Nuclear power can be the answer

This paper reviews the development of fast molten salt nuclear reactors (MSRs) to close the nuclear fuel cycle by processing future and existing nuclear waste so that it can be returned safely to the environment. It follows two earlier papers outlining the overall use of a range of MSR types and an outline of future proposed marketing of a universal modular thermal MSR design for general purposes. It is suggested that the future MSR industry will probably evolve into three major competitive global corporations. The first one, serving the Far East, seems likely to become entirely MSR based, whereas the other two serving Europe/Western Russia and the Americas may use the alternative lead-cooled fast reactor for waste disposal, which is the closest competitor to the MSR system. Although construction of full-scale fast (MSR) reactors for closing the fuel cycle may not eventuate until some years into the future, it is concluded that this need not delay the introduction of the general purpose thermal MSR reactor envisaged earlier. This new nuclear technology is considered essential to maintain base-load electricity in a world where agricultural needs are expected to take precedence over space requirements for wind and solar farms. Using Thorium, in addition to Uranium, nuclear fuel is sufficient for the next 1000 years. Thus this energy resource can be considered pseudo-sustainable and give us the time to restore our world to a state of balance and true sustainability. Attention is also drawn to the present dangers of continuing to increase the storage of nuclear waste and the refurbishing of old-design nuclear plant, which are already 40 years old

Integrated Molten-salt Nuclear Reactor Systems For Base-load Power Plants

Molten-salt reactors (MSRs) can provide inexpensive industrial process heating in addition to generating electricity. In most cases, this can be best accomplished by design simplification, which results in improvements to MSR’s already existing and inherently strong safety characteristics. This is just one of a number of possible future scenarios that will influence the way in which MSR technology can develop and become marketable. The emphasis in this paper is to develop a reactor with application to the widest possible range of industries. This paper concentrates on the need to develop the inherent safety characteristics of the single fluid thermal reactor with the expectation that sufficient reliability and safety will be achieved in design so that these power generators will eventually be accepted for close integration into the fabric of modern society. It seems inevitable that the required licensing procedures needed for MSRs will vary considerably depending on their type because different designs vary so much. Those used for low-temperature process heat in addition to power generation require much less demanding regulatory procedures than those operating at higher temperatures. This is largely because long-term corrosion is more problematic at higher temperatures and present-day construction materials limit the development of MSRs from reaching their full potential. With appropriate experience with operating early designs of MSRs it is reasonable to expect that lower temperature versions will become certifiable for use in close proximity to a large range of human activities. Ultimately these reactors will be controllable remotely without the local attendance of technical staff

Spin reorientation transition in the incommensurate stripe-ordered phase of La3/2Sr1/2NiO4

The spin ordering of La3/2Sr1/2NiO4 was investigated by magnetization measurements, and by unpolarized- and polarized-neutron diffraction. Spin ordering with an incommensurability epsilon ~ 0.445 is observed below T_so ~ 80 K. On cooling, a spin reorientation is observed at 57 +/- 1 K, with the spin axes rotating from 52 +/- 4 degrees to 78 +/- 3 degrees. This is the first time a spin reorientation has been observed in a La2-xSrxNiO4+delta compound having incommensurate stripe order.Comment: REVTex 4. 4 pages including 4 figures. Minor changes to text. Accepted to be published in Physical Review

Anomalous magnetic ordering in PrBa_2Cu_3O_{7-y} single crystals: Evidence for magnetic coupling between the Cu and Pr sublattices

In Al-free PrBa_2Cu_3O_{7-y} single crystals the kink in the temperature dependence of magnetic susceptibility chi_{ab}(T), connected with Pr antiferromagnetic ordering, disappears after field cooling (FC) in a field H || ab-plane. The kink in chi_c(T) remains unchanged after FC in H || c-axis. As a possible explanation, freezing of the Cu magnetic moments, lying in the ab-plane, caused by FC in H || ab, hinders their reorientation and, due to coupling between the Pr and Cu(2) sublattices, ordering of the Pr^{3+} moments. A field induced phase transition and a field dependence of the Pr^{3+} ordering temperature have been found for both H || c and H || ab.Comment: 11 pages (LaTex with elsart.sty), 5 EPS figs. Accepted to Physica

Magnetic spectrum of the two-dimensional antiferromagnet La2CoO4 studied by inelastic neutron scattering

We report measurements of the magnetic excitation spectrum of the layered antiferromagnet La2CoO4 by time-of-flight neutron inelastic scattering. In the energy range probed in our experiments (0-250 meV) the magnetic spectrum consists of spin-wave modes with strong in-plane dispersion extending up to 60 meV, and a nearly dispersionless peak at 190 meV. The spin-wave modes exhibit a small (~1 meV) dispersion along the magnetic zone boundary. We show that the magnetic spectrum can be described very well by a model of a Heisenberg antiferromagnet that includes the full spin and orbital degrees of freedom of Co2+ in an axially-distorted crystal field. The collective magnetic dynamics are found to be controlled by dominant nearest-neighbour exchange interactions, strong XY-like single-ion anisotropy and a substantial unquenched orbital angular momentum.Comment: 8 pages, 7 figure

The Temperature Evolution of the Out-of-Plane Correlation Lengths of Charge-Stripe Ordered La(1.725)Sr(0.275)NiO(4)

The temperature dependence of the magnetic order of stripe-ordered La(1.725)Sr(0.275)NiO(4) is investigated by neutron diffraction. Upon cooling, the widths if the magnetic Bragg peaks are observed to broaden. The degree of broadening is found to be very different for l = odd-integer and l = even-integer magnetic peaks. We argue that the observed behaviour is a result of competition between magnetic and charge order.Comment: 3 figure

Phonon Dispersion Relations in PrBa2Cu3O6+x (x ~ 0.2)

We report measurements of the phonon dispersion relations in non-superconducting, oxygen-deficient PrBa2Cu3O6+x (x ~ 0.2) by inelastic neutron scattering. The data are compared with a model of the lattice dynamics based on a common interaction potential. Good agreement is achieved for all but two phonon branches, which are significantly softer than predicted. These modes are found to arise predominantly from motion of the oxygen ions in the CuO2 planes. Analogous modes in YBa2Cu3O6 are well described by the common interaction potential model.Comment: 4 pages, 3 figures. Minor changes following referees' comment

Female facial appearance and health

The current study addressed whether rated femininity, attractiveness, and health in female faces are associated with numerous indices of self-reported health history (number of colds/stomach bugs/frequency of antibiotic use) in a sample of 105 females. It was predicted that all three rating variables would correlate negatively with bouts of illness (with the exception of rates of stomach infections), on the assumption that aspects of facial appearance signal mate quality. The results showed partial support for this prediction, in that there was a general trend for both facial femininity and attractiveness to correlate negatively with the reported number of colds in the preceding twelve months and with the frequency of antibiotic use in the last three years and the last twelve months. Rated facial femininity (as documented in September) was also associated with days of flu experienced in the period spanning the November-December months. However, rated health did not correlate with any of the health indices (albeit one marginal result with antibiotic use in the last twelve months). The results lend support to previous findings linking facial femininity to health and suggest that facial femininity may be linked to some aspects of disease resistance but not others

Spin gaps and magnetic structure of NaxCoO2

We present two experiments that provide information on spin anisotropy and the magnetic structure of NaxCoO2. First, we report low-energy neutron inelastic scattering measurements of the zone-center magnetic excitations in the magnetically ordered phase of Na0.75CoO2. The energy spectra suggest the existence of two gaps, and are very well fitted by a spin-wave model with both in-plane and out-of-plane anisotropy terms. The gap energies decrease with increasing temperature and both gaps are found to have closed when the temperature exceeds the magnetic ordering temperature T_m~22 K. Secondly, we present neutron diffraction studies of Na0.85CoO2 with a magnetic field applied approximately parallel to the c axis. For fields in excess of ~8T a magnetic Bragg peak was observed at the (0,0,3) position in reciprocal space. We interpret this as a spin-flop transition of the A-type antiferromagnetic structure, and we show that the spin-flop field is consistent with the size of the anisotropy gap.Comment: 9 pages, 7 figure