Feasibility study of a two-fluid small modular molten salt reactor with in core heat removal capability

A feasibility study of a two-fluid small modular molten salt reactor (MSR) with in core heat removal was performed. The initial fuel block dimension for the configuration was based on the Fuji MSR. The fuel was a mixed fluoride salt of density 3.25 g/cc, composed of 71 LiF - 16 BeF2 - 12 ThF4- 1 233UF4 molar percentages. The coolant salt was Li4(FLiBe) of density 1.94 g/cc. The work set out to establish whether or not such a reactor is thermodynamically feasible when optimized for various neutronics parameters. A Java based API was developed to facilitate the neutronics optimization of the reactor concept. In the simulation studies that followed (performed in MCNP), it was established that the optimal block dimension and fuel volume fraction to support under-moderation requirements are 20 cm across flats and 0.15 respectively. Fuel channel diameters varied from 12 cm to 9 cm such that neutron leakage could be suppressed while maintaining a radial power peaking factor of 2.20. In all the simulations except for temperature reactivity calculations, the reactor was assumed isothermal at 900 K. The average temperature coefficient of reactivity was calculated as -5.87E-5 Δk/k-K. Thermo hydraulic studies performed in STAR CCM+ revealed that complete in core heat removal cannot practically be achieved in a design purely optimized for neutronics. However, it was found that fractional heat removal ranging from 15% - 85% can be achieved with sufficient mass flow rates. Potential improvements necessary for complete in core heat removal are theorized and briefly discussed --Abstract, page iii

Strong suppression of heat conduction in a laboratory replica of galaxy-cluster turbulent plasmas

In conventional gases and plasmas, it is known that heat fluxes are proportional to temperature gradients, with collisions between particles mediating energy flow from hotter to colder regions and the coefficient of thermal conduction given by Spitzer's theory. However, this theory breaks down in magnetized, turbulent, weakly collisional plasmas, although modifications are difficult to predict from first principles due to the complex, multiscale nature of the problem. Understanding heat transport is important in astrophysical plasmas such as those in galaxy clusters, where observed temperature profiles are explicable only in the presence of a strong suppression of heat conduction compared to Spitzer's theory. To address this problem, we have created a replica of such a system in a laser laboratory experiment. Our data show a reduction of heat transport by two orders of magnitude or more, leading to large temperature variations on small spatial scales (as is seen in cluster plasmas)

Barriers to adequate follow-up during adjuvant therapy may be important factors in the worse outcome for Black women after breast cancer treatment

<p>Abstract</p> <p>Introduction</p> <p>Black women appear to have worse outcome after diagnosis and treatment of breast cancer. It is still unclear if this is because Black race is more often associated with known negative prognostic indicators or if it is an independent prognostic factor. To study this, we analyzed a patient cohort from an urban university medical center where these women made up the majority of the patient population.</p> <p>Methods</p> <p>We used retrospective analysis of a prospectively collected database of breast cancer patients seen from May 1999 to June 2006. Time to recurrence and survival were analyzed using the Kaplan-Meier method, with statistical analysis by chi-square, log rank testing, and the Cox regression model.</p> <p>Results</p> <p>265 female patients were diagnosed with breast cancer during the time period. Fifty patients (19%) had pure DCIS and 215 patients (81%) had invasive disease. Racial and ethnic composition of the entire cohort was as follows: Black (N = 150, 56.6%), Hispanic (N = 83, 31.3%), Caucasian (N = 26, 9.8%), Asian (N = 4, 1.5%), and Arabic (N = 2, 0.8%). For patients with invasive disease, independent predictors of poor disease-free survival included tumor size, node-positivity, incompletion of adjuvant therapy, and Black race. Tumor size, node-positivity, and Black race were independently associated with disease-specific overall survival.</p> <p>Conclusion</p> <p>Worse outcome among Black women appears to be independent of the usual predictors of survival. Further investigation is necessary to identify the cause of this survival disparity. Barriers to completion of standard post-operative treatment regimens may be especially important in this regard.</p

Using fusion-product spectroscopy to diagnose inertial confinement fusion implosions and study stopping power on OMEGA, the NIF, and Z

This thesis summarizes three distinct but related projects that use the spectroscopy of fusion products to diagnose areal densities in Inertial Confinement Fusion (ICF) implosions or study stopping power to better understand the areal density requirements of said implosions. The first project at the Z Facilty regards spectroscopy of the primary DD neutron spectra from Magnetized Liner Inertial Fusion (MagLIF) implosions enables diagnosing yields and liner areal densities. Both of these quantities are extremely important for assessing implosion performance on the Z. Traditional nToF spectrometers face additional challenges at the Z facility due to large scattering sources from the machine and long neutron burn widths. For this reason, a CR-39 based neutron-recoil spectrometer has been developed for measuring the DD spectrum at the Z. A proof of principle design was fielded and the data is presented. A improved shielded design for accurately measuring the liner areal density is also developed and presented. The second project at the Nation Ignition Facility (NIF), spectroscopy of secondary nuclear reactions from surrogate deuterium filled implosions are sensitive to hot spot areal density magnitude and asymmetry. Secondary DT neutrons are routinely measured on the NIF using four neutron time of flight (nToF) spectrometers positioned at different lines of sight. These measurements infer convergence ratios that differ from those inferred by x-ray imaging techniques. This discrepancy is explained by each method having different sensitivities to profiles and asymmetries. Additionally, the widths of the secondary DT neutron spectra are sensitive to mode-2 asymmetries and further confirm that these asymmetries are present in the hot-spot of NIF implosions. Finally, the third project at the OMEGA laser facility, a unique experimental platform for accurately characterizing and measuring the stopping power of Warm Dense Matter (WDM) plasmas has been developed. Understanding stopping power in this regime is critical for probing areal densities in the high-density fuel of ICF implosions. The platform uses X-ray Thomson Scattering (XRTS) to characterize the plasma’s temperature and ionization state. Proton spectroscopy is used to accurately measure the energy loss through the WDM subject. Results from several experiments 3 indicate that WDM plasmas consistently have higher stopping than cold matter when sufficiently heated. These results show good agreement with stopping power models that account for partial ionization.Sc.D

Fuel-ion diffusion in shock-driven inertial confinement fusion implosions

The impact of fuel-ion diffusion in inertial confinement fusion implosions is assessed using nuclear reaction yield ratios and reaction histories. In T3He-gas-filled (with trace D) shock-driven implosions, the observed TT/T3He yield ratio is ∼23lower than expected from temperature scaling. InD3He-gas-filled (with trace T) shock-driven implosions, the timing of theD3He reaction history is ∼50 ps earlier than those of the DT reaction histories, and average-ion hydrodynamic simulations cannot reconcile this timing difference. Both experimental observations are consistent with reduced T ions in the burn region as predicted by multi-ion diffusion theory and particle-in-cell simulations

Impact of asymmetries on fuel performance in inertial confinement fusion

Low-mode asymmetries prevent effective compression, confinement, and heating of the fuel in inertial confinement fusion (ICF) implosions, and their control is essential to achieving ignition. Ion temperatures (T[subscript ion]) in ICF experiments are inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn also impacts broadening and will lead to artificially inflated “T[subscript ion]” values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured T[subscript ion]. We report on intentionally asymmetrically driven experiments at the OMEGA laser facility designed to test the ability to accurately predict and measure line-of-sight differences in apparent T[subscript ion] due to low-mode asymmetry-seeded flows. Contrasted to chimera and xrage simulations, the measurements demonstrate how all asymmetry seeds have to be considered to fully capture the flow field in an implosion. In particular, flow induced by the stalk that holds the target is found to interfere with the seeded asymmetry. A substantial stalk-seeded asymmetry in the areal density of the implosion is also observed.United States. Department of Energy (Award DE-NA0002949