Analysis of an algae-based CELSS. Part 1: model development.

A steady state chemical model and computer program have been developed for a life support system and applied to trade-off studies. The model is based on human demand for food and oxygen determined from crew metabolic needs. The model includes modules for water recycle, waste treatment, CO2 removal and treatment, and food production. The computer program calculates rates of use and material balance for food. O2, the recycle of human waste and trash, H2O, N2, and food production supply. A simple non-iterative solution for the model has been developed using the steady state rate equations for the chemical reactions. The model and program have been used in system sizing and subsystem trade-off studies of a partially closed life support system.

Analysis of an algae-based CELSS. Part 2: options and weight analysis.

Life support components are evaluated for application to an idealized closed life support system which includes an algal reactor for food production. Weight-based trade studies are reported as "break-even" time for replacing food stores with a regenerative bioreactor. It is concluded that closure of the life support gases (oxygen recovery) depends on the carbon dioxide reduction chemistry and that an algae-based food production can provide an attractive alternative to re-supply for longer duration missions.

An integrally shielded transportable generator system for thallium-201 production.

An integrally shielded transportable 201Pb leads to 201Tl generator system for the production of 201Tl has been developed at the Crocker Nuclear Laboratory, University of California, Davis. The present generator design allows for processing of up to 4 Ci of 201Pb parent radioactivity yielding approximately 400 mCi of 201Tl in a chemical form easily converted to radiopharmaceutical quality. Larger capacity generator systems can be constructed since the use of depleted uranium for shielding purposes is becoming readily available. While the parent 201Pb radioactivity decays to the daughter 201Tl, the combination depleted uranium-lead shielded system (approximately 33 kg) can be transported to distant locations for final processing. In this manner, decay losses (approximately 25%) associated with transportation of bulk 201Tl can be avoided since transportation would occur during the time (approximately 32 h) needed for the growth of 201Tl via 201Pb(9.4 h) leads to 201Tl (73.5 h). Single small-volume elutions (15-20 ml) provide more than 95% of the 201Tl radioactivity with no detectable radioactive Pb breakthrough and less than 20 micrograms/ml of carrier Tl.

Cyclotron production of 128Cs (3.62 min). A new positron-emitting radionuclide for medical applications.

The cyclotron production of the short-lived positron emitter 128Cs (3.62 min) from its longer-lived parent 128Ba (2.42 d), based upon the 133Cs(p, 6n) 128Ba leads to 128Cs reaction (Q = -43.98 MeV), has been studied. Cesium-128 has potential applications in positron tomography, particularly for imaging the myocardium and/or for the assessment of regional blood flow. Thick-target yields (mCi/muAh) and cross sections (mb) for 128Ba, 131Ba, 129Cs and 132Cs were measured in the 67-36 MeV proton-energy region. Cyclotron production of 128Ba-128Cs (transient equilibrium) was measured as 3.1 mCi/muAh at end of bombardment (EOB) with a 2.32 g cm-2 thick CsCl target with a proton entrance energy of 67 MeV and exit energy of 54 MeV. Target-radiochemistry using ion-exchange methods allow the preparation of a generator-type system from which high-radionuclidic purity, radiopharmaceutical quality, no-carrier-added 128Cs can be obtained for immediate administration. In addition, with proper radiochemical handling of the 128Ba-128Cs generator, no-carrier-added, high-purity 129Cs (32.35 h, 372 keV, 32%) can also be produced for use in research applications.