Pure Fusion Research Articles

Laser Fusion Research in the USSR

The history of laser fusion experiments in the USSR is briefly reviewed. Stress is placed on recent key experimental and theoretical results. These results, taken together with data from the worldwide laser fusion community, support the feasibility of break-even and high-gain targets. Concepts for both pure fusion and hybrid reactors are outlined.

Protein-mediated fusion of liposomes with microsomal membranes of Aspergillus niger: evidence for a complex mechanism dealing with membranous and cytosolic fusogenic proteins

Membrane fusion is a fundamental and wide-spread phenomenon in the functioning of cells. Many studies were carried out concerning fusion of plasma membranes as for example cell-cell fusions or uptake by cells of lipid-enveloped viruses. The present study deals with the interaction of intracellular membranes of Aspergillus niger with artificial membranes (liposomes). Association is monitored by the uptake of radioactive liposomes by fungal microsomal membranes. The discrimination between aggregation and pure fusion is done by layering the liposomes-microsomes mixture on a continuous sucrose gradient. The accurate quantitation of the fusion phenomenon is monitored with a fluorescent assay based on resonance energy transfer (Struck, D.K. et al. (1981) Biochemistry 20, 4093–4099). Both methods show that, at physiological pH, there is a spontaneous fusion of microsomes with cholesterol-free liposomes. This phenomenon is protein dependent as trypsinized microsomal membranes are no longer able to fuse with liposomes. Biological significance of the fusion process has been demonstrated using microsomal intrinsic protein mannosylation assay; the enhancement of the lipid to protein ratio due to the fusion of liposomes with microsomes of A. niger results in an increase in the rate of endogenous roteins mannosylation. Moreover, cytosolic proteins of A. niger promote the fusion of any kind of liposomes with microsomes.

Studies of physics conditions for aneutronic and/or nonradioactive nuclear energy generation in 3He-induced fission of 6Li and 3He fusion in a steady state migma plasma

The physical properties of a steady state migma plasma consisting of reacting 3He, 6Li, and d nuclei with densities n ∼ 10 14 cm −3 and energies of 0.1–10 MeV, which corresponds to β ≥ 0.9, were studied using a zero-dimensional collisional model and simulated by an iterative code on a CRAY computer (β does not have the same physical meaning here as in thermal plasmas). We conclude that if migma plasma can achieve the density currently attained in thermal plasma devices (n ∼ 10 14 cm −3), it will produce net energy through radionuclide-free aneutronic nuclear reactions with a power density of ∼ 20 MW th/m 3. Specifically: synchrotron radiation looses from multi-MeV migma are ∼10 3 times lower than those from thermal plasma of the same density n ∼ 10 14 cm −3. We obtained a positive energy balance for the neutronless and radionuclide-free quasi-chain fission of 6Li, and the pure 3He fusion, with a “scientific” power output-to-input ratio Q = 1.7, as compared to the Q ∼ 10 −3 obtained in thermal plasma. The radionuclide fraction or “radioactivity” R = I rad/ I t and a neutron power fraction or “neutronicism” N = P n/ P nuc are R = 0.5%, N = 2% for (a) and R = N = 0.0% for (b). For in migma, we obtain Q ∼ ∞, R = 0.5%, and N = 3.5%. Our results suggest that in the next stage of simulation, the 3-component fuel d + 3He + 6Li should be used to obtain high Q and, simultaneously, low R and N. For nonradioactive aneutronic migma: (a) bitemperature migma is essential; ignition is not possible in a Maxwellian system; (b) nor is ignition possible in a closed system (end looses are essential); (c) the diamagnetic well is essential; (d) the system must confine ions up to E i = 10 MeV (15 MeV for D- 3He protons); and (e) migma does not become thermalized, which makes a steady state reactor operation feasible.

Analysis and use of the serum albumin binding domains of streptococcal protein G.

Streptococcal protein G is an IgG-binding receptor with a molecular weight of 63 kDa as predicted from the sequence of the corresponding gene. Here we show that a truncated recombinant protein of 23 kDa still has IgG-binding capacity and also interacts specifically with human serum albumin (HSA). This demonstrates that protein G is a bifunctional receptor. To investigate the structures needed for IgG- and albumin-binding, different parts of the receptor molecule were produced in E. coli using a coupled expression/secretion system. Affinity chromatography, using IgG or HSA immobilized on Sepharose, showed that the two binding activities are structurally separated. From these experiments, it was concluded that a region of 64 amino acid residues is sufficient for albumin-binding. The structure of this part of the protein suggests either a divalent or a trivalent binding capacity. The specific interaction to albumin was used to purify a heterologous protein by affinity chromatography to yield a pure fusion protein in a one-step procedure. The implication of this novel affinity system as a tool to facilitate protein immobilization and purification is discussed.

Muon catalysed fusion-fission reactor driven by a recirculating beam

The recent experimentally inferred values of multiplicity of deuterium-tritium fusion catalysed by muons have increased the interest in muon catalysed fusion reactors. Since the main energy expended is in pion (and consequent muon) production, it is tried to minimize the pion loss by magnetically confining pions where they are created. At the present time, it does not appear possible to achieve an energy gain by pure fusion, but it is possible to gain energy by combining catalysed fusion with fission blankets. Two new ideas for improvement of the muon fusion reactor concept are presented. The first idea is to combine the target which creates pions, the converter of pions to muons, and the synthesizer in one vessel (synergetic concept). This is accomplished by injecting a tritium or deuterium beam of 1 GeV per nucleon into DT fuel contained in a magnetic mirror. The confined pions slow down and decay to muons which are confined in the fuel whereby muon loss is kept small. The quantity of tritium necessary to keep the reactor viable has been derived. The second idea is to collect the beam passing through the target for reuse and to recirculate it, while directing the strongly interacting portion of the beam to electronuclear blankets. The present concepts are at the margin of known technologies and are based on known physical processes and data.

Thermal instability of a thermonuclear plasma in a DD fusion reactor. IV. Inhomogeneous plasma.

The thermal thermonuclear instability of a deuterium plasma with inhomogeneous temperature and number density in a strong magnetic field is studied theoretically. The distribution of the number density is supposed to be proportional to that of the temperature. By solving the basic equation which governs the reactions, the growth rates in a pure DD fusion reactor and a catalyzed DD fusion reactor are obtained. It is shown that the plasmas with inhomogeneous temperature and number density in the above reactors are unstable to the thermal instability.

The effect of 14 MeV neutron irradiation on the mechanical properties of Fe and stainless steels

The effect of 14 MeV neutron irradiation on the mechanical properties of pure Fe and fusion reactor candidate stainless steels such as JPCA (Japanese Prime Candidate Alloy) and JFMS (Japanese Ferritic/Martensitic Stainless Steel) have been investigated using small size tensile specimens. Both austenitic (JPCA) and ferritic/martensitic (JFMS) stainless steels showed significant hardening in the neutron fluence region between 1 sx 10 21 n/m 2 and 5 sx 10 22 n/m 2 for room temperatu irradiation and room temperature tensile testing. The increase of the yield stress roughly followed as 1 2 power of the neutron fluence. However, in lower fluence region behaviours were different, namely, no hardening was observed in JFMS and softening was observed in JPCA. The isochronal annealing experiments showed that the hardening recovers above 400°C. The results of pure Fe differed from the results of the alloys. The difference is attributed to the high mobility of radiation-induced defects in Fe.

Reactor Designs for Heavy-Ion Fusion

The Heavy-Ion Fusion Systems Assessment (HIFSA) Project is a study of the prospects for successful pure fusion commercial HIF electric power generation using heavy-ion induction linear accelerator (linac) drivers. Although the project is led by Los Alamos National Lab. (LANL), success requires substantial contributions from all members of a large interdisciplinary team representing a unique assemblage of talent from other national laboratories, universities, and industry. The four reactor concepts included in the HIFSA studies - CASCADE, HYLIFE, wetted-wall, and magnetically protected - can be coupled with heavy-ion induction linacs operating over a wide range of pulse repetition rates to permit thorough exploration of the potential advantages of induction linacs as drivers. These concepts incorporate several interesting options, including solid and liquid-metal blankets and first-wall protection concepts, conventional and advanced power generation cycles, etc. No substantive obstacles to adaptation of these laser fusion reactor concepts for HIF have yet been identified. In particular, the reactor/driver interfaces and achievement of the lower cavity atmosphere densities required for HIF and the reactor/driver interfaces do not present significant problems.

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A Comparison of Li and 83Pb-17Li Primary Coolant Designs for the Pulse*Star ICF Reactor

Two different primary coolants, Li and 83Pb-17Li, have been examined for use in Pulse Star, a pooltype inertial confinement fusion reactor, and a balance-of-plant design has been generated for each coolant. The use of 83Pb-17Li eliminates concern about the large amount of stored chemical energy found in pure Li fusion reactors. A secondary loop was not included in the 83Pb-17Li coolant design because of the relative nonreactivity of lead-lithium. The design utilizing Li as a primary coolant includes a sodium secondary loop to prevent direct contact between irradiated Li and high-pressure water in the case of a steam generator leak. The secondary loop requires additional piping, pumps, heat exchanger area, and steam generator buildings. These additional costs are mitigated by the low pumping power requirement of Li compared with that of high-density 83Pb-17Li. A cost analysis revealed that the additional costs of the Li coolant design are only slightly greater ($13.5 million) than the cost savings due to the lower pumping power. Preliminary studies indicate that tritium containment will be more costly for the 83Pb-17Li coolant design than for the one involving pure Li because the insolubility of tritium in 83Pb-17Li creates large driving forces for tritium leakage into themore » surrounding plant. The tradeoff between the two safety concerns of chemical stability in the case of 83Pb-17Li and practicable tritium containment in the case of pure Li needs to be investigated.« less

Thermonuclear fusion neutrons under “Currentless plasmas” in Heliotron E

Thermonuclear fusion neutron emissions of up to 3 × 10 9 neutrons/s have been observed in Heliotron E deuterium plasmas. “Currentless plasmas” were produced by electron cyclotron resonance (53 GHz, 150 kW) and further heated by hydrogen neutral beam injection (2.2 MW, H 0→D +). It is found that all observed neutron emissions have thermonuclear origin due to the absence of hard X-ray background. Agreement between neutron and charge exchange ion temperature measurements (500 eV < T i (0) × 900 eV) have been found at intermediate densities (1.5 × n e × 3 × 10 13 cm −3) . The neutrons reported in this paper are the first observations of pure thermonuclear fusion neutrons in a helical heliotron plasma confinement device.

Parametric Studies on the Neutronics of a Hybrid (Fusion-Fission) Blanket

Several neutronic calculations have been made for a specific hybrid blanket design in order to evaluate the capability that a fissile zone offers to improve the tritium or fissile fuel production and the energy gain of a fusion blanket. Studies with different fissile zone thickness show the usefulness of thin fissile zones to get high tritium breeding rates. Better total material (tritium plus fissile) production requires thicker fissile zones. Comparisons have been made between the materials neutronic damage expected in a pure fusion blanket and in a hybrid one, with greater energy to damage ratios obtained for the hybrid. Also, greater energy and damage rates are obtained for harder spectra (more 14 MeV neutrons in source) because of the higher potential of 14 MeV neutrons to produce fission in the hybrid blanket.

Thermonuclear Fusion Neutrons under “Currentless Plasmas” in Heliotron E

Thermonuclear fusion neutron emissions of up to 3×10 9 neutrons/sec have been observed in Heliotron E deuterium plasmas. “Currentless plasmas” were produced by electron cyclotron resonance (53 GHz, 150 kW) and further heated by hydrogen neutral beam injection (2.2 MW, H °→ D + ). It is found that all observed neutron emissions have thermonuclear origin due to the absence of hard X-ray background. Agreement between neutron and charge exchange ion temperature measurements (500 eV< T i (0)<900 eV) has been found at intermediate densities (1.5<\bar n e <3×10 13 cm -3 ). The maximum fusion power carried by neutrons, 1.2 mW, is about 10 -9 of the absorbed neutral beam powers. The neutrons reported in this paper are the first observation of pure thermonuclear fusion neutrons in a helical heliotron plasma confinement device.

Pulmonary Stenosis in Infants and Young Children

Twenty-four patients less than 3 years old underwent operation for pulmonary stenosis. Pulmonary dysplasia was diagnosed preoperatively in only 4 patients; in 20 patients the lesion was categorized simply as pulmonary stenosis. At operation, more severe valve deformities were often present in patients less than 2 years of age. Preoperative evaluation did not reveal the extent of the deformity in 7 additional patients. The deformities included not only valvular dysplasia (thickened redundant valve cusps) but also supravalvular and annular abnormalities. Relief of obstruction was obtained only when all components of the obstructive abnormality were relieved. Patch angioplasty of the right ventricular outflow tract was necessary in 13 patients with complex morphology. Valvotomy was effective only for pulmonary stenosis due to pure commissural fusion. A spectrum of the morphology of pulmonary stenosis is recognized, with more complex lesions than simple commissural fusion identified in younger children. The more complex lesions may require more extensive operations (outflow tract patch) to completely relieve the obstructive pathological condition in the outflow tract.

The Magnetic Booster Target Inertial Confinement Fusion Driver

A promising candidate for a near-term low-cost inertial confinement fusion driver is the magnetic booster target concept. In it a small high density magnetically confined plasma and which serves as booster stage, is compressed and ignited by hypervelocity impact. The energy released in the magnetic booster stage, after being transformed into black body radiation, ablatively implodes a high gain second stage target and which releases most of the thermonuclear energy. Alternatively, the energy released in the booster stage can be also used to compress and ignite a target as in impact fusion. The importance of this concept is that it permits to drive the booster stage with a mass accelerator at a velocity of a few 10 km/sec, which is small compared to the velocity required for pure impact fusion, even though it is more than one order of magnitude larger than what can be directly reached with ordinary guns or high explosives. The required velocities can probably be reached by magnetic guns and by fluid dynamic methods through the implosion of cylindrical or spherical shells driven by light gas gun fired projectiles. In comparison to laser- or charged particle beam drivers, the initial driver power is several orders of magnitude smaller and which should lead to a substantial reduction in the driver cost.

Chemically ignited thermonuclear reactions—A near-term means for a high specific impulse—High thrust propulsion system

The combination of metallic shells imploded with chemical explosives and the recently proposed magnetic booster target inertial fusion concept, could make possible the fissionless ignition of small thermonuclear explosions. In the magnetic booster concept a very dense but magnetically confined thermonuclear plasma of low yield serves as the trigger for an inertially confined thermonuclear plasma of high yield. For the most easily ignitable fusion reaction, the DT reaction, this could lead to a fissionless bomb propulsion system, with the advantage to have a much smaller yield of the pure fusion bombs as compared to either fission- or fission-induced fusion bombs, previously proposed for propulsion. Typically, the proposed propulsion concept should give a specific impulse of ∼ 3000 secs, corresponding to an exhaust velocity of ∼ 30 km/sec. If the energy released in each pure fusion bomb is of the order of 10 18 erg or the order of 100 tons of TNT, and if one fusion explosion per second takes place, the average thrust is of the order 10 3 tons. The propulsion system appears ideally suited for the fast economical transport of large spacecraft within the solar system.

The fusion breeder

The fusion breeder is a fusion reactor designed with special blankets to maximize the transmutation by 14 MeV neutrons of uranium-238 to plutonium or thorium to uranium-233 for use as a fuel for fission reactors. Breeding fissile fuels has not been a goal of the U.S. fusion energy program. This paper suggests it is time for a policy change to make the fusion breeder a goal of the U.S. fusion program and the U.S. nuclear energy program. There is wide agreement that many approaches will work and will produce fuel for five equal-sized LWRs, and some approach as many as 20 LWRs at electricity costs within 20% of those at today's price of uranium ($30/lb of U3O8). The blankets designed to suppress fissioning, called symbiotes, fusion fuel factories, or just fusion breeders, will have safety characteristics more like pure fusion reactors and will support as many as 15 equal power LWRs. The blankets designed to maximize fast fission of fertile material will have safety characteristics more like fission reactors and will support 5 LWRs. This author strongly recommends development of the fission suppressed blanket type, a point of view not agreed upon by everyone. There is, however, wide agreement that, to meet the market price for uranium which would result in LWR electricity within 20% of today's cost with either blanket type, fusion components can cost severalfold more than would be allowed for pure fusion to meet the goal of making electricity alone at 20% over today's fission costs. Also widely agreed is that the critical-path-item for the fusion breeder is fusion development itself; however, development of fusion breeder specific items (blankets, fuel cycle) should be started now in order to have the fusion breeder by the time the rise in uranium prices forces other more costly choices.

Investigation of Lanthanides as Neutron Multipliers for Hybrid and Fusion Reactor Blankets

The neutronic performance of three lanthanides (/sup 149/Sm, europium, and gadolinium) as neutron multiplier for the blanket of a fusion-fission (hybrid) and a pure fusion reactor has been evaluated and compared with that of beryllium and lead. During the calculations, the fission zone is made up of UO/sub 2/ rods from the LOTUS experimental hybrid facility now under construction at the Nuclear Engineering Laboratory of the Swiss Federal Institute of Technology in Lausanne. In fusion blanket the fuel zone is replaced by pure lithium. The calculations were performed for two different boundary conditions for the left boundary: (a) reflecting, representative of a typical confinement geometry, and (b) vacuum, which represents a typical blanket experiment in plane geometry. For a vacuum left boundary, threshold reactions are reduced by a factor of about 2 while 1/v-type reactions are decreased by a factor of between 5 and 10, as a consequence of the softer spectrum produced by a reflecting left boundary. In general, the results, notably tritium breeding and energy multiplication, are comparable for the lanthanide multipliers and for beryllium and lead if the left boundary is a vacuum. The use of /sup 149/Sm is slightly less effective than europium or gadolinium andmore » all of the lanthanides perform better for a vacuum left boundary than for the reflecting case. The analyses presented here also illustrate the importance of potential spectral shifts that can occur as the result of experimental exigencies.« less

The case for the fusion hybrid

The use of nuclear fusion to produce fuel for nuclear fission power stations is discussed in the context of a crucial need for future energy options. The fusion hybrid is first considered as an element in the future of nuclear fission power to provide long term assurance of adequate fuel supplies for both breeder and convertor reactors. Generic differences in neutronic characteristics lead to a fuel production potential of fusion-fission hybrid systems which is significantly greater than that obtainable with fission systems alone. Furthermore, cost benefit studies show a variety of scenarios in which the hybrid offers sufficient potential to justify development costs ranging in the tens of billions of dollars. The hybrid is then considered as an element in the ultimate development of fusion electric power. The hybrid offers a near term application of fusion where experience with the requisite technologies can be derived as a vital step in mapping a credible route to eventual commercial feasibility of pure fusion systems. Finally, the criteria for assessment of future energy options are discussed with prime emphasis on the need for rational comparision of alternatives.

The fusion hybrid

In the last few years nuclear fusion by magnetic confinement has made great progress. However, an economical pure fusion power plant is still many years away. In this article I will discuss how a combination of fusion and fission power might be much closer, and might be very helpful both to fission and fusion power.