[en] A field experiment was conducted for long term rice-soybean cropping system at Chiang Mai Field Crop Research Center, to estimate nitrogen fixation of soybean and residual benefit of the soybean stover to a following rice crop. Nitrogen fixation was estimated in the soybean using ¹⁵ N dilution technique and non nodulated groundnut as a standard crop. To estimate the residual nitrogen benefit to the rice crop was calculated by nitrogen-15 yield of rice where the soybean stover was either removed or returned. In the first year soybean fixed 48.42% of their nitrogen which producing 50.31 KgN/ha. Residual effect of soybean stover returned was 36.72% of nitrogen in rice which equal 50.62 KgN/ha. come from the soybean returned (stover plus root and nodule under the ground where the soybean stover was returned). The residual nitrogen-15 in the second year was too low to detect. No nitrogen fertilizer applied to the following rice plot where the soybean stover was returned, grain dry matter yield were up to 12% (1^st year) and 27% (2^nd year) grater than in the plots where the soybean stover was removed produce the highest grain dry matter yield which were higher 14 - 29% than the plots where the soybean stover was removed

[en] The development of an interfacing system for environmental radiation surveillance using radio communication network is aimed to improve a way by which environmental radiation measurement is transmitted and reported from the regional area monitoring station network. This also includes an automatic warning of beacon status via the radio link network to the center of environmental radiation control when an abnormal radiation level is detected. The interfacing system was developed by simulating the EGAT radio link network, the NT 2612, and can be separated into two parts. The first part was for a mobile station which can manage the output data from the radiation measurement system in the standard form of RS-232, IEEE-488, BCD and analog signal. This was accomplished by modulating the signal in selected baud rates ranging from 150 to 9600 bps using an economical radio packet capable of identifying and recalling the station code number. The other part is the linking system between the output data and the microcomputer equipped with a software to manage and evaluate the data from 10 surveillance stations for convenient handing of data output, statistical analysis and transmitting warning signal. Data transmission was tested using a baud rate of 1200 bps and was found to contain no detectable error when digital signal was transmitted while analog signal transmission resulted in deviations of less than ± 0.003%. The development of this radio link system provides a future trend for the environmental radiation monitoring network for countries with nuclear power plants or neighboring countries needed to continuously monitor for any abnormal radiation level in the environment. In case that the radiation surveillance system detects a high level of radiation, a warning signal will be transmitted and appropriate actions may be immediately exercised to control impacts of radiation on environment and living things according to international guidelines

[en] Radiation safety for medical personnel in using I-131 were assessed and carried out at the Department of Nuclear Medicine, Siriraj Hospital. Air sample were employed to determine concentrations of I-131 in laboratory environment. The air sampling was performed on a daily basis in front of a fume hood using for treatment of 169 hyperthyroid patients. The daily concentrations of I-131 in air were found at range of 0.94 to 262.66 Bq/m³. All values were well below the Derived Air Concentration (DAC) of Iodine-131 (700 Bq/m³). The place is safe for working with I-131

[en] The dispersion modeling of radioactive materials from a nuclear power plant was studied by U.S. EPA CAP88-P C model. Dose prediction was calculated by using annual release rate of radioisotopes, meteorological data, population and agricultural data of studied area in Changwat Prachuap Khiri Khan. The result of dispersion modeling from the normal operation of 600 M We nuclear power plant type PWR showed maximally exposed individual dose was 0.91 mren/y. Background tritium and carbon-14 concentrations in air were studied by cold traps and analyzed by LSC. The results showed that 0.1-0.4 Bq/m³ and 0.1-0.3 Bq/m³ respectively

[en] Co-precipitation method is suitable mean for determination of gross alpha activity in water with high salt compounds. Alpha emitters which are Actinides and those in Uranium-Radium series are co-precipitated with barium carrier and iron carrier. Although the activity is not indicative of any specific nuclides presented but it can be used as an index to the radioactive contamination of the waters

[en] Samarium-153 ethylenediamine-tetra methylene phosphonate (¹⁵³ Sm-EDTMP) has been proposed as a radionuclide therapeutic agent to palliate pain resulting from osteoblastic metastatic bone cancer. Six patients with disseminated skeletal metastases from a variety of tumor types underwent clinical trial of this agent obtained from the Office of Atomic Energy for Peace (OAEP), Thailand. All of the patients received 1 mCi/kg of ¹⁵³ Sm-EDTMP intravenously. The preferential localization of ¹⁵³ Sm-EDTMP in bony lesions was assessed and compared to the routine bone seeking agent, ^99mTc-MDP. Both radiopharmaceuticals showed similar uptake in lesional and nonlesional bone (p < 0.001). The retained skeletal activity varied from 56.54% to 76.23% of the administered dose and greater than 91% ± 6.77% of the non osseous activity was cleared in the urine within 6 hours in all patients. Fifty percents of the patients developed a transient exacerbation of their pre-¹⁵³ Sm-EDTMP pain and lasted within 1-2 weeks. The other patients lost follow up. This study indicates potential for ¹⁵³ Sm-EDTMP as a therapeutic radiopharmaceutical for pain palliation of cancer bone metastases

[en] Samarium-153 has suitable physical properties for metastatic bone cancer pain palliation with 46.7 hr half-life. Not only decays it with multi-energetic B-radiation but also emits a gamma-ray at 103 keV which is suitable for imaging during therapy. The optimization of ¹⁵³ Sm production, by irradiation ¹⁵² Sm₂ O₃ as a solid and liquid target, is conducted in TRIGA Mark III research reactor. The feasibility to label it with EDTMP, a bone seeking agent, is also studied. The specific activity obtained from liquid target is about 2 times higher than solid target. At least 500 mCi/week can be produced with specific activity about 50 to 70 mCi/mg Sm. EDTMP as Na-EDTMP and Ca-EDTMP is labelled with ¹⁵³ Sm at various conditions. The radiochemical purity achieved, is greater than 99% (85 mCi of ¹⁵³ Sm labelled with Na-EDTMP or Ca-EDTMP, molar ratio of Sm:EDTMP 1:10 and 1:100 respectively, pH 7.5-8). The biodistribution in animals of ¹⁵³ Sm-Na-EDTMP showed similar results as obtained from ¹⁵³ Sm-Ca-EDTMP but slightly higher uptake in various organs and showed high skeletal uptake up to 32% at 24 hr post injection. The labeled compound obviously undergoes rapid removal, completely clearance into urine within 24 hr. This labeled compound is under clinical trials

[en] The determination of uranium and thorium in monazite samples by Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES) technique were done. The spectra of rare earth elements, thorium and iron interfered those of uranium at 6 wavelengths. The spectra of thorium were interfered from those of rare earth elements at 374.118 and 401.913 nm wavelengths. The increasing of sulfuric acid and perchloric acid concentrations decreased the emission intensity of uranium and thorium. Hence, the quantity of sulfuric and perchloric acid in the standard and the sample solutions were equally added. Sulfuric acid was the best of all mineral acids to open the monazite mineral. The 7 ml of concentrate sulfuric acid (36 N) was selected for 1 gram of monazite. Rare earth and thorium elements were separated from uranium by the precipitation with ammonium oxalate. The 30 mg of ammonium oxalate is suitable for precipitation of 1 ml of 0.012 g rare earth and thorium weights. The precision and accuracy of the method were verified by using the known concentration of IGS-36 and NBS-7 A reference standard materials. The uranium and thorium values obtained in ten monazite samples were found to be in good agreement with those obtained by non-destructive neutron activation analysis method

[en] The computer program to compute the depth-dose curve of plane-parallel electron beams normally incident on a semi-infinite absorber consisting of single material. The algorithm of computer program is based on the simple model of T. Tabata R. Ito and S. Tsukul. The computer program has been developed, based on Microsoft Quick Basic version 4.5. In parallel with this study, the calculated results are compared to the experimental depth-dose curve for 1.0 MeV and 2.0 MeV electrons incident on layer of CT A film were obtained for broad-beam geometry as a function of thickness. Close agreements were found for both energy ranges of electron, but maximum depth-dose in CT A film was observed to be higher than that predicted by calculation by no more than 1% for 1 MeV and 0.3% for 2 MeV respectively

[en] Developmental work on computerized gamma-ray spectrum analysis has been completed with the result as a software package for Windows 95 and Windows N T operating systems. The application of analysis method in Fortran and C++ languages has been performed on the Microsoft Fortran Power Station 32 Version 4 and Microsoft Visual C++ Version 4. Stages of the analysis are consisted with peak-shape calibration, gamma-ray energy calibration, and detector's efficiency calibration, followed with peak searching, peak-area fitting, multiplet resolving, radionuclides identification and the final calculation of the activity for all identified isotopes