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V-Cr-Ti alloys are among the leading candidate materials for the frost wall and other structural materials applications in fusion power reactors because of several important advantages including inherently low irradiation-induced activity, good mechanical properties, good compatibility with lithium, high thermal conductivity and good resistance to irradiation-induced swelling and damage [1]. However, weldability of these alloys in general must be demonstrated, and laser welding, specifically, must be developed. Laser welding is considered to be an attractive process for construction of a reactor due to its high penetrating power and potential flexibility. This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. The effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld.

An irradiation experiment has been done in the ATR-A1 to investigate irradiation behavior of vanadium alloys in the low temperature regime from 200°C to 300°C with damage levels of 3 to 4 dpa. In creep measurements, creep tubes of V–3Fe–4Ti–0.1Si with inner pressures up to 165 MPa did not rupture during irradiation. The effective strain rate of creep was below 0.2% dpa−1 and it showed the same tendency as V–4Cr–4Ti alloys. In Charpy impact tests, all specimens of V–4Cr–4Ti–0.1Si and V–3Fe–4Ti–0.1Si showed brittle behavior at room temperature and the DBTT increased to 60–150°C. The fracture surface showed cleavage. Tensile tests conducted both at room temperature and at the irradiation temperature showed significant irradiation hardening and brittle responses. TEM showed that high densities of tiny defect clusters were formed in V–Cr–Ti and V–Fe–Ti alloys. Precipitates could not be seen in specimens irradiated below 300°C, however, fine defect clusters are considered to be the origin of brittle behavior in V–Cr–Ti alloys irradiated at low temperatures.

Key features of fusion energy relate primarily to potential advantages associated with safety and environmental considerations and the near endless supply of fuel. However, high-performance fusion power systems will be required in order to be an economically competitive energy option. As in most energy systems, the operating limits of structural materials pose a primary constraint to the performance of fusion power systems. In the case of fusion power, the first-wall/blanket system will have a dominant impact on both economic and safety/environmental attractiveness. This paper presents an assessment of the influence of key candidate structural material properties on performance limits for fusion first-wall blanket applications. Key issues associated with interactions of the structural materials with the candidate coolant/breeder materials are discussed.

Vanadium-base alloys were irradiated in three experiments to determine the effects of low-temperature neutron irradiation on their mechanical properties. The properties studied were tensile, Charpy impact and irradiation creep. The result of this study showed the alloys tested incurred significant hardening and embrittlement due to the irradiation. Heat-to-heat variations appeared to have little effect on hardening and embrittlement. Creep strains were measured from the specimens and a preliminary data set on creep strain rate was generated.

The self-cooled lithium–vanadium fusion blanket concept has several attractive operational and environmental features. In this concept, liquid lithium works as the tritium breeder and coolant to alleviate issues of coolant breeder compatibility and reactivity. Vanadium alloy (V–4Cr–4Ti) is used as the structural material because of its superior performance relative to other alloys for this application. However, this concept has poor attenuation characteristics and energy multiplication for the DT neutrons. An advanced self-cooled lithium–vanadium fusion blanket concept has been developed to eliminate these drawbacks while maintaining all the attractive features of the conventional concept. An electrical insulator coating for the coolant channels, spectral shifter (multiplier, and moderator) and reflector were utilized in the blanket design to enhance the blanket performance. In addition, the blanket was designed to have the capability to operate at average loading conditions of 2 MW/m2 surface heat flux and 10 MW/m2 neutron wall loading. This paper assesses the spectral shifter and the reflector materials and it defines the technological requirements of this advanced blanket concept.

Two large heats of V–4Cr–4Ti alloy were produced in the US in the past few years. The first, 832665, was a 500 kg heat procured by the US Department of Energy for basic fusion structural materials research. The second, 832864, was a 1300 kg heat procured by General Atomics for the DIII-D radiative divertor upgrade. Both heats were produced by Oremet-Wah Chang (previously Teledyne Wah Chang of Albany). Tensile properties up to 800°C and Charpy V-notch impact properties down to liquid nitrogen temperature were measured for both heats. The product forms tested for both heats were rolled sheets annealed at 1000°C for 1 h in vacuum. Testing results show the behavior of the two heats to be similar and the reduction of strengths with temperature to be insignificant up to at least 750°C. Ductility of both materials is good in the test temperature range. Impact properties for both heats are excellent – no brittle failures at temperatures above −150°C. Compared to the data for previous smaller laboratory heats of 15–50 kg, the results show that scale-up of vanadium alloy ingot production to sizes useful for reactor blanket design can be successfully achieved as long as reasonable process control is implemented (H. Tsai, et al., Fusion Materials Semiannual Progress Report for Period Ending 30th June 1998, DOE/ER-0313/24, p. 3; H. Tsai, et al., Fusion Materials Semiannual Progress Report for Period Ending 31st December 1998, DOE/ER-0313/25, p. 3).

A self-cooled lithium-vanadium blanket concept capable of operating with 2 MW/m{sup 2} surface heat flux and 10 MW/m{sup 2} neutron wall loading has been developed. The blanket has liquid lithium as the tritium breeder and the coolant to alleviate issues of coolant breeder compatibility and reactivity. Vanadium alloy (V-4Cr-4Ti) is used as the structural material because it can accommodate high heat loads. Also, it has good mechanical properties at high temperatures, high neutron fluence capability, low degradation under neutron irradiation, good compatibility with the blanket materials, low decay heat, low waste disposal rating, and adequate strength to accommodate the electromagnetic loads during plasma disruption events. Self-healing electrical insulator (CaO) is utilized to reduce the MHD pressure drop. A poloidal coolant flow with high velocity at the first wall is used to reduce the peak temperature of the vanadium structure and to accommodate high surface heat flux. The blanket has a simple blanket configuration and low coolant pressure to reduce the fabrication cost, to improve the blanket reliability, and to increase confidence in the blanket performance. Spectral shifter, moderator, and reflector are utilized to improve the blanket shielding capability and energy multiplication, and to reduce the radial blanket thickness. Natural lithium is used to avoid extra cost related to the lithium enrichment process.

The self-cooled lithium blanket concept with a vanadium structure offers a potential for high performance with attractive safety and environmental features. Based on blanket design studies, it became apparent that electrically insulating duct walls would be required to reduce the magnetohydrodynamic (MHD) pressure drop for liquid metal-cooled blankets for high magnetic field fusion devices. As a result, development of insulator coatings was recommended as the most appropriate approach for resolving this issue. Oxides such as CaO, Y 2 O 3 . BeO. MgO, MgAl 2 O 4 , and Y 3 Al 2 O 12 and nitrides such as A1N, BN and Si 3 N 2 were initially considered potential candidate coating materials. Based on results of scoping studies, CaO and A1N have been selected as primary candidates for further development. Progress on the development of CaO and A1N coatings, including in-situ formation and electrical properties measurements, are summarized in this paper.

The addition of genistein, a plant-to-bacteria signal molecule, to Bradyrhizobium japonicum cells prior to use as inocula has been shown to increase nodule number and promote soybean N 2 fixation at low root zone temperatures. Previous greenhouse and field experiments involving only two cultivars have indicated that soybean [Glycine max (L.) Merr.] cultivars can vary in their response to genistein application. The objective of this study was to evaluate a range of soybean cultivars for response to genistein application under short-season cool-spring Canadian conditions. A 2-year field study was conducted in 1997 and 1998 with a range of soybean cultivars recommended for Quebec. The 11 cultivars tested represented a range of yield potentials and maturity groups. They were inoculated with genistein-preincubated B. japonicum inocula or regular inocula, applied into the furrow at the time of planting. The results of these experiments indicated that neither maturity nor yield was correlated with increases in nodulation, biomass, and plant total nitrogen content resulting from genistein treatment and that all maturity groups responded to genistein application in essentially the same way. Thus, response of soybean cultivars to genistein addition is regulated by genotype characteristics other than maturity or yield level.

The absolute thick target yield of 6.129, 6.917 and 7.116 MeV γ-rays produced from the 19 F(p,αγ) 16 O source reaction has been measured for incident proton energies between 1.5 and 4.0 MeV. The angular distributions of the respective γ-lines have been determined for incident proton energies of 2.0 and 3.0 MeV. The experiments were performed at the 4.5 MV Tandem Van der Graaff accelerator at the Ohio University Edwards Accelerator Laboratory in Athens, Ohio, using a thick CaF 2 target and a 7.62 cm×7.62 cm Na(I) scintillation detector. The Monte Carlo code MCNP was used to calculate detector response functions for the three individual γ-rays. A least-squares fit of these functions to a selected region in the pulse height spectrum was carried out to determine the relative intensities of these γ-rays. The uncertainty in the fluence determination is based on the χ 2 of the fit, the uncertainty in the response functions, the statistics of the data, and the uncertainty in the recording of the proton charge. A maximum photon yield of 1.316×10 7 γ/μC/sr (at 90°) was determined for the sum of these three γ-rays at the highest incident proton energy of 4.0 MeV. The contribution of the individual lines to the total photon yield depends strongly on the incident proton energy. The angular distributions are isotropic to within 15%.

Holstein bull calves arriving at five special-fed veal farms (eight production groups) were scored for various physical condition traits and blood-sampled within 2 h after arrival and at 28 d, 84 d, and 1 wk prior to slaughter at 116 to 143 d. Of 1179 total calves in the production groups, 758 calves were scored and evaluated. Blood cell analyses (red and white blood cell counts, hemoglobin, and packed cell volume) were conducted at all four sampling times; total serum protein concentration was obtained at 0 and 28 d. The study was initiated in autumn and ended the following autumn. Mean initial and final body weights were 46.3 ± 0.17 and 209.7 ± 0.77 kg; mean mortality was 2.5%. Average daily gain of the eight groups ranged from 1.23 to 1.70 kg/d. Subjective scores of 5 = excellent to 1 = very poor condition were used to evaluate 16 different physical condition characteristics. With the exception of leg joint, hoof, and foot scores, most of the physical condition scores exhibited improvement during the first 28 d. Foot and leg impairments did not appear to hinder the ambulatory ability of the calves during the production period. Physical condition scores at d 0 and 28 were generally not related to numbers or types of medical treatments (enteric, respiratory, other, or total) or to average daily gain during the production period. Means for most erythrocytic and leukocytic traits upon arrival (d 0) were within normal ranges, although 27.4% of the calves were clinically or marginally anemic. Final mean hemoglobin and packed cell volume were 8.53 g/dl and 26.1%. Forty-three percent of the calves at d 0 were colostral deficient, assuming that total serum protein concentrations of

Phenobarbital (PHE) is a liver carcinogen in B6C3F1 mice and a weak mutagen that does not appear to form DNA adducts. To investigate PHE mutagenicity in vivo, B6C3F1 Big Blue(R) male transgenic mice harboring the lambdaLIZ shuttle vector containing the lacI target gene were fed PHE at 2500 ppm for 180 days. A modest increase in the mutant frequency (MF) from 5.02+/-2.4x10(-5) in the control group to 6.88+/-0.754x10(-5) in the PHE-treated group, which was marginally different (p

Cross sections have been measured with the activation technique at various neutron energies in the range of 16.0 to 20.5 MeV for the following 22 reactions: 19F(n,p)19O, 23Na(n,p)23Ne, 23Na(n,α)20F...

Vanadium alloys have been identified as a leading candidate material for fusion first-wall/blanket applications. Certain vanadium alloys exhibit favorable safety and environmental characteristics, good fabricability, high temperature and heat load capability, good compatibility with liquid metal coolants and resistance to irradiation damage. The current focus is on vanadium alloys with (3–9 wt%) Cr and (3–10 wt%) Ti with a V–4Cr–4Ti alloy as the reference composition. Substantial progress has been made in the development of vanadium alloys for the fusion first wall/blanket applications including production and welding, characterization of baseline properties, corrosion/compatibility, and effects of irradiation on the properties. This paper presents an overview of the development of vanadium alloys for fusion applications and a summary of key issues requiring further research.

Genistein is the major root produced isoflavonoid inducer of nod genes in the symbiosis between B. japonicum and soybean plants. Reduction in the isoflavonoid content of the host plants has recently been suggested as a possible explanation for the inhibition of mineral nitrogen (N) on the establishment of the symbiosis. In order to determine whether genistein addition could overcome this inhibition, we incubated B. japonicum cells (strain 532C) with genistein. Mineral N (in the form of NH4NO3) was applied at 0, 20 and 100 kg ha-1. The experiments were conducted on both a sandy-loam soil and a clay-loam soil. Preincubation of B. japonicum cells with genistein increased soybean nodule number and nodule weight, especially in the low-N-containing sandy-loam soil and the low N fertilizer treatment. Plant growth and yield were less affected by genistein preincubation treatments than nitrogen assimilation. Total plant nitrogen content was increased by the two genistein preincubation treatments at the early flowering stage. At maturity, shoot and total plant nitrogen contents were increased by the 40 μM genistein preincubation treatment at the sandy-loam soil site. Total nitrogen contents were increased by the 20 μM genistein preincubation treatment only at the 0 and 20 kg ha-1 nitrate levels in clay-loam soil. Forty μM genistein preincubation treatment increased soybean yield on the sandy-loam soil. There was no difference among treatments for 100-seed weight. The results suggest that preincubation of B. japonicum cells with genistein could improve soybean nodulation and nitrogen fixation, and at least partially overcome the inhibition of mineral nitrogen on soybean nodulation and nitrogen fixation.

It has long been recognized that attainment of the safety and environmental potential of fusion energy requires the successful development of low activation materials for the first wall, blanket and other high heat flux structural components. Only a limited number of materials potentially possess the physical, mechanical and low activation characteristics required for this application. The current US structural materials research effort is focused on three candidate materials: advanced ferritic steels, vanadium alloys and silicon carbide composites. Recent progress has been made in understanding the response of these materials to neutron irradiation.

The effects of electrolytes and transportation on lamb, pig, and calf production and behavior traits were evaluated in three twice-replicated trials. In all trials, animals were randomly allotted to three treatment groups stratified by sex, weight, and breed: 1) not transported, water (CW); 2) transported, electrolyte (TE); and 3) transported, water (TW). Comparisons of CW vs TW resulted in the determination of the effects of transportation when water was used; comparisons of TE vs TW allowed the determination of the effects of electrolyte use in transported animals. Each trial consisted of two transportation days 1 wk apart (transports 1 and 2). Each transportation day consisted of a 4-h rest period between two separate 80-km transports. Seventy-two Dorset lambs (average 105 d; 51 ewes and 21 wethers), 72 Yorkshire weaned pigs (average 51 d; 15 barrows and 57 gilts), and 39 Angus x Simmental cross heifers (average 265 d) were used. In the lamb trial, for transports 1 and 2, weight loss was not different (P>0.05) for TE vs TW; CW lost less (P 0.05) for TE vs TW; CW lost less (P

The data for this study were questionnaires from 280 dairy and 143 veal producers. The objective was to determine producer evaluations of the amount and importance of changes in the past 10 yr and those projected in the near future related to several animal management and facility factors. A part of the survey emphasized handling and transportation changes. Dairy producers indicated that nutrition (diet), herd health, quality assurance, ventilation/housing, and breeding management were the most important changes over the past 10 yr. These same management factors were projected to be the most important in the future, although the top-ranked factor was milking facilities/equipment, which was ranked only of moderate importance with regard to changes in the past. Veal producers identified calf health, medication use, quality assurance, nutrition, and veterinary use as the most important changes over the past 10 yr. Most important future changes were the above-mentioned factors (with exception of nutrition), with biosecurity and waste management becoming highly-ranked factors. The most important factors to reduce animal stress, prevent animal losses, and to improve on-farm management were identified by dairy producers as nonslip flooring, facilities to restrain and move calves, loading expertise, seasonal venting on transport vehicles, and biosecurity. Veal producers identified seasonal truck venting, market/packer personnel, driver expertise, and overloading as the most important factors in reducing stress and preventing losses, with overloading being of little importance in improving management. Loading expertise was the third-ranked factor in improving on-farm management. These results indicate that both dairy and veal farmers are cognizant of factors influencing animal well-being. Both dairy and veal producers also believe they have improved their level of animal care. In addition, dairy and veal producers feel that public opinion of their methods and industries has improved in the past 10 yr.

The objective of the experiment was to determine the effects of an electrical prod application on behavioral and physiological characteristics of weaned beef cattle. Twenty-one crossbred beef cattle (avg. age and wt., 273 ± 4.3 d and 313 ± 8.6 kg) were randomly allotted into seven trios with stratification by weight and breed. One animal from each trio was then randomly assigned to one of three treatment groups: 1) touched with electric prod, but not buzzed or shocked (o); 2) touched and buzzed simultaneously, but not shocked (b); and 3) simultaneously touched, buzzed and shocked (s). The (s) group was touched, shocked, and buzzed on d 2 and d 8 of the trial; on d 1, d 3 to d 7, and d 9 to d 13 the s group was touched and buzzed, and the o and b groups received their assigned treatments. Blood samples were taken on d 1, 7, and 13. Treatments were imposed as each individual entered the chute system. Behavior scores, length of time the calves spent in each section of the chute system, and videorecordings were obtained for each animal as they passed through the chute. Daily heart rate, respiration, and rectal temperatures were not affected by treatment (P>0.05). Effects of treatment applications on blood (erythrocyte, leukocyte, serum protein), and prompting scores (5 = no handler; 4 = handler sound; 3 = handler slap; 2 = handler twist tail; 1 = handler push) were not different among treatments (P>0.05). Some animal behaviors (5 = quiet, little reaction; 4 = docile, easy to handle; 3 = alert, slight resistance; 2 = excitable, difficult to handle; 1 = uncontrollable, resists handling), and time to move through the chute system were significantly different among treatment groups. Effects of electrical prod application (shock) apparently did not cause additional measurable distress compared to the distress from handling and moving calves with no mechanical handling aids. However, in this study, the electrical prod was applied sparingly and in a controlled manner.

Questionnaires requesting producers to identify management changes were mailed or handed out to 370 swine and 2050 beef producers. The survey response rate was 71 (19%) and 410 (20%) swine and beef, respectively. Respondents evaluated the amount and importance of changes (codes; 0=no change, 1=little change, 2=moderate change, 3=large change, and 4=not sure or not applicable) made to their enterprises in the past 10 yr, and changes intended in the near future. The questions included facilities, nutrition, handling, transport, herd health, biosecurity, and other management factors. In addition, respondents were requested to indicate the effects of these practices on animal stress, causing or preventing injury or mortality, and improving management of the enterprise. The most important changes identified by swine producers in the past were nutrition, herd health, and quality assurance and in the near future, ventilation, herd health, and quality assurance. Beef producers identified breeding management, nutrition, and herd health as most important changes in the past and in the near future breeding management, quality assurance, and nutrition. Loading and trucking ranked low (9th, 7th) for swine and beef, respectively, which indicates producer satisfaction or a lack of information on transportation and the frequency of associated negative factors (dark cutters, porcine stress syndrome, bruising, shrink, death loss). Waste management also ranked low (swine 7th, beef 9th), which was unanticipated, especially when considering Pennsylvania’s new nutrient management laws. Over all, producers expressed concern with animal well-being and contemporary animal issues. This is indicated by past and intended future changes and the importance producers place on critical management factors.

Mechanical properties and microstructural characteristics of laser and electron-beam welds of a 500-kg heat of V4Cr4Ti were investigated in as-welded condition and after postwelding heat treatment by impact testing, microhardness measurement, optical microscopy, X-ray diffraction, and transmission electron microscopy (TEM). Ductile-brittle transition temperatures of the laser and electron-beam welds were significantly higher than that of the base metal. However, excellent impact properties could be restored in both types of welds by postwelding annealing at 1000 C for 1 h in vacuum. Analysis by TEM revealed that annealed weld zones were characterized by extensive networks of fine V(C,O,N) precipitates, which clean away O, C, and N interstitial from the grain matrices. This process is accompanied by simultaneous annealing-out of the dense dislocations present in the weld zone. This finding could be useful in identifying an optimal welding procedure by controlling and adjusting the cooling rate of the weld zone by an innovative method to maximize the precipitation of V(C,O,N).

The published database for the tensile properties of unirradiated and irradiated vanadium-based alloys tested at Argonne National Laboratory (ANL) has been reviewed. The alloys tested are in the ranges of V-(0-18)wt.%Ti and V-(4-15)wt.%Cr-(3-15)wt.%Ti. A consistent methodology, based on ASTM terminology and standards, has been used to re-analyze the unpublished load vs. displacement curves for 162 unirradiated samples and 91 irradiated samples to determine revised values for yield strength (YS), ultimate tensile strength (UTS), uniform elongation (UE) and total elongation (TE). The revised data set contains lower values for UE ({minus}5{+-}2% strain) and TE ({minus}4{+-}2% strain) than previously reported. Revised values for YS and UTS are consistent with the previously-published values in that they are within the scatter usually associated with these properties.

One of the primary requirements for the development of fusion as an energy source is the qualification of materials for the frost wall/blanket system that will provide high performance and exhibit favorable safety and environmental features. Both economic competitiveness and the environmental attractiveness of fusion will be strongly influenced by the materials constraints. A key aspect is the development of a compatible combination of materials for the various functions of structure, tritium breeding, coolant, neutron multiplication and other special requirements for a specific system. This paper presents an overview of key materials integration issues for high performance fusion power systems. Issues such as: chemical compatibility of structure and coolant, hydrogen/tritium interactions with the plasma facing/structure/breeder materials, thermomechanical constraints associated with coolant/structure, thermal-hydraulic requirements, and safety/environmental considerations from a systems viewpoint are presented. The major materials interactions for leading blanket concepts are discussed.

Tensile and impact properties were investigated at

The Conceptual Design Activity (CDA) for the International Fusion Materials Irradiation Facility (IFMIF) has been conducted. For the IFMIF Target Facility, the conceptual designs of the following two main components have been performed. The design concept of IFMIF utilizes a high energy deuteron beam of 30–40 MeV and total current of 250 mA, impinging on a flowing lithium jet to produce high energy neutrons for irradiation of candidate fusion materials. (1) The target assembly: The kinetic energy of the deuteron beam is deposited on a Li-jet target and neutrons are produced through the d–Li stripping reaction in this target. The assembly is designed to get a stable lithium jet and to prevent the onset of lithium boiling. For 40-MeV deuteron beam (total current of 250 mA) and a beam footprint of 5 × 20 cm2 lithium jet dimensions are designed to be 2.5 cm thick and 26 cm wide. The lithium jet parameters are given. (2) Lithium loop: The loop circulates the lithium to and from the target assembly and removes the heat deposited by the deuteron beam containing systems for maintaining the high purity of the lithium required for radiological safety and to minimize corrosion. The maximum lithium flow rate is 130 l/s and the total lithium inventory is about 21 m3. The IFMIF policy requires that the lithium loop system be designed to guarantee no combustion of lithium in the event of a lithium leak. This can be achieved by use of multiple confinement of the lithium carrying components. The radioactive waste generated by the Target Facilities is estimated.

A series of tests is being conducted in the DIII-D tokamak to determine the effects of environmental exposure on a V-4Cr-4Ti vanadium alloy. These tests are part of the effort to build and install a water-cooled vanadium alloy structure in the DIII-D radiative diverter upgrade. Data from the test series indicate that the performance of the V-4Cr4Ti alloy would not be significantly affected by environmental exposure. Interstitial absorption by the material appears to be limited to the surface, and neither the tensile nor the impact properties of the material appear to be affected by the exposure.

The current status of research and development on unirradiated and irradiated V-Cr-Ti alloys intended for fusion reactor structural applications is reviewed, with particular emphasis on the flow and fracture behavior of neutron-irradiated vanadium alloys. Recent progress on fabrication, joining, oxidation behavior, and the development of insulator coatings is also summarized. Fabrication of large (>500 kg) heats of V-4Cr-4Ti with properties similar to previous small laboratory heats has now been demonstrated. Impressive advances in the joining of thick sections of vanadium alloys using GTA and electron beam welds have been achieved in the past two years, although further improvements are still needed.

A Russia/US collaborative irradiation experiment on low-activation structural materials, mainly vanadium alloys, was recently completed in the BOR-60 reactor at the Research Institute of Atomic Reactors (RIAR) in Russia. The experiment, designated Fusion-1, was designed to investigate the effects of neutron-induced displacement damage on the microstructure and mechanical properties of these materials at low temperatures, 300–360°C. For purpose of heat transfer and impurity control, the specimens were lithium-bonded to the capsule. After reaching the goal damage dose of 20 displacements per atom (dpa) in approximately 1 year of irradiation, the capsule was discharged and disassembled in a hot cell at RIAR. All specimens were retrieved from the capsule. This paper summarizes the experiment, covering capsule construction, lithium purification and filling, irradiation, disassembly and specimen retrieval, and calculated results of specimen temperatures and damage dose.

The self-cooled lithium/vanadium blanket concept has several attractive features for fusion power systems, including reduced activation, resistance to radiation damage, accommodation of high heat loads and operating to temperatures of 650–700°C. The primary issue associated with the lithium/vanadium concept is the potentially high MHD pressure drop experienced by the lithium as it flows through the high magnetic field of the tokamak. The solution to this issue is to apply a thin insulating coating to the inside of the vanadium alloy to prevent the generation of eddy currents within the structures that are responsible for the high MHD forces and pressure drop. This paper presents the progress in the development of an insulator coating that is capable of operating in the severe fusion environment, progress in the fabrication development of vanadium alloys, and a summary of MHD testing. A large number of small scale tests of vanadium alloy specimens coated with CaO and A1N have been conducted in liquid lithium to determine the resistivity and stability of the coating. In-situ measurements in lithium have determined that CaO coatings, ∼5 μm thick, have resistivity times thickness values ( p * t ) exceeding 10 6 Ω cm 2 . These results have been used to identify fabrication procedures for coating a large vanadium alloy (V–4Cr–4Ti) test section that was tested in the ALEX (Argonne Liquid metal Experiment) facility. Similar test sections have been produced in both Russia and the USA.

To meet the technical objectives of the ITER extended performance phase (EPP) an advanced tritium breeding lithium/vanadium (Li/V) blanket was developed by two home teams (US and RF). The design is based on the use of liquid Li as coolant and breeder and vanadium alloy (V-Cr-Ti) as structural material. The first wall is coated with a beryllium protection layer. Beryllium is also integrated in the blanket for neutron multiplication and improved shielding. The use of tungsten carbide in the primary shield and in vacuum vessel provides adequate protection for toroidal field coils. A self-healing electrical insulator in the form of CaO or AlN coating layer is utilized to reduce MHD pressure drop in the system. To have a self-consistent ITER design, liquid metal cooling of the divertor and vacuum vessel is considered as well.

Vanadium alloys have been identified as a leading candidate low-activation structural material for fusion first-wall blanket applications. Candidate vanadium alloys exhibit favorable safety and environmental characteristics, good fabricability, high temperature and heat load capability, good compatibility with liquid metals and resistance to irradiation damage. The focus of the vanadium alloy development program has been on the vanadium-chromium-titanium (0–15%Cr, 1–20%Ti) alloy system. Investigations include effects of minor alloy elements such as Si, Al and Y and substitution of iron for chromium in the ternary alloy. A V-4Cr-4Ti alloy is currently regarded as the reference alloy. Significant progress has been made in the development of vanadium alloys for fusion applications. Two production-scale heats (500 and 1200 kg) of the V-4Cr-4Ti alloys have been produced with controlled levels of impurities. The baseline properties of the 500 kg heat are similar to those of the previous laboratory-scale heats. Additional data have been obtained on baseline tensile and fracture properties. Results obtained on several heats with minor variations in composition indicate high uniform and total elongation of these alloys at temperature from RT to 700°C. Results obtained to date indicate that the V-Cr-Ti alloys are resistant to swelling and embrittlement after exposure to relatively high neutron fluences at temperatures of 400–600°C. The properties are not significantly different when modest amounts of helium are generated during neutron irradiation by the dynamic helium charging experiment method. However, recent results have indicated that these alloys are susceptible to irradiation embrittlement at lower temperatures. Additional irradiation experiments are in progress to investigate these effects at temperatures of 200–400°C. This paper presents an update on the experimental results on candidate low activation vanadium alloys.

The accumulation, retention and distribution of 95mTc has been compared in lobsters and edible crabs kept under identical experimental conditions. The steady-state concentration factor (Css) for the uptake of 95mTc from seawater was significantly greater for female crabs (Css=17·9) than for males (Css=14·4), whereas in lobsters there was no such sex difference and the Css of 1161 was much greater than in crabs. The uptake of technetium from food (as indicated by whole body counts) was only moderately greater in lobsters than crabs. Retention of 95mTc was similar for crabs and lobsters of both sexes but the clearance rate was greater after the nuclide had been taken up from seawater (tb1/2=51 days) than from food (tb1/2=108 days). In all crabs and most male lobsters 95mTc was predominantly in the hepatopancreas while in a few male and all female lobsters it was mainly in muscle. Lobster ovaries consistently contained more activity than testes but this difference was not seen in crabs. In hepatopancreas cells of both species 95mTc occurred mainly in the cytosol and some initial steps were taken to determine the relationship between technetium and cytosol proteins. The results for crab and lobster are compared with those from previous studies on these and other crustacean species. The possible basis for the much higher concentrations of technetium in lobsters than crabs is discussed and further research suggested.

Excitation functions were measured for the {sup 52}Cr(n,2n){sup 51}Cr, {sup 52}Cr(n,p){sup 52}V, {sup 53}Cr(n,p){sup 53}V, {sup 53}Cr(n,np+pn+d){sup 52}V, {sup 54}Cr(n,p){sup 54}V, {sup 54}Cr(n,np+pn+d){sup 53}V, and {sup 54}Cr(n,{alpha}){sup 51}Ti reactions from 9 to 21 MeV. Use was made of the activation technique in combination with high-resolution {gamma}-ray spectrometry. Monoenergetic neutrons produced via the {sup 2}H(d,n){sup 3}He and {sup 3}H(d,n){sup 4}He reactions were used to irradiate samples of metallic chromium, {sup 52}Cr{sub 2}O{sub 3}, {sup 53}Cr{sub 2}O{sub 3}, and {sup 54}Cr{sub 2}O{sub 3}. The neutron fluence rates were determined via the {sup 27}Al(n,p){sup 27}Mg, {sup 27}Al(n,{alpha}){sup 24}Na, {sup 56}Fe(n,p){sup 56}Mn, and {sup 93}Nb(n,2n){sup 92m}Nb monitor reactions. Short-lived activities were investigated using a pneumatic sample transport system. Statistical model calculations taking into account preequilibrium effects were performed for all the reactions using a consistent set of model parameters. The experimental excitation functions helped appreciably to resolve the discrepancies in evaluated data files. Good agreement was found between our experimental data and the new model calculations. {copyright} {ital 1998} {ital The American Physical Society}

Lobsters and edible crabs have been exposed to 95 Tc m in their sea water or in their food, and the uptake, retention and distribution of the isotope in their bodies examined. The steady-state concentration factor C 85 for uptake of 95 Tc m from sea water was significantly greater for female crabs (C 95 =17.9) than for males (C 95 =14.4). There was no such sex difference in lobsters and they took up 95 Tc m to much higher levels with a C 95 of 1160. Retention of the isotope was similar for crabs and lobsters and for animals of both sexes. However the route of uptake was important with more rapid clearance after uptake from sea water (t hi = 51 days) than after uptake from food (t hi = 108 days). Technetium was found predominantly in the hepatopancreas of all crabs and most male lobsters. In a few male lobsters and all females it was mainly in muscle. Lobster ovaries consistently contained more activity than testes but this difference was not seen in crabs. At the subcellular level 95 Tc m in hepatopancreas cells of both lobster and crab occurred mainly in the cytosol. Results of initial studies into the relationships between technetium and cytosol proteins are given and the possible basis for the much greater accumulation of the element by lobsters than crabs discussed.

Brown trout were exposed to 32 P in their tank water (7.4 Bq l −1 ) and the uptake to muscle followed over 6 weeks. A steady-state concentration factor (C ss ) of 1.7 and a biological half-time for clearance ( t b 1 2 ) of 45 days were calculated from the results. The low C ss indicates that uptake from water is not a major route of 32 P accumulation in these fish. Brown trout were given a single 32 P-spiked meal, and the uptake and clearance in muscle, liver and blood followed over 6 weeks. Assimilation of the isotope by these organs was low, the maximum activity in whole muscle reaching only 0.2–0.4% of that in the meal with lower values in the other two organs. There was no appreciable clearance of 32 P from muscle during the experiment. The slow clearance of 32 P after uptake from water and lack of any clearance after uptake from food indicates that the C ss for this isotope following uptake by either route is likely to depend on radioactive decay rather than intake rate and physiological clearance.

The method for characterizing neutrons produced by bombardment of beryllium with deuterons at energies from 3.0 to 7.0 MeV is discussed. Similar work for the characterization of the neutrons produced by the bombardment with protons from 2.0 to 4.0 MeV is presented. Both NE213 and lithium glass detectors were used in the time of flight measurement of the neutron spectra. The neutron spectrum from 27Al(d,n) was measured at 7.440 MeV deuteron energy and an angle of 120° with a 235U fission chamber.

In the soybean (Glycine max. (L.) Merr)– Bradyrhizobium japonicum symbiosis, suboptimal root zone temperatures (RZTs) slow nodule development by disruption of the interorganismal signal exchange between the host plant and bradyrhizobia. Two field experiments were conducted on two adjacent sites in 1994 to determine whether the incubation of B. japonicum with genistein prior to application as an inoculant, or genistein, without B. japonicum, applied onto seeds in the furrow at the time of planting, increased soybean nodulation, N fixation, and total N yield. The results of these experiments indicated that genistein application increased nodule number and nodule dry matter per plant and hastened the onset of N fixation during the early portion of the soybean growing season, when the soils were still cool. Because these variables were improved, total fixed. N, fixed N as a percentage of total plant N, and N yield increased due to genistein application. The interaction between genistein application and soybean cultivars indicated that genistein application was more effective on N-stressed plants.

Despite being a group of particular interest in considering relationships between genome size and metabolic parameters, bats have not been well studied from this perspective. This study presents new estimates for 121 “microbat” species from 12 families and complements a previous study on members of the family Pteropodidae (“megabats”). The results confirm that diversity in genome size in bats is very limited even compared with other mammals, varying approximately 2-fold from 1.63 pg in Lophostoma carrikeri to 3.17 pg in Rhinopoma hardwickii and averaging only 2.35 pg ± 0.02 SE (versus 3.5 pg overall for mammals). However, contrary to some other vertebrate groups, and perhaps owing to the narrow range observed, genome size correlations were not apparent with any chromosomal, physiological, flight-related, developmental, or ecological characteristics within the order Chiroptera. Genome size is positively correlated with measures of body size in bats, though the strength of the relationships differs between pteropodids (“megabats”) and nonpteropodids (“microbats”).

To test the magnetohydrodynamic (MHD) pressure drop reduction performance of candidate insulator coatings for the ITER Vanadium/Lithium Breeding Blanket, a test section comprised of a V-4Cr-4Ti liner inside a stainless steel pipe was designed and fabricated. Theoretically, the MHD pressure drop reduction benefit resulting from an electrically insulating coating on a vanadium-lined pipe is identical to the benefit derived from an insulated pipe fabricated of vanadium alone. A duplex test section design consisting of a V alloy liner encased in a SS pressure boundary provided protection for vanadium from atmospheric contamination during operation at high temperature and obviated any potential problems with vanadium welding while also minimizing the amount of V alloy material required. From the MHD and insulator coating point of view, the test section outer SS wall and inner V alloy liner can be modeled simply as a wall having a sandwich construction. Two 52.3 mm OD x 2.9 m long V-alloy tubes were fabricated by Century Tubes from 64 mm x 200 mm x 1245 mm extrusions produced by Teledyne Wah Chang. The test section`s duplex structure was subsequently fabricated at Century Tubes by drawing down a SS pipe (2 inch schedule 10) over one of themore » 53.2 mm diameter V tubes. 2 refs., 2 figs., 2 tabs.« less

The lithium target facility design has been developed in the Conceptual Design Activities for the International Fusion Materials Irradiation Facility (IFMIF). As for the lithium target design, the replaceable backwall concept is selected as a reference design with the cell environment of 10{sup -1}Pa, and the free jet and Fusion Materials Irradiation Test Facility (FMIT) type design are carried as the option. In the lithium loop design the single loop is layed out to provide the lithium flow to the two targets with redundant components including tanks, heat exchangers, lithium purification systems, and lithium monitoring systems for high availability. Total lithium flow capability of 120 liter/s is provided by single electromagnetic pump, and the total lithium inventory is 22,300 liters. 9 refs., 5 figs., 2 tabs.

V base alloys have advantages for fusion reactor first-wall and blanket structure. To screen candidate alloys and optimize a V-base alloy, physical and mechanical properties of V-Ti, V-Cr-Ti, and V-Ti- Si alloys were studied before and after irradiation in Li environment in fast fission reactors. V-4Cr-4Ti containing 500-1000 wppM Si and

Vanadium alloys exhibit important advantages as a candidate structural material for fusion first-wall/blanket applications. These advantages include high temperature and high wall load capability, favorable safety and environmental features, resistance to irradiation damage, and alloys of interest are readily fabricable. A substantial data base has been developed on laboratory-scale heats of VTi, VCrTiSi alloys before and after irradiation. Investigations in recent years have focused primarily on compositions of V(0–15)Cr(0–20)Ti(0–1)Si. Results from these investigations have provided a basis for identifying a V4Cr4Ti alloy as the US reference vanadium alloy for further development. Major results obtained on one production-scale heat and three laboratory heats with compositions of V(4–5)Cr(4–5)Ti are presented in this paper.

Advantages of vanadium alloys for fusion reactor structural applications are: low induced activation, excellent thermal stress factor, high strength at elevated temperatures, and superior ductility at low temperatures. Resistance to irradiation damage is also very impressive, i.e. very small DBTT shift by irradiation and low swelling. Research and development of vanadium alloys have made a remarkable progress in recent years partly supported by ITER-related activities. Composition range centered about V4Cr4Ti is the target of many of the studies conducted in the US, Japan and RF. Most of the studies have demonstrated the superior performance of this alloy family, while some alloys containing large amount of impurities have shown relatively poor properties. In addition to the baseline mechanical properties, neutron irradiation effects, e.g., swelling and radiation embrittlement are covered in this paper. Of particular importance is the study of the effects of dynamically-charged helium on mechanical properties and swelling. Recent developments of insulator coatings and welding are also covered. The importance of mechanistic studies of the damage behavior is emphasized for efficient alloy development and prediction of materials life in service.

Vanadium alloys are attractive candidate structural materials for fusion power plants because of their potential for minimum environmental impact due to low neutron activation and rapid activation decay. They also possess favorable material properties for operation in a fusion environment. General Atomics in conjunction with Argonne National Laboratory and Oak Ridge National Laboratory has developed a plan for the utilization of vanadium alloys as part of the radiative divertor upgrade for the DIII-D tokamak. The plan will be carried out in conjunction with General Atomics and the Materials Program of the US Department of Energy. This application of a vanadium alloy will provide a meaningful step in the development of advanced materials for fusion power devices by: (1) developing necessary materials processing technology for the fabrication of large vanadium alloy components and (2) demonstrating the in-service behavior of a vanadium alloy (V4Cr4Ti) in a tokamak environment. The program consists of three phases: first, small vanadium alloy coupon samples will be exposed in DIII-D at positions in the vessel floor and within the pumping plenum region of the existing divertor structure; second, a small vanadium alloy component will be installed in the existing divertor, and third, during the forthcoming radiative divertor modification, scheduled for completion in mid-1997, the upper section of the new double-null, slotted divertor will be fabricated from vanadium alloy product forms. This program also includes research and development efforts to support fabrication development and to resolve key issues related to environmental effects.

One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of {approx} 0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18--31 dpa at 425--600 C in Li-filled capsules in a sodium-cooled fast reactor. This paper presents results of postirradiation examination and tests of microstructure and mechanical properties of V-5Ti, V-3Ti-1Si, V-8Cr-6Ti, and V-4Cr-4Ti (the latter alloy has been identified as the most promising candidate vanadium alloy). Effects of helium on tensile strength and ductility were insignificant after irradiation and testing at > 420 C. However, postirradiation ductilities at {minus}150 C in DHCE specimens. Predominantly brittle-cleavage fracture morphologies were observed only at {minus}196 C in some specimens that were irradiated to 31 dpa at 425 C during the DHCE. For the helium generation rates in this experiment ({approx} 0.4--4.2 appm He/dpa), grain-boundary coalescence of helium microcavities was negligible and intergranular fracture was not observed.

Several fast-neutron activation reactions for copper, europium, hafnium, iron, nickel, silver, terbium and titanium that are important to fusion energy have been investigated in three distinct neutron fields generated by accelerators at Argonne National Laboratory (ANL) and Los Alamos National Laboratory (LANL), U.S.A., and Japan Atomic Energy Research Institute (JAERI), Tokai, Japan. The experimental data acquired from this collaboration, which has been organized by the International Atomic Energy Agency, include both differential cross sections at 10.0 and 14.7 MeV and integral cross sections for the Be( d , n ) thick-target spectrum produced by 7-MeV deuterons. 58 Ni( n , p ) 58 g + m Co and 93 Nb ( n ,2 n ) 92 m Nb were used as neutron fluence standards, and the 238 U( n , f ) cross section was measured at 10.0 MeV to validate the experimental techniques. Measured differential cross sections are compared with corresponding experimental data from the literature and with values obtained from nuclear model calculations and evaluations. Measured integral cross sections are compared with some earlier experimental results from ANL and with calculated values based on available differential cross-section excitation functions and various representations of the Be( d , n ) neutron spectrum. Reasonably good agreement is observed in many of these comparisons.

BACKGROUND: There has been increasing concern since 1979 about the emergence of Pseudomonas cepacia (Burkholderia cepacia) in patients with cystic fibrosis in the UK and elsewhere. Colonisation of the sputum has been shown to be associated with increased morbidity and mortality. Evidence suggests person to person transmission and some centres have segregated those colonised with B cepacia from other patients with cystic fibrosis. The outcome of patients colonised by B cepacia has been studied, together with the effects of strict segregation. METHODS: The outcome in 18 patients with sputum colonised by B cepacia was compared with that in age, sex, and severity matched controls with no evidence of B cepacia colonisation by a retrospective case note study. RESULTS: No difference between cases or controls were found in the 24 month period prior to colonisation by B cepacia in lung function, number of days in hospital, or outpatient visits. Colonisation led to an increased rate of loss of lung function and utilisation of hospital services. There was an increase in the numbers of transplants and deaths amongst the cases. Since 1992 there have been only three new cases of B cepacia colonisation and the incidence and prevalence of the organism has fallen dramatically since segregation commenced. CONCLUSIONS: B cepacia appears to be linked to the decline in colonised individuals. There was no evidence that colonisation occurred in patients declining for other reasons. B cepacia colonisation confers a worse prognosis than Pseudomonas aeruginosa alone. Segregation appears to limit the spread of the organism from infected individuals to other patients with cystic fibrosis.

Vanadium alloys have been identified as a leading candidate material for fusion first-wall—blanket applications. Certain vanadium alloys exhibit favorable safety and environmental characteristics, good fabricability, high temperature and heat load capability, good compatibility with liquid metals and resistance to irradiation damage effects. The current focus is on vanadium alloys with (3–5)% Cr and (3–5)% Ti, with a V4Cr4Ti alloy as the leading candidate. The available database indicates that the VCrTi alloys provide the following advantages: 1. (1)|These alloys are readily formable and weldable; however, atmospheric contamination must be avoided during welding and high temperature processing. 2. (2)|The relatively high thermal conductivity and low thermal expansion provide for a high heat load capability. 3. (3)|These alloys exhibit good high temperature tensile and creep properties which permit high temperature operation. 4. (4)|VCrTi alloys exhibit low long-term activation and low radioactive decay heat which provide safety and environmental advantages. 5. (5)|These alloys are characteristically resistant to liquid metal corrosion. 6. (6)|Alloys with a few per cent titanium are highly resistant to irradiation-induced swelling, which provides for the possibility of long lifetime. 7. (7)|Results obtained to date indicate that the V4Cr4Ti alloy is highly resistant to irradiation-induced degradation of the mechanical properties. Substantial progress has been made in the development of these alloys for fusion application. Larger heats of the V4Cr4Ti alloy have been prepared in the USA and Russia. The baseline property database has been expanded. Recent results indicate that these alloys are resistant to irradiation damage. The irradiation-induced swelling is low, the uniform elongation of alloys irradiated at 400–600 °C remains above 8% and the ductile—brittle transition temperature of the V4Cr4Ti alloy after irradiation remains well below room temperature. Preliminary results indicate that the crack growth rates of certain alloys are not highly sensitive to irradiation. Results from the dynamic helium charging experiment (DHCE) which simulates fusion relevant helium/dpa ratios are similar to results from neutron-irradiated material.