Bangladesh Atomic Energy Commission Research Articles

Thermoluminescent characterization and defect studies of graphite-rich media under high dose neutron exposure

Thermoluminescence (TL) materials have a broad variety of uses in various fields, such as clinical research, individual dosimetry, and environmental dosimetry, amongst others. However, the use of individual neutron dosimetry has been developing more aggressively lately. In this regard, present study establishes a relationship between the neutron dosage and the optical property changes of graphite-rich materials caused by high doses of neutron radiation. This has been done with the intention of developing a novel, graphite-based radiation dosimeter. Herein, the TL yield of commercially graphite-rich materials (i.e. graphite sheet, 2B and HB grade pencils) irradiated by neutron radiation with doses ranging from 250 Gy to 1500 Gy has been investigated. The samples were bombarded with thermal neutrons as well as a negligible amount of gamma rays, from the nuclear reactor TRIGA-II installed at the Bangladesh Atomic Energy Commission. The shape of the glow curves was observed to be independent of the given dosage, with the predominant TL dosimetric peak maintained within the region of 163 °C–168 °C for each sample. By studying the glow curves of the irradiated samples, some of the most well theoretical models and techniques were used to compute the kinetic parameters such as the order of kinetics (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ). All of the samples were found to have a good linear response over the whole dosage range, with 2B grade of polymer pencil lead graphite (PPLGs) demonstrating a higher level of sensitivity than both HB grade and graphite sheet (GS) samples. Additionally, the level of sensitivity shown by each of them is highest at the lowest dosage that was given, and it decreases as the dose increases. Importantly, the phenomenon of dose-dependent structural modifications and internal annealing of defects has been observed by assessing the area of deconvoluted micro-Raman spectra of graphite-rich materials in high-frequency areas. This trend is consistent with the cyclical pattern reported in the intensity ratio of defect and graphite modes in previously investigated carbon-rich media. Such recurrent occurrences suggest the idea of employing Raman microspectroscopy as a radiation damage study tool for carbonaceous materials. The excellent responses of the key TL properties of the 2B grade pencil demonstrate its usefulness as a passive radiation dosimeter. As a consequence, the findings suggest that graphite-rich materials have the potential to be useful as a low-cost passive radiation dosimeter, with applications in radiotherapy and manufacturing.

A Study on Shield Design Aspects of a Semi-Industrial Co-60 Gamma Irradiation Facility at Gamma Source Division of Institute of Food and Radiation Biology of the Bangladesh Atomic Energy Commission

The aim of this work is to investigate the existing shield design aspects of a semi-industrial Cobalt- 60 Gamma Irradiation Facility for 100 kCi, designed for irradiation of pharmaceutical products and daily foodstuffs as well as for research and development purposes at the Institute of Food and Radiation Biology (IFRB) of the Bangladesh Atomic Energy Commission. Earlier, the initial activity of this facility was 65 kCi and stone based reinforced concrete (SBRC) of density 2.60 g/cc and specific thicknesses were used to shield the facility for safety to operational personnel and outside public. Due to a large demand for irradiation of pharmaceutical products as well as of daily foodstuffs, IFRB has decided to increase the initial activity up to 100 kCi for this facility. For this reason, the shielding design aspects of this facility were needed to be recalculated and checked for safety. This analysis was done using the Point-kernel Shielding Code Micro-Shield 5.05 and public domain Point-kernel Shielding code QAD-CGGP2 respectively considering the radiation worker dose limit of 10 μSv/hr of the International Commission on Radiological Protection, ICRP-60, 1990. The corresponding dose limit for public at large is 0.5 μSv/hr. The calculated dose rates at different locations around the facility are far below 10 μSv/hr except in one area. This location is inside the source room. No one is allowed to enter the room when the facility is in the ON mode. However, except one location, positions outside the facility have dose rates about 3 time higher than 0.5 μSv/hr, the dose limit for public at large. Therefore, this analysis shows that the existing shield design aspects of IFRB’s Co-60 gamma source room is safe for a 100 kCi source from the viewpoint of radiation safety to operating personnel but not for public at large within proximity of the facility.
 Bangladesh Journal of Medical Physics Vol.15 No.1 2022 P 1-7

Installation of First Medium Energy Medical Cyclotron in Bangladesh at National Institute of Nuclear Medicine and Allied Sciences (NINMAS) for PET radiopharmaceuticals Production

PET-CT (positron emission tomography and computed tomography) is a gold-standard cancer imaging tool for diagnosis and management, as well as prognostic information based on treatment. Positron-emitting radionuclide 18F (Fluorine) is generated by accelerating particles to energies high enough to cause a certain nuclear reaction 18O(p,n)18F within the particle accelerator, the cyclotron. Mannose triflate is converted to 2-[18F] Fluoro-2-deox-D-yglucose ([18F]FDG) via nucleophilic reaction. Under the ownership of Bangladesh Atomic Energy Commission installed a medium energy (18/9 MeV, IBA) Cyclotron at National Institute of Nuclear Medicine and Allied Sciences (NINMAS). The facility was established in the oncology Building (Block F) of Bangabandhu Sheikh Mujib Medical University (BSMMU). Cyclotron vault and the Control room are located in the underground i.e. basement floor. Each wall of the cyclotron vault and ceiling is made of concrete with a density of 2.35 g/cm3 and a thickness sufficient to shield gamma and neutron radiation. On the ground floor, there are Synthesis room, Quality control laboratory, and the Decontamination room. PET-CT rooms are located on the first floor. Identification, Radionuclide purity (Gamma spectrum detection and half-life measurement), Radiochemical Purity, Chemical purity, Residual solvent measurement, pH measurement, Sterility, and bacterial endotoxins (LAL test) are performed to maintain the quality of the product. The current uses of the Cyclotron are mostly for the synthesis of 18F-FDG. Bangladesh J. Nuclear Med. 24(1&2): 48-50, 2021

Gamma Irradiation to Sterilize Active Ingredients, Consumer Foodstuffs and Beverages in Bangladesh

Nowadays, the utilization of gamma irradiation (e.g., Cobalt-60 source) to sterilize different materials have been increasing enormously. As terminal sterilization, gamma irradiation is being used popularly to sterilize different materials throughout Bangladesh. Compare to other conventional methods of sterilization (e.g., alpha, beta, other chemicals), this method is highly applicable for its well acceptance in the world. It has high penetration power with the short wave lengths, isothermal characteristics for its negligible rise in the temperature, no contact with any toxic chemicals without having any unirradiated portion. In this process, the assurance level of the sterility of product is far better than other aseptic processing. The chemical bonds in the microbes are broken to produce reactive oxygen species (ROS) by gamma irradiation, and attack DNA/RNA of microbes for killing. The mutations in the genetic materials (DNA/RNA) of microbes are usually happened through gamma irradiation and consequently restrict the cellular division of microbes. This characteristic of gamma ray is mostly applicable in the commercial purposes. This review discusses the general applications of gamma irradiation to the broaden arena of different materials (active pharmaceutical ingredients, consumer products, beverages etc.). A summarized description of materials those are irradiated using Cobalt-60 source in Bangladesh, in particular, at the Institute of Radiation & Polymer Technology (IRPT), Bangladesh Atomic Energy Commission, is described here. The information may further assist to enhance the dissemination of the applicability of gamma irradiation throughout Bangladesh.

Structural and dosimetric study of sub-kGy neutron-irradiated graphitic media

Associated with the marked difference between the mechanism of neutrons interactions relative to that of low linear-energy transfer (LET) radiations, few convenient dosimeters offer well differentiated measurement of neutron doses at useful sensitivity and spatial resolution. Present study has made use of highly uniform 2B and HB grade polymer pencil lead graphite (PPLG) (approximately 95 wt % and 61 wt % graphite content, respectively), addressing variation in lattice structure and defects resulting from sub-kGy neutron-doses. The latter have been provided by the TRIGA-II nuclear reactor located at the Bangladesh Atomic Energy Commission. Raman, photoluminescence (PL), and thermoluminescence (TL) techniques were used to perform structural and luminescence characterization of PPLGs. Comparison was made with highly-oriented pyrolytic graphite (HOPG), a pure ordered synthetic form of graphite. The dose-dependent defects produced in graphitic structures were characterized based on the Raman ID/IG intensity ratio, with observation of the Wigner effect. Analysis of PL spectra provides an average band gap energy in the range of 1.111–1.114 eV. All samples have been found to provide excellent linear response within the dose range 0–200 Gy, 2B grade PPLGs showing greater sensitivity compared to that of HB. The outcomes from this research may contribute to the development of cost effective, versatile graphite-based dosimeters, with particular applications to ionizing radiation dosimetry in clinical radiotherapy and industrial spheres.

Neutronic performance optimization of reconfigured TRIGA cores

The study deals with the neutronic analysis of the reference core and six reconfigured cores (C-1 to C-6) of the existing BAEC (Bangladesh Atomic Energy Commission) TRIGA Research Reactor using MCNP. The developed reference core model was validated by benchmarking the neutronic parameters with the experimental, calculation and Safety Analysis Report (SAR). The reconfigured cores were developed by considering three factors: (i) sub-criticality, (ii) symmetrical geometry, and (iii) substitution between fuel and graphite dummy element. Under room temperature conditions global, local and the kinetic parameters were calculated for the reconfigured cores and compared with the reference core. Cores burnup simulations were carried out up to 1200 MWD to investigate fuel depletion, flux trend, and activity accumulation. Based on neutronic performance, the results show that the reconfigured cores C-1 and C-3 are more qualified than the reference core and, in some cases; C-3 represents a better performance than the core C-1.

Implementation of Local Area Network (LAN) & Build a Secure LAN System for BAEC Head Quarter

Network security is the process of taking physical and software preventative measures to protect the underlying networking infrastructure from unauthorized access, misuse, malfunction, modification, destruction, or improper disclosure, thereby creating a secure platform for computers, users, and programs to perform their permitted critical functions within a secure environment. A local area network (LAN) is a computer network within a small geographical area such as a home, school, computer laboratory, office building or group of buildings. A LAN is composed of inter-connected workstations and personal computers which are each capable of accessing and sharing data and devices, such as printers, scanners and data storage devices, anywhere on the LAN. LANs are characterized by higher communication and data transfer rates and the lack of any need for leased communication lines. A data network is an interconnected system of computers, peripherals and software over which data files and messages are sent and received. LAN is only one type of computer network. LAN define is Data com system allowing a number of independent devices to communicate directly with each other, within a moderately sized geographic area over a physical communications channel of moderate data rates. Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference is required. This type of communication can transmit voice, video, and telemetry through local area networks or across long distances. Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Researchers at Bell Labs have reached a record bandwidth distance product of over 100 petabit × kilometers per second using fiber optic communication. Communication between remote parties can be achieved through a process called Networking, involving the connection of computers, media and networking devices. When we talk about networks, we need to keep in mind three concepts, distributed processing, network criteria and network structure. The purpose of this Network is to design a Local Area Network (LAN) for a BAEC (Bangladesh Atomic Energy Commission) Head Quarter and implement security measures to protect network resources and system services. To do so, we will deal with the physical and logical design of a LAN. The goal of this Network is to examine of the Local Area Network set up for a BAEC HQ and build a secure LAN system. Keywords: LAN, Secure LAN, BTCL, UTP, RJ-45, Bandwidth, Wavelength, ISP, Firewall, BAEC

Design, Deployment and Implementation of Local Area Network (LAN) at BAEC Head Quarter

A local area network (LAN) is a computer network within a small geographical area such as a home, school, computer laboratory, office building or group of buildings. A LAN is composed of interconnected workstations and personal computers which are each capable of accessing and sharing data and devices, such as printers, scanners and data storage devices, anywhere on the LAN. LANs are characterized by higher communication and data transfer rates and the lack of any need for leased communication lines. Communication between remote parties can be achieved through a process called Networking, involving the connection of computers, media and networking devices. When we talk about networks, we need to keep in mind three concepts, distributed processing, network criteria and network structure. The purpose of this Network is to design a Local Area Network (LAN) for a BAEC (Bangladesh Atomic Energy Commission) Head Quarter and implement security measures to protect network resources and system services. To do so, we will deal with the physical and logical design of a LAN. The goal of this Network is to examine of the Local Area Network set up for a BAEC HQ and build a secure LAN system.

Dosimetric Characteristics of 6 MV Medical Linac at BAEC

Dosimetric characteristic is one of the essential parameters of a medical linear accelerator (LINAC), which must be obtained before clinical use. The dosimetric characteristics for 6 MV photon beam were measured and compared with the corresponding published data. The study was done using a Varian linear accelerator (Model Clinac-iX) at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission (BAEC). The data is taken for 10 field sizes (2 × 2, 3 × 3, 5 × 5, 7 × 7, 10 × 10, 15 × 15, 20 × 20, 25 × 25, 30 × 30 and 40 × 40 cm2) at same conditions. The measured Percent Depth Dose (PDD) curves were obtained for 6 MV photon beams with the field as mentioned above and compared with the calculated PDD curves. The measured depth dose (Dmax) for reference field size (FS) 10 × 10 cm2 is 15.99 mm, and the PDD at 10 cm depth (D10) is 66.87% for 6 MV photon energies that are found to be compatible with the published report BJR supplement 25. The measured PDD curves for photon energies show a good agreement with the standard PDD curves. The photon beam dosimetry data found in the current study are compatible and all the tolerances are within the clinically acceptable tolerance limit.

Comparative Studies of Absolute Dose in Water Phantom, Solid Water Phantom and MatriXX with MULTICube Phantom

Introduction: Radiotherapy is one of the important treatment modalities in cancer treatment. To maintain the treatment procedure accuracy, the phantom is an essential tool for absolute dosimetry conformation and Quality Assurance routine cheek up. This work aims to study the absorbed dose of various phantoms and hence to make a comparison of the result with the IAEA recommendation (TRS 398) for daily QA of Linac. Materials and Methods: The experiment has been done at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission. For external beam radiation, 6 MV and 15 MV photon beams of Varian Clinac iX Linear Accelerator (Linac) were used. One dimensional (1D) water phantom, solid water phantom, and MatriXX with MULTICube phantom and associate accessories were used to experiment. Results: We have measured and compared the absorbed dose data of the phantoms. The variation of sold water phantom from the 1D water phantom is +2.8% at 6 MV and +3.5% at 15 MV. The variation MatriXX with MULTIcube phantom from the 1D water phantom is +8.0% at 6 MV and +3.2% at 15 MV. This study revealed that the 1D water phantom was the best absolute dose conformation among the other phantoms and the deviation was within the acceptable limit (±5%), except MatriXX with MULTICube Phantom for low energy beam (8%). Conclusion: It was observed that the accuracy of dose estimation was better in the 1D water phantom rather than the other two. It is also known that the 1D water phantom is low cost but needs a long time to set up for the experimental arrangement. Solid water or MatriXX with MULTICube phantom can be used to overcome this problem, which takes only a few minutes for setup and is comparatively faster than 1D water phantom.

Characterization Process of Silicon Solar Cell in BAEC Lab

This paper represents the characterization process of mono-facial solar cell in Bangladesh Atomic Energy Commission (BAEC) Lab. Mono-facial solar cell characterization performance analysis using surface reflection method, Sheet resistance method, SEM, Surface photo voltage and LIV test. The morphology of silicon wafer surface has been studied using scanning electron microscopy. It is found that the pyramid type structures are formed on the textured surface which helps to trap more light during conversion to electricity. The sheet resistance of raw and diffused sample is measured by using four point probe method. Results show that the resistivity of the wafer is decreased after diffusion which indicates the formation of n-type layer during diffusion process. The surface photo voltage data is used to find the diffusion length and life time. It is found the diffusion length 81.5μm and life time is 2.5μs. Finally, the efficiency of monofacial solar cell measured by LIV tester. Results show that the monofacial solar cell achieved fill factor (FF) of 0.310423 with a conversion efficiency (η) of 5.193843% where the active surface area is 96 cm2.

Technical feasibility study of BAEC TRIGA reactor (BTRR) as a neutron source for BNCT using OpenMC Monte Carlo code

Cancer treatment is a challenging task in the medical field around the world. Most of the cases of the treatment procedures often have limitations and harmful side effects. Boron Neutron Capture Therapy (BNCT) is a method of cancer treatment where it is found to be less toxic and more effective in some form of tumor cells. BNCT requires a neutron beam, and a research reactor is the most reliable source of it. This study is about the technical feasibility of the Bangladesh Atomic Energy Commission TRIGA research reactor (BTRR) used as a neutron source for BNCT. The BTRR reactor has three irradiation sites (2 beam tubes (BTs), and a thermal column) currently unutilized. This study checks the technical feasibility of BNCT treatment neutron beam requirements (epithermal beam) in different external irradiation sites of the reactor. Monte Carlo simulation toolkit OpenMC was used to carry out the reactor model and flux calculation. It was found that the thermal column would be the best place to house the patient for the treatment. An epithermal flux of 1.0E+09 is available about halfway into the thermal column graphite.

Human bone and amniotic membrane banking in Bangladesh for grafting: the impact of the international atomic energy agency (IAEA) programme.

The idea of establishing a human tissue bank in Bangladesh was started in 1985. However, in 2003, with the active cooperation of international atomic energy agency (IAEA) and Bangladesh Atomic Energy Commission, a tissue bank laboratory was upgraded as a unit for tissue banking and research. Due to increasing demand of allograft, this unit was transformed as an independent institute "Institute of Tissue Banking and Biomaterial Research (ITBBR)" in 2016. This is the only human tissue bank in Bangladesh, which processes human bone and amniotic membrane to provide safe and cost-effective allografts for transplantation. Importantly, banking of human cranial bone as autograft has also started at ITBBR. These processed grafts are sterilized using gamma radiation according to the IAEA Code of Practice for the radiation sterilization of tissues allografts. The amount of grafts produced by the ITBBR from 2007 to 2018 were 120,800cc of bone chips, 45,420cm2 of amniotic membranes, 277 vials of de-mineralized bone granules (DMB), 95 pieces of massive bones, and 134 pieces of cranial bones. Overall, 112,748cc of bone chips, 40,339cm2 of amniotic membranes, 174 vials of DMB, 44 pieces of massive bones, and 64 pieces of cranial bones were transplanted successfully. Nevertheless, to cope up with the modern advanced concepts of cell and tissue banking for therapeutic purpose, ITBBR is working to set up facilities for skin banking, stem cells banking including amniotic and cord blood derived stem cells and scaffold designing. To ensure the quality, safety, ethical and regulatory issues are sustainable in cell and tissue banking practices, ITBBR always works with the Government of Bangladesh for enhancing the national tissue transplantation programme within the contemporary facilities.

Experimental study of <SUP align=right>41</SUP>Ar activity release rate from the Bangladesh Atomic Energy Commission TRIGA research reactor

The present study focused on the monthly or annual 41Ar activity release rate and ground level activity concentration measurement including the estimation of public dose level at the ground and stack positions of the Bangladesh Atomic Energy Commission TRIGA Research. During the experimental work, a Geiger-Muller (G-M) counter was used for the air sample count rate study. The experimental results demonstrated that the obtained maximum monthly or annual 41Ar activity release rate (2.48 × 1010 Bq/month or 6.25 × 1011 Bq/year) and monthly maximum ground level 41Ar activity concentration (6.40 × 101 Bq/m3) were within the permissible limits set by the regulatory body. This report also confirmed that the estimated public dose levels (0.29 mSv/yr and 0.0002 mSv/yr) at the stack and ground positions were far below the IAEA acceptable limit (1.0 mSv/yr) which was significant for the research reactor safety.

Experimental study of <SUP align=right>41</SUP>Ar activity release rate from the Bangladesh Atomic Energy Commission TRIGA research reactor

The present study focused on the monthly or annual 41Ar activity release rate and ground level activity concentration measurement including the estimation of public dose level at the ground and stack positions of the Bangladesh Atomic Energy Commission TRIGA Research. During the experimental work, a Geiger-Muller (G-M) counter was used for the air sample count rate study. The experimental results demonstrated that the obtained maximum monthly or annual 41Ar activity release rate (2.48 × 1010 Bq/month or 6.25 × 1011 Bq/year) and monthly maximum ground level 41Ar activity concentration (6.40 × 101 Bq/m3) were within the permissible limits set by the regulatory body. This report also confirmed that the estimated public dose levels (0.29 mSv/yr and 0.0002 mSv/yr) at the stack and ground positions were far below the IAEA acceptable limit (1.0 mSv/yr) which was significant for the research reactor safety.

Thyroid Uptake of Tc-99m and Its Agreement with I-131 for Evaluation of Hyperthyroid Function

Thyroid uptake and scintigraphy using Tc-99m pertechnetate has proven to be more advantageous than with I-131 iodide, since the images have better quality, the procedure is faster and the patient is submitted to a lower radiation dose. Tc-99m has been used worldwide to study the thyroid function because of a number of advantages such as short half-life, short biological half-life, short effective half-life, short retention in gland and no Beta (β-) radiation, providing low dose to gland (10,000 times less than that of I-131), low cost and readily availability. Otherwise, I-131 with its high radiation burden (1-3 rad/mCi) has long half-life and causes Beta (β-) particle emission. Its main gamma photon has high energy (364 keV) which also causes poor image quality. The experiment is carried out at the Institute of Nuclear Medicine and Allied Sciences (INMAS), Bangladesh Atomic Energy Commission, Dhaka Medical College Hospital Campus, Dhaka-1000. In the present work, the study consists of 109 patients (76 female and 33 male) with ages ranging from 14 to 66 years. The patients studied with Tc-99m found to be hyperthyroid of 57 and in case of I-131, the findings were 60. The agreement between I-131 and Tc-99m is 95% and the correlation coefficient, r between Tc-99m & I-131 is = 0.879, which indicates strong correlation between them. So, it is statistically significant and makes a good agreement. The outcome of this study may provide valuable information about thyroid treatment and also may play important role in the management of thyroid patient.

Radiation Shielding Analysis and Design of tof PET-CT Facility at Institute of Nuclear Medical Physics under Bangladesh Atomic Energy Commission, Bangladesh

High resolution (4 mm) tof PET-CT (positron emission tomography-computed tomography) from Philips of model Ingenuity TF is newly installed at Institute of Nuclear Medical Physics (INMP). 128 slice CT component incorporated with PET provides comparatively lower dose than the 511 keV annihilation photons associated with positron decay from PET scan. So, for designing shielding in our PET-CT facility, only 511 keV annihilation photons energy has been considered. The main objective of this paper is to show what measures have been taken to protect patients, occupational workers as well as environment from PET-CT radiation hazard through a cost effective design that satisfy the national regulatory demand. In this paper, AAPM (American Associations of Physicists in Medicine) Task group 108 analysis for PET and PET-CT shielding requirements is followed for our PET-CT facility shielding design. From theoretical calculation as shielding requirement, 1.1 cm Pb thickness or, 13 cm concrete thicknesses are found. Practically, all walls and ceiling are of 30.48 cm (1 foot) thick made of concrete with density 2.35 gcm-3 for more safety. As x-ray from CT is not taken into account for shielding analysis, Bangladesh Atomic Energy Commission (BAEC) conducted an extensive radiation survey at controlled, supervised and public area for CT. The report that is found meets the national regulatory requirements.

Measurement of Feedback Reactivity Effects of the Baec Triga Reactor

The aim of this study is to measure the feedback reactivity effects of the Bangladesh Atomic Energy Commission (BAEC) TRIGA Research Reactor (BTRR). Using digital instrumentation and control (I&C) system, feedback parameters such as reactivity coefficients of fuel, moderator and power effects are measured. At 300 kW reactor power, the obtained results for fuel temperature coefficient are 0.664 ꬿ/0c and 0.765 ꬿ/0c at C1 and D3 core positions respectively. The results for 100 kW to 400 kW reactor power show its increasing nature as the reactor power increases. The measured value of the moderator temperature coefficient is found to be 0.419 ꬿ/0c at 500 kW reactor power. The power coefficient of reactivity is measured for several power ranges from 50 kW to 2.5 MW and the average value is found to be 0.0757 ꬿ/kw. The measured values of the reactivity coefficients are found to be in a good agreement with the GA Safety Analysis Report (SAR) provided for BTRR.
 Journal of Bangladesh Academy of Sciences, Vol. 42, No. 2, 183-190, 2018

Fabrication and Identification of the Efficiency of a Si-Based Solar Cell

This research represents the fabrication and characterization of a solar cell which is based on a thin p-type silicon (Si) wafer. Solar cells are the basic building blocks of Solar Panels or Modules. There are presently nine companies manufacturing solar modules in the country. Nowadays a large amount of electricity comes from solar cell. The total demand for solar cells in assembling solar modules of the nine companies are about 80-90MWp annually. Mainly, cost of solar cell depends on the Brand, type of crystal structure (Mono or Multi) and the shape or size of wafer. For the first time in the country, ‘Bangladesh Atomic Energy Commission (BAEC)’ has set up a laboratory to fabricate crystalline solar cells on a pilot basis. The method used to fabricate solar cells is the low-cost diffusion technique using POCl 3 gas source. Several solar cells of 150×150 mm 2 sizes and 200 micrometer thick are produced and characterized in the laboratory. A p-type silicon wafer is cleaned and textured to make its surface pyramid shape for absorbing more sunlight. The p-n junction used in Si-based solar cell is created after applying diffusion technique using Phosphorus-oxy-try chloride (POCl 3 ) within the silicon wafer and putting Aluminum (Al) paste on one side of the wafer. Perfectly texturing ensures the excellent pyramid height of the silicon wafers. The pyramid heights of raw, textured and doped wafers are 8233.2 A, 15222.5 A and 55654.1 A respectively. The pyramid surface shows the increasing light absorption by the solar cell that can lead to an increase in conversion efficiency of the device. The efficiency of the produced solar cell is 3.3%. The results have shown that some challenges and good opportunities in getting the high-efficient and cost effective solar cells. If the cost effective technology can be made familiar in Bangladesh then it will help in solving the power crisis in the country a great deal.

Assessment of N-16 activity concentration in Bangladesh Atomic Energy Commission TRIGA Research Reactor

Abstract An assessment for determining N-16 activity concentrations during the operation condition of Bangladesh Atomic Energy Commission TRIGA Research Reactor was performed employing several governing equations. The radionuclide N-16 is a high energy (6.13 MeV) gamma emitter which is predominately created by the fast neutron interaction with O-16 present in the reactor core water. During reactor operation at different power level, the concentration of N-16 at the reactor bay region may increase causing radiation risk to the reactor operating personnel or the general public. Concerning the safety of the research reactor, the present study deals with the estimation of N-16 activity concentrations in the regions of reactor core, reactor tank, and reactor bay at different reactor power levels under natural convection cooling mode. The estimated N-16 activity concentration values with 500 kW reactor power at the reactor core region was 7 . 40 × 10 5 Bq / cm 3 and at the bay region was 3 . 39 × 10 − 5 Bq / cm 3 . At 3 MW reactor power with active forced convection cooling mode, the N-16 activity concentration in the decay tank exit water was also determined, and the value was 4 . 14 × 10 − 1 Bq / cm 3 .