Workshop on Institutional Aspects of Proliferation Resistance

Prepared for the U.S. Dept. of Energy under Contract no. EN-77-S-02-4571.A000. Organized by the MIT Dept. of Nuclear Engineering, PSIA, and the U.S. Dept. of Energy

International management of spent fuel storage : technical alternatives and constraints, topical report

Prepared for the U.S. Dept. of Energy under Contract no. EN-77-S-02-4571.A000.Some of the important technical issues involved in the implementation of a spent fuel storage regime under international auspices are discussed. In particular, we consider: the state of the art as far as the different possible storage modes are concerned, the relevant accident, sabotage, and transportation considerations, and the impact of recent technical spent fuel safeguards initiatives on the nonproliferation rationale for international spent fuel management

Nuclear Power and Energy Security: A Revised Strategy for Japan

SUMMARY During the period of nuclear power's rapid growth, shared assumptions regarding uranium resources and technological capabilities led the majority of industrial nations to remarkably similar strategies for nuclear power deployment. These common assumptions motivated the choice, more than 40 years ago, of the Light Water Reactor (LWR) as the near-term power reactor, to be followed, as soon as possible, by the introduction and deployment of the Fast Breeder Reactor (FBR). The FBR, which uses much less uranium than an LWR of the same capacity, was a crucial part of the strategy because uranium was then believed to be a scarce resource. This strategy, based on the LWR producing the startup fuel for the FBR, implicitly included spent fuel reprocessing, plutonium recycle, and disposal of separated wastes in geologic repositories. Nations with limited indigenous energy reserves, most notably France and Japan, made particularly strong commitments to this strategy. This article was originally presented as a paper at the PARES Workshop: Energy Security in Japan, Tokyo, Japan, 13 July 1998. Lidsky, Miller With the passage of time, it has become clear that the technology associated with this strategy has serious problems. More significant, however, has been the gradual realization that uranium is a widely available resource, with large, inexpensive terrestrial reserves and with essentially inexhaustible marine reserves recoverable at prices which would have minimal impact on the busbar cost of nuclear electricity. It was the predicted near-term (i.e., before 1990) acute shortage of uranium that was the main justification for the choice of LWR/FBR technology. That choice would not have been made otherwise, because other nuclear reactor designs, and other fuel cycles, were known to have substantial advantages with respect to safety, economy, proliferation resistance, and energy security. The LWR is costly, necessarily complex in its dependence on the strategy of "defense-in-depth" to minimize the risk of serious accidents, and relatively unforgiving of error. Development of the particular FBR design that was chosen to meet the predicted near-term shortage, the liquid metal (sodium) cooled FBR (LMFBR), encountered numerous unanticipated technological problems and is unable to meet many of its original design goals. The fuel reprocessing and recycling required for the LWR/FBR fuel cycle, is complex and uneconomical in comparison to the LWR once-through fuel cycle, creates multiple waste streams, and significantly increases the risk of misuse of the fuel cycle for the acquisition of nuclear weapons. 1 As a result of these factors, the United States and other countries which have made a major investment in developing and deploying nuclear power have abandoned the LWR/FBR route to energy security, and are de-emphasizing the LWR as a future energy source. Japan has been reluctant to follow this route because of its near total dependence on imported fuels. Even if energy security were not an issue, Japan's considerable investment in nuclear power argues against a sudden change in its long range plans to rely on nuclear power for a significant fraction of its electrical power needs. However, there is a simple and economic multistage strategy that can guarantee the continued contribution of the existing LWR-based nuclear sector to Japan's energy security in the near and intermediate terms, while enhancing long-term energy security and economic gain by adding reactor types which have the potential for easier local deployment and a significant export market. This strategy includes research and development of reactors which could provide high temperature process heat, thus allowing nuclear power to play a greater role in assuring energy security and supply. The proposed near-to-intermediate-term strategy is based on the stockpiling of natural or low enriched (reactor grade) uranium in sufficient quantity to Nuclear Power and Energy Security 129 ensure continued operation of the installed LWR reactor fleet on a once through cycle for a period of at least several decades. The expense of such an "insurance stockpile" could be largely, if not completely, offset by savings made available by redirection of spending from the breeder to research and development of reactors operating on once-through cycles with enhanced safety, reduced long-lived waste generation, higher efficiency, and process heat potential. The need to develop, and eventually to deploy, new reactor designs does not arise only from concerns regarding uranium supply. Even with assured fuel availability, the "monocultural" LWR fleet is itself a source of insecurity because of the impossibility of demonstrating by actual test that safety, based on defense-in-depth, can prevent catastrophic failures. Generic flaws, either real or suspected, can result in reduced availability or even shut-down of the entire fleet. This possibility has become an increasingly important impediment to growth of the nuclear sector. Thus, there is strong incentive to develop fundamentally different reactor types that could be deployed without arousing such safety concerns. Such reactors could better take advantage of the technological progress in reactor design and power conversion systems that has occurred since the choice of LWR technology nearly 50 years ago. The Modular Gas-cooled Reactor with gas turbine power conversion, for example, offers enhanced safety, process heat capability and, the potential of a very profitable export market. 2 A diversified reactor fleet would enhance energy security whether or not external uranium supplies were available. Continued reliance on nuclear power for electricity and process heat in the long term would be assured by the availability of seawater-derived uranium in large quantities at a cost that would have only marginal effects on the price of nuclear energy production. Although studies on "mining" uranium from seawater were initiated more than 30 years ago in England, 3 it is the R&D carried out in Japan which has established the technical and economic feasibility of the technology

Isolation and Genetic Characterization of Rift Valley fever virus from Aedes vexans arabiensis, Kingdom of Saudi Arabia

An outbreak of Rift Valley fever in the Kingdom of Saudi Arabia and Yemen in 2000 was the first recognized occurrence of the illness outside of Africa and Madagascar. An assessment of potential mosquito vectors in the region yielded an isolate from Aedes vexans arabiensis, most closely related to strains from Madagascar (1991) and Kenya (1997)

Genes contributing to Porphyromonas gingivalis fitness in abscess and epithelial cell colonization environments

Porphyromonas gingivalis is an important cause of serious periodontal diseases, and is emerging as a pathogen in several systemic conditions including some forms of cancer. Initial colonization by P. gingivalis involves interaction with gingival epithelial cells, and the organism can also access host tissues and spread haematogenously. To better understand the mechanisms underlying these properties, we utilized a highly saturated transposon insertion library of P. gingivalis, and assessed the fitness of mutants during epithelial cell colonization and survival in a murine abscess model by high-throughput sequencing (Tn-Seq). Transposon insertions in many genes previously suspected as contributing to virulence showed significant fitness defects in both screening assays. In addition, a number of genes not previously associated with P. gingivalis virulence were identified as important for fitness. We further examined fitness defects of four such genes by generating defined mutations. Genes encoding a carbamoyl phosphate synthetase, a replication-associated recombination protein, a nitrosative stress responsive HcpR transcription regulator, and RNase Z, a zinc phosphodiesterase, showed a fitness phenotype in epithelial cell colonization and in a competitive abscess infection. This study verifies the importance of several well-characterized putative virulence factors of P. gingivalis and identifies novel fitness determinants of the organism

Mutations in maltose-binding protein that alter affinity and solubility properties

Maltose-binding protein (MBP) from Escherichia coli has been shown to be a good substrate for protein engineering leading to altered binding (Marvin and Hellinga, Proc Natl Acad Sci U S A 98:4955–4960, 2001a) and increased affinity (Marvin and Hellinga, Nat Struct Biol 8:795–798, 2001b; Telmer and Shilton, J Biol Chem 278:34555–34567, 2003). It is also used in recombinant protein expression as both an affinity tag and a solubility tag. We isolated mutations in MBP that enhance binding to maltodextrins 1.3 to 15-fold, using random mutagenesis followed by screening for enhanced yield in a microplate-based affinity purification. We tested the mutations for their ability to enhance the yield of a fusion protein that binds poorly to immobilized amylose and their ability to enhance the solubility of one or more aggregation-prone recombinant proteins. We also measured dissociation constants of the mutant MBPs that retain the solubility-enhancing properties of MBP and combined two of the mutations to produce an MBP with a dissociation constant 10-fold tighter than wild-type MBP. Some of the mutations we obtained can be rationalized based on the previous work, while others indicate new ways in which the function of MBP can be modified