraction procedure was summed in square with the sigma of the measured reaction rate to obtain the cross-section uncertainty. The extracted cross-section values are shown in Figures 4–11. The extracted cross sections from the previous measurements on the same experimental setup(4) are shown where available. Figure 4. View largeDownload slide Measured cross sections for the reaction 197Au(n,2n)196g+m+m2Au with the values from previous work(4). Figure 4. View largeDownload slide Measured cross sections for the reaction 197Au(n,2n)196g+m+m2Au with the values from previous work(4). Figure 5. View largeDownload slide Measured cross sections for the reaction 59Co(n,2n)58g+mCo with the values from previous work(4). Figure 5. View largeDownload slide Measured cross sections for the reaction 59Co(n,2n)58g+mCo with the values from previous work(4). Figure 6. View largeDownload slide Measured cross sections for the reaction 59Co(n,3n)57Co with the values from previous work(4). Figure 6. View largeDownload slide Measured cross sections for the reaction 59Co(n,3n)57Co with the values from previous work(4). Figure 7. View largeDownload slide Measured cross sections for the reaction 59Co(n,p)59Fe with the values from previous work(4). Figure 7. View largeDownload slide Measured cross sections for the reaction 59Co(n,p)59Fe with the values from previous work(4). Figure 8. View largeDownload slide Measured cross sections for the reaction 54Fe(n,2n)53g+mFe. Figure 8. View largeDownload slide Measured cross sections for the reaction 54Fe(n,2n)53g+mFe. Figure 9. View largeDownload slide Measured cross sections for the reaction 59Co(n,α)56Mn. Figure 9. View largeDownload slide Measured cross sections for the reaction 59Co(n,α)56Mn. Figure 10. View largeDownload slide Measured cross sections for the reaction 169Tm(n,2n)168Tm. Figure 10. View largeDownload slide Measured cross sections for the reaction 169Tm(n,2n)168Tm. Figure 11. View largeDownload slide Measured cross sections for the reaction 169Tm(n,3n)167Tm. Figure 11. View largeDownload slide Measured cross sections for the reaction 169Tm(n,3n)167Tm. DISCUSSION The reaction rates determined in this work agree within the experimental accuracy with our previous measurements (available for elements Au, Bi and Co). The neutron spectra that were used in the cross-sections extraction procedure were determined on the basis of the Time-Of-Flight measurements, the 7Be activity induced in the lithium target and the empirical formula for the forwardness of the peak neutrons. The extracted cross sections do not agree within experimental uncertainties with the evaluation and our older measurements. The agreement of the reaction rates and the disagreement trends of the extracted cross sections suggest the problems with the neutron spectra determination. From the spectroscopic point of view, all the studied reactions are good candidates for neutron flux and spectrum monitoring with the exception of the reaction 54Fe(n,2n)53g+mFe. The relatively short decay time of this isotope (8.51 m) and the fact that it has the isomeric state (2.58 m) allowed us to measure the production of this isotope only with the use of the fast pneumatic transport system of the samples from the irradiation position to the HPGe detector. We also noticed the disagreement between the evaluated cross sections and measurements for this reaction. The values presented in this paper are ca. 2 times lower than the other set of measured cross sections(10), while the IRDFF evaluation is in between. CONCLUSION This work provided new experimental data on the (n,2−3n), (n,p) and (n,α) reactions in materials 197Au, 209Bi, 59Co, natFe and 169Tm. The accuracy of the newly measured reaction rates was optimized with the additional measurement of the integral neutron flux based on the 7Be activity of the lithium target and the Time-Of-Flight measurements of the neutron spectra. The disagreement of the extracted cross sections with the evaluation and our older experimental data (although the reaction rates agree) might be the underestimation of the neutron spectra below the monoenergetic peak and the incorrect estimation of the forward directed neutrons. We intensively study both possibilities experimentally and by Monte Carlo simulations. FUNDING This work was supported by Ministry of education, Youth and Sports of the Czech Republic under the project LM2015056 and the International Atomic Energy Agency (IAEA). REFERENCES 1 Capote , R. , Zolotarev , K. I. , Pronyaev , V. G. and Trkov , A. Updating and extending the IRDF-2002 dosimetry library . J. ASTM Intern. (JAI) 9 ( 4 ), JAI104119 ( 2012 ). Google Scholar CrossRef Search ADS 2 Zsolnay , E. M. , Capote , R. , Nolthenius , H. K. and Trkov , A. Technical Report INDC(NDS)-0616, IAEA, Vienna, 2012 ; https://www-nds.iaea.org/IRDFF/ 3 Otuka , N. , Dupont , E. , Semkova , V. , Pritychenko , B. , Blokhin , A.I. , Aikawa , M. , Babykina , S. , Bossant , M. , Chen , G. , Dunaeva , S. , Forrest , R.A. , Fukahori , T. , Furutachi , N. , Ganesan , S. , Ge , Z. , Gritzay , O.O. , Herman , M. , Hlavač , S. and Zhuang , Y. Towards a more complete and accurate experimental nuclear reaction data library (EXFOR): international collaboration between Nuclear Reaction Data Centres (NRDC) . Nucl. Data Sheets 120 , 272 ( 2014 ) http://dx.doi.org/10.1016/j.nds.2014.07.065 . Google Scholar CrossRef Search ADS 4 Majerle , M. , Bém , P. , Novák , J. , Šimečková , E. and Štefánik , M. Au, Bi, Co and Nb cross-section measured by quasimonoenergetic neutrons from p + 7Li reaction in the energy range of 18–36 MeV . Nuc. Phys. A 953 , 139 – 157 ( 2016 ) DOI:10.1016/j.nuclphysa.2016.04.036 . Google Scholar CrossRef Search ADS 5 MCNPX 2.7.0, information is available on https://mcnpx.lanl.gov/ 6 Mashnik , S. G. , Chadwick , M. B. , Young , P. G. , MacFarlane , R. E. and Waters , L. S. Li(p,n) Nuclear Data Library for Incident Proton Energies to 150 MeV, Report LA-UR_00-1067, Los Alamos 2000 . 7 Schery , S. D. , Young , L. E. , Doering , R. R. , Austin , S. M. and Bhowmik , R. K. Activation and angular distribution measurements of 7Li(p, n)7Be(0.0+0.49 MeV) for Ep=25-45 MeV: a technique for absolute neutron yield determination . Nucl. Instrum. Meth. 147 , 399 ( 1977 ) DOI:10.1016/0029-554x(77)90275-0 . EXFOR ID: B0127. Google Scholar CrossRef Search ADS 8 Uwamino , Y. , Soewarsono , T. S. , Sugita , H , Uno , Y , Nakamura , T , Shibata , T , Imamura , M and Shibata , S-I. High-energy p-Li neutron field for activation experiment . Nucl. Instrum. Meth. A 389 , 463 – 473 ( 1997 ) DOI:10.1016/S0168-9002(97)00345-8 . EXFOR ID: E1826. Google Scholar CrossRef Search ADS 9 SAND-II-SNL . : Neutron Flux Spectra Determination by Multiple Foil Activation-iterative Method, RSICC Shielding Routine Collection PSR-345, Oak Ridge 1996 10 Soewarsono , T. S. , Uwamino , Y. and Nakamura , T. JAERI-M Reports, No. 92,027, p. 354 ( 1992 ). © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

Radiation Protection DosimetryOxford University Press

Published: Aug 1, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off