Investigation of radiation-induced surface activation effect in austenitic stainless steel under ultraviolet and γ-ray irradiations

The radiation-induced surface activation (RISA) effect will be applied to the core design in supercritical light water reactor (SCWR) in order to achieve a high performance with excellent economy and safety. The purpose of the present study is to investigate the RISA effect in the candidate fuel cladding materials in SCWR such as PNC1520. The change of weldability due to RISA effect and the related microstructure analysis were performed in oxidized PNC1520 and 304 stainless steel with various oxidization periods. The phases contained in the surface oxide layer of the present specimen were identified as Fe₂CrO₄, γ-Fe₂O₃, and Fe₂O₃. The lifetime of 13.8 days for wettability improving factor was confirmed in the ultraviolet (UV) irradiation. Meanwhile, the long life of 13.8 days and short life of 0.8 days for wettability improving factors were identified in the γ-ray irradiation. Based on the fact that the band gap energies of Fe₂CrO₄, γ-Fe₂O₃, and Fe₂O₃ were, respectively, 2.1, 2.0, and 2.2 eV, and the photo energies of UV and γ-ray irradiation were 4.48 eV and 13.3 MeV, it is therefore clarified that the hydrophilization on the oxide layer is ascribed to the RISA effect.     

Reduction of self-heating effect in SOI MOSFET by forming a new buried layer structure

An inherent self-heating effect of the silicon-on-insulator (SOI) devices limits their application at high current Ievels. In this paper a novel solution to reduce the self-heating effect is proposed, based on N+ and O+ co-implantation into silicon wafer to form a new buried layer structure. This new structure was simulated using Medici program, and the temperature distnbution and output characteristics were compared with those of the conven-tional SOI counterparts. As expected, a reduction of self-heating effect in the novel SOI device was observed.     

Radiogenotoxicological effect of signal nuclide 134Cs on somatic and germ cells

Chromosome at aberation rates in bone marrow cells and micronucleus formation in bone marrow polychromatic erythrocytes both rise with increase in radioactivities of 134Cs,and can be fitted to power functions of radioactivities of 134Cs.In spermatogonia 134Cs mainly induced chromatid breakage,and abnormalities in sperm can also be experessed as power functions of radioactivities of 134 Cs.     

Uptake of phosphorus by ryegrass and effect of adding organic matter on inorganic P absorption in red soil

^32-Plabelled KH2PO4 with or without unlabelled ryegrass and ^32P-labelled ryegrass with unlabelled KH2PO4 were respectively applied to red soil,and ryegrass was grown in the fertilized oil and harvested one month after sowing and then the radioactivities and total P content in ryegrass were measured.Results show that addition of organic matter to red soil can significantly stimulate the uptake of P by ryegrass seedlings from inorganic P applied to red soil;absorption of P from inorgain source is much greater than that from organic source;at the same application level of P,larger proportion of P derived from labelled inorganic phosphate was distributed in shoots than that from the labelled ryegrass.     

Metabolic peculiarity of 134Cs and its radioimmunotoxicological effect on central and peripheral immune cells

A fitted equation with least square method to describe the retention of ^134Cs in whole body is obtained by a whole body counter.That is R(t)=18.04exp(-9.3175t) 45.13exp(-0.0423t),where R(t) is in %,and t in d.The equationn consists of two half-life components,the fast component is T1/2=0.07d,and the slow is T1/2=16.14d,Study on the localization of ^134Cs at cellular level was carried out by freezing microautoradiography.The results indicate of ^134Cs at cellular level was carried out by freezing microautoradiography.The results indicate that ^134Cs was chiefly in ionizing form accumulated in red as well as white blood cells.In bone marrow cells ^134Cs predominantly deposited in young cells and less in mature cells.Distribution of ^134Cs penetrated quickly into the tissue cells.The observation of investigating radioimmunotoxicological effect induced by ^134Cs shows that the inhibition of thymocytes is higher than bone marrow cells,the spleen T lynmphocytes are more sensitive to ^134Cs than B lymphocytes and lymphocytes of peripheral immune cells are more sensitive to radiation than central immune cells.     

Sustained mutagenic effect in bone marrow cells induced by signal nuclide ~(134)Cs retention in skeleton

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Inhibition of NF-KB activity in rabbit vascular smooth muscle cells by lovastatin

Nuclear factor NF-KB is believed to play an important role in regulating the production of matrix met-alloproteinases (MMPs), which induce atherosclerosis, restenosis and plaque rupture. We incubated rabbit vascular smooth muscle cells(RVSMCs)with 5 nmol/L lovastatin in the presence of IL-1-a and PDGFBB (20g/L, respectively) to study whether lovastatin inhibited NF-KB binding activity induced by IL-1 and PDGF. The NF-KB activity was detected by electrophoretic mobility shift assay (EMSA); MMP-1 and MMP-3 were measured by western blotting; and MMP-9 was detected by zymography. The result showed that lovastatin strongly reduced NF-KB activity upregulated by IL-1 combined with PDGF, and lovastatin also dose-dependently inhibited the expression of MMP-1, -3 and -9 induced by IL-1 and PDGF. It suggested that the beneficial effects of statins may extend to mechanisms beyond cholesterol reduction.     

Determination of energy absorption in a mixed flux of fast neutrons and γ-rays by an ionization method

The possibility of separate determinations of the energy absorption of fast neutrons and -rays in the mixed radiation flux from a reactor has been studied with ioni/ation chambers. Three chambers with different hydrogenous fillers were used: polyethylene with an ethylene filler; graphite with a CO₂ filler and a chamber made from aerion, a conducting plastic, which was filled with a mixture of ethylene and CO₂. Calculations have been carried out to ascertain the sensitivity of these chambers to neutrons with energies ranging from 0.2–8 Mev. Variation of the neutron spectrum over wide limits has no effect on the accuracy in the determination of the absorbed dose in the hydrogenous substrates. A calculation shows that the error in the determination of the absorbed energy for fast neutrons is approximately 15% and is a weak function of the relative doses of neutrons and -rays.In conclusion the authors wish to express their gratitude to Yu. F. Chernilin for help in this experiment and T. B. Radzievskii for discussion of the results.     

Peroxidation of Polymethylhydrogensiloxane and Cellulose by γ-Irradiation in Air and Grafting Induced by Their Decomposition

The peroxides of polymethylhydrogensiloxane, cellulose and a mixture of both were determined by ferrous ion method. The relation between the decomposition of the peroxide and the degree of grafting by standing at an elevated temperature after irradiation was examined.

The G-value for the peroxide formation of polymethylhydrogensiloxane was found to be 8.7, and the activation energy for the peroxide decomposition was determined from calculation to be 43 kcal/mol. The ratio of G-values of silicone between those terminated by methyl radical and by methyl radical is estimated to be about 2/1. It would thus appear certain that the rate of peroxidation is affected by the end group. The peroxidation is not a chain reaction at room temperature, and the peroxide is produced by the recombination of the peroxy radical. At least two types of peroxide are produced by irradiation in air, and one is decomposed at 80°C but the other is relatively stable.

On the other hand, the G-value for the peroxide formation of cellulose is equal to 5.6.

The tendency seen for the decrease of the peroxide corresponds to that of increasing degree of grafting, and it may be concluded that only 1/10 of the peroxides formed in the cellulose–silicone system results in grafting, since it has been calculated that the G-value for the grafting through the peroxide is about 1.0.     

Killing effect of Chinese hamster V79 cells exposed to accelerated carbon ions and RBE determination

Survival curves of Chinese hamster V79 cells exposed to accelerated carbon ions with linear energy transfers of 125.5, 200 and 700keV/μm were measured, respectively. Inactivation cross sections corresponding to the irradiation above were deduced from the V79 cell survival curves. They are 7.86±0.17, 10.44±1.11 and 32.32±3.58μm2 in turn. With the surviving response of V79 cells to 60Co γ-rays as a reference value, relative biological effectiveness at 10%, 20%, 50% and 80% survival levels were given for the accelerated carbon ions. The results showed that carbon ions with LET of 125.5keV/μm had a higher value of RBE at all the four survival levels than the carbon ions with other LETs. It was prompted that the maximum value of RBE for the V79 cell surviving as the biological endpoint emerged at the LET below 200 keV/μm for carbon ions.     

Comparison of DNA double—strand breaks induced by ^16O^8＋ in deproteinized DNA and intact cells

The yield of DNA double-strand breaks(DSBs) is sure to be influenced by the environment around DNA molecule.Inverse pulsed-field gel electrophoresis(PIGE)has been applied to compared the sensitivity of B16 cells and their DNA in DSBs induced by 75MeV/u 16O^8 beam.Results show that the percentages of DNA released from the plug(PR)in both kinds of the samples increase with the dose and approach a similar quasi-threshold of about 81%.A simple new equation was presented to calculated the break level of DNA molecules.Within a certain dose,the relationship between the break level and the dose is linear.THe yield of DSBs in deproteinized DNA was 1.11DSBs/100Mbp/Gy,while that in intact cells was 0.60DSBs/100Mbp/Gy.it is testified that deproteinized DNA is more sensitive to oxygen ions irradiation than intact cells.     

The effect of a strong magnetic field on the magnetohydrodynamic stability of plasma and the containment of charged particles in the “Tokamak”

Results of an investigation of plasma in the toroidal apparatus TM-2 in a strong longitudinal magnetic field (up to 22 kOe) are described. It is shown that increasing the magnetic field sharply decreases the low frequency oscillations in the oscillograms of the loop voltage and discharge current derivative, and also weakens the interaction between the plasma and the wails of the discharge chamber.For a large enough ratio of the longitudinal field intensity to the intensity of the current selffield, oscillations are not observed. According to radiointerferometric measurements, the mean electron density in this case hardly alters during the course of the operations. The conductivity reaches a value of about 10¹⁶ cgs.Translated from Atomnaya Énergiya, Vol. 15, No. 5, pp. 363–369, November, 1963     

Locating and Transferring of Uranium-Bearing Particles in Swipe Samples by Fission Track and Micromanipulation

Fission track and micromanipulation technique is an effective method for locating and transferring of the uranium-bearing particles in swipe samples. It is very important especially for sparse samples. So this technique was studied and established in our …     

Locating and Transferring of Uranium-Bearing Particles in Swipe Samples by Fission Track and Micromanipulation

Fission track and micromanipulation technique is an effective method for locating and transferring of the uranium-bearing particles in swipe samples. It is very important especially for sparse samples. So this technique was studied and established in our laboratory. The method includes two steps as follows：     

Separation-purification of U and Pu in Environmental Samples by TOPO Extraction Chromatography

A method for separation and purification of U and Pu in environmental samples by TOPO extraction chromatography was investigated. 20 mL 2 mmol/L ascorbic acid-1.5 mol/L HCOOH and 30 mL 0.8 mol/L (NH4)2CO3 were used to elute Pu and U correspondingly, and t…     

Magnetic Sensorless Control of Plasma Position and Shape in a Tokamak

Magnetic sensorless sensing and control experiments with the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made to focus on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem with the integrator of wagnetic sensors. Two kinds of control experiments have been carried out： to keep the position constant and swing the position in a triangular waveform, And magnetic sensorless sensing of plasma shape is discussed.     

Monte-Carlo Calculation of the γ-Ray Dose Distribution Inside a Wall of a Building and in Air

The Monte Carlo method is used to calculate the coefficients used to convert from the measured (using retrospective luminescence dosimetry) -ray dose inside the wall of a building to the dose in air. The -ray dose distributions in the wall and in air were calculated simultaneously. The calculations were performed for a -ray sources located in air, on the surface of soil, and in a 0–5 cm thick top layer of soil. The -ray spectra in air and inside a wall are calculated and it is shown that the spectrum depends strongly on the type of source – the average energy of the spectrum is 0.25 MeV for a source located on a soil surface, 0.39 MeV for a source located inside the soil, and 0.53 MeV for a source located in air.     

Diagnostics of electron temperature and ions distribution in expanding Al plasmas pumped by a ns-pulsed 1.06μm laser

1. IntroductionX-r8y spectroscopy can provide much informationabout the plasma parameters, and it is often usedas a diagnostic tool for hot plasmas [1]. Resonancelines, such as Ly a and He cr, are often used for theanalysis of soft xrny spectra from highly--chargedplasmas [2,3,4,5,6], and their adjacent dielectronicsatellite lines are used to investigate the line opac-ity and intensity distribution of these resonance Iines[7,8,9,l01. In fact, dense plasmas produced by a ns-pulsed laser are op…     

Coupling effect between film boiling heat transfer and evaporation drag around a hot-particle in cold liquid

Extremely rapid evaporation could occur when high-temperature particles contact withlow-temperature liquid. This kind of phenomenon is associated with the engineering safety and the problems in high-transient multi-phase fluid and heat transfer. The aim of our study was to design and build an observable experiment facility. The first series of experiments were performed by pouring one or six high-temperature particles into a low saturated temperature liquid pool. The particle's falling-down speed was recorded by a high-speed camera, thus we can find the special resistant feature of the moving high-temperature particles, which is induced by the high-speed evaporation surrounding the particles. The study has experimentally verified the theory of evaporation drag model.