An experiment was carried out to study the feasibility of 99Mo production using an electron accelerator based epi-cadmium neutron source. The neutrons were produced by the interaction of bremsstrahlung end-point energy of 10 MeV with BeO blocks and the neutrons thus produced were moderated using High Density Polyethylene blocks. Effective cross-section of 98Mo(n,γ)99Mo reaction was measured using foil activation method. An enhancement in the effective cross-section due to resonances in the epi-cadmium region was observed. The photons and neutron production/transport in the experimental set-up were simulated using the FLUKA Monte Carlo code. The simulations were found to be in good agreement with the experimental findings.

An Advanced Heavy Water Reactor (AHWR) based on thorium fuel is being designed and developed in India. The design has many inherent safety features; the most important among them is its negative coolant void coefficient. An experimental facility, named AHWR Critical Facility, has been built to validate the physics design parameters. Coolant void worth which is an important safety parameter was measured using differential critical height in a thoria based experimental MOX fuel assembly placed in the center of the core. The voiding effects were experimentally determined with both water and high density polyethylene (HDP) coolant. Different fractional voids were obtained using combinations of HDP block of compatible shape and sizes. The aim of the experiment was to validate the code systems used in physics design and in particular, to assess their capability of modeling the voiding conditions in thorium based fuel cluster. The validation exercise was performed with both deterministic and stochastic methods. The theoretical estimates of the void worth were found in very good agreement with that of the measurement. The results have enhanced the confidence in the code system used for AHWR physics design.

Activation analysis is a well-known radio-analytical technique to carry out the material characterization using neutrons. In this, the sample of material is irradiated in an ambient neutron flux and the induced radioactivity is studied to infer the composition of material. K0 based neutron activation analysis (k0-NAA) is a method used for characterising variety of materials using neutrons. Knowledge of neutron energy spectrum and it’s shaping factor (α) at neutron irradiation location is essential for application of (k0-NAA) method. The objective of the present work is to determine α at central location in AHWR-Critical Facility, a nuclear reactor at Bhabha Atomic Research Center, Mumbai, India. The determination of α was carried out by various analytical methods. The basic inputs required for determination of α were produced by modelling the reactor using in-house developed Monte Carlo code PATMOC. The results were cross checked by generating neutron energy spectrum in the reactor.

Dhruva is a 100 MW tank-type research reactor with natural metallic uranium as fuel and heavy water as coolant, moderator, and reflector. The reactor is utilized for production of a large variety of radioisotopes for fulfilling growing demands of various applications in industrial, agricultural, and medicinal sectors, and neutron beam research in condensed matter physics. The core consists of two on-power tray rods for radioisotope production and 15 experimental beam holes for neutron beam research. Recently, a self-serve facility has also been commissioned in one of the through tubes in the reactor for carrying out short-term irradiations. To get accurate information about thermal neutron flux, measurements have been carried out in self-serve facility and on-power tray rod K-09 of Dhruva reactor. The present report describes measurement method, analysis technique, and results. Theoretical estimations for neutron flux were also carried out and a comparison between theoretical and experimental results is made.

Measurement of reactivity in deep sub critical system using neutron noise method is challenging due to the modal effect. This paper addresses the issue of modal effect in such system in a new and better way. The measurements were carried out in the ADS experimental facility BRAHMMA commissioned recently at Bhabha Atomic Research Centre (BARC), India. The BRAHMMA assembly is a deep sub critical system having multiplication factor (Keff)∼0.9. The data analysis was carried out using two commonly used neutron noise techniques namely the Feynman alpha and the auto correlation function methods. The modal effect was eliminated by placing the neutron detectors at strategically chosen locations in the core. The detector locations were decided on the basis of the detailed modal analysis of the core. The modal analysis and calculations of the kinetic parameters of the core were carried out using a diffusion theory code. The measured reactivity was found to be in good agreement with the theoretical estimate.

Introduction AHWR Critical Facility (AHWR CF) is a “zero power” reactor designed to carry out various reactor physics experiments for validation of AHWR design [1]. The standard reference core of AHWR-CF consisted of 55 regular 19-rod nat. Uranium Fuel Assemblies (FA) at 245 mm square pitch, six cadmium shut-off rods and one cadmium absorber rod for experimental purposes. First Approach to Criticality for the facility was carried out with this core on 7 th April, 2008. Since then, a number of experiments have been carried out in the facility. In this paper, we present brief description of various experiments carried out using different Thorium based experimental clusters.

The (n, γ) and (n, 2n) reaction cross-section of 238 U at average neutron energies of 13.5 and 17.28 MeV from the 7 Li(p, n) 7 Be reaction has been determined using activation and off-line γ-ray spectrometric technique.The experimentally determined 238 U(n, γ) 239 U and 238 U(n, 2n) 237 U reaction cross-sections from present work were compared with the evaluated data of ENDF/BVII.0and JENDL-4.0,JEFF-3.1/A and CENDL-3.1 (referenced in text).The experimental values were found to be in general agreement with the evaluated values obtained using ENDF/BVII.0,JENDL-4.0 and JEFF-3.1/Abut it differs with the values obtained using CENDL-3.1.The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between 238 U(n, γ), (n, f), (n, nf) and (n, xn) reactions channels.The 238 U(n, γ) and 238 U(n, 2n) reaction cross-sections were also calculated theoretically using the TALYS 1.4 computer code and were found to be in general agreement with the experimental data.Keywords-238 U (n, γ) 239 U and 238 U(n, 2n) 237 U Reaction Cross-Sections; 7 Li(p, n) 7 Be Reaction; Average Neutron Energy; E n = 13.5 and 17.28 MeV; Off-Line γ-Ray Spectrometric Technique; TALYS Calculation

The 232Th(n, γ) reaction cross-section at average neutron energies of 13.5, 15.5 and 17.28 MeV from the 7Li(p, n) reaction has been determined for the first time using activation and off-line γ-ray spectrometric technique. The 232Th(n, 2n) cross-section at 17.28 MeV neutron energy has also been determined using the same technique. The experimentally determined 232Th(n, γ) and 232Th(n, 2n) reaction cross-sections from the present work were compared with the evaluated data of ENDF/BVII and JENDL-4.0 and were found to be in good agreement. The present data, along with literature data in a wide range of neutron energies, were interpreted in terms of competition between 232Th(n, γ), (n, f), (n, nf) and (n, xn) reaction channels. The 232Th(n, γ) and 232Th(n, 2n) reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be in good agreement with the experimental data from the present work but were slightly higher than the literature data at lower neutron energies.

The 232Th(n, γ ) reaction cross-section at average neutron energies of 13.5, 15.5 and 17.28 MeV from the 7Li(p, n) reaction has been determined for the first time using activation and off-line γ -ray spectrometric technique. The 232Th(n, 2n) cross-section at 17.28 MeV neutron energy has also been determined using the same technique. The experimentally determined 232Th(n, γ ) and 232Th(n, 2n) reaction cross-sections from the present work were compared with the evaluated data of ENDF/BVII and JENDL-4.0 and were found to be in good agreement. The present data, along with literature data in a wide range of neutron energies, were interpreted in terms of competition between 232Th(n, γ ), (n, f ), (n, n f ) and (n, xn) reaction channels. The 232Th(n, γ ) and 232Th(n, 2n) reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be in good agreement with the experimental data from the present work but were slightly higher than the literature data at lower neutron energies.

The 232 Th( n , γ ) reaction cross-section at average neutron energies of 13.5, 15.5 and 17.28 MeV from the 7 Li( p , n ) reaction has been determined for the first time using activation and off-line γ -ray spectrometric technique. The 232 Th( n , 2 n ) cross-section at 17.28 MeV neutron energy has also been determined using the same technique. The experimentally determined 232 Th( n , γ ) and 232 Th( n , 2 n ) reaction cross-sections from the present work were compared with the evaluated data of ENDF/BVII and JENDL-4.0 and were found to be in good agreement. The present data, along with literature data in a wide range of neutron energies, were interpreted in terms of competition between 232 Th( n , γ ), ( n , f ), ( n , nf ) and ( n , xn ) reaction channels. The 232 Th( n , γ ) and 232 Th( n , 2 n ) reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be in good agreement with the experimental data from the present work but were slightly higher than the literature data at lower neutron energies.