β-肾上腺素受体放射配基分析法的条件探讨

本文对β-肾上腺素受体放射配基分析法中的缓冲液、膜受体制备条件、胰蛋白用量、结合与游离配基的分离方法及非特异性结合的控制等方面作了探讨和改进,使方法的稳定性和可靠性有了明显的提高,并对所建方法进行了较完整的考核。     

Experimental measurements and numerical simulations to evaluate the electrode kinetics for 316 stainless steel under PWR-relevant conditions

The local environment in an occluded region of a pressurized water reactor (PWR) depends on its geometry, its access to the bulk and the nature of the electrode kinetics at the metal surfaces. In PWR-relevant, oxygen-free, boric acid-lithium hydroxide solutions the dominant anodic and cathodic electrode reactions are found to be hydrogen oxidation and water reduction, respectively. The hydrogen oxidation reaction kinetics have been quantified using potentiostatic measurements - at 300 °C, under various dissolved hydrogen concentrations, for 1000 ppmB and 2 ppmLi. The reaction kinetics have been verified by modelling of a crevice experiment performed in an autoclave at 300 °C for 1000 ppmB, 2 ppmLi and 25 STP ccH₂/kg.     

On the experimental determination of the migrating defect fraction under cascade damage conditions

Information on the fraction of defects surviving intracascade recombination, escaping the cascade volume and migrating until their annihilation (“migrating defect fraction”, MDF) can be obtained from the analysis of radiation enhanced diffusion (RED) or radiation induced segregation (RIS) and maximum swelling rates. RED and RIS yield the ratio of the MDF over the effective sink strength whereas maximum swelling rates give lower bound estimates of the MDF. The basic assumptions made in the previous analysis of RED (RIS) and swelling are critically examined in the light of the present understanding of defect production in displacement cascades. MDF values deduced previously from RED are found to be clearly below the lower bound estimates obtained from maximum swelling rates. The discrepancy becomes even larger if the conventional monodefect dislocation bias is used in the analysis of swelling. Possible reasons for this discrepancy are discussed: (1) differences in the contribution of mobile defect clusters produced in cascades to RED and swelling, and (2) an underestimation of both the sink strength evolving during cascade damage conditions and the driving force for the swelling. We argue that the conventional method to deduce the sink strength from sink densities observed in TEM and the application of the conventional monodefect dislocation bias indeed yield only lower bound estimates for the sink strength and for the swelling rate, respectively. If the MDF were established by some other method RED (or RIS) could be used to measure the sink strength.     

陶粉样品的光晒退实验研究

本文绘出了用红、黄和白炽等普通灯泡以及荧光灯做的陶粉样品的光晒退实验结果;分析了光晒退与光强和光谱分布的关系。     

An experimental study on rewetting phenomena in transient conditions of bwrs

It is known that rod temperature rise after boiling transition (BT) is not excursive and that the peak cladding temperature (PCT) is suppressed by rewetting to return to nucleate boiling, even if BT occurs under severe conditions exceeding abnormal operational transients for a BWR. The purpose of this study is to develop and verify the rewetting correlation. The rewetting correlation was developed based on single rod data, as a function of quality, mass flux, pressure and heat flux. The transient thermal-hydraulic code used in the BWR design analysis (SCAT) with this rewetting correlation was compared with transient rod temperature result after the occurence of BT obtianed by the 8×8 and 4×4 rod bundle. It is concluded that the transient code with the developed rewetting correlation predicts the PCT conservatively, and the rewetting time well.     

Theoretical and experimental study on single-phase natural circulation under inclined conditions

The natural circulation reactor is widely used in marine environments where thermo-hydraulic performance is heavily affected by the heaving, pitching, and inclining of a ship. This paper theoretically and experimentally investigated steady-state single-phase natural circulation under inclined conditions. Results showed that energy transported by natural circulation was proportional to 1.5 times the power of the temperature difference between the hot leg and the cold leg. Furthermore, a parameter, k, was presented that revealed the comprehensive influence of working fluid properties, resistance characteristics, gravity fields, and loop configurations. k was treated as the criterion for the circulation ability of a loop and it also acted as the basis for evaluating and optimizing different designs. Analysis under the guidance of k was confirmed by a series of experiments performed on a symmetrical two-circuit loop. Both theoretical and experimental results showed that the inclination restrained overall circulation due to the decrease in average altitude difference between the steam generators and the electric heater. The disparity in branch circulations increased with the increase in the inclined angle. A loop design consisting of a large altitude difference and a small width was preferable to confine the influence of inclination. However, if the loop width was too small, it caused a severe reduction in the circulation ability for large angle inclinations.     

Lead and tungsten pinhole inserts for I-131 SPECT tumor imaging:experimental measurements and photon transport simulations

The potential use of lead and tungsten pinhole inserts for high-resolution SPECT imaging of intratumor activity in I-131 radioimmunotherapy was investigated using experimental point source measurements and photon transport simulations. I-131 imaging is challenging because the primary photon emission is at 364 keV and penetration through the insert near the pinhole aperture is significant. Point source response functions (PSRF's) for lead (Pb) and tungsten (W) pinhole inserts were measured experimentally. These response functions were simulated using a photon transport computer code that modeled the primary emission at 364 keV and secondary emissions at 284, 637, and 723 keV. Scatter within the pinhole insert, camera shielding, and scintillation crystal was modeled. There was good agreement between the experimental and simulated PSRF's. Simulated point source response functions for geometrically identical Pb and W pinhole inserts were narrower for the W insert due to reduced penetration. SPECT pinhole imaging with these inserts was simulated for 3-cm-diameter tumors with a central core and 3-5-mm-thick shells. For one set of simulations there was no core activity, and for a second set the shell:core activity concentration ratio was 5:1. In both cases, the tumor shells were better resolved with the W insect. As a result, shell:core activity ratios were more accurate and contrast was improved with the use of the W pinhole insert. This study suggests that W inserts have potential advantages over Pb inserts for high-resolution I-131 pinhole imaging     

Determination of fuel burnup distribution of a research reactor based on measurements at subcritical conditions

This paper presents the determination of the fuel burnup distribution of the Dalat nuclear research reactor(DNRR) using a method of measurements at subcritical conditions. The method is based on the assumption of linear dependence of the reactivity on the burnup of fuel bundles and the measurements at subcritical conditions.The measurements were taken for seven selected fuel bundles in two different measuring sequences. The measured burnup values have also been compared with the calculations for verifying the method and the measurement procedure. The results obtained with the three detectors have a good agreement with each other with a discrepancy less than 1.0%. The errors of the measured burnup values are within 6%. Comparison between the calculated and measured burnup values shows that the discrepancy of the C/E ratio is within 9% compared to unity. The results indicate that the method of measurements at subcritical conditions could be well applied to determine the relative burnup distribution of the DNRR.     

Use of the MCNP-polimi code for time-correlation safeguards measurements

Active nuclear safeguards measurements that rely on the time correlation between fast neutrons and gamma rays from the same fission are becoming a useful technique. In previous works we have shown the feasibility of this method, in conjunction with the use of the well-known MCNP simulation code and the use of artificial neural networks, to estimate the mass and enrichment of fissile samples enclosed in special, sealed containers.

In a more recent works, we pointed out some features of MCNP that represent a drawback in the simulation of correlation measurements. In fact, MCNP is not intended for obtaining second order moments. Therefore, to achieve an agreement between the simulations and the experiment, we resorted to the use of effective physical parameters (for example detection threshold and light output). Recently, by suitably modifying MCNP, we developed the MCNP-PoliMi code, which attempts to simulate the physics of each interacton more realistically.

In this paper, we present the results of the calibration of a plastic scintillator using a Cf-252 source, traditionally used in the above-mentioned nuclear safeguards experiments. We show that the physical parameters found by calibration and used in the MCNP-PoliMi simulations are reasonable for this type of detector, and that the correlation functions thereby obtained are in good agreement with the experiment.     

System for optimizing activation measurements

Mining Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 6, pp. 482-492, December, 1992.     

Selection criteria for the best secondary water chemistry

This paper describes, for PWR plants, the approach for selecting the best chemistry—pH, amine, corrosion inhibitors—according to the secondary system characteristics, such as presence or not of copper alloys, steam generator tubing alloy, tube support plate design, sludge pile importance. The impact of condensate polisher, sludge lancing, chemical cleaning, as well as other ways of eliminating undesirable compounds or mitigating them are also discussed.For plants with simultaneous presence of carbon steel and copper alloys, alternate amines like morpholine, or new reagents such as ethanolamine (ETA), can be selected to manage erosion-corrosion of carbon steel and decrease corrosion transport, at a pH acceptable for copper alloys (9.2 at 25 °C).In more recent units, with an all ferrous system, a high pH operation, with only hydrazine addition, the easiest way, or with combined hydrazine and morpholine or ETA will be of some benefit against steam generator corrosion.When Alloy 600 has been selected, inhibitors such as boric acid, or maybe titanium oxide or cerium in the future, needs to be added in steam generators in order to decrease intergranular corrosion progression.In addition, caustic and lead contaminations must be strictly avoided, while sludge and deposits will be eliminated by lancing and chemical cleaning, if necessary.     

脉冲XeCl激光与K9光学玻璃相互作用中反射光波形的测量与分析

选用K9光学玻璃作为靶材料,在不同环境气压条件下利用高功率XeCl准分子激光进行了打靶实验,测量得到了不同气压条件下靶面的反射光波形,分析反射光波形表明,气压对K9玻璃靶前等离子体的形成和发展有着重要的影响。     

Computer simulation of transmission sputtering of thin films and experimental measurements of recoil implantation of gold into silicon

Transmission sputtering of thin (up to 300 Å) gold films bombarded by 10 to 20 keV Ar ions is simulated by using the MARLOWE computer code. The energy spectra, angle of ejection and depth of origin distributions of ejected particles are presented. The results indicate that even for a thin film the cascading of the recoils is sufficient to produce an E^?2 energy spectrum and a cosine angular distribution. The evaluated transmission-sputtering yields for various film thicknesses are compared with the amount of gold retained in a silicon substrate in dynamic recoil mixing experiments.