Effects of Catalysts on the Preparation and Properties of Organometallic Compounds

It has been shown that the formation of RM compounds can be accelerated photochemically and by the use of varying quantities of selected reagents. Also, the rates of reaction between RM compounds and various reactants can be accelerated by small quantities of catalysts like cuprous chloride. For example, the time required for complete interaction of benzonitrile and phenylmagnesium bromide is reduced significantly by the addition of small amounts of compounds like cuprous chloride. It appears that these particular catalysts function by first forming very unstable organometallic compounds like phenylcopper, in the case mentioned. Then the phenylcopper decomposes to give copper and diphenyl, probably via free phenyl radicals which then set up chain reactions

Criticality benchmark guide for light-water-reactor fuel in transportation and storage packages

This report is designed as a guide for performing criticality benchmark calculations for light-water-reactor (LWR) fuel applications. The guide provides documentation of 180 criticality experiments with geometries, materials, and neutron interaction characteristics representative of transportation packages containing LWR fuel or uranium oxide pellets or powder. These experiments should benefit the U.S. Nuclear Regulatory Commission (NRC) staff and licensees in validation of computational methods used in LWR fuel storage and transportation concerns. The experiments are classified by key parameters such as enrichment, water/fuel volume, hydrogen-to-fissile ratio (H/X), and lattice pitch. Groups of experiments with common features such as separator plates, shielding walls, and soluble boron are also identified. In addition, a sample validation using these experiments and a statistical analysis of the results are provided. Recommendations for selecting suitable experiments and determination of calculational bias and uncertainty are presented as part of this benchmark guide

On the Complex Network Structure of Musical Pieces: Analysis of Some Use Cases from Different Music Genres

This paper focuses on the modeling of musical melodies as networks. Notes of a melody can be treated as nodes of a network. Connections are created whenever notes are played in sequence. We analyze some main tracks coming from different music genres, with melodies played using different musical instruments. We find out that the considered networks are, in general, scale free networks and exhibit the small world property. We measure the main metrics and assess whether these networks can be considered as formed by sub-communities. Outcomes confirm that peculiar features of the tracks can be extracted from this analysis methodology. This approach can have an impact in several multimedia applications such as music didactics, multimedia entertainment, and digital music generation.Comment: accepted to Multimedia Tools and Applications, Springe

Identification of novel common variants associated with chronic pain using conditional false discovery rate analysis with major depressive disorder and assessment of pleiotropic effects of LRFN5

Chronic pain is a complex trait that is moderately heritable and genetically, as well as phenotypically, correlated with major depressive disorder (MDD). Use of the conditional false discovery rate (cFDR) approach, which leverages pleiotropy identified from existing GWAS outputs, has been successful in discovering novel associated variants in related phenotypes. Here, genome-wide association study outputs for both von Korff chronic pain grade and for MDD were used to identify variants meeting a cFDR threshold for each outcome phenotype separately, as well as a conjunctional cFDR (ccFDR) threshold for both phenotypes together. Using a moderately conservative threshold, we identified a total of 11 novel single nucleotide polymorphisms (SNPs), six of which were associated with chronic pain grade and nine of which were associated with MDD. Four SNPs on chromosome 14 were associated with both chronic pain grade and MDD. SNPs associated only with chronic pain grade were located within SLC16A7 on chromosome 12. SNPs associated only with MDD were located either in a gene-dense region on chromosome 1 harbouring LINC01360, LRRIQ3, FPGT and FPGT-TNNI3K, or within/close to LRFN5 on chromosome 14. The SNPs associated with both outcomes were also located within LRFN5. Several of the SNPs on chromosomes 1 and 14 were identified as being associated with expression levels of nearby genes in the brain and central nervous system. Overall, using the cFDR approach, we identified several novel genetic loci associated with chronic pain and we describe likely pleiotropic effects of a recently identified MDD locus on chronic pain

HETEROGENEOUS REACTIVITY E m C T S IN MEDIUM-AND HIGH-ENRICHED URANIUMMETALWATER SYSTEMS

The submiad mBOIISP'lpt Bas ken nutbod by I omtractor of me U S Government auder omNa DEACO5-96OR22464. AefonUngiy, tbt US. The effect of heterogeneity on reactivity of low-, medium-, and high-enriched, water-moderated uranium metal systems has been examined for various hydrogen-tofissile ratios using the CSAS 1X sequence in SCALE' and M O P ? For the calculations, an infinite array of closepacked unit cells was modeled which consisted of centered uranium metal spheres surrounded by water (see The enrichments used correspond to the average enrichments of hgmented fuel plates in three proposed waste shipments from Oak Ridge National Laboratory. The analysis performed to obtain peak reactivity for each enrichment as a function of particle size and WX ratio led to the development of the topic discussed in this paper. II. ANALYTICAL METHOD The CSASlX control module of the SCALE code system invokes the functional modules BONAMI and NITAWL to perform resonance self-shielding calculations and XSDRNPM to solve the one-dimensional (1-D) Boltzmann transport equation. BONAMI and MTAWL include a corrective factor, the Dancoff factor, that is applied to the escape probability from a fuel lump to approximate the effect of the presence of other fuel lumps in the system. Currently, SCALE treats interaction of the first, second, and third nearest neighbors for a spherical lattice. Interaction to neighbors beyond the third nearest is treated by an approximation based on the untreated solid angle method.' III. CALCULATIONS M i t e neutron multiplication factor, k, calculations using the SCALE 238-group ENDFB-V cross-section liirary and involving an infinite array of cells were performed where the pitch (and thus wx) was varied for a particular uranium metal sphere diameter at 8.29, 15.18, 44.93, and 92.98% enrichments. SCALE calculations of infinite homogeneous uranium metal-water mixtures were performed at several WX ratios for comparison purposes. By examining the SCALE Dancoff factor at small particle sizes and explicitly modeling the cell in the Monte Carlo continuous energy code MCNP, insight can be gained into the amount of error in a heterogeneous calculation that is attriiutable to the Dancoff factor. The MCNP models consisted of a uranium metal sphere in a water-moderated cell of various pitch values and a mirror reflection boundary condition ( M i t e system). Two immediate observations from the figures are (1) that the 8.29 and 15.18% enriched uranium exhibits a thermal peak reactivity while the 44.93 and 92.98% enriched uranium exhiits a fast and thermal peak reactivity, and (2) that the thermal peak reactivity approaches the fast peak reactivity as the particle size increases. Some difficulty in distinguishing the effect of heterogeneity occurs in the SCALE calculations due to a breakdown that is observed in SCALE for the spherical lattice systems when the particle diameter is small (ie., -0.02 cm). Small particle systems have a predicted behavior in that they physically approach an infinite homogeneous system. For these systems very near an WX of zero, the Dancoff factor of SCALE should and does approach 1.0, and the small particle size system reactivity approaches that of the S i t e homogeneous system. However, as the WX ratio begins to increase fiom its minimum for small particle sizes, a breakdown in the calculation of k, occurs. The breakdown is a result of a deficiency in the algorithm that calculates Dancoff factors for systems where the fourth and further neighbors become important. Eventually, as the WX ratio increases, the Dancoff factor begins to approach zero, and the fourth and further neighbors become unimportant as heterogeneous effects become unimportant (the single fuel lump becomes isolated in the moderator). At this point, the reactivity of small particle sizes calculated by SCALE again physically approaches the infinite homogeneous systems calculated by SCALE and the small particle size systems calculated by MCNP. IV. RESULTS Figures The MCNP curves follow the homogeneous curves for a 0.02-cm-diam particle more closely than SCALE because MCNP does not rely on a Dancoff correction. The difference in k, for the small particle MCNP and SCALE homogeneous system calculations may result &om code approximations, uncertainty in Monte Carlo calculations, cross sections, etc. The MCNP results are in good agreement with SCALE, and homogeneous system results indicate that the merence between the SCALE 0.02-cmdiam particle system calculations and homogeneous system calculations are principally a result of error in the Dancoff approximation. MCNP predicts about a 1% heterogeneous effect at a particle size of 0.02 cm and SCALE predicts about a 2% effect. The difference is probably attributable to SCALE. This is reaffirmed by the additional MCNP calculations at larger particle diameters. These MCNP calculations agree very well with SCALE since the Dancoff correction for the distant neighbors becomes less important as particle size increases. It is known that the Dancoff factor correction in SCALE has the property of being slightly high for a spherical system so that the bias in will be positive, as seen here. As the particle size increases, the error in the Dancoff correction decreases. Again, this can be observed from the MCNP calculations with 0.90-cm-diam, 2.0-cm-d~am, 1.25-crn-dmq and 1.25-cm-diamparticles for 8. 29, 15.18,44.93, and 92.98% enrichments, respectively. The calculated k, difference between MCNP and SCALE at these diameter particles is significantly less than that for 0.02-cm-diam particles. For low WX ratios there is a potential for underestimating reactivity of enriched uranium systems if heterogeneous effects are neglected. It is generally accepted that homogeneous systems are more reactive in the medium-and high-enrichment range for minimum volume (generally occurring around the peak kJ and minimum mass (at an WX -500 for uranium systems). From the figures, heterogeneous reactivity effects are seen to be negligible above WX -500; however, heterogeneous reactivity effects would influence the minimum volume system's reactivity possibly by as much as 10-12% for 8.29% enriched uranium, 5-8% for 15.18% enriched uranium, and 5 7 % for 44.93% enriched uranium Ifrelying on limited moderation (i.e., WX < 20), neglecting heterogeneous effects could underestimate k, by as much 7% for 15.18,44.93, and 92.98% enriched uranium. ACKNOWLEDGMENT

Assessment and recommendations for fissile-material packaging exemptions and general licenses within 10 CFR Part 71

This report provides a technical and regulatory assessment of the fissile material general licenses and fissile material exemptions within Title 10 of the Code of Federal Regulations Part 71. The assessment included literature studies and calculational analyses to evaluate the technical criteria; review of current industry practice and concerns; and a detailed evaluation of the regulatory text for clarity, consistency and relevance. Recommendations for potential consideration by the Nuclear Regulatory Commission staff are provided. The recommendations call for a simplification and consolidation of the general licenses and a change in the technical criteria for the first fissile material exemptions

Assessment of the US regulations for fissile exemptions and fissile material general licenses

The paragraphs for general licenses for fissile material and exemptions (often termed exceptions in the international community) for fissile material have long been a part of the US Code of Federal Regulations (CFR) 10 CFR Part 71, Packaging and Transportation of Radioactive Material. More recently, the Nuclear Regulatory Commission (NRC) issued a final rule on Part 71 via emergency rule-making procedures in order to address an identified deficiency related to one of the fissile exemptions. To address the specified deficiency in a general fashion, the emergency rule adopted the approach of the 1996 Edition of the IAEA: Regulations for the Safe Transport of Radioactive Material (IAEA 1996), which places restrictions on certain moderating materials and limits the quantity of fissile material in a consignment. The public comments received by the NRC indicated general agreement with the need for restrictions on certain moderators (beryllium, deuterium, and graphite). The comments indicated concern relative to both the degree of restriction imposed (not more than 0.1% of fissile material mass) and the need to limit the fissile material mass of the consignment, particularly in light of the subsequent NRC staff position that the true intent was to provide control for limiting the fissile mass of the conveyance. The purpose of the review is to identify potential deficiencies that might be adverse to maintaining adequate subcriticality under normal conditions of transport and hypothetical accident conditions. In addition, ORNL has been asked to identify changes that would address any identified safety issues, enable inherently safe packages to continue to be unencumbered in transport, and seek to minimize the impact on current safe practices