Bhabha Atomic Research Centre Research Articles

High-Precision Measurement of the 238Pu/239Pu Isotope Ratio by TIMS.

With an aim to improve the precision of isotopic standards of special nuclear materials like uranium and plutonium, National Bureau of Standards (NBS) undertook the recertification of isotopic standards prepared between 1960 and 1970. In a recent initiative, Lawrence Livermore National Laboratory (LLNL) in collaboration with New Brunswick Laboratory Program Office (NBL PO) undertaken efforts to recertify SRM 946, SRM 947, and SRM 948. The primary goal of this drive is to lower the uncertainties associated with the isotopic compositions of plutonium standards. The drive is also aims to minimize the uncertainty associated with measurement of the 238Pu content from 2% to ∼0.3%. In this connection, our laboratory at the Fuel Chemistry Division, Bhabha Atomic Research Centre, proposes a novel indicator "minima in the (RMO254/(i+16))/(RM238/i) curve" (where i = m/z 233 or 235 amu), which is the ratio of the isotope ratio of metal oxides (238M16O/iM16O) to that of metal ions (238M/iM) of uranium in determining the accurate 238Pu content by thermal ionization mass spectrometry. Various enriched uranium spikes have been employed to study the efficacy of the minima in the (RMO(254)/(i+16))/(RM238/i) curve. With the combination of monitoring the minima in the (RMO(254)/(i+16))/(RM238/i) curve and the application of the 233U spike (with an isotope abundance of 238U ∼ 0.05%), an external precision of 0.2% has been achieved in the determination of the 238Pu/239Pu isotope ratio for isotopic standard SRM 947.

Intake dose rate due to various granite samples of Bangalore city, India

The majority of total radiation dose received by the world population comes from background natural radiation. The distinguishing features of this radiation include relatively persistent exposure of a population at a specific place. The amount of background radiation that is generally present in the environment is greatly influenced by the inhalation of radon (Rn), thoron (Tn), and their offspring. In light of this, measurement of dose rate exposure due to granite flooring has been attempted in Bangalore. Fifteen different granite samples, used as flooring for construction in buildings, were examined for a period of three years. Solid state nuclear track detector-based dosimeters, can technique, and radiation survey meters have been used. All the experimental observations were made according to the standard protocols provided by the Bhabha Atomic Research Centre, Mumbai, India. The arithmetic mean dose rate varied between 1.39 ± 0.06 and 2.09 ± 0.10 mSv y1. The values of dose rates were found to be higher in granite and lower in coarse-grained dolerite. All 15 types of granite samples have undergone a minimum of 30 measurements. The greater activity concentration of radionuclides found in granite samples leads to higher dose rates.

Imino‐BODIPY‐Based, Highly Sensitive, Fluorescent Dosimeter for Low‐Dose Gamma Radiation**

AbstractThe Front Cover image is provided by Dr. Soumyaditya Mula of Bhabha Atomic Research Centre and Homi Bhabha National Institute, Mumbai, India. The image shows quick and efficient sensing of gamma (g) radiation via conversion of non‐fluorescent imino‐BODIPY dye to green fluorescent formyl BODIPY after interaction with g‐rays. Read the full text of the Research Article at 10.1002/cptc.202300245.

Design, fabrication, and characterization of a drift tube linac type double gap re-buncher cavity.

The Low Energy High Intensity Proton Accelerator (LEHIPA) at Bhabha Atomic Research Centre, India, has recently been commissioned to the target energy of 20MeV by beam acceleration through a 352MHz radio frequency quadrupole (RFQ) and drift tube linac (DTL). The medium energy beam transport (MEBT) line of LEHIPA matches the 3MeV beam from RFQ to the DTL using four electromagnetic quadrupoles and a re-buncher cavity. In the beam transport lines of high frequency linacs, TM010 mode single gap buncher cavities are conventionally used, while a double gap re-buncher cavity was chosen for the short length LEHIPA MEBT based on beam dynamics simulations. The 352MHz double gap re-buncher cavity has been designed in a DTL type geometry with a cell length of βλ. This double gap cavity is found to be more power efficient with a higher shunt impedance and transit time factor than the conventional single gap buncher cavity. Electromagnetic design simulations, fabrication details, low power and high-power RF test results, and beam test results of the re-buncher cavity are presented in this paper.

Gas sheet beam induced fluorescence based beam profile measurement for high intensity proton accelerators

The paper describes the design simulations, developmental details and characterization results of a dual gas sheet generator system for non-invasive beam profile measurement of high-intensity proton beams. The system is being developed for the Low Energy High Intensity Proton Accelerator facility at Bhabha Atomic Research Centre, India. To our knowledge, this is the first time an intense low energy proton beam was used to directly view the beam induced fluorescence of a gas sheet. The system works by generating two thin nitrogen gas sheets which produces fluorescence when a charged particle beam passes through them, thereby providing a visual representation of the beam's intensity profile. The gas sheets are generated at 45° to the beam axis, which allows the fluorescence created by the interaction to be viewed directly through a viewport or camera capture. The beam profile measurements were carried out with a typically 20 keV, 10 mA pulsed proton beam from an ECR ion source under different operating parameters like gas sheet pressure, beam current, beam energy and focusing magnetic field. The Geant4 simulation has been performed to study the scintillation process and optical transport. It may become useful to study methods of reconstructing the beam profile from image obtained.

Estimation of the buildup of He-3 and Li-6 poisoning, He-4 and tritium activity in beryllium oxide reflector block in APSARA-U reactor

The Apsara-U research reactor, situated at the Bhabha Atomic Research Center, began its operation in 2018. This facility employs a fuel core configuration employing low-enriched uranium and reflector assemblies made of beryllium oxide. In neutron-rich environment of a nuclear reactor, these beryllium oxide reflector blocks participate in nuclear reactions identified as 9Be(n,α) and 9Be(n,2n). The 9Be(n,α) reaction initiates the formation of isotopes such as 4He, 6Li, 3He, and 3H in the process. The accumulation of gasses like 3He, 4He, and 3H causes the beryllium oxide reflector to swell, ultimately restricting how long it can effectively serve as a reflector or moderator material within the reactor. Extended periods of reactor shutdown result in a significant increase in the concentrations of 3He, mainly due to the radioactive decay of 3H. 6Li and 3He nuclei have significant neutron capture cross-sections, leading to a reduction in the reactor's reactivity, a phenomenon termed "poisoning". This effect varies depending on factors like neutron flux, neutron flux spectrum, and the reactor's operational history. Thorough investigations have been carried out to gain insights into the accumulation of 4He, 3He, 6Li, and 3H within beryllium oxide and their effects on reactivity considering the diverse levels of neutron exposure it encounters.

Overview of the physics challenges in design of new energy systems

Today's energy systems have diverse objectives catering to enhanced safety, ease of operation and better fuel utilization both for power generation and several other applications of nuclear reactions. Bhabha Atomic Research Centre (BARC) has been engaged in the design of new energy systems such as Advanced Heavy Water Reactor (AHWR), Indian Pressurised Water Reactor (IPWR), Molten Salt Reactor (MSR) and High Temperature Reactors (HTRs). The design optimisation of these reactors has varied challenges as they involve new fuel, newer materials, complex geometries, and inherent safety. AHWR, MSR and HTRs based on thorium fuel cycle while IPWR is optimized for longer cycle length with enriched uranium. HTRs are being developed as nuclear power packs for remote areas and they have interesting physics features of long-life cores and hence more challenging to be modelled.New designs use new materials and therefore require updated thermophysical and neutronic properties. Neutron-nuclear interaction cross sections are required in uncharted regimes. Modelling of physical phenomena in an MSR or HTR is very different than in water-cooled reactors.The neutronic tools also are required to be made state-of-the-art in order to model these multi physics phenomena. An exercise was taken up for a coupled neutronic-thermal hydraulic simulations for the natural circulation based boiling water cooled AHWR. Several new algorithms were also developed for fuel management of advanced thermal reactors. Monte Carlo methods and improved deterministic methods have been continuously developed. This paper brings out the challenges in design of these advanced reactors and the need for new experiments and irradiations of new fuel in research reactors.

Benchmarking exercise of indigenous Monte Carlo neutron transport code PATMOC for hexagonal full core reactor geometry

An indigenous Monte Carlo neutron transport code, named PATMOC, has been designed and developed at Bhabha Atomic Research Centre (BARC) for reactor physics design applications. The code has been extensively tested for its algorithmic accuracy against numerous international numerical benchmarks, has also been validated on practical nuclear reactor systems like Advanced Heavy Water Reactor Critical Facility (AHWR-CF) and Apsara-U pool type research reactor located at BARC, and is now in regular use for day-to-day reactor physics studies. These reactor systems and most of the benchmark problems used for the verifications and validation of the code have square lattice arrangement in the core. In this paper, we present the results of verification of PATMOC code on whole-core reactor system with hexagonal lattice arrangement of fuel elements. In this exercise, we have analyzed the High Temperature engineering Test Reactor (HTTR) whole-core benchmark for integral and differential parameters at both lattice and core level. The results demonstrate the algorithmic accuracy of the code on hexagonal reactor systems also. This exercise will help make use of this code for reactor physics design studies also for the reactor systems with hexagonal arrangement.

Analysis of Kobayashi benchmark with indigenous Monte Carlo neutron transport code PATMOC

The solution of the neutron transport equation is the basic input for the reactor physics design of a nuclear reactor system. Because of the complexities of geometry and cross-section data, the neutron transport equation is generally solved using numerical methods. One of the difficulties in the solution using these methods concerns the accuracy of distribution of neutron flux in the system containing void regions in a highly absorbing medium. The difficulty arises because of the issue in the continuity of flux at the void and material interface. There is a sudden and large change in the flux at this interface. Kobayashi benchmarks are widely used problems for testing the ability and accuracy of reactor physics codes to compute neutron flux distribution on such systems. An indigenous Monte Carlo neutron transport code, named PATMOC, has been designed and developed at Bhabha Atomic Research Centre (BARC) for reactor physics design applications. The Kobayashi benchmarks have been used to test the PATMOC code to verify its accuracy in flux computation for systems with voids in-between high absorbing materials. Our results show that the PATMOC estimated values of flux distribution in the system compare very well with the reference results provided with the benchmark. In this paper we present the detailed results and analyses of this benchmark with PATMOC code.

Single Stretch Wire and vibrating wire measurement system for characterization of multipole accelerator magnets

A stretch wire magnetometer is a versatile instrument and can be treated as the primary standard of magnetic qualification of accelerator magnets. Bhabha Atomic Research Centre has developed a Stretch wire magnetic measurement system to cater to the requirements of magnetic measurements on accelerator magnets. This bench also includes a vibrating wire system. The scheme used in this instrument for measurements of magnetic flux ensures drift compensations after each scan. This feature along with post-signal processing gives an accuracy of homogeneity measurements comparable to that of a rotating coil magnetometer. Unlike conventional stretch wire systems, wire moves in the r-z plane (along r-axis) at different azimuthal angles. This provides the opportunity for drift compensation at each scan. This has immensely enhanced the measurement accuracy of non-homogeneity of integral fields to less than 3 units. The same is cross-verified with a rotating coil system. The comparison between rotating coil and stretch wire is presented. The Paper gives the step-wise procedure for the measurement of key performance indicators of an accelerator magnet. This paper brings out salient features of the system along with design and calibration results.

11–20 MeV Alvarez Drift Tube Linac for low energy proton accelerator

Bhabha Atomic Research Centre is developing Low Energy High Intensity Proton Accelerator (LEHIPA) as a pre-injector for proposed Accelerator Driven Sub-Critical Reactor Systems (ADSS). Drift Tube Linac is one of the two major accelerating structures of LEHIPA, the other being the Radio Frequency Quadrupole (RFQ). Like all particle accelerating structures, DTL needs multi-disciplinary expertise for design, production, qualification, and installation. This paper describes the comprehensive design, production, qualification, and installation of the ∼ 11–20 MeV section of DTL. It details the design of all sub-components which form part of the DTL RF cavity. Several novel concepts were implemented in course of this development. Important among them are DT-DTL alignment, referencing methodology, robust vacuum design and hermetically sealed DTs. This paper is a comprehensive coverage of design, development and installation aspects of Alvarez DTL. At present, the DTL is ready for beam commissioning.

Magnetic Refrigeration: An Environment-friendly Cooling Technology

Magnetic Refrigeration: An Environment-friendly Cooling Technology

188 Re-N-DEDC Lipiodol for Treatment of Hepatocellular Carcinoma (HCC)-A Clinical and Prospective Study to Assess In-Vivo Distribution in Patients and Clinical Feasibility of Therapy.

Objective The incidence of inoperable hepatocellular carcinoma (HCC) with/without malignant portal vein thrombosis (PVT) is increasing in India for the last decade; thus, Bhabha Atomic Research Centre (BARC), Mumbai, India, developed diethydithiocarbamate (DEDC), a new transarterial radionuclide therapy (TART) agent. 188 Re-N-DEDC lipiodol is an emerging radiotherapeutic agent for inoperable HCC treatment due to its simple and onsite labeling procedure, cost-effectiveness, and least radiation-induced side effects. This study aimed to evaluate in-vivo biodistribution and clinical feasibility of 188 Re-N-DEDC lipiodol TART in HCC and optimization of labeling procedure to assess post-labeling stability and radiochemical yield of labeled lipiodol with 188 Re-N-DEDC complex. Materials and Methods DEDC kits were obtained as gift from BARC, Mumbai. Therapy was given to 31 HCC patients. Post-therapy planar and single-photon emission computed tomography/computed tomography (SPECT/CT) imaging were performed to see tumor uptake and biodistribution. Clinical feasibility and toxicity were decided by Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v 5.0). Statistical Analysis Descriptive statistics was done for data using SPSS v22. Values was expressed as mean ± standard deviation or median with range. Results Post-therapy planar and SPECT/CT imaging showed radiotracer localization in hepatic lesions. Few patients showed lungs uptake due to hepato-pulmonary shunt (lung shunt < 10%). Maximum clearance was observed through urinary tract with very less elimination through hepatobiliary route due to slow rate of leaching of tracer. No patient showed myelosuppression or any other long-term toxicity over median follow-up of 6 months. Mean overall % radiochemical yield of 188 Re-N-DEDC lipiodol was 86.04 ± 2.35%. The complex 188 Re-N-DEDC was found to be stable at 37°C under sterile condition over a period of 1 hour without any significant change on the % radiochemical purity (90.83 ± 3.24%, 89.78 ± 3.67%, 89.22 ± 3.77% at 0, 0.5, 1 hours, respectively). Conclusion Human biodistribution showed very high retention of radiotracer in hepatic lesions with no long-term toxicity with this therapy. The kit preparation procedure is ideally suited for a busy hospital radio-pharmacy. By this procedure, 188 Re-N-DEDC lipiodol can be prepared in high radiochemical yield within a short time (∼45 minutes). Thus, 188 Re-N-DEDC lipiodol can be considered for TART in advanced and/or intermediate HCC.

Production of Bauxite Certified Reference Material (BARC‐B1201) for Nine Property Values (Al2O3, Fe2O3, SiO2, TiO2, V2O5,MnO, Cr2O3, MgO and LOI) Traceable to SI Units

The National Centre for Compositional Characterisation of Materials (NCCCM) / Bhabha Atomic Research Centre (BARC) and National Aluminium Company Limited (NALCO), India have produced an Indian origin bauxite certified reference material (CRM), referred to as BARC‐B1201, certified for major (Al2O3, Fe2O3, SiO2, TiO2, loss on ignition ‐ LOI) and trace contents (V2O5, MnO, Cr2O3, MgO). Characterisation was undertaken by strict adherence to ISO Guides. A method previously developed and validated in our laboratory, using single step bauxite dissolution and subsequent quantitation (of Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO, Cr2O3 and MgO) by ICP‐AES (SSBD ICP‐AES) was used for homogeneity studies and an inter‐laboratory comparison exercise (ILCE) of the candidate CRM. LOI was determined by thermo‐gravimetric analysis. Property values were assigned after an ILCE with participation from seventeen reputed government and private sector laboratories in India. The CRM was certified for nine property values: Al2O3, Fe2O3, SiO2, TiO2, V2O5, MnO, Cr2O3, MgO and LOI, which are traceable to SI units.

Exposure of Dose Rate due to Granites of Bangalore Metropolis Area, India

Introduction: The majority of total radiation dose received by the world's population comes from natural radiation. The distinguishing features of this radiation include relatively persistent exposure to a population at a specific place. Inhalation of 222Rn (radon), 220Rn (thoron), and their offspring contributes the majority of the dose from natural radiation in background regions that are typically present. In light of this, a measurement of dose rate exposure due to some granite floorings has been attempted in Bangalore Metropolis, Karnataka, India. For a period of three years, fifteen distinct granite samples that were used as flooring for construction in buildings were examined.&#x0D; Objectives: Measurement of exposure of dose rate due to building construction materials by the inhabitants of Bangalore city&#x0D; Methods: Solid state nuclear track detector based dosimeters, CAN techniques and radiation survey meters were used and all the experimental observations were made as per the standard protocols provided by the Bhabha atomic research centre, Mumbai, India were followed.&#x0D; Results: The arithmetic mean values of dose rate varied between 2.09 ± 0.10 and 1.39 ± 0.06 mSvy-1. The observed dose rates were found to be higher in granite and lower in coarse-grained dolerite.&#x0D; Conclusions: All 14 types of granite samples have undergone a minimum of 30 measurements. The greater activity concentration of radionuclides found in granite samples leads to higher dose rates.

Investigation of 220Rn and its Progeny Distribution in a Test Chamber

Introduction: Due to the widespread belief that 220Rn's levels are minimal due to its shorter half life and that its contribution to the overall inhalation dose is neglected in the presence of other important natural radiation sources, data for 220Rn in indoor and industrial environments are few.&#x0D; Objectives: To find the distribution of radon, thoron and their progeny levels with wall and floor distances.&#x0D; Methods: The experimental methodology is as per the standard protocol provided by the Environmental Assessment Division, Department of Atomic Energy, Bhabha Atomic Research Centre, Government of India, Mumbai for radon groups working in the country. Measurements of radiation levels and the concentrations of radionuclides in the environment are accomplished employing appropriate nuclear instruments. The radon, thoron and their progeny levels were determined using Solid State Nuclear Track Detectors and the tracks formed in these films were counted by Spark Counter detailed methods are discussed elsewhere.&#x0D; Results At the room's walls, ceiling, and floors, 220Rn concentrations were highest and rapidly decreased as one moved away from them. Indoors, the concentration of 220Rn progeny is independent of the distance between walls. Research on 220Rn diffusion from each wall of the construction materials used and factors affecting the levels of 220Rn progeny in homes are two examples of the extensive and continuous study needed to estimate the dosage due to 220Rn and its offspring.&#x0D; Conclusions: The assessment of public exposure to natural radiation, particularly the exposure from 220Rn and its offspring, has to be conducted more thoroughly across the country.

A Detailed Study of the Radon and Progeny Levels in Houses of Bangalore Metropolis, Karnataka, India

Introduction: Radon, a radioactive inert gas that makes up a significant portion of the background radiation to which people are exposed, can endanger public health when it builds up in inadequately ventilated residential and commercial spaces. The lungs' exposure to alpha particles after inhaling Radon decay products accounts for around half of the overall radiation effective dose to the general public. Objectives: To observe the variation of radon and progeny levels in different locations and different houses of Bangalore city having variety of features viz., season, walls, rooms, flooring, volume and diurnal various. Methods: Standard protocols provided by Environmental Assessment division, Bhabha atomic research centre, Mumbai is followed for the all the measurements. Results: In this outlook, the interior atmosphere must have to be carried out for both 222Rn (radon) and 220Rn (thoron) levels in order to provide an accurate assessment of the natural breathing dose. For the present study a sizable number of measurements had been made for more than eight years which examined the effective dose rates caused by indoor levels of 222Rn, 220Rn, and their progeny during various seasons of the year. In order to lessen the effective dosage rate, it is advised that lower size houses have sufficient ventilation and granite floorings to be avoided. Conclusions: More thorough research should be planned and carried out in this area and across the nation on the evaluation of public exposure to natural radiation, particularly the exposure from 222Rn, 220Rn and their offspring.

Evaluation of seismic margins for nuclear power plant piping systems using ratcheting criterion

In the wake of recent beyond design basis earthquakes, it is very essential to evaluate seismic margins of nuclear power plant piping systems. Better seismic margins will ensure the safety in the event of less probable bigger seismic event beyond consideration of design level. At present, permissible codal stress limits are used to evaluate these margins and it has been experimentally demonstrated that ratcheting is the significant failure mode for piping systems subjected to reversing dynamic load. Hence, it is more prudent to use actual failure criterion for evaluation of seismic margins. In this paper, a detailed framework is provided for evaluation of seismic margins of piping systems using ratcheting criterion. As ratcheting is the potential mode of failure for piping systems under earthquake load, two strain-based performance levels based on code practice and experience gained with experiments carried out by Bhabha Atomic Research Centre, are used for margin assessment. It is usual practice to carry out stress-based response spectrum analysis for design and qualification of piping systems under earthquake load. In order to offer a practical, simpler and feasible solution for ratcheting evaluation, the same response spectrum analysis in iterative way, can be used to evaluate ratcheting in the piping systems. Experimentally validated numerical procedure is used for ratcheting evaluation. This procedure is demonstrated for a piping system of a typical nuclear power plant. Seismic margins for the piping system are evaluated using codal provision and two ratcheting based performance levels for deterministic and probabilistic methods.

Evaluation of natural radioactivity in the soil surrounding Bhabha Atomic Research Centre, Visakhapatnam, Andhra Pradesh, India

Abstract Activity concentrations of naturally occurring radionuclides in soil samples collected during 2013–2018 from different 53 locations around Bhabha Atomic Research Centre (BARC), Visakhapatnam, Andhra Pradesh, India, were determined using high-purity germanium gamma-ray spectrometry. An R and D center of BARC is upcoming at Visakhapatnam, North coastal Andhra Pradesh. The annual effective dose (AED) and the radiation indices from the soil activity were evaluated to generate the baseline data for this area. The average activity concentrations of the naturally occurring radionuclides 238U, 226Ra, 232Th, and 40K in the soil samples studied are 29 ± 8 Bq/kg, 31 ± 1 Bq/kg, 188 ± 2 Bq/kg, and 471 ± 10 Bq/kg, respectively. The concentration of 226Ra and 40K in the collected samples is comparable with the world average concentrations of 33 Bq/kg and 420 Bq/kg, however, 232Th is observed to be higher than the world average of 45 Bq/kg. AED due to external terrestrial radiation from the region studied is in the range the range 0.37 to 2.5 mSv/y with an average of 0.9 mSv/y. The mean radium equivalent activity values for around 70% of the studied samples are lower than the permitted levels of 370 Bq/kg. The mean external exposure index has been determined to be around the safe criterion limit of unity. The mean value of the representative level index Iϒ is 2.4. Higher values in some locations are due to thorium in monazite deposits. This report will be useful as preoperational study to evaluate the impact on the environment due to ongoing and future man-made developments.

Performance investigation of ultra-high pressure ratio cryogenic turboexpanders for helium liquefaction system

Availability of ultra-high pressure ratio turboexpanders present numerous options to the helium liquefier/refrigerator designer as it allows to conceptualize a compact plant by making use of high-pressure process compressors and eliminates placement of turboexpanders in series for large pressure heads in the process cycle. Setting out with this objective, a new series of cryogenic turboexpanders comprising of two high pressure ratio variants has been developed at Bhabha Atomic Research Centre (BARC). These turboexpanders are designed using the Enhanced midstream design method (EMDM) which has been reported by the authors earlier. Enhancement of pressure ratio of these variants from the earlier reported value of 4 to the new value of 6 is achieved through redesigning the inlet nozzle. For each variant of the turboexpanders, two types of inlet nozzle are designed using the EMDM. Type ‘A’ is based on an aerofoil section with ideal blade loading and type ‘B’ is based on a non-aerofoil section and non-ideal blade loading distribution. These remodelled, ultra-high pressure ratio variants of the turboexpanders are experimentally investigated using the BARC developed helium refrigerator CP1000.