• Maitreyee Nandy

      Articles written in Pramana – Journal of Physics

    • An empirical fit to estimated neutron emission cross sections from proton induced reactions

      Moumita Maiti Maitreyee Nandy S N Roy P K Sarkar

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      Neutron emission cross section for various elements from9Be to209Bi have been calculated using the hybrid model code ALICE-91 for proton induced reactions in the energy range 25 MeV to 105 Me V. An empirical expression relating neutron emission cross section to target mass number and incident proton energy has been obtained. The simple expression reduces the computation time significantly. The trend in the variation of neutron emission cross sections with respect to the target mass number and incident proton energy has been discussed within the framework of the model used.

    • Quantum molecular dynamics approach to estimate spallation yield fromp +208Pb reaction at 800 MeV

      P K Sarkar Maitreyee Nandy

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      The spallation yield of neutrons and other mass fragments produced in 800 MeV proton induced reaction on208Pb have been calculated in the framework of quantum molecular dynamics (QMD) model. The energy spectra and angular distribution have been calculated. Also, multiplicity distributions of the emitted neutrons and kinetic energy carried away by them have been estimated and compared with the available experimental data. The agreement is satisfactory. A major contribution to the neutron emission comes from statistical decay of the fragments. For mass and charge distributions of spallation products the QMD process gives rise to target-like and projectile-like fragments only.

    • Accelerator driven systems from the radiological safety point of view

      P K Sarkar Maitreyee Nandy

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      In the proposed accelerator driven systems (ADS) the possible use of several milliamperes of protons of about 1 GeV incident on high mass targets like the molten lead–bismuth eutectic is anticipated to pose radiological problems that have so far not been encountered by the radiation protection community. Spallation reaction products like high energy gammas, neutrons, muons, pions and several radiotoxic nuclides including Po-210 complicate the situation. In the present paper, we discuss radiation safety measures like bulk shielding, containment of radiation leakage through ducts and penetration and induced activity in the structure to protect radiation workers as well as estimation of sky-shine, soil and ground water activation, release of toxic gases to the environment to protect public as per the stipulations of the regulatory authorities. We recommend the application of the probabilistic safety analysis technique by assessing the probability and criticality of different hazard-initiating events using HAZOP and FMECA.

    • Measurement and theoretical estimation of induced activity in $^{\text{nat}}$In by high energy neutrons

      Maitreyee Nandy P K Sarkar N Nakao T Shibata

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      Induced radioactivity in natural indium ($^{\text{nat}}$In) foils by high energy neutrons was measured at the KENS Facility, KEK, Japan, where a 16.7 cm thick W target was bombarded by protons of 500 MeV. High energy neutrons consequently produced irradiated the In targets placed at different depths inside a 4 m thick concrete shield placed at the beam exit. The measured activities were compared with the results calculated using the nuclear reaction model codes ALICE-91 and EMPIRE-2.18. To estimate the induced activity, excitation functions of the various radionuclides were calculated using the two codes and folded with the appropriate neutron energy distribution at different depths of the concrete shield. The calculated excitation functions of a given nuclide were found to vary widely from one another in some cases. The performances of the codes for different input parameters like level densities and inverse cross-sections are reported in this paper. Our analysis shows that neither of the two codes reproduced all the measured activities satisfactorily, requiring further improvements in the models adopted.

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