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[en] After the formation by decay of ²²²Rn, the freshly generated ²¹⁸Po ions in recoil routes are most positively charged and react fast with trace gases and vapors in air and become small particles called clusters or, unattached 'decay products', the unattached ²¹⁸Po clusters can react with other aerosol particles and become attached ²¹⁸Po. This process has been accepted in past records. But how the neutralization of the charge ²¹⁸Po happened and the conditions have many uncertainties. This neutralization process is a foundation of radon measurements that depend on electrostatic collection of charged decay products and the dose of radon decay products. This study has been concerned by many scholars in recent years and has obtained many new progresses. Three neutralization mechanisms of ²¹⁸Po were individually described, including electron scavenging by OH radicals formed by radiolysis of water vapor, recombination with small air ions and charge transfer by molecules of lower ionization potential. The three neutralization mechanisms happened differently in different conditions, such as gas concentration in the air, the ionization rate, temperature, the humidity concentration, radon concentration and the age of radon progeny and so on. (authors)

[en] To develop a effective measurement method of radon mitigation efficiency for interior wall paint. By using a local static method, the average radon flux rate of a measured material surface during the period of monitoring can be gotten. The method has been developed using organic glass to make radon cumulation chamber, lint board with a single smooth surface to make samples, PCMR-1 continuous radon monitor and GD-LI gas-through solid radon source. The same measurement conditions can be realized easily and the measurement results can be compared very well. The method can meet the need of radon mitigation efficiency measurement for interior wall paint

[en] Using the CIAE-30 cyclotron, a ¹²⁴Xe gas target system for the production of high purity ¹²³I was established. This system includes ¹²⁴Xe gas target station and the transmission line of the 30 MeV proton beam, the He cooling system for the sealed windows of target and beam-line, the water cooling system, the vacuum system for target chamber, the system for ¹²⁴Xe processing and the system for the chemical processing of ¹²³I. It also includes ¹²⁴Xe retention system, LN₂ transfer system, He gas transfer system and the system for ¹²⁴Xe supplement, as well as the system for beam current adjusting, measuring and controlling, and the system for radiation protection and detection. The performance tests for the system, and the setting up of the conditions for the experiments prove that this system can offer 111-148 GBq (3-4 Ci) of ¹²³I in one batch with a production rate greater than 296 MBq/(μA•h) (8 mCi/(μA•h)). The radionuclide purity of ¹²³I is better than 99.8%, and the radiochemical purity is better than 95%, which fits the needs of the production in scale. (authors)

[en] The theory of thermal neutron measurement using CR-39 SSNTD is described. The method of making thermal neutron CR-39 SSNTD and its preliminary application for personal dose monitoring are introduced

[en] PURPOSE: To test the preliminary clinical performance of 4 rings/7 slices, AFOV 8 cm PET scanner made in China. METHODS: Based on phantom test and animal study, PET imaging were performed on a normal volunteer and 7 patients 1.5 hours after intravenous injection of 370 MBq of ¹⁸F-FDG. The acquisition time of whole body imaging for adult was 1.5 hours (11 bed position), whereas myocardium and brain imaging was 0.5 hours (2∼3 bed position). RESULTS: Φ1∼3 cm positive and negative foci could be displayed in phantom. 8 cases of coronal and sagittal whole body tomographic images were clearly demonstrated. Brain, myocardium and bladder were significantly displayed in normal volunteer with normal food and drink. 6 malignant lesions of 2 patients concentrated ¹⁸F-FDG significantly and 2 benign lesions of 2 patients did not concentrated it. Recurrence and metastasis were excluded in 2 patients with carcinoma after operation and chemotherapy. Whether normal myocardium display or not were dependent on glucose loading. ¹⁸F-FDG myocardium images matched well with ^99mTc-MIBI myocardial perfusion images in a patient with remote myocardial infarction. Cerebral cortex images well visualized in all subjects. CONCLUSIONS: The performance of this PET scanner showed that it reached the level of middle stage of 8th decade's 4 rings/7 slices PET and possessed the coronal and sagittal whole body tomographic function of 9th decade's PET. It can be used in whole body tumor imaging, myocardial viability evaluation and preoperation localization of functional epileptic foci, but operating and software function should be improved

[en] In order to improve the sensitivity of radon measurement method, Fast and Multi-functional Radon Monitor with Electret, Sensitive Miner Radon Monitor, fast and Multifunctional Radon Monitor with High Voltage and PCMR-1 Passive and Continuous Radon Monitor were developed. Except Sensitive Miner Radon Monitor suits for radon concentration measurement only, the others can be used to measure both radon concentration and radon flux rate. Their measurement principles. specifications, quality assurance system, advantages and disadvantages are introduced. The simultaneous measurement results indicate that the errors among them are less than 5% and 10%, respectively, for the average radon concentration measurement and for the average radon flux rate measurement

[en] The simultaneous radon and thoron monitoring method based on the difference of the half-life between radon and thoron, the thoron monitoring method with absorber based on the difference of the energy of α particles emitting from radon, thoron and their progenies, and the sensitive thoron monitoring method with electret based on the charged characteristics of thoron daughters are developed. The simultaneous method can be used to measure radon and thoron concentrations simultaneously; the thoron monitoring method with absorber can measure not only thoron exposure, but also the thoron exhalation rate released from the material surface directly. The sensitive method is of the advantage of higher sensitivity, and will be used widely for the environmental investigation, and for study of the characteristics of thoron and its progenies. (authors)

[en] Cryptand kryptofix 2.2.2 forms stable complex with lead (II) in the citric acid-NaOH media of pH 6.4. The lead cryptate, absorbance coming to maximum immediately after being developed, having the peak absorption at 253 nm, with stable colour and good reproducibility, is suitable for the determination of microcryptand (2.2.2) in ¹⁸FDG product by UV-spectrophotometry. The linear correlation coefficient of calibration 20∼100 μg cryptand (2.2.2) and absorbance is more than 0.999. The relative standard deviation for the determination of 5∼10 μg cryptand (2.2.2) is +-10%∼+-15%. The detection limit is 1∼2 μg. The procedure is simple and speedy. The QC analysis of three parallel ¹⁸FDG samples can be completed within 20 min. (11 refs., 5 figs., 5 tabs.)

[en] A method of discriminating radon from thoron by using an absorber has been developed. This discriminating method realizes direct passive and integrating thoron monitoring, but reduces thoron measurement sensitivity. By means of using electrostatic collection inside the sampling chamber, the sensitivity can be increased largely