Tarun Patel

Evaluation of Spatial Correction Factors for BRAHMMA Subcritical Assembly

Abstract The reactivity measurement in a subcritical assembly using the area ratio method is affected by the detector location and needs to be corrected for spatial dependence. One of the approaches to calculate the spatial correction factor is based on steady-state numerical simulation as proposed by Bell and Glasstone. This paper discusses the evaluation of the spatial correction factor for the BRAHMMA (BeO Reflected And HDPe Moderated Multiplying Assembly) subcritical assembly, India. The factors have been used to correct experimentally measured reactivity values from the area ratio method at different locations inside the core.

Associated particle technique in single-sided geometry for detection of explosives

Associated particle technique (APT) for detection of explosives is well established but has been implemented mostly for fixed portal systems. In certain situations, a portable system is required where the suspect object cannot be moved from site. This paper discusses the development of a portable APT system in single-sided geometry which can be transported to site and requires only one-sided access to the object. The system comprised D-T neutron source and bismuth germanate (BGO) detectors fixed on a portable module. Different aspects of the system have been discussed such as background contribution, time selection, and elemental signatures. The system was used to detect benign samples and explosive simulants under laboratory condition. The elemental ratios obtained by analyzing the gamma spectra show good match with the theoretical ratios.

Reactivity Measurement Using the Area-Ratio Method in the BRAHMMA Subcritical System

The online reactivity monitoring of accelerator-driven systems is a crucial issue in reactor control and monitoring. The area-ratio method is one of the techniques for measuring the reactivity of subcritical systems using a pulsed neutron source. This technique has been used to measure reactivity at different locations in the subcritical assembly BRAHMMA developed at the Bhabha Atomic Research Centre, India. Since the reactivity measured by the area-ratio method is spatially dependent on the detector location, the Bell-Glasstone correction factor was used to correct the measured reactivity.

Pulsed Neutron Source Measurements in the BRAHMMA Accelerator-Driven Subcritical System

Abstract The use of accelerator-driven systems for incineration of nuclear waste and energy production requires monitoring of different parameters that govern reactor safety. One of the most important parameters is the multiplication factor keff. The present paper describes the results of experiments carried out on a subcritical system (BRAHMMA) using a pulsed neutron source. The value of the multiplication factor keff obtained from time responses of the core that were measured in situ using neutron detectors after insertion of a neutron pulse matches well with the calculated value.

Feasibility study of prompt gamma neutron activation analysis (PGNAA) of explosives simulants and bulk material using DD/DT neutron generator

Elemental characterization of low Z elements (C,H,Cl,Fe) inside bulk materials were performed using PGNAA technique. Samples having elemental composition similar to explosives were used for such experimentations using moderated DD neutrons as well as DT(14MeV) neutrons. We could observe characteristic prompt capture gamma rays of hydrogen (2.224MeV), nitrogen (10.83 MeV), chlorine (6.11 MeV) and Fe (6.02MeV and 7.63MeV) also (n,n’γ) prompt gamma signal (4.43MeV) of carbon. BGO detector has been used for gamma spectrum acquisition. These experimentations has been carried out for initial feasibility studies of detecting prompt gamma lines as a part of PGNAA technique based explosive detection system development. A detail description of experimental set up and procedure has been discussed in paper.