Number 4 (June 1977)

A Status Report on the Bayou Darter, Etheostoma rubrum, and the Bayou Pierre System. By R.D. Suttkus and G. Clemmer, plus News Notes, 4 pp

A Review of Graphite and Gold Surface Studies for Use as Substrates in Biological Scanning Tunneling Microscopy Studies

The current status of biological Scanning Tunneling Microscopy (STM) investigations and the importance of using a well-characterized substrate are discussed. The findings of over two years of experiments and over 1,000 images obtained on gold substrates prepared by a variety of different methods are statistically summarized and compared to a very flat reference substrate, highly oriented pyrolytic graphite (HOPG). In an effort to begin to corroborate STM results with those obtained from other more established techniques, the results of Auger Electron Spectroscopy (AES) and Electron Spectroscopy for Chemical Analysis (ESCA) of biomolecular STM samples are presented

TCODE: a computer code for analysis of tritium and vacuum systems for tokamak fusion reactors

TCODE can be used for either near-term experimental reactors or for commercial reactors. The code provides options for items that may be included in a commercial reactor such as a divertor, neutral beam heating, and a breeding blanket. The code was used to calculate tritium and vacuum system parameters for the near term reactors ITR, TNS-UP and EPR as well as for some commercial reactor designs, the UWMAK series. A selected sample of the tritium and vacuum parameters for these reactor designs is shown. Also shown are parameters for a hypothetical reactor UWMAK-III M having similar characteristics to UWMAK-III but with a higher fractional burnup (5.0% cf. 0.83%). The impact of the reactor design scenario upon major tritium and vacuum systems is discussed

Development of tritium breeding blankets for DT-burning fusion reactors

This study examines the status of understanding of blanket tritium recovery and the performance of potentially viable tritium breeding materials under conditions anticipated in a DT-fueled fusion reactor environment. The existing physicochemical, thermophysical, and ceramographic data for candidate liquid and solid breeders are reviewed and appropriate operating conditions defined. It is shown that selection of a breeding material and an appropriate tritium recovery method can impose significant constraints upon blanket design, particularly when considerations of breeder/coolant/structure compatibility and temperature limitations are taken into account

Tritium-handling considerations for ETF and STARFIRE

The tritium handling requirements for both the ETF and the STARFIRE fusion reactor designs are analyzed. The use of a limiter/vacuum system for STARFIRE produced a high fractional burnup (0.42) which resulted in a low tritium inventory in the fueling system. The importance of a fast process flow rate is achieving a rapid cleanup after a tritium release is demonstrated; another important factor is the rate at which HTO is released from building surfaces. A complete fusion reactor tritium facility is described

Modeling of tritium transport in lithium aluminate fusion solid breeders

Lithium aluminate is a candidate tritium-breeding material for fusion reactor blankets. One of the concerns with using LiAlO/sub 2/ is tritium recovery from this material, particularly at low operating temperatures and high fluences. The data from various tritium release experiments with ..gamma..-LiAlO/sub 2/ and related materials are reviewed and analyzed to determine under what conditions bulk diffusion is the rate-limiting mechanism for tritium transport and what the effective bulk diffusion coefficient should be. Steady-state and transient models based on bulk diffusion are developed and used to interpret the data. Design calculations are then performed with the verified models to determine the steady-state inventory and time to reach equilibrium for a full-scale fusion blanket

The LISA-1 and TRIO in-pile tests

The in-pile tests TRIO and LISA-1 involve measurement of in-situ tritium release as a function of time, temperature and sweep gas conditions. These in-situ tritium recovery experiments are similar in concept to other in-pile tests such as the VOM series, Exotic, and the LILA series. TRIO used a single capsule with lithium aluminate. The results from TRIO have been compiled, evaluated and reported. The LISA-1 experiment had six test capsules: one lithium aluminate, one lithium orthosilicate (Li/sub 4/SiO/sub 4/), and four lithium metasilicate (Li/sub 2/SiO/sub 3/). A previous report gives a description of the experimental setup, experimental observations, and preliminary results. Presented herein is a more detailed evaluation of the LISA-1 experimental results for the three breeder materials. The results from LISA are then compared to those of TRIO

Liquid Li-Pb-Bi, a new tritium breeder

In light of their potential utility as tritium breeder-blanket materials, a study was conducted to identify and characterize low-melting phases in the lithium-lead-bismuth system. It is found that a low-melting ternary phase field did in fact exist, e.g., compositions with less than or equal to 20 atom percent lithium and Pb/Bi = 0.773 melted at or below 140/sup 0/C. In addition, the qualitative reactivity of Li-Bi-Pb alloys with water was tested, and although minimal evidence of exothermic chemical reaction was observed, a physical vapor explosion did occur in one of the tests

Janus kinase mutations in mice lacking PU.1 and Spi-B drive B cell leukemia through reactive oxygen species-induced DNA damage

Precursor B cell acute lymphoblastic leukemia (B-ALL) is caused by genetic lesions in developing B cells that function as drivers for the accumulation of additional mutations in an evolutionary selection process. We investigated secondary drivers of leukemogenesis in a mouse model of B-ALL driven by PU.1/Spi-B deletion (Mb1-CreΔPB). Whole-exome-sequencing analysis revealed recurrent mutations in Jak3 (encoding Janus kinase 3), Jak1, and Ikzf3 (encoding Aiolos). Mutations with a high variant-allele frequency (VAF) were dominated by C¡T transition mutations that were compatible with activation-induced cytidine deaminase, whereas the majority of mutations, with a low VAF, were dominated by C¡A transversions associated with 8-oxoguanine DNA damage caused by reactive oxygen species (ROS). The Janus kinase (JAK) inhibitor ruxolitinib delayed leukemia onset, reduced ROS and ROS-induced gene expression signatures, and altered ROS-induced mutational signatures. These results reveal that JAK mutations can alter the course of leukemia clonal evolution through ROS-induced DNA damage