Technology Development Program for an Advanced Potassium Rankine Power Conversion System Compatible with Several Space Reactor Designs

This report documents the work performed during the first phase of the National Aeronautics and Space Administration (NASA), National Research Announcement (NRA) Technology Development Program for an Advanced Potassium Rankine Power Conversion System Compatible with Several Space Reactor Designs. The document includes an optimization of both 100-kW{sub e} and 250-kW{sub e} (at the propulsion unit) Rankine cycle power conversion systems. In order to perform the mass optimization of these systems, several parametric evaluations of different design options were investigated. These options included feed and reheat, vapor superheat levels entering the turbine, three different material types, and multiple heat rejection system designs. The overall masses of these Nb-1%Zr systems are approximately 3100 kg and 6300 kg for the 100- kW{sub e} and 250-kW{sub e} systems, respectively, each with two totally redundant power conversion units, including the mass of the single reactor and shield. Initial conceptual designs for each of the components were developed in order to estimate component masses. In addition, an overall system concept was presented that was designed to fit within the launch envelope of a heavy lift vehicle. A technology development plan is presented in the report that describes the major efforts that are required to reach a technology readiness level of 6. A 10-year development plan was proposed

Investigating the effects of vitreous humour (crude extract) on growth and differentiation of rat mesenchymal stem cells (rMSCs) and human NTERA2 cells

It is very well documented that retinoic acid (RA) reduces growth rate by induction of cell differentiation in certain conditions and cell lines. On the other hand, hyaluronic acid (HA) is known for its growth induction on cultured cells. A natural source of HA, rabbit vitreous humour (VH), was previously shown to promote wound repair in model animals. In search for its possible mechanisms, VH extract was tested on the cultured mesenchymal stem cells and NTERA2 as human embryonal carcinoma cells in the presence of RA. Changes in some cellular and molecular markers (A2B5, Oct4, Sox2) showed that VH and possibly HA interfere with differentiating effects of RA. Therefore, this reagent may affect cell proliferation and tissue regeneration by inhibition of cell differentiation.Хорошо известно, что ретиноевая кислота (RA) снижает темпы роста, индуцируя дифференциацию клеточных линий в определенных условиях. Вместе с тем известно, что гиалуроновая кислота (HA) индуцирует рост культивируемых клеток. Ранее было показано, что естественный источник НА, стекловидное тело (VH) кролика, вызывает заживление ран у модельных животных. В поисках возможного механизма этого процесса экстракт стекловидного тела был исследован на культивируемых мезенхимальных стволовых клетках и клетках NTERA2 эмбриональной карциномы человека в присутствии RA. Изменения некоторых клеточных и молекулярных маркеров (A2B5, Oct4, Sox2) показали, что VH и, возможно, HA влияют на дифференцирующие эффекты RA. Таким образом, это вещество может влиять на пролиферацию клеток и регенерацию тканей, ингибируя дифференциацию клеток.Добре відомо, що ретиноєва кислота (RA) знижує темпи росту, індукуючи диференціацію кліткових ліній в певних умовах. Разом з тим відомо, що гіалуронова кислота (НА) індукує ріст культиво- ваних клітин. Раніше було показано, що природне джерело НА, склоподібне тіло (VH) кроля, викликає загоєння ран у модельних тварин. В пошуках можливого механізму цього процесу екстракт склоподібного тіла був досліджений на культивованих мезенхімальних стовбурових клітинах та клітинах NTERA2 ембріональної карциноми людини в присутності RA. Зміни деяких клітинних та молекулярних маркерів (A2B5, Oct4, Sox2) показали, що VH і, можливо, НА впливають на диференціюючі ефекти RA. Таким чином, ця речовина може впливати на проліферацію і регенерацію тканин, інгібуючи диференціацію клітин

Heat transfer near spacer grids in rod bundles

Heat transfer data from several sources have been assembled which show the effect of spacer grids on local heat transfer within a rod bundle. Both single phase (air and steam) data and two phase (steam/water) data show heat transfer augmentation in the grid region. Heat transfer improvement immediately beyond the grid ranges from a few percent to over fifty percent in these experiments, depending on flow conditions. The data are examined using several nondimensional parameters which relate the above effects to known quantities. The relative effect of the grid on local heat transfer is altered by both the Reynolds number and blockage ratio. Twenty to thirty hydraulic diameters are required before the local effect of the grid dissipates. Locally, both the single phase and two phase data show the same trends. Comparison of the single and two phase data also shown some differences. Some film boiling data indicate that an altered heat transfer regime may exist near the grid. High rod heat transfer coefficients at the grid locations indicate either a rewet of the rods or at least a change from film boiling to transition boiling near the spacer. The comparison also indicates that the film boiling data is affected on a global as well as local basis. This is due to the effect of the grid on the liquid distribution

Analysis of alkali liquid metal Rankine space power systems

Space power systems must have both high power density (kW/m/sup 3/) and high specific power output (kW/kg), while maintaining high reliability. Several power source and conversion options are available. A sketch of the Rankine system under consideration is shown. The design for the 100 kWe system analyzed here uses the same basic design concept as described by Jones for a 5 MWe system. In brief, it consists of a uranium nitride fuel pin reactor core with a tungsten/lithium hydride shield. Potassium at approx. 25% quality exits the reactor core. A separator is used to provide potassium vapor (at approx. 99%+ quality) to a full impulse turbine. Liquid from the separator is recirculated back to the core inlet using jet pumps. A heat pipe radiator condenses the vapor exiting the turbine while a separate turbine driven boiler feed pump returns the condensed liquid to the core inlet. Sizes and weights for the various system components were determined using design algorithms or were scaled from previous design studies

Liquid metal heat transfer issues

An alkali liquid metal cooled nuclear reactor coupled with an alkali metal Rankine cycle provides a practicable option for space systems/missions requiring power in the 1 to 100 MW(e) range. Thermal issues relative to the use of alkali liquid metals for this purpose are identified as these result from the nature of the alkali metal fluid itself, from uncertainties in the available heat transfer correlations, and from design and performance requirements for system components operating in the earth orbital microgravity environment. It is noted that, while these issues require further attention to achieve optimum system performance, none are of such magnitude as to invalidate this particular space power concept

Annular burnout data from rod-bundle experiments. [PWR]

Burnout data for annular flow in a rod bundle are presented for both transient and steady-state conditions. Tests were performed at the Oak Ridge National Laboratory in the Thermal Hydraulic Test Facility (THTF), a pressurized-water loop containing an electrically heated 64-rod bundle. The bundle configuration is typical of later generation pressurized-water reactors with 17 x 17 fuel arrays. Both axial and radial power profiles are flat. All experiments were carried out in upflow with subcooled inlet conditions, insuring accurate flow measurement. Conditions within the bundle were typical of those which could be encountered during a nuclear reactor loss-of-coolant accident

Evaluation of nonequilibrium effects in bundle dispersed-flow film boiling. [PWR; BWR]

The effects of thermodynamic nonequilibrium in dispersed flow film boiling heat transfer are examined. Steady-state and transient rod-bundle data are used to evaluate several empirical heat-transfer models commonly employed to predict post-CHF behavior. The models that account for thermodynamic nonequilibrium perform adequately, while those that ignore nonequilibrium effects incur errors in wall superheat as high as 190/sup 0/K. Nonequilibrium effects can also be treated by explicitly modeling the phenomena. The thermal-hydraulic code COBRA-TF employs this approach. Using bundle data, the models in the code are evaluated. Analysis suggests that the interfacial heat transfer is overpredicted

The development of a preliminary correlation of data on oxide growth on 6061 aluminum under ANS thermal-hydraulic conditions

The corrosion of aluminum alloy 6061 is being studied in a special test loop facility under the range of thermal-hydraulic conditions appropriate for fuel plate operation in the Advanced Neutron Source (ANS) reactor core. Experimental measurements describing the growth of the boehmite (Al{sub 2}O{sub 3}H{sub 2}O) films on the exposed aluminum surfaces are now available for a range of coolant conditions and heat fluxes, and these results have been analyzed to demonstrate the influence of several important experimental variables. A subset of our data base particularly appropriate to the ANS conditions presently anticipated was used to develop a preliminary correlation based on an empirical oxidation model