•
RESEARCH
Can Fluidization Serve Reactors? Fluidized feeds for nuclear reactor heat control may be a possibility, say British researchers In die case of slurries, where solids are transported by the fluid, the fluid velocities required must b e higher than needed by fluidized beds. Thus more heat can b e transported. Mixed phase systems would allow useful heat to b e extracted as both sensible and latent heat. Rapid mixing in the fluidized bed would cause fairly uniform flash evaporation throughout the bed. Partial recycle of the gas will provide a fluidizing material independent of evaporating liquid to maintain the bed. Higher heat transport without any more difficulties in solids entrainment than in other fluidized systems makes a mixed phase system particularly advantageous, say Morris, Nicholls • Safety—hazard of radioactive dusts and Fenning. or spray escaping to the atmosphere must l>e controlled. • Erosion and corrosions—equipment damage difficult or impossilble to repair or replace may occur. • Fuel investment—if fmel is transported as well as fluidizedL, investment may "be large.
JL.ONO applied in petroleuan cracking and a host of chemical processes, fluidization techniques may prove useful for temperature control antdlieat removal in nuclear reactors- J. JB, Mlorris, C. M. Nicholls, and F. W. Feiioing of the U- KJs Atomic Energy Hesesarch Establishment at Harwell have investigated fluidization technique possibilities and find several favorable features: good heat transfer; essentially cv*en temperature throughout the reactor; and if a compatible combination o£ fuel, coolant, materials of constroctioai, and moderator is possible, avoîdaruce of costly fuel fabrication. But difficulties become apparent too:
Consideration must be given to materials used in the bed. The prime requirement is chemical and physical stability to radiation. A useful amount of heat can be extracted from a reactor with a gas fluidized bed canly by using a particle size of 1 mm. or larger. And the gas must be under pressure—of the order of 100 atmospheres—according to Morris, Nicholls, and Fennting. Hydrogen appears best for use with coarse solids, but differences between gases are so small that other considerations would determine which t o use—safety, cost, and power generation method (either open or closed gas cycle turbines, or steam turbines via a heat exchanger). • Liquid Fluidized Systems. Pressurized -water has the best heat transport for a particular particle size and temperature rise for ^thermaT* neutron reactors, Morris, Nictiolls and Fennfng say. I n nonpressurized systems, liquid sodium and lithium give the hest heat removal over a wide range of solid densities. Then, since liquid, metals permit greater temperature rise, these "would allow more dfavos-able over-all heat removal (transfer and transport). 3754
C&EN
AUG, 6. 1956
• Research Need- Any fluidized system developed beyond the research stage wul require an engineering standard not dreamed of in present industrial practice, say these investigators. Systems at first attractive may be ruled out by considerations other than heat removal. A system's fluidization characteristics must be known well. Flow velocities and solid entrainment of possible fluids would have to b e determined. Research is needed on transient density behavior, and heat transfer, erosion, corrosion, and attrition characteristics of systems selected. In a fluidized bed reactor, heat would be generated within solid particles if they contained fissionable material. Heat transfer from these particles to coolant requires study. Safety aspects need attention, particularly on the effect of coolant failure. When a reactor is shut down, and the bed allowed to collapse, it must go into some arrangement for safe containment of fission products. Even after shut down, the problem of heat dissipation remains. The fission products contained in the fuel will still yield heat equal to about 10% of the operating heat; this fission product heat decaying to 1% in a few hours. Extreme care would be needed to en-
Six Million Medical Center Architect's conception of $6 million medical research center being built at Brookhaven National Laboratory, Upton, L. I., N . Y., by Malan Construction. Cylindrical building, rear center, will house nuclear reactor designed specifically for medical research and treatment. Treatment beam will have intensity 50 times greater than that provided b y Broofchaven's general research reactor. Buildings at right will house patients. Square building, extreme left, will contain research divisions in medical physics, biochemistry, pathology, microbiology, physiology, and clinical chemistry. Construction, already started, -will b e completed in 1958Architects are Eggers & Higgins of N e w York.
We
m- r.
^î^e'AMDisquNiS -rroRS^^CAPXa glMPROVEç|:%ryisç|
ISCG>1SITTBNL
SU^TO^}|*îfiLECTRÎSia
riME^>HESiyEs|>^J>RKSUM:
β8ΒΒΗΚΒΒ88™ ΟΑΤ,ΜΓ
ELECTRIC A g i S X i r a CEMENTS '£'*£*£RÊCM ^RESURE SENSITIVE^DlrlK }^BÀÛN^:coi^pôuiaDS^4 v ^ ^NGSTè *v. PROTECtlVE;COAl|i ^ASPiiALTiSPEClAkTlKÇja ^^«1NSUlATI»e?AND,SOW
ÏHD^MP^OyER4^X>5§
l^fe^^MPDIHERÎ^t>£
^^R^»ÏKÎTRÎëÀlSfiL
' lELEGTONg*î
:E^^^^SP« lE^ENsmyEp^
ç
r ^ A ^ - w ^ v^^^jiSftg^K, .kr*«—*cJ
JMATJ
merrq
a new source of s u p p l y . . . Cosden POLYVIS is an oily,, liquid synthetic polymer. Its viscosity and tackiness increase with molecular weight. Cosden POLYVIS has a n excellent color, almost water white, and possesses extreme clarity. It is not subject to normal atmospheric oxîdaMon, has excellent aging characteristics and does not deteriorate or depolymerize enuring storage. Cosden POLYVIS retains its tackiness and viscosity, and does- not harden, set or dry nor become gummy or waxy. Polybutenes lend themselves to many diverse applications. The high degree of stability and the modifying effect upon the properties of other materials are characteristics which renaW Cosden POLYVIS applicable in a wide variety of industrial uses. Price, delivery inforrmation and complete specifications on viscosity ranges for your particular needs will be seat promptly on request.
j^^^
write: organic chemicals division department Β
COSDEN
PETROLEUM
CORPORATION
B.G
SP* I N C .
TEXAS
distributors in principal Midwest cities
AUG.
6.
1956
C&EN
3755
RESEARCH are being continued by Broida, A. Bass, and O . Lutes of the Bureau's Temperature Measurements Laboratory. Theoretical investigations of the systems are being studied by C. M. Herzfeld. T o date, solids containing atomic nitrogen and oxygen, and possibly atomic hydrogen and an unstable hydroxy molecule, have been produced. The solids have very unusual properties, emitting bright glows, blue "flames," and colored flashes of light. When warmed 2 0 or 3 0 degrees, they combine very actively, releasing large quantities of stored energy, principally as heat. According to the Bureau, the method has other possible applications in tbe fields of solid state physics and basic chemistry. The entrapped atoms could be used as powerful probes into the solids containing them. A study of their properties could shed light on the arrangement of atoms and molecules in the solid and the forces acting Capturing Free Radicals on them. Additionally, the mechanism of diffusion of atoms and of reNew NBS technique captures actions between atoms and molecules and stores highly reactive could be studied. In the new method, gases containing free radicals molecules of nitrogen, hydrogen, oxyA TECHNIQUE whereby free radicals gen, or water are first passed through are stored in highly excited states, mak- a high-frequency electric discharge, ing it possible to study and analyze then frozen very suddenly at 4.2° K., them by spectroscopic techniques, has a few degrees above absolute zero. been developed b y t h e National Bu- The discharge is maintained in a w a v e reau of Standards. The new method guide resonator by a 2450-Mc power also makes possible longer storage i n supply. A glass tube leading from the resonator guides the molecular fragthe uncombined form. The experiments, begun at NBS in ments into an evacuated metal vessel 1954 by H. P. Broida and J. R. Pellam, containing a cold surface in contact with a liquid helium bath. Upon reaching the cold surface, the gases freeze into solid form. To prevent solidification of the discharge products at temperatures above 4.2° K., the passageway is kept near room temperature by contact with warm helium gas. The resulting solids can be studied by various techniques. Windows in the metal vessel allow spectrographs of different types to be aimed at the cold surface; the light given off b y the frozen solids can thus be analyzed. T o study light absorbed b y the solids, the gases are condensed on a transparent cold surface, light is passed through the windows of the vessel, the condensed material, the cold surface, and finally into the spectroscopes. Heat evolved by recombination of atoms is determined by condensing the gases into a small, simple low-temperature calorimeter. As material warms up, heat evolved can be measured. Studies of spectra obtained from Diagram of apparatus designed at A p - studies with nitrogen show that the plied Physics Laboratory for collection structure of the solid condensed from and spectroscopic observation of free the discharge differs from that of ordiradicals at low temperatures nary solid nitrogen, says the Bureau.
sure that no dusts o r liquid sprays could escape from the reactor and t h e fluidizing system. Techniques must b
