Determination of Neutron Fluxes and Spectrum Shaping Factors in Irradiation Sites of Ghana’S Miniature Neutron Source Reactor (mnsr) by Activation Method After Compensation of Loss of Excess Reactivty

Affiliation(s)

Ghana Atomic Energy Commission, National Nuclear Research Institute, P.O. Box LG80, Legon, Ghana.

Ghana Atomic Energy Commission, National Nuclear Research Institute, P.O. Box LG80, Legon, Ghana.

ABSTRACT

Accurate neutron flux values in irradiation channels of research reactors are very essential to their usage. The total neutron flux of the Ghana Research Reactor-1(GHARR-1) was measured after a beryllium reflector was added to its shim to compensate for excess reactivity loss. The thermal, epithermal and fast neutron fluxes were determined by the method of foil activation. The experimental samples with and without a cadmium cover of 1-mm thickness were irradiated in the isotropic neutron field of the irradiation sites of Ghana Research Reactor-1 facility. The induced activities in the sample were measured by gamma ray spectrometry with a high purity germanium detector. The necessary correction for gamma attenuation, thermal neutrons and resonance neutron self-shielding effects were taken into account during the experimental analysis. By defining cadmium cutoff energy of 0.55eV, Al-0.1% Au wires of negligible thickness were irradiated at 3kW to determine the neutron fluxes of two irradiation channels, outer channel 7 and inner channel 2 whose Neutron Shaping Factor (α) were found to be (0.037 ± 0.001) and (–0.961 ± 0.034). The neutron flux ratios at the inner irradiation site 2 were found to be, (25.308 ± 3.201) for thermal to epithermal neutrons flux, (0.179 ± 0.021) for epithermal to fast neutrons flux and (4.528 ± 0.524) for thermal to fast neutrons flux, in the outer irradiation site 7, the neutron flux ratios were found to be, (40.865 ± 3.622) for thermal to epithermal neutrons flux, (0.286 ± 0.025) for epithermal to fast neutrons flux and (11.680 ± 1.030) for thermal to fast neutrons flux.

Accurate neutron flux values in irradiation channels of research reactors are very essential to their usage. The total neutron flux of the Ghana Research Reactor-1(GHARR-1) was measured after a beryllium reflector was added to its shim to compensate for excess reactivity loss. The thermal, epithermal and fast neutron fluxes were determined by the method of foil activation. The experimental samples with and without a cadmium cover of 1-mm thickness were irradiated in the isotropic neutron field of the irradiation sites of Ghana Research Reactor-1 facility. The induced activities in the sample were measured by gamma ray spectrometry with a high purity germanium detector. The necessary correction for gamma attenuation, thermal neutrons and resonance neutron self-shielding effects were taken into account during the experimental analysis. By defining cadmium cutoff energy of 0.55eV, Al-0.1% Au wires of negligible thickness were irradiated at 3kW to determine the neutron fluxes of two irradiation channels, outer channel 7 and inner channel 2 whose Neutron Shaping Factor (α) were found to be (0.037 ± 0.001) and (–0.961 ± 0.034). The neutron flux ratios at the inner irradiation site 2 were found to be, (25.308 ± 3.201) for thermal to epithermal neutrons flux, (0.179 ± 0.021) for epithermal to fast neutrons flux and (4.528 ± 0.524) for thermal to fast neutrons flux, in the outer irradiation site 7, the neutron flux ratios were found to be, (40.865 ± 3.622) for thermal to epithermal neutrons flux, (0.286 ± 0.025) for epithermal to fast neutrons flux and (11.680 ± 1.030) for thermal to fast neutrons flux.

Cite this paper

nullR. Sogbadji, B. Nyarko, E. Akaho and R. Abrefah, "Determination of Neutron Fluxes and Spectrum Shaping Factors in Irradiation Sites of Ghana’S Miniature Neutron Source Reactor (mnsr) by Activation Method After Compensation of Loss of Excess Reactivty,"*World Journal of Nuclear Science and Technology*, Vol. 1 No. 2, 2011, pp. 50-56. doi: 10.4236/wjnst.2011.12009.

nullR. Sogbadji, B. Nyarko, E. Akaho and R. Abrefah, "Determination of Neutron Fluxes and Spectrum Shaping Factors in Irradiation Sites of Ghana’S Miniature Neutron Source Reactor (mnsr) by Activation Method After Compensation of Loss of Excess Reactivty,"

References

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[2] W. E. Burcahm, “Nuclear Physics, an introduction,” Longman, London, 1970, pp. 12-15, 25-28.

[3] S. Anim-Sampong, B. T. Maakuu, E. H. K. Akaho, A. Andam, J. J. R. Liaw and J. E. Matos, “Progress in the Neutronic Core Conversion (HEU-LEU) Analysis of Ghana Research Reactor-1,” 2006 International RERTR Meeting, Cape Town, 29 October- 2 November 2006, pp. 6-7.

[4] R. B. M. Sogbadji, et al., Nuclear Engineering and Design, Vol. 240, 2010, pp. 980-984. doi:10.1016/j.nucengdes.2009.12.020

[5] G. I. Bell and S. Glasstone, “Nuclear Reactor Theory,” Chapter 7, Van Nostrand Reinhold, New York, 1970,

[6] E. H. K. Akaho and B. J. B. Nyarko, “Characterization of Neutron Flux Spectra in Irradiation Sites of MNSR Reactor Using the Westcott-Formalism for the Ko Neutron Activation Analysis Method,” 2002, p. 268.

[7] M. Karandag, H. Yücel, M. Tan and A. ?zmen, “Measurement of Thermal Neutrons and Resonance Integral for 71Ga(N,Γ) 72Ga and 75As (N, Γ )76As by Using 241Am-Be Isotopic Neutron Source,” 2003, pp.524-527.

[8] K. Khattab, “Measurement of Fast Neutron Flux in the MNSR Inner Irradiation Site,” Applied Radiation and Isotopes, Vol. 65, No. 1, 2005, pp. 46-48. doi:10.1016/j.apradiso.2005.11.020

[9] T. Elnimr and I. I. Bondouk, “The Use of Ke,0 Factors as a Tool for a Critical Evaluation of Reactor Thermal and Epithermal (N, Γ) Cross-Section and of Absolute Gamma Intensities,” 1983, pp. 1409-1414.

[10] F. De Corte, A. De Wispelaere and L. Hoste, “Accuracy and Applicability of ko Method,” Journal of Radioanalytical Chemistry, Vol. 113, No. 1, 1987, pp. 145-161. doi:10.1007/BF02036056

[11] G. Kennedy, J. St. Pierre, K. Wang, Y. Zang, J. Preston, C. V. Grant, “Activation Constant of SLOWPOKE and MNSR Reactors Calculated from the Neutron Spectrum and Ko and Qo Values,” Journal of Radioanalytical Chemistry, Vol. 245, No. 1, 2000, pp. 167-172. doi:10.1023/A:1006749820638

[12] E. H. K. Akaho and B. J. B. Nyarko, “Characterization of Neutron Flux Spectra in Irradiation Channels of MNSR Reactor, Using Wescott-Formalism for the Ko Neutron Activation Analysis,” Applied Radiation and Isotopes, 2002, pp 265-273. doi:10.1016/S0969-8043(02)00106-9

[13] F. De Corte, K. S. Hammami, L. Moens, A. Simonits, A. De Wispelaere and J. Hoste, “The Accuracy of the Experimental Alpha-Determination in the Epithermal Reactor Neutron Spectrum,” Journal of Radioanalytical Chemistry, Vol. 62, No. 1-2, 1981, pp. 209-255. doi:10.1007/BF02517354

[14] E. K. Osae, B. J. B. Nyarko, Y. Serfor-Armah and E. O. Darko, “An Empirical Expression for the Full Energy Peak Efficiency of an N-Type High Purity Germanium Detector,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 242, No. 3, 1999, pp. 618-619. doi:10.1007/BF02347370

[15] F. De Corte and A. De Wispelaere, “Recalibration of the Irradiation Facilities in the Thesis Reactor with an Examination of the Α Versus E Behavior in Kev Neutron Energy Range,” Vol. 257, No. 3, 2003, pp. 519-523.

[16] C. O. Mustra, M. C. Freitas, S. M. Almeida, “Neutron Flux and Associated Ko Parameters in the RPI after the Last Configuration Change,” Journal of Radioanalytical and Nuclear, Vol. 257, No. 3, 2003, pp. 539-543. doi:10.1023/A:1025432329915

[17] Y. A. Ahmed, I. O. B. Ewa, I. M. Umar, T. Bezborah, M. Johri and E. H. K. Akaho, “The Low Power Miniature Neutron Source Reactors: Design, Safety and Applications,” The Abdus Salam International Centre for Theoretical Physics, Trieste, 2006.

[18] S. A. Jonah, G. I. Balogun, I. M. Umar and M. C. Mayaki, “Neutron Spectrum Parameters in Irradiation Channel of the Nigeria Research Reactor-1(NNRI-1) for the Ko-NAA Standardization,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 266, No. 1, 2005, pp. 83-88. doi:10.1007/s10967-005-0873-8

[19] S. A. Jonah, G. I. Balogun, I. M. Umar and M. C. Mayaki, “Neutron Spectrum Parameters in Irradiation Channels of the Nigeria Research Reactor-1 (NIRR-1) for the K0-NAA Standardization,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 266, No. 1, 2004, pp. 82-85.

[20] L. Moen, F. De Corte, A. Simonits, A. Wispelaere and J. Hoste, “The Effective Resonance Energy Er as a Parameter for the Correction of Resonance Integrals, 1/E(1+ Α) Epithermal Neutron Spectra: Tabulation of Er for 96 Isotopes,” Journal of Radioanalytical Chemistry, Vol. 52, No. 2, 1979, pp. 379-387. doi:10.1007/BF02521289

[21] S. Jovanovic, P. Vukotic, R. Jacimovic, N. Mihaljevic and P. Stegnar, “Epithermal Neutron Flux Characterization of the TRIGA II Reactor, Ljugljana, Yugoslavia for Use in NAA,” Journal of Radioanalytical Chemistry, Vol. 113, No. 1, 1989, pp. 177-185.

[22] R. G. Nisle, “A Unified Formulation of the Specification of Neutron Flux Spectra in Reactors, Neutron Dosimetry,” IAEA-TECH Report 1. 1963, pp. 111-152.

[23] R. F. Fleming, International Journal of Applied Radiation and Isotopes, 33, 1982, p. 1263. doi:10.1016/0020-708X(82)90247-2

[24] M. Abramowitz, I. A. Stegun, “Handbook of mathematical Functions US,” Government Printing Office, Washington, DC, 1964.

[1] S. Glasstone and A. Sesonske, “Nuclear Reactor Engineering: Reactor Design Basics,” Kluwer Academic Publishers, Norwell, 1994, pp. 59-71, 77-79

[2] W. E. Burcahm, “Nuclear Physics, an introduction,” Longman, London, 1970, pp. 12-15, 25-28.

[3] S. Anim-Sampong, B. T. Maakuu, E. H. K. Akaho, A. Andam, J. J. R. Liaw and J. E. Matos, “Progress in the Neutronic Core Conversion (HEU-LEU) Analysis of Ghana Research Reactor-1,” 2006 International RERTR Meeting, Cape Town, 29 October- 2 November 2006, pp. 6-7.

[4] R. B. M. Sogbadji, et al., Nuclear Engineering and Design, Vol. 240, 2010, pp. 980-984. doi:10.1016/j.nucengdes.2009.12.020

[5] G. I. Bell and S. Glasstone, “Nuclear Reactor Theory,” Chapter 7, Van Nostrand Reinhold, New York, 1970,

[6] E. H. K. Akaho and B. J. B. Nyarko, “Characterization of Neutron Flux Spectra in Irradiation Sites of MNSR Reactor Using the Westcott-Formalism for the Ko Neutron Activation Analysis Method,” 2002, p. 268.

[7] M. Karandag, H. Yücel, M. Tan and A. ?zmen, “Measurement of Thermal Neutrons and Resonance Integral for 71Ga(N,Γ) 72Ga and 75As (N, Γ )76As by Using 241Am-Be Isotopic Neutron Source,” 2003, pp.524-527.

[8] K. Khattab, “Measurement of Fast Neutron Flux in the MNSR Inner Irradiation Site,” Applied Radiation and Isotopes, Vol. 65, No. 1, 2005, pp. 46-48. doi:10.1016/j.apradiso.2005.11.020

[9] T. Elnimr and I. I. Bondouk, “The Use of Ke,0 Factors as a Tool for a Critical Evaluation of Reactor Thermal and Epithermal (N, Γ) Cross-Section and of Absolute Gamma Intensities,” 1983, pp. 1409-1414.

[10] F. De Corte, A. De Wispelaere and L. Hoste, “Accuracy and Applicability of ko Method,” Journal of Radioanalytical Chemistry, Vol. 113, No. 1, 1987, pp. 145-161. doi:10.1007/BF02036056

[11] G. Kennedy, J. St. Pierre, K. Wang, Y. Zang, J. Preston, C. V. Grant, “Activation Constant of SLOWPOKE and MNSR Reactors Calculated from the Neutron Spectrum and Ko and Qo Values,” Journal of Radioanalytical Chemistry, Vol. 245, No. 1, 2000, pp. 167-172. doi:10.1023/A:1006749820638

[12] E. H. K. Akaho and B. J. B. Nyarko, “Characterization of Neutron Flux Spectra in Irradiation Channels of MNSR Reactor, Using Wescott-Formalism for the Ko Neutron Activation Analysis,” Applied Radiation and Isotopes, 2002, pp 265-273. doi:10.1016/S0969-8043(02)00106-9

[13] F. De Corte, K. S. Hammami, L. Moens, A. Simonits, A. De Wispelaere and J. Hoste, “The Accuracy of the Experimental Alpha-Determination in the Epithermal Reactor Neutron Spectrum,” Journal of Radioanalytical Chemistry, Vol. 62, No. 1-2, 1981, pp. 209-255. doi:10.1007/BF02517354

[14] E. K. Osae, B. J. B. Nyarko, Y. Serfor-Armah and E. O. Darko, “An Empirical Expression for the Full Energy Peak Efficiency of an N-Type High Purity Germanium Detector,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 242, No. 3, 1999, pp. 618-619. doi:10.1007/BF02347370

[15] F. De Corte and A. De Wispelaere, “Recalibration of the Irradiation Facilities in the Thesis Reactor with an Examination of the Α Versus E Behavior in Kev Neutron Energy Range,” Vol. 257, No. 3, 2003, pp. 519-523.

[16] C. O. Mustra, M. C. Freitas, S. M. Almeida, “Neutron Flux and Associated Ko Parameters in the RPI after the Last Configuration Change,” Journal of Radioanalytical and Nuclear, Vol. 257, No. 3, 2003, pp. 539-543. doi:10.1023/A:1025432329915

[17] Y. A. Ahmed, I. O. B. Ewa, I. M. Umar, T. Bezborah, M. Johri and E. H. K. Akaho, “The Low Power Miniature Neutron Source Reactors: Design, Safety and Applications,” The Abdus Salam International Centre for Theoretical Physics, Trieste, 2006.

[18] S. A. Jonah, G. I. Balogun, I. M. Umar and M. C. Mayaki, “Neutron Spectrum Parameters in Irradiation Channel of the Nigeria Research Reactor-1(NNRI-1) for the Ko-NAA Standardization,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 266, No. 1, 2005, pp. 83-88. doi:10.1007/s10967-005-0873-8

[19] S. A. Jonah, G. I. Balogun, I. M. Umar and M. C. Mayaki, “Neutron Spectrum Parameters in Irradiation Channels of the Nigeria Research Reactor-1 (NIRR-1) for the K0-NAA Standardization,” Journal of Radioanalytical and Nuclear Chemistry, Vol. 266, No. 1, 2004, pp. 82-85.

[20] L. Moen, F. De Corte, A. Simonits, A. Wispelaere and J. Hoste, “The Effective Resonance Energy Er as a Parameter for the Correction of Resonance Integrals, 1/E(1+ Α) Epithermal Neutron Spectra: Tabulation of Er for 96 Isotopes,” Journal of Radioanalytical Chemistry, Vol. 52, No. 2, 1979, pp. 379-387. doi:10.1007/BF02521289

[21] S. Jovanovic, P. Vukotic, R. Jacimovic, N. Mihaljevic and P. Stegnar, “Epithermal Neutron Flux Characterization of the TRIGA II Reactor, Ljugljana, Yugoslavia for Use in NAA,” Journal of Radioanalytical Chemistry, Vol. 113, No. 1, 1989, pp. 177-185.

[22] R. G. Nisle, “A Unified Formulation of the Specification of Neutron Flux Spectra in Reactors, Neutron Dosimetry,” IAEA-TECH Report 1. 1963, pp. 111-152.

[23] R. F. Fleming, International Journal of Applied Radiation and Isotopes, 33, 1982, p. 1263. doi:10.1016/0020-708X(82)90247-2

[24] M. Abramowitz, I. A. Stegun, “Handbook of mathematical Functions US,” Government Printing Office, Washington, DC, 1964.