Reactor Operation & Maintenance UnitPhone: 88-02-7789285; 88-02-7788454
The TRIGA (Training, Research, Isotope Production General Atomics) Mark-II Research Reactor of Bangladesh Atomic Energy Commission (BAEC) is the only nuclear reactor of the country. It is a tank type research reactor and is used for training, research and isotope production. The reactor was designed and constructed by the General Atomics of the USA. The installation of the reactor was started at the end of 1980 under a non-turnkey project, where local participation was about 50%. The reactor achieved its first criticality in the morning of September 14, 1986. The reactor was tested and commissioned fully at the end of October 1986. Since its commissioning, the reactor has been used in various fields of research and utilization, such as, neutron activation analysis (NAA), neutron radiography, neutron scattering experiments, production of radioisotopes, training of manpower, education, etc. Reactor Operation and Maintenance Unit (ROMU) is responsible for the preparation of various Safeguards and additional protocol reports on routine basis. These reports are send to the International Atomic Energy Agency (IAEA) every year in order to fulfill the requirements as set forth in the agreements signed with the IAEA under the International Nuclear Non-Proliferation regime. It is to be mentioned that BAEC TRIGA reactor is an important facility for providing training to the manpower that would be needed for Nuclear power program of the country.
The BAEC TRIGA research reactor has a maximum continuous thermal power output of 3 MW. The reactor can be operated under three operation modes namely, (1) steady state mode, (2) square wave mode and (3) pulse mode. The steady state mode of operation can be performed under two cooling modes - (1) Natural Convection Cooling Mode (NCCM) and (2) Forced Convection Cooling Mode (FCCM). The NCCM can be used for a power level of up to 500 kW. During NCCM of reactor operation, heat generated in the reactor core is removed by the tank water through natural convection cooling mechanism. For operation at higher level including the full power of 3 MW, FCCM is used. While operating under FCCM, heat produced in the reactor core is dissipated into the atmosphere through a cooling system consisting of primary and secondary cooling circuits.
When the primary water passes through the reactor core (at a rate of 13,230 liters/min), the oxygen atom present in the water interacts with neutron and gets converted into highly radioactive N-16 according to the following (n, p) reaction:
Primary water containing this highly radioactive N-16 is passed through the decay tank (capacity: 32,000 liters), which holds the water for about 140 seconds. During this period activity of the short lived N-16 (T1/2= 7.4 sec) decays down to low level. The decay tank and the piping connecting it with the reactor tank are covered with about 102cm thick heavy concrete shielding in order to attenuate the high energy gamma emitted by the N-16 nuclei.
- Reactor Tank
The reactor tank (which is also called the pool liner) accommodates the reactor core. The reactor core is located near the bottom of the reactor tank. The tank is made of special aluminum alloy and has a length of 8.23m and a diameter of 1.98m. It is filled up with 24,865 liters (6578 gallons) of demineralized water.
- Reactor Core
The reactor core consists of a total of 100 fuel elements (including 5 fuel follower control rods), 6 control rods, 18 graphite dummy elements, 1 dry Central Thimble (CT), 1 pneumatic transfer system irradiation terminus and 1 Am Be neutron source. All these items are placed and supported in-between two 55.25cm dia grid plates and arranged in a hexagonal lattice. Two Instrumented Fuel Elements (IFEs) in the core measure the fuel temperature during reactor operation.
The TRIGA reactor of BAEC is fueled with LEU (low enriched uranium) fuel, which is composed of 19.7% enriched uranium (U235), ZrH (prime moderator) and burnable poison Er-167. The fuel material is housed in a stainless steel cladding. The single most important safety feature of the TRIGA fuel is the Prompt Negative Temperature Coefficient of Reactivity (PNTCR). The nominal value of the PNTCR is about 1.07x10-4 % Δk/k/°C. Because of this characteristic of fuel, the reactor can safely be operated in pulse mode.
- Control Rods
The reactor is controlled by six control rods, which contain boron carbide (B4C) as the neutron absorber material. When these rods are fully inserted into the reactor core, the neutrons continuously emitted from the start-up source are absorbed by the rods and the reactor remains sub-critical. If the absorber rods are withdrawn from the core, the number of fission in the core as well as the power level increases. The reactor can be shutdown either manually or automatically by the safety instrumentation and control system.
Instrumentation and control (I&C) system plays the key role in ensuring safe operation of a nuclear reactor. The reactor I&C system is a computer based system which include instrumentation for monitoring reactor parameters during all operational states and for recording all variables important to reactor operation. It all so manages all control rod movements taking into account the choice of operating mode and interlocks. There are three major system components the control system console (CSC), Data Acquisition and control (DAC) and Reactor protection System (RPS). The (CSC) provides the necessary controls to safety operate the reactor in its various modes of operation. It Contents the indicators, enunciators and monitors to present to present the date in meaningful engineering units and graphic displays to the operator, The DAC is a computer –based system that provides interface functions between the CSC and the reactor. It acquires date in the form of electronic signals from instrumentation in the reactor and auxiliary systems, processes it. And transmits it to the CSC for display. The primary function of the RPS is to scram the reactor by causing the control rods to insert into the core in response to certain abnormal reactor operating conditions.
The power level of the reactor is monitored by four neutron channels during normal operation. These channels use fission chambers as neutron detecting element. These four channels detector cable connected to four separate modules to detect the reactor power. The Startup function and precise of reactor power level is achieved by the Nuclear Log Wide Range Channel (NLW-1000)/Nuclear Linear Power Channel (NMP-1000) of the (I&C) system of the reactor. The Channel indicates the current level which is proportional the neutron flux form source level (approximately 2 nv) to full power level (7.46x10 13nv).
The BAEC TRIGA Mark-II reactor is equipped with a number of irradiation devices which are listed below:
- Dry central irradiation tube
- Neutron beam tubes
- Pneumatic transfer system
- Rotary specimen rack
- Triangular cut-outs in the core
- Hexagonal cut-out at the center of the core
- Thermal column for future use (presently filled up with heavy concrete blocks)
In the dry CT, samples can be irradiated at a maximum thermal neutron flux of about 7.46 x 1013 nv. The pneumatic transfer system having a transfer time of about 4.6 sec. is used to irradiate samples that produce short-lived radioisotopes. This system is particularly used for the purpose of neutron activation analysis (NAA). Four neutron beam tubes (BT), which are named as tangential BT, piercing BT, radial BT #1 and radial BT #2, permit extraction of neutron beams of all energies into the reactor hall for the purpose of neutron and solid-state physics experiments. At present, the piercing BT is being used for triple axes spectrometer, and the tangential BT for neutron radiography. The neutron radiography facility is used for non-destructive testing (NDT), particularly with a view to knowing about hydrogen or neutron absorber material in solid matter. This facility uses neutron irradiation similar to X-ray radiography. The Lazy Susan (LS) or the rotary specimen rack is a 'donut' shaped watertight device placed in the upper part of the graphite reflector assembly around the reactor core. This rack has 41 sample holding tubes. Each of these tubes (except the 1st one) can accommodate two 14cm long and 3.2cm dia standard specimen containers in it. Sample is loaded into the rotary specimen rack through the 3.3cm dia loading tube, which extends up to the top of the reactor shield structure and terminate at the center channel. A position control mechanism allows loading of samples in different chambers of the LS. The triangular and hexagonal cutouts in the core allow in-core irradiation of large diameter samples, which are not suitable for insertion into the dry CT or in to the LS.
Area of Utilization
BAEC TRIGA research reactor has so far been used for carrying out research and development works in various fields of nuclear science and technology. It has also been used for production of isotopes and education and training of manpower. Areas of utilization of the research reactor since its commissioning is presented in the figure below.
- Neutron Activation Analysis (NAA)
When materials absorb neutrons, they become radioactive and emit mostly gamma rays with energies that depend on the material itself. In activation analysis, the composition of a material including the trace amount of impurities present in it can be determined by measuring such emitted gamma radiation.
- NAA for determination of arsenic in ground water, rice and vegetables samples of different areas of Bangladesh.
- NAA for determination of U and Th in rock samples.
- NAA for determination of trace element concentrations in soil and foodstuff, etc.
- Neutron Scattering Experiments
Neutron scattering is a technique that is used to find answers to fundamental questions about the structure and composition of materials. By examining the status of scattered neutron on a material, the atomic/molecular structure and kinetic status the material can be determined. Cold neutrons make it possible to observe the structure of high polymer materials such as fiber synthesis and plastics.
- Neutron Radiography
The neutron radiography facility is used for non-destructive testing (NDT), particularly with a view to know about hydrogen or neutron absorber material in solid matter. This facility uses neutron irradiation similar to X-ray radiography.
- Radioisotope Production
The reactor facility is used for production of 99mTc, 131I and 46Sc radioisotopes. 99mTc and 131I are used in the nuclear medicine centers while 46Sc for isotope hydrology applications. At present, one of the most important objectives of the reactor facility is to enhance the production of 131I such that all the needs of the country could be met. The current demand of 131I in the country is about 1Ci per fortnight.
Activities of ROMU
Reactor Operation and Maintenance Unit (ROMU) is responsible for operation and maintenance of the reactor. At present 9 engineers/ scientists and 25 supporting personnel are working in different Divisions/Sections of ROMU. Major activities carried out in ROMU are as follows:
- Conduction of routine operation and maintenance of the reactor and associate systems/facilities,
- Upgrading of the reactor operational and safety documentations based on IAEA safety standards/guides,
- Training and retraining of Reactor Operators (ROs) and Senior Reactor Operators (SROs),
- Preparation of various documents in connection with IAEA Safeguards and Protocol Additional to the Safeguards Agreement,
- Preparation of various operational and safety documents as required by the Nuclear Safety and Radiation Control Rule (Rule-97),
- Preparation/upgrading of SRO/RO training manuals,
- Providing supports to various reactor related academic activities being conducted in BAEC,
- Planning and implementing various works related to the upgrading of different systems of the reactor facility, etc.
Reactor Operation & Maintenance Unit
Atomic Energy Research Establishment
Bangladesh Atomic Energy Commission
Ganakbari,Savar,GPO BOX NO.-3787
Phone: +88027789285, +88027788454