Measurement of Cross Section of (n,γ) Nuclear Reactions for Chlorine and Bromine Induced by Thermal Neutrons

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1 International Journal of Chemical and Physical Sciences, ISSN: for and Bromine Induced by Thermal Neutrons M. S. TANPURE 3, V. K. MULIK 4 1 Department of Physics, Haribhai V. Desai College, Pune, Maharashtra, India. genupansare@gmail.com Abstract The Cross-section values of nuclear reactions 37 Cl(n,γ) 38 Cl, and 81 Br (n, ) 82 Br induced by thermal neutrons of energy.25ev have measured using the NaI(Tl) gamma ray spectrometer coupled to the 8K Multichannel Analyzer and Computer software. The thermal neutron flux was measured using the nuclear reactions. 55 Mn(n, ) 56 Mn and 75 As(n, ) 76 As. The induced gamma ray activities of radioisotopes 37 Cl (E =16KeV), 82 Br (E =78KeV), 56 Mn (E =84KeV) and 76 As (E =559KeV) were measured from the respective gamma ray spectra counted using NaI(Tl) detector and M.C.A. Measured values of thermal neutron cross-section of and Bromine isotopes are found to be.46 barns and 2.39 barns respectively. The results are in good agreement with literature values. Keywords: Thermal neutrons, Nuclear Reactions, Cross-section, NaI(Tl) gamma ray detector, 8K M.C.A., Neutron flux.. Introduction Elements such as and Bromine have potential applications in many fields such as Medical, Industrial, Environmental pollution and basics researches [ 1,2,3,4 ]. -36 is used in fuel arises from the activation of 35 Cl. is used to kill bacteria in drinking water and swimming pools. It is also used in disinfectants and bleach for the same reason. is very effective against e coli bacteria. It is more regularly used by terrorist groups. is used to make plastics. compounds are widely used as cleaning and disinfecting agents in medical facilities all over the world, especially for disinfecting the machines and equipment used in these facilities. Bromine is used in many areas such as agricultural chemicals, dyestuffs, insecticides, pharmaceuticals and chemical intermediates. Bromine compounds can be used as flame retardants. They are added to furniture foam, plastic casings for electronics and textiles to make them less flammable. Silver bromide is a chemical used in film photography. Interaction of thermal neutrons with and Bromine can be understood in terms of capture cross-section. Many workers have measured the cross-section of (n,γ) nuclear reactions for these element at thermal neutron energy[5,6,7]. Literature serve indicate that large variations exist in the measured values of nuclear reaction cross-section at thermal neutron energy. It is essential to update the present data of cross-section values. At present, precise nuclear data, advance data acquisition systems and computer software are available which will help to improve the accuracy in the measurement of cross-section values. In view of this, cross-section of 37 Cl(n,γ) 38 Cl, and 81 Br (n, ) 82 Br nuclear reaction have measurement at thermal neutron energy of.25ev. M. S. TANPURE 3, V. K. MULIK

2 International Journal of Chemical and Physical Sciences, ISSN: Experimental Details In the present work, thermal neutron source, Cf-252 available in the Savitribai Phule Pune University was used. The induced gamma-ray activities of the thermal neutron irradiated samples were measured with the help of NaI(Tl) scintillation spectrometer. The gamma-ray spectrometer was coupled to the computer based 8K M.C.A. NaI(Tl) detector was calibrated using standard gamma ray sources. The measured gamma ray spectrum was analyzed using the computer software. Sample preparation and neutron irradiation The samples are prepared from pure powders of Sodium Chloride (99.9 %), Potassium Bromide (99.9%), Manganese (99.9%) and Arsenic (99.9%). Three samples of each element are prepared. Each sample was made by packing known weight in range of 5mg to mg in polyethylene bag. Along with each sample, Manganese powder of known weight was packed in separate polyethylene bag to calculate the thermal neutron flux as standard. Similarly, along with each Bromine sample, known weight of Arsenic powder was packed in separate polyethylene bag to calculate the thermal neutron flux as standard. Each sample along with standard sample was irradiated with thermal neutron flux ~ n/cm 2 sec and neutron of energy.25 ev from the Cf-252 neutron source for different time periods.gamma ray activity of each irradiated sample and monitor was counted using the NaI(Tl) gamma ray detector available in the Department of Physics, of H. V. Desai College, Pune. The induced gamma ray activities of 38 Cl (E γ =16 KeV), Bromine 82 Br (Eγ = 78 KeV), Manganese 56 Mn (Eγ = 84 KeV) and Arsenic 76 As (Eγ= 55 KeV) were counted separately.table 1 shows the experimental activation parameters, irradiation time t 1,cooling time t 2 and counting time t 3. Name of Element Nuclear Reaction Irradiation time t 1 Cooling time t 2 37 Cl(n,γ) 38 Cl Bromine 81 Br(n, )Br Manganese 55 Mn(n, )Mn Arsenic 75 As(n, )As Counting time t 3 Table 1: Details of nuclear reactions and nuclear data used, irradiation time, cooling time and counting time. Name Element of Nuclear Reaction Abundance (%) Half life T Gamma Energy (KeV) Table 2 : Details of neutron activation experimental parameters *Elements used for flux measurements as a standard or monitor. Disintegration probability F d (%) 37 Cl(n,γ) 38 Cl Bromine 81 Br(n, )Br Manganese* 55 Mn(n, )Mn Arsenic* 75 As(n, )As M. S. TANPURE 3, V. K. MULIK 4-6 -

3 B 16KeV counts International Journal of Chemical and Physical Sciences, ISSN: Calculations of neutron flux and cross section From the induced gamma ray activity of 56 Mn, E γ = 84 KeV, and 76 As, E γ =559KeV, thermal neutron flux of Cf 252 source was calculated using the following activation relation [ 8]. φ=aλ/ Nf d ε(1-e -λt 1 ) (e -λt 2) (1-e -λt 3)..(1) σ is cross section for (n, γ) reaction, Ф is neutron flux, A is total count under photo peak, λ is decay constant, f d is number of disintegration/gamma quanta, N is number of target atoms, Є is detector efficiency for gamma ray, t 1 is irradiation time, t 2 is cooling time (time between end of irradiation and start of counting), t 3 is counting time. The induced gamma ray activities of the reaction products, 38 Cl, 82 Br, 56 Mn and 76 As were calculated from the gamma ray spectra of respective radio nuclide. Using these values of gamma ray photon activities the thermal neutron flux received by the respective samples were calculated using the above relation [1]. The thermal neutron flux was calculated using the values of cross-section of nuclear reactions 55 Mn(n, )Mn 56 and 75 As(n, )As 76,13.3 barn and 4.28 barn respectively. Experimental values of the cross sections of nuclear reactions under study were calculated using the relation [8]. σ = Aλ/ФNε f d (1-e -λt 1 ) (e -λt 2) (1-e -λt 3).(2) The parameters involved were for respective nuclear reaction. The details of the nuclear data, which includes gamma ray energies, branching ratio of gamma photons (f d ), half life of generated radioisotopes were taken from the literature[9]. The Table 2 shows different nuclear parameters used for calculation of thermal neutron flux and cross-section values. The measured values of cross-section are given in Table 3. Figure 1,2,3 and 4 shows gamma ray spectra of thermal neutron irradiated samples of, Bromine, Manganese and Arsenic respectively. 1 B Irradiation Time(t 1 )= 4.96Hrs. Cooling Time (t 2 )= 1.3Hrs. Counting Time (t 3 )= 3 Hrs KeV channel no Figure 1: Gamma ray spectrum of 38 Cl Channel No. Figure 2: Gamma ray spectrum of 82 Br M. S. TANPURE 3, V. K. MULIK

4 Counts Counts International Journal of Chemical and Physical Sciences, ISSN: KeV. Irradiation Time(t 1 )= 43.46Hrs. Cooling Time (t 2 )= 1.98Hrs. 12 Irradiation time(t 1 )=4.96hrs. Cooling time(t 2 )=4.68hrs. counting time(t 3 )=3 hrs Counting Time (t 3 )= 1 Hrs. 6 (559KeV) Channel No. Figure 3: Gamma ray spectrum of 56 Mn Chnnel No. Figure 4: Gamma ray spectrum of 76 As Results and Discussion Gamma ray spectra of thermal neutrons irradiated samples of, Bromine, Manganese and Arsenic shown in figures1, 2, 3 and 4 indicate that thermal neutrons produced the sufficient measurable gamma ray activities of 38 Cl, 82 Br, 56 Mn and 76 As in the samples. Therefore thermal neutron activation technique can be used effectively for the analysis of these elements in any sample.the measured values of cross-section of neuclear reactions 37 Cl(n,γ) 38 Cl and 81 Br(n, )Br 82 are given in Table 3. The results are in good agreement with reported literature values [5,6,7]. Name of Element Nuclear Reaction Measured cross-section values (barn) Literature reported values (barns) 37 Cl(n,γ) 38 Cl Bromine 81 Br(n, )Br , 4.1, 2.25 Conclusion Table 3: The measured values of cross-section of neuclear reactions. The experimentally measured cross -section for the formation of 38 Cl and 82 Br at thermal neutrons energies formed through the nuclear reaction 37 Cl(n,γ) 38 Cl and 81 Br (n, ) 82 Br are respectively.46 barn and 2.39 barn. These experimental measured values of cross-section in the present work are in good agreement with literature values reported earlier [5,6,7]. The Manganese and Arsenic elements can be used as standards for the measurements of thermal neutron flux and can be used for the measurements of cross-section of nuclear reactions for different elements of interest. Acknowledgements Authors are thankful to the Head, Department of Chemistry, Savitribai Phule Pune University for permission of using the thermal neutron source. Authors are also thankful to BCUD, Savitribai Phule Pune University and P.K.G, Mandal for financial assistance. References: [1] W. S. Lyon, Manganese Bath Measurement Of U 233 and U 235 Nucl. Sci. Engg. 8, 378 (196). [2] L. Seren, H.N. Friedlander, S.H. Turkel, Phys. Rev.72,888 (1947) M. S. TANPURE 3, V. K. MULIK

5 International Journal of Chemical and Physical Sciences, ISSN: [3] J. S. Coursey, D.J. Schwab, J. J. Tsai and R. A. Dragoset (21) Report-National institute of standards and Technology, accessed (December214). [4] T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London (1954). [5] F.Farina Arbocco, P. Vermaercke, K. Smits, L.Sneyers, K.Strijckmans, Experimental Determination Of k, Q, $$\bar{e}_{r}$$ factors And Neutrons Cross-section For 41 isotopes of interest in Neutron Activation Analysis J.Radioannal. Nucl. Chem.296, 931 (213). [6] S. F. Mughabghab, M. Divadeenam, N. E. Holden. Neutron Cross Sections, Academic Press, Vol.1, New York & United States, (1981). [7] A. Susumu V. N. Bhoraskar, Kikuichi and K. Toshio Cross-section Measurement of (n,n ) and (n,2n) Reactions on Zirconium And Lead Targets at 14.8MeV J. Nucl. Sci. Technol. 18, 323 (1981). [8] G.R. Pansare, P. M. Dighe and V.M. Bhoraskar Estimation of Zirconium In Fe and Ti Based Alloyes Throught Formation of Zr-9 m at 14.7 Mev Neutrons Radiat. Phys. Chem. Vol. 4, No. 3, pp (1992). [9] C.M. Lederer and Shirley V.S,Tables of isotopes,7 th Edn. Wiley, New York.(1978). M. S. TANPURE 3, V. K. MULIK