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Stencil contact printing is widely used to fabricate conductive patterns, and it is particularly used with solder paste to create interconnections. However, stencil contact printing is becoming inefficient for electronic components owing to the ever decreasing size of the components. An alternative method for fine pattern formation is screen printing, i.e. gap printing with a screen mask, which exploits the thixotropic characteristics of solder paste. Nevertheless, the mesh of the screen mask prevents the paste from permeating, resulting in irregular patterns. To address this issue, we propose gap printing with a mesh-cut screen mask. In this paper, we describe the fabrication procedure of the mask, and demonstrate the effectiveness of the proposed printing in the formation of fine and thick circular patterns; the patterns are shown to have low variations in size compared with conventional printing methods. The proposed method is expected to contribute to the further miniaturisation of electronic devices.

The effect of cold working on the corrosion behavior of austenitic stainless steels in liquid lead–bismuth eutectic (LBE) was studied to develop accelerator-driven systems for the transmutation of long-lived radioactive wastes and lead–bismuth cooled fast reactors. Corrosion tests on solution-treated, 20% cold-worked and 50% cold-worked 316SS and JPCA (15Cr–15Ni–Ti) were conducted in oxygen-controlled LBE. Slight ferritization caused by Ni dissolution and Pb–Bi penetration were observed for all specimens in the corrosion test conducted at 500 °C for 1000 h in liquid LBE with an intermediate oxygen concentration (1.4 × 10 −7 wt.%). In the corrosion test performed at 550 °C for 1000 h in liquid LBE with a low oxygen concentration (4.2 × 10 −9 wt.%), the depth of the ferritization of 316SS and JPCA increased with the extent of cold working. Only oxidation was observed in the corrosion test that was performed at 550 °C for 1000 h in liquid LBE with a high oxygen concentration (approximately 10 −5 wt.%). Cold working accelerated the formation of the double layer oxide and increased the thickness of the oxide layer slightly. In contrast, the ferritization accompanied by Pb–Bi penetration was widely observed with oxidation for all specimens corrosion tested at 550 °C for 3000 h under the high-oxygen condition. Cold working increased the depth of the ferritization of 316SS and JPCA. It is considered that cold working accelerated the ferritization and Pb–Bi penetration through the enhanced dissolution of Ni into LBE due to an increase in the dislocation density under conditions in which the protective oxide layer was not formed in liquid LBE.

The corrosion behavior of Si-enriched steels in liquid lead–bismuth was studied in order to develop accelerator driven systems for transmutation of long-lived radioactive wastes and lead–bismuth cooled fast reactors. The corrosion tests of 316SS, Si-enriched 316SS, Mod.9Cr–1Mo steel (T91) and Si-enriched T91 were conducted at 550 °C in liquid lead–bismuth at the two controlled oxygen levels. Both the additions of 2.5 wt.% Si to 316SS and 1.5 wt.% Si to T91 had the effect of reducing the thickness of oxide layer in liquid lead–bismuth at the high oxygen concentration (2.5 × 10 −5 wt.%). Although the Si addition to 316SS reduced the depth of ferritization caused by Ni dissolution in liquid lead–bismuth at the low oxygen concentration (4.4 × 10 −8 wt.%), it could not suppress the ferritization and the penetration of Pb and Bi completely. The Si addition to T91 did not have the effect of preventing the penetration of Pb and Bi in the liquid lead–bismuth at the low oxygen concentration. The oxide scales formed on both Si-enriched steels did not have sufficient corrosion resistance under the low oxygen condition.

An Al-alloy coating method using Al, Ti and Fe powders and the laser beam heating has been developed for nuclear systems using liquid lead–bismuth eutectic (LBE). Main defects formed in the coating process were surface defects and cracks. It was effective to decrease a laser beam scanning rate to 20 mm/min to avoid surface defects. It was necessary to adjust the Al concentration in the coating layer to be lower than 12 wt.% in order to avoid significant cracking. A static corrosion test was conducted in liquid LBE at the controlled oxygen concentrations of 10 −6 –10 −3 wt.% at 550 °C for 3000 h. The Al-alloy coating layer on 316SS prevented severe corrosion attack such as Ni dissolution, partial loss of grains and LBE penetration which were observed in 316SS without Al-alloy coating. Liquid LBE penetrated into the surface defects formed in the Al-alloy coating layers produced using a laser beam with the scanning rate of 60 mm/min. The Al-alloy coating layer, which was formed without surface defects and cracks under the optimum condition of the scanning rate of 20 mm/min, exhibited good corrosion resistance in liquid LBE.

Reduction of burden caused by radioactive waste management is one of the most critical issues for the sustainable utilization of nuclear power. The Partitioning and Transmutation (P&T) technology provides the possibility to reduce the amount of the radiotoxic inventory of the high-level radioactive waste (HLW) dramatically and to extend the repository capacity. The accelerator-driven system (ADS) is regarded as a powerful tool to effectively transmute minor actinides (MAs) in the “double-strata” fuel cycle strategy. The ADS has a potential to flexibly manage MA in the transient phase from light water reactors (LWRs) to fast breeder reactors (FBRs), and can co-exist with FBR symbiotically and complementarily to enhance the reliability and the safety of the commercial FBR cycle. The concept of ADS in JAEA is a lead–bismuth eutectic (LBE) cooled, tank-type subcritical reactor with the power of 800 MWth driven by a 30 MW superconducting LINAC. By such an ADS, 250 kg of MA can be transmuted annually, which corresponds to the amount of MA produced in 10 units of LWR with 1 GWe. The design study was performed mainly for the subcritical reactor and the spallation target with a beam window. In Japan, Atomic Energy Commission (AEC) has implemented the check and review (C&R) on P&T technology from 2008 to 2009. In the C&R, the benefit of P&T technology, the current status of the R&D, and the way forward to promote it were discussed.

The static corrosion tests in lead–bismuth eutectic (LBE) were conducted from 450 °C to 600 °C to understand corrosion behavior and develop corrosion resistant materials for heavy liquid metal systems. While increase of Cr content in steels enhances corrosion resistance in LBE, the effect approaches a constant value above 12 wt% of Cr. Corrosion depth in LBE increases with increasing temperature and corrosion attack becomes severe above 550 °C even under the condition of high oxygen concentration. Nickel dissolution and Pb–Bi penetration occur in 316SS and JPCA above 550 °C under the condition of high oxygen concentration. When oxygen concentration decreases below the level of Fe oxide formation, corrosion attack on these steels also becomes violent due to dissolution of various elements and grain boundary corrosion. Whereas additions of 1.5 wt% Si to T91 and 2.5 wt% Si to 316SS improve corrosion resistance, the effect is insufficient taking fluctuation of oxygen concentration in LBE into consideration. Furthermore, addition of 1.5 wt% Si to T91 causes rise in DBTT. A new coating method using Al, Ti and Fe powders produces corrosion resistant coating layers on 316SS. The coating layers containing 6–8 wt% Al exhibit good corrosion resistance at 550 °C for 3000 h in LBE containing 10−6–10−4 wt% of oxygen.

A new Al-alloy coating method using Al, Ti and Fe powders has been applied to 316SS in order to develop corrosion resistant coating in liquid lead-bismuth eutectic (LBE). The 316SS plates with coating layers of different Al concentrations were exposed to liquid LBE with controlled oxygen concentrations of 10−6 to 10−4 mass% at 823 K for 3600 ks. While surface oxidation and grain boundary corrosion accompanied by liquid LBE penetration are observed in 316SS without Al-alloy coating, the Al-alloy coating is effective to protect such severe corrosion attacks in liquid LBE. Although the coating layer containing 2.8 mass% Al does not always keep sufficient corrosion resistance, good corrosion resistance is obtained through the Al-oxide film formed in liquid LBE in the coating layer where the average Al concentration is 4.2 mass%. Cracks are formed in the coating layer containing 17.8 mass% Al during the coating process. The Al-powder-alloy coating applied to 316SS is promising as a corrosion resistant coating method in liquid LBE environment.

The conceptual design study of the beam window of the spallation target is one of the critical issues in the R&D of the accelerator-driven system (ADS). In this study, the investigation to create a feasible concept of the beam window for the ADS was performed by changing the proton beam profile from the Gaussian distribution to the parabolic and the flat distributions. Detailed analyses were performed by considering the particle transport of protons and neutrons in the spallation target region, the thermal hydraulics of lead bismuth eutectic (LBE) around the beam window, and the structural strength of the beam window. The calculation results showed that the difference in the temperature between the inner and outer surfaces at the top of the beam window was reduced by changing the beam profile from the Gaussian to the parabolic and the flat distributions. By this reduction, in the parabolic case, the thermal stress at the top position was also reduced and the buckling pressure increased by about 20%. On the other hand, in the flat case, the thermal stress at the peripheral region instead of at the central position increased and the buckling pressure slightly deteriorated. The buckling mode was also changed in the flat case. From these calculation results and discussions, it was confirmed that all three cases, the Gaussian, the parabolic, and the flat, were feasible and it was concluded that the concept with the parabolic distribution would be the most feasible under the current ADS design condition.

Control of oxygen concentration in liquid lead–bismuth is one of the most important tasks to develop accelerator driven systems. In order to improve the reliability of oxygen sensors, re-activation treatments were investigated as well as characterization of oxygen sensors for use in liquid lead–bismuth. The oxygen sensor with a solid electrolyte of yttria-stabilized zirconia and a Pt/gas reference electrode showed almost the same electromotive force values in gas and liquid lead–bismuth, respectively, as the theoretical ones at temperatures above 400 °C or 450 °C. After long-term use of 6500 h, the outputs of the sensor became incorrect in liquid lead–bismuth. The state of the sensor that indicated incorrect outputs could not be recovered by cleaning with a nitric acid. However, it was found that the oxygen sensor became a correct sensor indicating theoretical values in liquid lead–bismuth after re-activation by the Pt-treatment of the outer surface of the sensor.

Corrosion tests of ferritic/martensitic (F/M), austenitic stainless and Si-added austenitic steels were conducted at 450 to 600°C for 2000 h or 3000h in oxygen-saturated lead-bismuth eutectic (LBE) to clarify temperature effect on corrosion behavior. While the corrosion depth is small at 450°C because of oxide film formation with low growth rate, it increases at 500°C due to additional grain boundary corrosion/internal oxidation and node formation. At 550°C, extensive grain boundary corrosion/internal oxidation is observed in F/M steels. Ferritization characterized by selective dissolution of Ni and Cr, and LBE penetration occurs in austenitic stainless steels, JPCA and 316SS. Corrosion attack becomes very severe for most steels at 600°C. LBE penetration follows grain boundary corrosion/internal oxidation in F/M steels and ferritization advances deeply in JPCA and 316SS. The compound corrosion layer of oxidation, dissolution and LBE penetration often peels off. Addition of Si to austenitic steels is useful to improve corrosion resistance.

In the present neutronics design of the Accelerator-Driven System (ADS) cooled by lead-bismuth eu-tectic (LBE), we investigated several methods to reduce the power peak and beam current, and estimated the temperature reductions of the cladding tube and beam window from the conventional design. The methods are adjustment of inert matrix ratio in fuel in each burn-up cycle, multiregion design in terms of pin radius or inert matrix content, and modification of the level of the beam window position and the height of the central fuel assemblies. As a result, we optimized the ADS combined with the adjustment of the inert matrix ratio in each burn-up cycle, multiregion design in terms of inert matrix content and deepened window level. The maximum temperatures of the optimized ADS at the surface of the cladding tube and the beam window were reduced by 91 and 38°C, respectively. The maximum beam current was improved from 20.3 to 15.6 mA.

The feasibility for the lead-bismuth-cooled accelerator-driven system (ADS) to transmute minor actinides partitioned from high-level radioactive waste is discussed. Since lead-bismuth will cause co...

Corrosion tests in pots were conducted to elucidate corrosion behavior of various steels in liquid lead–bismuth for 3000 h under the condition of an oxygen concentration of 5 × 10 −8 wt% at 450 °C and an oxygen concentration of 3 × 10 −9 wt% at 550 °C, respectively. Significant corrosion was not observed at 450 °C for ferritic/martensitic steels, F82H, Mod.9Cr–1Mo steel, 410SS, 430SS except 2.25Cr–1Mo steel. Pb–Bi penetration into steels and dissolution of elements into Pb–Bi were severe at 550 °C even for ferritic/martensitic steels. Typical dissolution attack occurred for pure iron both at 550 °C without surface Fe 3 O 4 and at 450 °C with a thin Fe 3 O 4 film. Ferritization due to dissolution of Ni and Cr, and Pb–Bi penetration were recognized for austenitic stainless steels, 316SS and 14Cr–16Ni–2Mo steel at both temperatures of 450 °C and 550 °C. The phenomena were mitigated for 18Cr–20Ni–5Si steel. In some cases oxide films could not be a corrosion barrier in liquid lead–bismuth.

Corrosion tests of CrN-coated steels for nuclear reactors were conducted in liquid lead-bismuth (Pb-Bi) at 450°C and 550°C for 3000 h to investigate the applicability of CrN coating to a liquid Pb-Bi environment. CrN coatings on F82H (Fe-8Cr-2W-0.3V-0.04Ta-0.1C) and 316SS exhibited good compatibility in liquid Pb-Bi during corrosion test at 450°C. The CrN coating layer suffered heavy damage such as cracking and spalling, and showed no effectiveness as a protective layer in corrosion test at 550°C. Nickel and chromium in 316SS dissolved into Pb-Bi through the damaged coating layer at 550°C. The cracking and spalling were not found after heating CrN-coated steels in Ar gas at 550°C. It is considered that stresses caused by the difference of thermal expansion coefficients between CrN and steels led to cracking and spalling of the CrN coating through corrosion attack by liquid Pb-Bi at 550°C.

Corrosion tests of CrN-coated steels were conducted in liquid lead-bismuth (Pb-Bi) at 450°C and 550°C for 3000 h to investigate the applicability of CrN coating to a liquid Pb-Bi environment. CrN coatings on F82H (Fe-8Cr-2W-0.3V-0.04Ta-0.1C) and 316SS exhibited good compatibility in liquid Pb-Bi during corrosion test at 450°C. The CrN coating layer suffered heavy damage such as cracking and spalling, and showed no effectiveness as a protective layer in corrosion test at 550°C. Nickel and chromium in 316SS dissolved into Pb-Bi through the damaged coating layer at 550°C. It is considered that stresses caused by the difference of thermal expansion coefficients between CrN and steels led to cracking and spalling of the CrN coating through corrosion attack by liquid Pb-Bi at 550°C.

Experimental study using the transpiration method investigates equilibrium evaporation behavior of radionuclide polonium (210Po) generated and accumulated in liquid lead-bismuth eutectic (LBE) cool...

JAERI is conducting R&D on the Accelerator Driven System (ADS) to transmute minor actinides (MAs). The present study discusses the design of the ADS plant and various R&D on the ADS. The reference design of ADS plant in JAERI is the 800 MW, Pb–Bi eutectic (LBE) cooled, tank-type subcritical reactor loaded with (MA+Pu) nitride fuel. LBE is selected as a spallation target material. In our results of the optimization study on the neutronics of the ADS, we have adopted the maximum multiplication factor ( k eff ) of 0.97. From the results of thermal-hydraulic and structural analysis, the feasibility of the beam window was confirmed for steady state. The R&D activities in JAERI cover the development of superconducting proton linear accelerator, the LBE technology, the irradiation damages of materials, and the reactor physics of the subcritical reactor.

Static corrosion tests of various steels were conducted in oxygen-saturated liquid Pb–Bi eutectic at 450 °C and 550 °C for 3000 h to study the effects of temperature and alloying elements on corrosion behavior in liquid Pb–Bi. Corrosion depth decreases at 450 °C with increasing Cr content in steels regardless of ferritic/martensitic steels or austenitic steels. Appreciable dissolution of Ni and Cr does not occur in the three austenitic steels at 450 °C. Corrosion depth of ferritic/martensitic steels also decreases at 550 °C with increasing Cr content in steels whereas corrosion depth of austenitic steels, JPCA and 316SS becomes larger due to ferritization caused by dissolution of Ni at 550 °C than that of ferritic/martensitic steels. An austenitic stainless steel containing about 5%Si exhibits fine corrosion resistance at 550 °C because the protective Si oxide film is formed and prevents dissolution of Ni and Cr.

An experimental study on the equilibrium evaporation of lead-bismuth eutectic (LBE) was conducted to acquire essential and fundamental knowledge about the vaporization of LBE. The experiments were conducted using the transpiration method in which saturated vapor in an isothermal evaporation pot was transported by inert carrier gas and collected outside of the pot. The weight of the LBE pool in the pot was about 500 g. The investigated temperature range was from 450 to 750° C. We obtained data on the saturated vapor pressure of LBE, the vapor concentration of Pb, Bi and Bi2 in the LBE saturated gas phase, the activity coefficient of Pb in the LBE, and the LBE evaporation rate. The LBE vapor pressure equation is represented by logP LBE(Pa)=10.2–10, 100/T(K) in the temperature range from 550 to 750°C.

Corrosion tests were performed in oxygen-saturated liquid Pb–Bi at 450 °C and 550 °C in a pot for 3000 h for Al-surface-treated steels containing various levels of Cr contents. The Al surface treatments were achieved using a gas diffusion method and a melt dipping method. Al2O3, FeAl2 and AlCr2 produced by the gas diffusion method exhibited corrosion resistance to liquid Pb–Bi, while the surface layer produced by the melt dipping method suffered a severe corrosion attack. Fe4Al13 and Fe2Al5 produced by the melt dipping method disappeared during the corrosion test at 550 °C and only FeAl remained.

Japan Atomic Energy Research Institute carries out research and development on accelerator-driven system (ADS) to transmute minor actinides and long-lived fission products in high-level radioactive waste. The system is composed of high intensity proton accelerator, lead-bismuth spallation target and lead-bismuth cooled subcritical core with nitride fuel. About 2500 kg of minor actinide is loaded into the subcritical core. Annual transmutation amount using this system is 250 kg with 800 MW of thermal output. This transmutation amount corresponds to the amount of minor actinides produced from 10 units of 1GWe power reactors annually. A superconducting linear accelerator with the beam power of 20–30 MW is connected to drive the subcritical core. To maximize the transmutation efficiency, the nitride fuel without uranium, such as (Np, Am, Pu)N, is selected. The nitride fuel irradiated in the ADS is reprocessed by pyrochemical process followed by the re-fabrication of nitride fuel. Many research and development activities are under way and planned in the fields of subcritical core design, spallation target technology, lead-bismuth handling technology, accelerator development, and minor actinide fuel development. Especially, to study and evaluate the feasibility of the ADS from physics and engineering aspects, the transmutation experimental facility (TEF) is proposed under a framework of the High-Intensity Proton Accelerator Project.

The corrosion properties of three austenitic steels with different Si contents were studied under oxygen-saturated liquid Pb–Bi condition for 3000 h. The three austenitic steels did not exhibit appreciable dissolution of Ni and Cr at 450 °C. At 550 °C, the thick ferrite layer produced by dissolution of Ni and Cr was found in JPCA and 316SS with low Si contents while the protective oxide film composed of Si and O was formed on 18Cr–20Ni–5Si steel and prevented dissolution of Ni and Cr.

Nippon Oil Exploration Ltd. farmed into the WA-191-P permit located in the Dampier Sub-basin, North West Shelf, off Australia in March, 1997. Exploration Well, Pitcairn-1 was drilled immediately after the farm-in, and oil was found at the top of Upper Jurassic Angel Formation sandstone. After the drilling of Pitcairn-1, it turned out that there is a marked difference in a time-depth relation between Pitcairn-1 and a nearby well previously drilled, and also that there is a lateral change on the stacking velocity map generated from 2D seismic data. The velocity trends were carefully reviewed with the existing check shot data and seismic stacking velocities, with the result that lateral change in p-wave velocity is conspicuous especially in the Tertiary Mandu Formation which mainly consists of carbonates, and this velocity change corresponds to the interval indicating a distinct clinoform, suggesting that the lithology laterally changes. Depth conversion using a newly constructed velocity model demonstrated the presence of another anticlinal closure with a low relief to the north of Pitcairn-1. For the better definition of depth mapping with dense velocity data, a new 3D seismic acquisition was conducted in the western part of WA-191-P including Pitcairn and other leads. After constructing a new depth map using a detailed velocity model utilizing this 3D seismic data, Mutineer, Norfolk and Exeter prospects were identified to the north, east and west of Pitcairn prospect respectively. Later, these prospects were drilled and oil was found in the Angel Formation, proving to have commercial size of oil accumulation. Currently, detailed studies are being conducted toward the development of the Mutineer/Pitcairn/Norfolk complex and Exeter oil fields by the Joint Venture Partners.

Lead bismuth eutectic (LBE) is favored by spallation neutron sources and coolant in the sub-critical reactor at the accelerator driven nuclear transmutation system (ADS). Technical issues of ADS are material technology of how to compromise with flowing lead bismuth, high-energy proton accelerator technology and a sub-critical reactor system technology. This paper describes LBE technology developed at JAERI. First a scenario in order to realize the ADS is shown. The concept of spallation target test facility is introduced with a target design of thermo-fluid dynamics. Base data of flow rate and temperature of Pb-Bi during LBE circulation are described. The results of LBE loop operation under the flowing conditions of target design concept are reported. The stagnant corrosion tests were done to know the controlling parameters among the various steels. The tube-type oxygen sensor with having the solid electrolyte was studied. Cleaning techniques were developed to remove LBE from materials.

Corrosion tests of austenitic stainless tube were done under flowing Pb–Bi conditions for 3000 h at 450 °C. Specimens were 316SS produced as a tubing form with 13.8 mm outer diameter, 2 mm thickness and 40 cm length. During operation, maximum temperature, temperature difference and flow velocity of Pb–Bi at the specimen were kept at 450, 50 °C, and 1 m/s, respectively. After the test, specimen and components of the loop were cut and examined by optical microscope, SEM, EDX, WDX and X-ray diffraction. Pb–Bi adhered on the surface of the specimen even after Pb–Bi was drained out to the storage tank from the circulating loop. Results differed from a stagnant corrosion test in that the specimen surface became rough and the corrosion rate was maximally 0.1 mm/3000 h. Mass transfer from the high temperature to the lower temperature area was observed: crystals of Fe–Cr were found on the tube surface in the low-temperature region. The sizes of crystals varied from 0.1 to 0.2 mm. The depositing crystals were ferrite grains and the chemical composition ratio (mass%) of Fe to Cr was 9:1.

The program of corrosion study in liquid Pb–Bi at Japan Atomic Energy Research Institute (JAERI) is described. It was planned to clarify effects of parameters such as temperature, temperature difference between high-temperature and low-temperature parts, oxygen concentration in liquid Pb–Bi, flow rate, irradiation, stress and chemical composition of materials. The program contains the basic corrosion study in static Pb–Bi for elucidation of corrosion mechanism and effects of oxygen concentration in liquid Pb–Bi and ion irradiation on corrosion behavior. It also contains the corrosion study in flowing Pb–Bi using a corrosion testing loop. From the initial result of the static corrosion tests in oxygen saturated Pb–Bi at 550 ° C for 500 h, it was shown that the thickness of the corrosion film decreases with increasing Cr content in steels.

Recent status of study on accelerator driven system (ADS) in Japan is presented. The double-strata fuel cycle concept has been proposed by Japan Atomic Energy Research Institute (JAERI) under the `OMEGA' program as a system for partitioning and transmutation (P&T) of long-lived radioactive nuclides. The ADS dedicated to transmutation is the key technology of the double-strata fuel cycle concept. The proposed system is a lead–bismuth cooled, nitride fuel 800 MW ADS for transmutation of minor actinides and long-lived fission products. JAERI has carried out a conceptual design study under the joint project between JAERI and KEK (High Energy Accelerator Research Organization) on high-intensity proton accelerators. In addition to a high-intensity proton accelerator complex, two experimental facilities are planned for development and demonstration of accelerator driven transmutation technology: The major objective of an ADS physics experimental facility is to obtain reactor physics data of hybrid subcritical system. The major objective of an ADS engineering experimental facility is to accumulate material data for the design of a lead–bismuth target system.

A series of weldability and creep tests of the weld metals were conducted to develop a filler metal with excellent weldability and high creep strength of the weldments of Ni-Cr-W superalloy. Contents of minor elements have a large effect on susceptibility to cracking in weldments. In particular, Zr, B, Y and Nb make the susceptibility to cracking high and addition of optimum contents of Ti or Mg reduce it slightly. A good correlation between values of the CSC (coefficient of susceptibility to cracking) of the filler metals and the weldability is recognized. On the basis of the knowledge, a filler metal with excellent weldability was developed for the Ni-18.5Cr-21W superalloy. The weld metal prepared using the developed wire possesses the creep rupture strength almost equal to that of the base metal which has a creep rupture strength above 9.8 MPa for a 1 × 10 5 h life at 1 000°C.

In addition to post-irradiation creep tests, in-pile creep tests were performed using newly developed technology with in situ measurement under different neutron spectra. The in-pile creep properties of type 304 stainless steel at 550°C appear to depend on neutron spectrum, but a spectral effect on post-irradiation creep properties is not clearly seen. The rupture time of in-pile creep under a high thermal neutron flux condition is the shortest. The order of the rupture time following the high thermal flux condition is post-irradiation creep, in-pile creep with a thermal neutron shield condition and finally creep of unirradiated material, all in increasing order. It is suggested that the acceleration of creep deformation and fracture observed in irradiation creep tests may be related to enhancement of thermal creep in terms of FMD increased under a high thermal neutron flux in addition to increased helium embrittlement.

Creep tests of base metal, weld metal and welded joint of Hastelloy XR, which had the same chemical composition as Hastelloy XR produced for an intermediate heat exchanger of the High-Temperature Engineering Test Reactor, were conducted in simulated primary coolant helium. The weld metal and welded joint showed almost equal to or longer rupture time than the base metal of Hastelloy XR at 850 and 900°C, although they gave shorter rupture time at 950° C under low stress and at 1,000°C. The welded joint of Hastelloy XR ruptured at the base metal region at 850 and 900°C. On the other hand, it ruptured at the weld metal region at 950 and 1,000°C. The steady-state creep rate of weld metal of Hastelloy XR was lower than that of base metal at 850, 900 and 950°C. The creep rupture strengths of base metal, weld metal and welded joint of Hastelloy XR obtained in this study were confirmed to be much higher than the design allowable creep-rupture stress (SR ) of the Design Allowable Limits below 950°C.

The creep rupture properties in air environment were studied at 900, 1000 and 1050°C for bar, plate and seamless tube materials of a NiCrW superalloy developed for use at service temperatures around 1000°C. The long-term creep rupture strength is estimated by applying the time-temperature parameter method to the creep rupture data. Data of anomalous behaviour due to oxidation strengthening, which is observed in creep curves with rupture times above ∼ 10 000 h at 1000°C, are corrected for the application of the time-temperature parameter method. The Larson-Miller parameter method is better than the Orr-Sherby-Dorn parameter method in respect of curve fitting to the present creep rupture data. The creep rupture strength of the bar material with grain sizes above ASTM No. 2 and of the plate material is above 9.8 MPa for a 1 × 105 h life at 1000°C, which is the final target of this program. The creep rupture strength increases with increasing grain size and heat treatment temperature.

The relationship between creep rupture lives and cavitation damage is examined in a welded Ni-base alloy, Hastelloy XR, in an impure He gas at 1123–1273 K. The rupture lives of the welded joints are almost the same as those of the base metal at lower temperatures of 1123–1173 K, whereas the former lives become shorter than the latter ones at higher temperatures of 1223–1273 K. Microstructural observations reveal that the activity of cavitation in the weld metal is lower than that in the base metal at the lower temperatures, resulting in failure at base metal region, whereas the former becomes higher than the latter at the higher temperatures, resulting in failure at the weld metal region. The enhanced activity of cavitation and the resultant diminished rupture lives in the welded joints can be attributed to the enhanced recrystallization of the weld metal at the higher temperatures.

The creep properties of Hastelloy XR, in solution-treated and in 20% cold-worked conditions, were studied at 800, 900 and 1000°C. At 800°C, the steady-state creep rate and rupture ductility decrease, while rupture life increases after cold work to 20%. Although the steady-state creep rate and ductility also decrease at 900°C, the beneficial effect on rupture life disappears. Cold work to 20% enhances creep resistance of this alloy at 800 and 900°C due to a high density of dislocations introduced by the cold work. Rupture life of the 20% cold-worked alloy becomes shorter and the steady-state creep rate larger at 1000°C during creep of the 20% cold-worked alloy. It is emphasized that these cold work effects should be taken into consideration in design and operation of high-temperature structural components of high-temperature gas-cooled reactors.

Additive-type printing techniques such as gravure-offset printing and screen printing are effective for low-cost and ecofriendly electrode pattern formation. Gravure-offset printing is effective for fine pattern formation with widths on the order of 10–20 µm, whereas screen printing is effective for the formation of large-area patterns. However, it is difficult to simultaneously form fine and large-area patterns using these printing techniques. In this study, we demonstrate that fine (minimum width of 15 µm) and medium- as well as large-area patterns can be formed simultaneously using our developed screen-offset printing technique, which is a combination of screen printing on a silicone blanket and transfer printing from the blanket to a substrate. Furthermore, we demonstrate the application of our method to printing on adhesive materials, which allows electrode formation without applying heat to the film substrate.

Small and medium reactors using lead alloys as coolants are one of the promising reactor concepts with improved safety because of their thermal-physical and chemical properties. This paper focuses on the development of Al-alloy coating for nuclear systems using liquid lead-bismuth eutectic (LBE). Since corrosion attack becomes severe against structural steels at high temperatures in liquid LBE, it is necessary to improve the corrosion resistance of steels. An Al-alloy coating method using Al, Ti, and Fe powders, and laser beam heating has been developed. The main defects formed in the Al-powder-alloy coating process are surface defects and cracks. The conditions required to avoid these defects are the employment of the laser beam scanning rate of 20 mm/min and the adjustment of the Al concentration in the coating layer. According to the results of the corrosion tests at 550 °C in liquid LBE, the Al-alloy coating layers on 316SS prevent severe corrosion attack such as grain boundary corrosion and LBE penetration observed in the 316SS without coating. The good corrosion resistance of the Al-alloy coating is based on the thin Al-oxide film, which can be regenerated in liquid LBE. From the viewpoint of the soundness of the produced Al-powder-alloy coating layers and the preservation of their corrosion resistance, it is estimated that the range of adequate Al concentration in the coating layer is from 4 to 12 wt. %.

Creep and rupture tests were conducted on Hastelloy XR (a modified version of the conventional Hastelloy X) at 1, 073, 1, 173 and 1, 273K in simulated high-temperature gas-cooled reactor helium. The test section of creep testing machine was designed and constructed with special care for impurity chemistry in helium. A device for counting Moire patterns was developed for contamination-free creep strain measurement. The test results up to 10, 000h showed no significant degradation in creep properties. Comparing the data on the stresses to rupture, to cause 1% total strain and to the onset of tertiary creep, the stress to cause 1% total strain is judged to be the dominant factor for the allowable stress (St) in the ASME Code. Carbon analysis for ruptured specimen showed that caburization was limited to the region near the ruptured portion and slight carbon intrusion occurred only in the early stage of exposure. Surface cracks were not responsible for creep-rupture, because they were blunted at the depth of approximately 100μm from the specimen surface at 1, 173K and 200μm at 1, 273K. Internally formed cracks were initiated at the sites of carbide precipitation at grain boundary, growing nearly perpendicular to the stress axis. Recrystallization observed was localized at 1, 173K but became pronounced at 1, 273K. Creep deformation enhanced coasening of the grain boundary carbide under tensile stress.

Liquid lead and lead-bismuth eutectic(LBE) are promising candidate materials as coolant of fast reactors with improved safety because of their good thermal-physical and chemical properties. Liquid LBE is also a primary candidate material for high-power spallation targets and coolant of accelerator driven systems (ADSs) for transmutation of long-lived radioactive wastes. In order to apply these liquid lead and LBE to nuclear systems, development of systems for controlling oxygen concentration in the liquid mediums is one of important research subjects (Gromov et al., 1999; Shmatko & Rusanov, 2000; OECD/NEA Handbool, 2007). Liquid lead and LBE are corrosive for steels at high temperatures and likely to cause plugging due to PbO formation in low-temperature components of systems. It is generally accepted that maintaining a certain level of oxygen concentration in them is crucial from the viewpoints of mitigating corrosion attack at high-temperature parts and avoiding PbO formation at low-temperature parts. The active oxygen control within the range between Fe3O4 and PbO formation has been proposed (Shmatko & Rusanov, 2000; Li, 2002; OECD/NEA Handbool, 2007). Effective control of the oxygen concentration requires devices for removing and adding oxygen in liquid lead alloys and oxygen sensors for monitoring the oxygen concentration. It is essential to measure oxygen concentration correctly in lead alloys online for the active oxygen control. Electromotive force measurement using oxygen sensors with a solid electrolyte is a useful means to measure oxygen concentration in liquid lead alloys. Oxygen sensors employing yttria-stabilized zirconia (YSZ) and magnecia-stabilized zirconia (MSZ) as a solid electrolyte enable us to measure oxygen concentration in lead alloys. While oxygen sensors using YSZ as a solid electrolyte and Pt/gas as a reference system are often used in automobile industries, the operating temperature of the sensors is generally rather high. It has been reported that oxygen sensors were used in liquid lead and LBE in Russia where research on nuclear systems using them has been conducted for a long term (Gromov et al., 1999; Shmatko & Rusanov, 2000). The special sensor using YSZ as a solid electrolyte and Mo/Bi-Bi2O3 as a reference system gave accurate measurement of oxygen concentration and long service lifetime(Shmatko & Rusanov, 2000). Recently, oxygen sensors for use in liquid lead alloys have been manufactured and examined worldwide.

Small and medium reactors using lead alloys as coolant are one of the promising reactor concepts with improved safety because of their thermal-physical and chemical properties. This paper focuses on development of Al-alloy coating for nuclear systems using liquid lead-bismuth eutectic (LBE). Since corrosion attack becomes severe against structural steels at high temperatures in liquid LBE, it is necessary to improve corrosion resistance of steels. An Al-alloy coating method using Al, Ti and Fe powders, and laser beam heating has been developed. Main defects formed in an Al-powder-alloy coating process are surface defects and cracks. Conditions required to avoid these defects are employment of the laser beam scanning rate of 20 mm/min and adjustment of the Al concentration in the coating layer. According to results of the corrosion tests at 550°C in liquid LBE, the Al-alloy coating layers on 316SS protect severe corrosion attack such as grain boundary corrosion and LBE penetration observed in 316SS without coating. The good corrosion resistance of the Al-alloy coating is based on the thin Al-oxide film which can be regenerated in liquid LBE. From the viewpoints of the soundness of produced Al-powder-alloy coating layers and preservation of their corrosion resistance, it is estimated that the range of the adequate Al concentration in the coating layer is from 4 to 12 wt%.Copyright © 2011 by ASME

Focal mechanisms around Ontake Volcano, central Japan, were investigated by using the data set obtained by a seismic observation project of the 1986 Joint Seismological Research in Western Nagano Prefecture (JSR'86). The data set included P-wave first motions of aftershocks of the 1984 Western Nagano Prefecture Earthquake (M=6.8) mainly. A total of 556 events was selected for the focal mechanism analysis. The P-wave data from the surrounding university routine networks were also utilized additionally. Four hundred two events were successfully analyzed. Based on the types of focal mechanisms and on the spatial distribution of the events, we classify these events into the following 4 groups: (1) events of strike-slip fault type with a common nodal plane parallel to the ENE-WSW striking nodal plane in the fracture zone of the 1984 main shock; (2) events of reverse fault type in the area of the preexisting earthquake swarm to the northeast of the main shock, in a possible relation with an earthquake swarm activated by the main shock; (3) events of reverse fault type that occurred near the largest aftershock (M=6.2), but are not the continued aftershock sequence of the largest aftershock; (4) events of strike-slip fault type at depths to the easternmost part where no activity had been observed before the operation of JSR'86. The plural types of focal mechanisms obtained and the spatial distribution of foci suggest a complex seismo-tectonic structure that consists of at least 2 kinds of fracturings around Ontake Volcano.

A dense temporary seismograph network was set up in the aftershock area of the 1984 Western Nagano Prefecture Earthquake of M 6.8 by the group for the 1986 Joint Seismological Research in Western Nagano Prefecture. Seismograms of about 1,500 events were obtained during the observation period of 52 days from September 1 to October 22, 1986, and 530 events in and around the aftershock area were located precisely. Extent of the aftershock area is about 20 km in the east-west and about 7 km in the north-south.

The detailed three-dimensional P and S wave velocity structure in the focal region of the 1984 Western Nagano Prefecture Earthquake occurring close to an active volcano, Mt. Ontake, central Japan, is derived from a tomographic inversion of travel time data obtained by the 1986 Joint Seismological Research in Western Nagano Prefecture. The data set includes 7, 693 P-wave and 6, 070 S-wave arrival times observed at 49 stations from 212 local earthquakes and 2 explosions. The velocities in the shallow portion of upper crust are determined at each grid point with its spacing of 1-2 km and good resolutions are obtained from the Earth's surface to a depth of 4 km. There exist strong lateral heterogeneities especially from the surface to a depth of 1 km. The seismic velocity map obtained in the height of 1 km above sea level well corresponds to the maps of surface geology and Bouguer gravity anomaly. This correspondence, however, is not so clear in the deeper layers. And, the greater the depth, the less heterogeneous the velocity structure. The velocity distribution on the fault seems to correspond to the distribution of dislocation and rupture front estimated from an analysis of strong motion and geodetic data: the low velocity region has the large amount of dislocation and the retarded rupture front.

The Japan Atomic Energy Research Institute (JAERI) is conducting the research and development (R&D) on the accelerator-driven subcritical system (ADS) for the effective transmutation of minor actinides (MAs). The ADS proposed by JAERI is an 800 MWth, Pb-Bi cooled, tank-type subcritical reactor loaded with nitride fuel (MA+Pu). Pb-Bi is also used as the spallation target. In this study, the feasibility of the ADS was discussed by focusing on the design around the beam window. The partition wall was placed between the target region and the ductless-type fuel assemblies to keep the good cooling performance for the hot-spot fuel pin. The flow control nozzle was installed to cool the beam window effectively. The thermal-hydraulic analysis showed that the maximum temperature at the outer surface of the beam window could be repressed below 500 C even in the case of maximum beam power (30 MW). The stress caused by the external pressure and the temperature distribution of the beam window was below the allowable limit.