[en] Abstract Background: Having a half-life of 5730 a, ¹⁴C is the radionuclide of greatest concern in nuclear graphite, which arises principally through the interaction of reactor neutrons with nitrogen via ¹⁴N(n, p) reaction. Purpose: This study aims to propose a mechanism for the production and retention of ¹⁴C in graphite and needs to be verified. Methods: The specific activities for ¹⁴C have been calculated and experimentally determined. Nitrogen exists in heavy water research reactor (HWRR) graphite in two forms: impurity N and interstice N₂. A comparison between ¹⁴C specific activities in ground and unground graphite samples has been done. Results: The ¹⁴C atoms produced by the interstice N₂ usually exist in 'hot atom' state and immediately form ¹⁴CO₂, part of which may resides in graphite and the other part may eventually escape to air. Conclusion: A comparison between ¹⁴C specific activities in ground and unground graphite samples reveals that the interstice ¹⁴CO₂ accounts for 30% approximately of total ¹⁴C in the thermal column graphite of heavy water research reactor. (authors)

[en] Objective: To judge the running states of the waste water tanks of a heavy water research reactor (namely 101 reactor). Methods: The groundwater, soil and transit pumping rooms around the waste water tanks were investigated through on-site measurement or laboratory analysis to identify areas with high soil contamination or high radiation dose levels. Results: Results of the soil and groundwater around the waste water tank showed that the waste water tank had no adverse impact on the surrounding soil and groundwater during the past operations; the results of transit pumping rooms indicated that the soil under the room area and the ground inside the rooms had been contaminated in different degrees. Conclusion: In general, the waste water tanks of the heavy water research reactor are in good condition. (author)

[en] Objective: To calculate the Wigner energy of the graphite reflector of heavy water research reactor (HWRR), and provide technical support for the decommissioning of HWRR. Methods: Based on the position, direction cosine and energy information of neutrons acquired from the PTRAC card of MCNP, the energy distribution of primary knock-on atoms (PKA) can be obtained. After data filtering, an input file is generated from MATLAB for SRIM code to simulate the cascading damage process of PKA in graphite. Considering the effect of temperature on the irradiation damage, the distribution of Wigner energy accumulation in the graphite reflector is obtained. Results: The result shows that the Wigner energy in the graphite reflector of the heavy water research reactor (HWRR) is concentrated on the inner layer close to the core, and located in the upper region of reflector with a maximum value of 1215.4 J/g. Conclusion: The basic agreement between the results from Hanford experiment and our calculation indicates that the simulation method established in this study is workable for calculating the accumulated Wigner energy in graphite of reactor reflector. (authors)

[en] In this paper,an empirical formula for the efficiency calibration of bulky source in cylindrical geometry is proposed. The simple but accurate empirical formula is able to effectively predict the efficiencies of summing effect free γ-rays from a cylindrical bulky source (φ30 mm x 40 mm) at different source-to-detector distance. The relative difference between experimental and calculated data at 0, 20, 40, and 80 mm source-to-detector distances is smaller than 5%. (authors)

[en] An ultrasonic wave cerium (IV) decontamination technology for stainless steel wastes produced in decommissioning process of nuclear facilities has been investigated. Using an orthogonal experiment method, the effects on corrosion weight loss rate and decontamination factor of stainless steel have been studied in different conditions, including concentrations of HNO₃ and Ce(NH₄)₂(NO₃)₆, temperature of solution, and ultrasonic time. Results showed that temperature and Ce(NH₄)₂(NO₃)₆ concentration would be the major influence factors. A maximum corrosion rate of 8.07 μm/h was obtained with the optimal parameters of Ce(NH₄)₂(NO₃)₆ 0.15 mol/L), HNO₃ (1.0 mol/L) and 85 ℃ for the decontamination process. The corrosion behavior of coupons was observed by a scanning electron microscope (SEM), and the results showed that cavitation corrosion was caused by ultrasonic wave occurred on the surface of a decontaminated coupon. A decontamination experiment for a section of spent fuels storage tube for demonstration was conducted, and a decontamination factor of 158.8 was achieved. (authors)

[en] Aiming at the quality problem of the CFRP inner wall in the CFRP/Ti laminated material assisted vibration drilling technology, the acoustic emission (AE) signals of different processing parameters during drilling are collected. Analyze the relationship between the characteristics of the acoustic emission signals and the roughness of the CFRP inner wall under different processing parameters and different number of holes. The test results and analysis show that other parameters are kept unchanged during the test process, only one parameter is changed. When the amplitude and spindle speed increase, the AERMS value increases while the CFRP inner wall roughness decreases. When the feed rate increases, the AERMS value and CFRP inner wall roughness increase simultaneously. The energy ratio of the wavelet packet of the AE signals is also closely related to the roughness of the CFRP inner wall. Therefore, in the actual machining process, the CFRP inner wall roughness can be monitored by monitoring the AE signals to improve the processing efficiency. (paper)

[en] Objective: To analyze the CT findings of tuberculous lymphadenitis in parotid gland, so as to improve the diagnostic accuracy of tuberculosis of parotid gland. Methods: Nine cases with tuberculous lymphadenitis in parotid gland confirmed by surgical pathology and acid-fast bacilli after preoperative spiral CT plain scan and two phases dynamic enhancement scan were retrospectively analyzed. Imaging findings of CT were reviewed and compared with surgical pathology. Results: Seven of the 9 cases of tuberculosis of the parotid gland occurred in the left side, and 2 in the right side, and superficial lobe involvement occurred in 8 cases and deep lobe in 1 case. The lesion was classified as tumour type (8 cases) and infiltration type (1 case). In turnout type, the number of lesion was from 1 to 4, and the size was from 2.7 to 5.3 cm in diameter. One case of infiltration type measured 3.4 cm in diameter. On CT plain scan, the lesions showed homogeneous slight high-density with regular edge in 5 cases and irregular low-density in 4 cases, and 2 of them with partly blurred edge. On CT enhanced scan, uniform moderate enhancement was seen in 3 cases, circular enhancement in 4 cases, inhomogeneous enhancement in 1 case, and lace-like enhancement in 1 case. Local infiltration occurred in 6 cases. Lymphadenovarix in the same side of lesion occurred in 2 cases. Conclusion: CT findings of tuberculous lymphadenitis in parotid gland present diversification, which correlate well with pathological changes. Understanding of characteristic CT findings of tuberculous lymphadenitis in parotid gland is helpful for differential diagnosis, but final diagnosis still depends on pathology and acid-fast bacilli. (authors)

[en] China Institute of Atomic Energy (CIAE) has participated in the technology research and development of nuclear facility decommissioning field and developed a lot of technologies since the decontamination major project was set up in 1990s. The current status of nuclear facility decommissioning technologies in CIAE was reviewed, which includes characterization survey, decontamination, cutting and dismantling, radioactive waste detection and so on. This review also contains recommendation for the future research needed to address decommissioning technologies in CIAE. (authors)

[en] CR-39 samples were irradiated with sulphur ions from HI-13 tandem accelerator to produce latent tracks at China Institute of Atomic Energy. Ultraviolet light with wavelength 360 nm was used to sensitize the bombarded CR-39 samples before chemical etching by NaOH solution. The latent tracks were then developed into pores or holes with certain diameter. Silver black was coated on the surface of etched CR-39 using evaporation in inert gas argon ambience. The SEM images indicate that the silver nano-particles are 60-100 nm in diameter at the pressure of 50-100 Pa, and the diameter of spherical clusters formed by nano-particles is 3 μm. The reflectivity indices were measured for all CR-39 samples, untreated and treated with above-mentioned procedures, within the wavelength of 2.5-25 μm. The results indicate that CR-39 modified with a combination of solid state nuclear tracks and silver black coating can decrease the reflectivity index to 0.9% for the wavelength range of 8.0-25 μm, and that is 82% reduction compared to CR-39 without modification. The blank reflectivity indices of CR-39 at wavelength of 5.8 μm and 7.8 μm are reduced from 9.0% and 13.0% to 5.0% and 6.8%, respectively. (authors)

[en] In this paper, we first propose a new Uzawa-SOR method for fourth-order block saddle point problems. Then we study its convergence conditions through some lemmas and theorems. Finally, the numerical results are presented to prove the 4-USOR method we proposed has less workload per iteration and higher accuracy for large linear system than the other Uzawa-type methods for solving the fourth-order block saddle point problem, which shows the effectiveness and feasibility of our method.