Document 44YE9jKj2Onak96Mz6yLNGwz1

THE STUDIES continued mateiy 500-C temperoture and higher. 2. Slurries, such os dispersions of Inter-metallic compounds or alloys of uranium in low-melting-point alloys. 3. Fused salts. To postpone the need (or solving many problems of fluid fuels, solid fuel is preferred choice at present. Yet some of the advantages of fluid fuels can be gained through the use of relatively low-melting materials even though in ootid form. Uranium alloy is a reason able choice for the original effort. Ciclvilon Area. Present safety rules require a very large exclusion area around on atomic plant. Thus, to build a reactor within the distribution terri tory of the Detroit Edison Co. would cost, per kw for land alone. 50% of present steam-plont cost. For the Brat few reactors built this moy be a critical factor in total cost. One way out would be to locate the reactor offshore in o body of water close to the distribution territory. Re actor and appurtenances could be installed on a barge or ship, floated to location and sunk in shallow water, or anchored there. Steel tanks, filled with sand and water, woutd provide shield ing. Inilioily only the reactor with its integrated separation facilities would be built, to hold down first costs. Heat produced con be readily "dumped'' in such a spot. Electrical generation and transmission facilities could be added later. Reactor Types. Table 1 gives data on mechanical arrangements, which might meet all or part of the desired require ments listed previously: 1. A jet-mixed centrifugally sepa rated liquid-cooled unit with liquid fuel, continuous processing (C in table). 2. A design with liquid fuel con tained in reactor "pot," with coolant in tubes, (A-/ in table). 3. Coolant outside fuel tubes with liquid or mobile fuel Inside tubes, with or without last, continuous processing. Column B In table outlines first de sign to be investigated. It uses a ura nium alloy In solid form. This type promises to provide many of the needed characteristics and should be capable of quite early development. Future Reactors. The uttimate objec tive (C in table) should be o fast re actor with a true fluid fuel, ft would include, metallurgical processing ond would not have conventional heattransfer surfaces. It might be built of refractory materials that would be rea sonably good for either thermal (slow) or high-energy neutrons. The core would be all molten metal. Fertile material (that la, convertible into fissionable material) might be either depleted uranium or thorium, depending on product desired Another basically almple type of mobile fuel reactor is one in which a pot of molten fuel is cooled by coolant flowing through it in tubes or metal hells (so-called "radiator" type). Here the container material becomes a critical problem. In table, A-l, A-2 and A-J are voriations of this. Type B is a variation In whieh fuel flows In ond out of pot in o molten state, but is held os a solid at a some what lower temperoture during most of its stay In the reactor. Monsanto Chemical - Union Electric At a first step, these companies fover a sodium-cooled graphitemoderated slow-neutron reactor using natural uranium. For each of two reactor layouts, varying In detail, their report com pares power cycles using the heat output in different ways The Monsanto Chemical-Union Elec tric team wos asked to study the feasi bility of a reactor to produce both plutonium and power-one that could be built within the next few years. Studies assumed production of military plutonium for five years. After that, plant would be run for power alone. Table I summarises characteristics of two similar reactors considered. Hanford reactors gave a starting point of experience to speed design and construction. Because water os a cool ant In a Hanford reactor would not permit high-enough temperature for economical power production, sodium was chosen. Sodium at low pressure can remove more heat than pressurised water. Alto, it does not corrode stoinless steel up. to 900 P or higher. As plutonium production vs nearly propor tional to heat output, sodium coolant permits making more plutonium from a given site reactor. Flrst-ChoUt Reactor. For this sodium- cooled and graphite-moderated design, metallic uranium was chosen because it minimises enrichment required and this material is relatively well known. A maximum uranium temperature of 1100 F was chosen to leave a margin of safety. Two potential designs were arrived at. Both have the same general arrangement but differ in the eoolant systems and techniques of loading and unloading (see table). Moderator and surrounding 2-ftthick reflector is assembled from graph ite blocks to form an octagonal prism 24 ft high by 29 ft across the flats. Cooling-channel holes are spaced in a square lattice. Tubular fuel elements, placed in holes by a suitable loading mechanism, are cooled by sodium flow ing both through ond around them. Hot sodium flows through hcot ex changer and Is then pumped back to reactor. Special protection prevents odium vapor from diffusing into graphite, spots sodium leaks, hnd cools graphite. Fual channals can be loaded and un loaded while running at full load. After a few doya "cooling," irradiated fuel assemblies moved from the reoctor ore transferred to Icod shipping "coffins" with 12-in. walls. All fuel handling equipment Is remote controlled. Studies indicate that the most eco-. nomica! plutonium-power reactor uses enriched fuel. Cost of enriching Is more than offset by resulting production of more plutonium, lower unit cost. Coolant Circuits. To prevent contact end resulting violent reaction between sodium and water, shelUand-tube heat 96 REPOST ON ATOMIC ENERGY town Bp^harotieriiticv of Sodium-Cooled .Graphite Reactors j Pu#pOM Neutron Huat output. Material! and aMOVAtll iSreatoadcMioaloi U233 Aaoool e! uralv". lS two! otaMAtc Moderator ftucto# Shield Prlaory cooloni fertile malarial Pval, mae vronlum lamp, t Plutonium and power Thermal (slow) 1000 0.19 J14JD00 Ulernol cooled tube. GrapMto OrepMte Concrete Sodium uni MOO Plutonium and power Thermal ftlaw) 3000 0.93 114.000 Internal, eeternal cooled l< Oraptiite Oraptiite 'Sodium U23I MOO Coolant liilol lamporatwra, P Outlet temperature, f Moilmum velocity. tp Opm ct 300 P Clm at 100 E PumplAQ power {30% If), kw 300 630 90 70,000 9000 3000 303 900 10 110.000 16,000 3000 Olmantloen Cora fleeter tMclitett.ft Octagonal prlim TO tl high, 33 tl ocrats Holt 3 Octagonal prlim, 10 II high, 33 II arrest fists 3 rc `Tyr llmatqdlleitHe Power tost!; t- Com A Com S Mo4ero feom plant Coplrol cot, $10* Net Output, kw Con. 2/kw 26 310,000 124 flO'/yr Mill!/kwh# 61 334,000* M0 flOVr# mih./kwh. 44 260000 169 HOVyr MJU./kwhf Depreciatloa** Property lutt, loiuraece Fuel <ot {tool 9 33</IO' Stu| Operating tot 3.20 0J2 0JO 0.79 3JO 0.33 0.0 0J0 12.20 1.23 OO 3.10 . 2.94 0.29 0.0 0.30 1.26 0.IS 4.63 0.9S 0.63 0.43 1.37 0.30 Total 6J1 03 13.54 3J3 7JS 3.97 Aitumpttonti Plutonium tote ollteti all Iwet cotlt, operating lime. 7300 hr/yrj laiet, Intureaco, 1%,deprerlalton, 10%. 'Hoot >elected below 300 f, *'20% on cotot A, S, 2,16% for coot plant exchanger would have double concen tric tubes with mercury-filled barrier space between. Safety haiards of so dium leaks, and radioactivity of so dium in the recirculating system, re quire that entire sodium circuit be completely leoktight. Fortunately, valve steins eon be sealed by double bellows with a leak detector between bellows to show fail ure of the first line of defense. For pump shafts, the literature sug gests such possibilities as canned ro* tutors, floating shofts, canned motors, froren seals, etc. But the only com pletely leakproof pump developed to d*te U the clectromognetic type. It is turned it will be used for any plant Planned in the immediate future. The sodium-to-water heat exchanger, and sodium pumps and piping, must be Welded for gamma radiation, prefer ably each unit separately protected. Internal Coaling. Power cycle for Cass A, Table I, is based on receiving odium from the reactor at 6S0 F ond returning it at 300 F. Heat exchangers generate 3 million lb per hr of dry sat urated steam at 150 ptl. Turbine cycle has a gross thermal efficiency of about 22%. Blectricol output is obout 220 mw from two units. Auxiliary power totals about S.S% of gross capability. Such a bulky low-pressure turbinegenerator is a far dry from today's typical unit. It requires four 18-in. steam inlets with live-steam reheat between stages. Regenerative feedheating can't be used because condensate must go back to heat exchangers os cold as possible. This is to take advantage of low sodium inlet temperature and also to gel lowest capital cost per kw even at a alight decrease in efficiency. Internal, Bxlomol Cooling. Two power cycles are considered for the Casa B reactor with intemol and external cool ing. One cycle usea heat output of so dium over entire temperature range of 300 to IKK) F. The other rejects heat of coolant below 500 F. This greatly re duces investment ond givea a power output of more readily marketable sise. For both cycles, steam conditions have been taken as 400 psia and 746 F to'the turbine. Absolute pressure at condenser Is 1.5 In. Hg. In the first cycle, about 8.8 million lb of steam per hr is fed to turbine, with o gross ther mal efficiency of about 28%. Resulting gross electrical output mns about 878 mw from Ave units. Auxiliary power, including sodium pumping, is about 5% of gross capability. In the second scheme, about 4.8 mil lion lb per hr Is used, with same effi ciency as in the first. Oross electrical output ia .about 579 mw from three units. Net output is obout 554 mw. Heat from the coolant in temperature range from 300 to 500 F would be re jected by producing steam at 25 psia and condensing it at 20 psia in a watercooled heat exchanger. Clectrlc Power Only. Studies assume limiting plutonium production to a 5-yr period. Power plant should be amortised in this period unless there Is some way of making it useful later. After Ave years there would be several ways to continue power production in an era when power, rather than pluto nium, would be the controlling factor. For example, the reactor could be run for power alone. But even with equipment fully amortised, cost of electricity from such a source might be just as high as from conventional fuelburning plants. Yet such operation could be advantageous from o notional point of view; the reactor, in continu ous operation, would be immediately available as a military plutonium pro ducer when needed. Value of having a standby plant In operating condition should be credited to reactor operation. This woutd reduce power cost Another course would be to shut down the reactor and replace it by a modem high-pressure boiler ond highpressure topping unit. Or, again, a high-pressure boiler alone might be built to supply the turbine. This as sumes the original plant to have been designed to produce steam ot some high pressure where cycle efficiency could be loter improved through use of superheat. Costs in Table-II, bosed on prelim inary information, do not Include such items os lond, financing charges, public liability, insurance, Federal income taxes and profit. JVIT I9J) REPORT ON ATOMIC ENERGY 97