Small angle neutron scattering study of CTAB and gemini surfactant at room temperature

17.1.6 Small angle neutron scattering study of CTAB and gemini surfactant at room temperature

The data have been analysied using Hayter and Penfold model to calculate the interparticle structure factor S(Q) taking into account the screened Coulomb interactions between the dimeric micelles. Peak occurs at Q_m= 2/d, where d is the average distance between the micelles for CTAB. SANS analysis showed that the micellar structure depends on spacer length. The fractional charge on the micelle increases with the increase in spacer length and decreases when the concentration is increased. The packing parameter is high for the Gemini surfactants having short spacers. The value of the packing parameter decreases with an increase in spacer length. The experimental results are in good agreement with the theoretical prediction based on the packing parameter.

Hazaribagh is the largest tannery region in Bangladesh. This area consists of more than 200 tanneries which generate 7.7 million liters of liquid waste and 88 million tons of solid waste every day. The direct discharge of these wastes contaminates the ground and surface water with dangerously high concentrations of chromium, as well as cadmium, arsenic and lead. About 12 million people of Dhaka city largely depend on the Buriganga’s water for drinking, fishing and carrying merchandise. To find the contamination level of Buriganga river caused by the Hazaribagh tannery, 9 sediment samples were collected from 3 locations at 3 depths with 30 ft interval for covering 90 ft bank of Buriganga river. The samples were collected by using acrylic pipe with a rubber stopper and a rubber sample remover. The collected samples and Certified Reference materials (IAEA-Soil-7, IAEA-SL-1, NIST 1633b Coal Fly Ash) were prepared for irradiation. Two irradiation schemes were performed using pneumatic transfer (rabbit) system at the TRIGA Mark –II research reactor: (i) Long irradiation was performed with the thermal neutron flux of 2.75×10¹³ n/cm²/sec for 14 minutes and (ii) Short irradiation was performed separately for each sample with the thermal neutron flux of 2.75×10¹² n/cm²/sec for 40 seconds. After irradiation, gamma-ray counting was performed with a high purity germanium (HPGE) detector (CANBERRA, 25% relative efficiency, 1.8 keV resolution at 1332.5 keV of ⁶⁰Co) coupled with a digital gamma spectrometer (ORTEC, DSPEC Jr^TM). The quantification was performed based on relative standardization approach. The results revealed that some heavy metals like As (arsenic is a metalloid, but is usually classified as a heavy metal), Cr, Fe, Mn, Zn etc. are found to be in elevated levels in the Buriganga river compared to the world references. Even the presently measured Cr concentration is two to three times higher compared to the former studied (Mohiuddin et al., 2011; Ahmed et al., 2010) in the same river. This indicates that contamination level is increasing day by day. The present data will be utilized as a baseline data to determine the future pollution status. As fishes from the Buriganga river being a major source of protein, they can accumulate the investigated heavy metals and migrate to the human body and can cause several adverse health effects. The sources of these metals in the Buriganga river are mostly industrial like tannery, refinery, etc. and municipality wastes. Further deterioration of this situation may lead to a biologically dead river having severe impact on aquatic life and city dwellers. The immediate action must be taken by the environment controlling authority to enforce the industrialist to use treatment plant prior their effluent disposal.

Biological concrete shielding surrounding a nuclear reactor accumulates radioisotopes induced by (n, γ) reaction through operation life-time and cause difficulty in waste management of the activated shielding after decommissioning. To protect humans and environment from this residual radioactivity there has been a strong desire to develop a concrete that retains little residual radioactivity. With the aim of developing a low activation concrete using local ingredients, in this study cement samples from local markets of Dhaka were collected and analyzed by instrumental neutron activation analysis (INAA). Around 60 mg of each sample and standard was irradiated altogether using pneumatic transfer system (thermal neutron flux: 2.0x10¹³ cm^-2s¹) of 3MW TRIGA MARK-II research reactor at Atomic Energy Research Establishment (AERE), Savar, Dhaka. Elemental concentrations of Ce, Hf, Fe, Sb, Sc, Tb, Ta, Zn, Cs, Co and Eu, which are mainly responsible for producing long-lived radionuclides in the concrete shielding, were determined in the cement samples. It is observed that among the ordinary Portland cements (OPC), fly ash free OPCs contain lower concentrations of the studied elements. When average concentrations of the studied elements in white Portland cements (WPC) are compared to those in OPCs, WPC contains lower concentrations of the elements. Activity concentrations of primordial radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K are also determined in the samples by using high resolution gamma-ray spectrometry system. To develop a low activation shielding, it is necessary to choose concrete compositions with low concentrations of the mentioned elements and primordial radionuclides. Data of elemental composition of the studied cements can be used to choose aggregates necessary for constructing nuclear shielding especially for the future nuclear power plant projects in Bangladesh.

Feeds production for fish and poultry from tanned skin-cut wastes is the most direct phenomenon of chromium eco-toxicity leading to food chain contamination in Bangladesh. So, it is important to find out the Cr and other toxic element in fish and poultry feed as well as in poultry chicken and in cultivated fish to complete the toxicity identification in the entire chain. As a case study, the Agro Industry in Bogra has been considered. Four categories of poultry feeds, five categories of fish feeds and nine raw materials (Used to prepare the feeds) were collected from this industry. In order to determine wide range of elements in the sample reactor based neutron activation analysis were used. To apply relative standardization approach, three standards: IAEA-Soil-7, IAEA-SL-1 and NIST-1633b (Coal Fly Ash) were irradiated with samples at 3MW TRIGA MARK-ІІ Research Reactor for 2 hours at Dry Central Thimble (DCT) with a neutron flux of 1.52  10¹³ x/cm²/sec. Concentrations of some heavy metals such as Cr, Fe, Sb, Th, Zn etc. were detected in the samples. Among these elements only Cr exceed by the levels allowed by the world references for fish feeds and raw material (Fish meal). The raw materials for fish feed has been made locally (Bangladesh). This elevated level of Cr content indicating that the fish feed raw material might be produced from tanned skin-cut wastes. The poultry feeds for which raw materials (meat and bone meal) imported from the Netherland, no Cr toxicity was observed in it. The Cr content in local fish meal was found to be 10293 ppm and all the fish feeds were contaminated accordingly. Further study is necessary for the determination of Cr in fish and poultry chicken from the same industry to investigate the chain of contamination.

In order to control the quality of the 12 participating laboratories from eight countries (Australia, Bangladesh, Indonesia-4 labs, Japan-2 labs, Kazakhstan, Malaysia, Thailand and Vietnam) under the FNCA RRU/NAA project, three samples namely AGAL-10 (Hawkesbury River Sediment), Biosoil AGAL-12 (Mixture of sausage sludge and loam) from National Measurement Institute of Australia Reference Materials and JSD-2 Stream Sediment from Geological Survey of Japan have been distributed for the determination of major, minor and trace elements using NAA method. We have analyzed these samples based on short and long irradiation for the determination of wide range of elements. The analytical results have submitted to the FNCA authority in due time. All the data have compiled and compared the results among the member states laboratories. The BAEC-NAA results are quite comparable with the assigned values of sediments that ensure the quality of the analytical status.

Neutron radiography technique has been applied in the present study to detect the internal structure of electronic components RAM DDR-2 and Motherboard of Nokia-3120. In present experiment, electronic RAM model: DDR-2 and motherboard of mobile phone, NOKIA-3120 was collected from local market. Thermal neutron radiography facility of 3MW TRIGA MARK-II research reactor at Atomic Energy Research Establishment, Savar, Dhaka has been adopted for present research. A series of neutron radiographic images were taken to find the optimum exposure time for the samples. The optimum exposure time is 2 minutes 45 seconds evaluated in this experiment. Some spots have been identified from the neutron radiographic image of each sample.

Neutron Radiography (NR) is a powerful tool for non-destructive testing of materials for industrial applications and research. At present, NR application is being used in agricultural research also. In this study, neutron radiography technique has been adopted to know morphological changes during ripening process of an oil seed plant. Thermal NR facility of 3MW TRIGA Mark-II Research Reactor of AERE, Savar, Dhaka, Bangladesh, has been utilized in the present study. In the present work oil seed plant named Brassica napus L and Hyacinth bean are used as samples. These samples were collected from Bangladesh Agriculture Research Institute. A series of neutron radiographic images have been taken to study morphological changes of these samples at different times of interest after flowering up to ripening. Finally, the seeds were found only in hydrogenated material inside the pods.

Neutron radiography (NR) technique has been adopted to study the internal structure and quality of the KAB bricks made by Hoffman kiln method. Thermal neutron radiography facility installed at the tangential beam port of 3 MW TRIGA Mark-II Research Reactor, AERE, Savar, Dhaka, Bangladesh is used in the present study. Measurements were made to determine the internal structure and quality of the automated machine made environmentally friendly brick sample. In this case, optical density/gray values of the neutron radiographic images of the sample have been measured. From these measurements, the porosity, water penetrating height, water penetrating behavior, initial rapid absorption of water (IRA), elemental distribution/homogeneity and incremental water intrusion area in the sample have been found. From the observation of different properties, it is seen that, homogeneity of the Hoffman kiln brick KAB is not perfectly homogeneous and contains small internal porosity; the incremental water intrusion area is very poor, and the water penetrating height through the two edges is higher than the middle part; the initial rapid absorption (IRA) rate is also very poor and the water penetrating behavior of the samples is different as like as stair, capillary, wave and zigzag shape. From these points of view, it is concluded that the quality of the environmentally friendly brick KAB is better. The results obtained and conclusion made in this study can only be compared to the properties of bricks produced under similar conditions with similar raw materials.

Neutron radiography is a powerful non-destructive testing (NDT) technique for internal evaluation of materials, such as voids/cavity, cracks, homogeneity, water absorption behavior, etc. It involves attenuation of a neutron beam by an object to be radiographed and thus to make the registration of the attenuation process (as an image) on a film or video. In the present investigation neutron radiography (NR) imaging technique has been adopted to study the quality like homogeneity, porosity, water penetrating height, behavior of incremental intrusion area, initial rapid absorption (IRA) of the brick-DK sample. Thermal neutron radiography facility installed at the tangential beam port of 3MW TRIGA MARK-II reactor is used in this study. In this cases optical density or gray values of the neutron radiographic images of the sample is measured. From this measurement it is found that the contents of the sample is not uniformly distributed all over the sample which indicates the presence of large number of internal porosity, at the two edges water uptake is slightly poorer than the middle part and initial rapid absorption is very high. Water penetrating inside the sample is faster. The results obtained and conclusion made in this study can only be compared to the properties of bricks produced under similar conditions with similar raw materials.

1. One member successfully completed the national workshop on “Nuclear Security Culture in Bangladesh” held in 18-20 June 2013, at BAEC organized by IAEA in cooperation with the BAEC.

2. One member successfully completed the national workshop on “Human Resources Development for Strategy and Plan of Rooppor Nuclear plant.” held in 15-18 March 2013, at BAEC under RNPP project of BAEC.

3. One member successfully completed the training course on “Nuclear and radiological emergency preparedness course at BAEC” on 09 -13 December 2012, TI, AERE, Savar, Dhaka.

4. One member successfully completed the training course on “reactor engineering course at BAEC-1” at 10-20 February 2013, TI, AERE, Savar, Dhaka.

5. One member successfully completed the training course on “Programming with JAVA” at 25 March – 15 May 2013, ICS, AERE, Savar, Dhaka.

The TRIGA Mark-II research reactor of Bangladesh Atomic Energy Commission (BAEC) is the only nuclear reactor in the country. It has a maximum steady-state thermal power of 3 MW. The reactor achieved its first criticality on 14 September 1986. The reactor has so far been used in various fields of research and utilization such as, Neutron Activation Analysis (NAA), Neutron Radiography (NR), Neutron Scattering (NS), production of radioisotopes, training of manpower (local and foreign) etc. Reactor Operation & Maintenance Unit (ROMU) is responsible for the operation and maintenance of the reactor and it’s associated equipment and systems ensuring appropriate level of safety as delineated in the Safety Analysis Report (SAR). ROMU is also responsible for the preparation of various Safeguards and Additional Protocol related reports on routine basis. These reports are sent to the IAEA through Nuclear Safety and Safeguards Division (NSSD) and International Affairs Division (IAD) of BAEC.

Since its first commissioning (1986), the reactor is operated using analog control system. Most of the spare parts of analog control system are going to out of date. It has become very difficult and almost impossible in some cases and very much expensive to procure spare parts for the maintenance of the analog control system of the reactor. In this situation, the analog control system was replaced with the digital control system under an ADP project titled “Nuclear Safety and Radiation Control Division 2^nd Phase and Installation of Digital Control System for the TRIGA Mark-II Research Reactor”. The installation work of the digital control system was commenced on July 20, 2011 and completed on June, 2012. The digital control system was tested and commissioned by ROMU personnel in presence of GA-ESI, USA experts.

After successful installation of the Digital Control System, the reactor was operated at different power levels for 8 hours and 48 hours in presence of the GA-ESI, USA representative. The main purpose of this operation was to check the performance of the digital control system and other safety related systems of the reactor. Commissioning test of the digital control system of BAEC 3 MW TRIGA Mk-II research reactor is performed satisfactorily except few spurious high power spikes which caused automatic scram of the reactor. Finally, ROMU personnel fixed the scram problem successfully.

18.3 Maintenance Work

Several preventive as well as corrective maintenance works were carried out on the cooling system, ventilation system, radiation measuring systems, beam-ports and Instrumentation & Control (I&C) system of the reactor during the reporting period. Some of the major maintenance works carried out during the reporting period were as follows:

1. 
   Design and fabrication of reactor pool level switches support to install float level switches at different height of reactor pool.
   
2. 
   Maintenance and draw tube of Shim#1 and Regulating control rod of the reactor were cleaned.
   
3. 
   The high voltage power supply of linear multi-range power channel (NMP-1000) was replaced by a new one.
   
4. 
   The faulty module of primary coolant flow was replaced and calibrated.
   
5. 
   250 kVA DG was repaired by replacing automatic voltage regulator (AVR) and speed controller.
   
6. 
   2 kVA UPS battery of DAC (supplied by GA-ESI, USA under digital console project) were replaced by six (6) numbers of new batteries.
   
7. 
   Four (4) numbers of sealed lead acid batteries were replaced in solar 1 kVA UPS and it was installed at Thermal Power Calculator (TPC).
   
8. 
   Modified and developed pneumatic control system of the reactor hall main entry door and installed by replacing the old one. A new air compressor was also installed for supplying air to the pneumatically operated reactor hall main entry door system.
   
9. 
   Repair and maintenance of fire detection and alarm system.
   
10. 
    Maintenance of all CCTV camera system of research reactor building.
    
11. 
    Calibration of Thermal Power Calculator.
    
12. 
    Installation of new Ion chamber near reactor core.
    
13. 
    Repair and maintenance of secondary pump 2 (change bearing, seal, gaskets, etc.)
    

During the reporting period the reactor was operated at different power levels (50 W-3000 kW) to provide neutron beam to various reactor users. A total number of ninety nine (99) irradiation requests (IRs) were catered during the period for conducting the performance tests and calibration of High Performance Powder Diffract meter and various R&D activities. Reactor and Neutron Physics Division (RNPD) of INST used the neutron beam of the reactor for carrying out various R&D activities. The reactor also operated for testing and commissioning of the new digital control console, and other I&C system of the reactor. During this period, the total burn-up of the reactor fuel was about 554.482 MWh. Monthly operation data of the reactor during the reporting period are shown in Table 1.