T E C H N O L O G Y

Liquid Metal Loop Gets Under Way Martin will collect engineering data on molten lithium at high temperatures for help in designing nuclear reactors for space

Martin Co As nuclear division is putting the finishing touches on a new facility near Baltimore, Md.. for getting engi­neering data on liquid metal coolants tor reactors. Molten lithium above 1800 ; F. will be the first liquid metal studied. The company is seeking data on corrosion, mass transfer, heat trans­fer, fluid flow, and purification tech­niques, as well as other information needed in high temperature liquid metal coolant systems.

The work is part of a three-pronged research and development program for direct conversion nuclear reactors for use in space. The other two ap­proaches involve experimental investi­gations on thermionic conversion of heat directly to electricity, and prepa­ration of conceptual engineering de­signs of thermionic reactor systems.

While a great deal of information has been collected on such liquid metal svstems as molten sodium or

XaK at temperatures of around 1400 F., little is available at the higher temperatures Martin is investi­gating, or on lithium.

Heart of the facility is a large, 1-in. diameter, forced convection loop of niobium alloy. Liquid metal will cir­culate through the various pumps, heat exchangers, and other components of the loop, while numerous thermo­couples give the data needed for de­termining heat transfer rates under various conditions. Containing the hot, reactive lithium is a tough engi­neering problem. Also, the niobium picks up nitrogen and oxygen from the air under certain conditions.

To keep air away, the loop is placed in a horizontal, cylindrical environ­mental chamber 19 ft. long and 7 ft. in diameter. The chamber can be evacuated to about 10 ό mm. Hg, or it can be filled with an inert gas—argon— at 1 atm. Evacuations are alternated

with refilling with argon several times to ensure that the trace of residual gases left in the evacuated chamber is chiefly argon, and the quantity of oxy­gen and nitrogen present is extremely low. For ease of maintenance and modification, the loop is mounted within a framework which can be rolled out of the chamber, and moved about on a wheeled stand.

Niobium alloy has good corrosion and creep resistance qualities. It is, however, expensive—nearly $100 per foot for 1-in. o.d. tubing with 4-mil wall thickness. And it's difficult to weld in such a way that welds will re­sist liquid metal corrosion. Physical specifications for a material with such a relatively small volume of sales are much less detailed than those for a big volume material such as stainless steel. A small defect in an ingot shows up as a weak spot or hole when it is rolled into a thin sheet.

NIOBIUM LOOP. Technician assembles heat exchanger which is part of the 1-in. diameter niobium tubing test loop. Nickel foil is used for reflective insulation. Data are for

design of a nuclear reactor with elements of the type at the right. Each element contains a thermionic generator for converting heat directly to electricity

42 C & Ε Ν M A R C H 12, 1962

NEW HONEYWELL CHROMATOGRAPHY RECORDER

The new Honeywell Chromatography Recorder offers t rue versatil i ty in a quality recorder. Specifically de­signed to meet demanding chromatography needs, the new unit provides the high impedance, high gain, and high stray rejection required for all available detec­tion methods. Here are the operating and service features tha t make the new chromatography recorder the ultimate in reliable inst rumentat ion : • high impedance—up to 25,000 ohm source • high gain, high torque servo drive—one second pen

speed, spans from one to 100 millivolts • high stray rejection—transverse 5000 :1 (5 times span) ;

longitudinal 10,000,000:1 (10V ac) ; d-c longitudinal 12,000,000:1 (12V dc)

• true modular design—amplifier, constant voltage unit, measuring circuit contained in separate modules for maximum flexibility and ease of servicing

Chart paper for the new Honeywell Chro­matography Recorder is available with special easy- tear edge per­forations to facilitate tr imming of laboratory char t records to f i t s tandard 8V2" x 1 1 " repor t f o r m a t .

• quick-change range cards—have integral zero and span adjus tments ; cards interchangeable after initial calibration

• Zener diode constant voltage standardizing—eliminates batteries, s tandard cells, and standardizat ion mech­anisms

• al l-new remote reservoir capillary pen

• adaptable for auxiliary devices—integrators, a larm switches, re t ransmi t t ing slidewires, digital encoder, etc.

• flush, surface, or bench-top (lab feet) mounting

• optional 4-speed manual shift chart drive—base speeds from one inch per hour to one inch per second in 1:2:3:4 ratio

• optional dual speed chart drive mechanism — reduces base speeds 6 :1 , 10:1, 30:1 or 60:1.

And with the new recorder goes the big plus of Honeyivell fast, expert service. More than four hun­dred factory-trained service engineers are spotted s tra­tegically throughout 125 service centers in the United States and Canada. No mat ter where you are, you're sure of get t ing the service you need. For complete details on the New Chromatography Kecorder, contact your nearby Honeywell field engineer. MINNEAPOLIS-HONEYWELL, Wayne and Windrim Aves., Philadelphia 44, P a . In C a n a d a , Honeywell Con­t r o l s , L td . , To­ronto 17, Ontario

Honeyivell HOKfYWFIl I ^m^

HONEYWELL INTERNATIONAL Sales and Service offices in principal cities of the world. Manufacturing in United States, United Kingdom, Canada, Netherlands, France, Japan.

C & Ε Ν 43

METAL ENVIRONMENT. The test loop at the left is mounted on a framework which can roll on a track into the environmental chamber at the rear. The chamber can be either evacuated or filled with argon at 1 atm.

Metal Heated. Schematically, the loop is in the form of a figure 8—with an economizer at the central point, where the line crosses over itself. This heat exchanger heats up liquid metal from the first part of the loop from 1750z F. to 2050 F. as it passes through. On the return journey through the other side of the heat ex­changer the stream is cooled a similar amount. The exchanger is a simple, annular type.

A radiant heater with three tantalum heating elements adds another 50 F. to the temperature of the hot leg stream.

The thermocouples used are gener­ally of chromium and alumel. Some have stainless steel sheathing, others tantalum. However, at temperatures of 2150e F., nickel-cadmium thermo­couples are used.

An electromagnetic pumping system is used. The magnetic field set up in a conducting coil wound around a pipe containing the liquid metal moves it along. The flow meter is a magnetic unit.

Lines of the loop are insulated with reflective material. An ordinary insu­lator, such as magnesite powder, re­tains gases which would gradually re­lease, making it difficult to keep a high vacuum in the environmental chamber. Reflective insulation con­sists of a number of layers of nickel foil wrapped around the piping. These are separated by a nickel knitted wire. Each of the nickel foil layers tends to reflect heat back to the pipe.

Big Problem. Purification is a big problem in any liquid metals system. A continuous system must be used to eliminate impurities picked up. Lith­ium oxide and lithium nitride, from reactions with minute quantities of air and which somehow find their wray into the system, are the most impor­

tant impurities. To remove the oxide -usually present at 3000 to 4000 p.p.m. in lithium as it is purchased— part of the metal in the loop is made to flow through a cold trap. This reduces the temperature to 400° F., causing the oxide to settle out.

The argon system must also contain a purification setup. An argon blan­ket is used in the surge tank for the molten metal. Molecular sieves re­move moisture, a hot trap removes oxygen and nitrogen.

In addition to the large facility, Martin has a number of smaller loops which it has used in screening mate­rials of construction and determining corrosion resistance. The small loops use V. rin. i.d. piping, and liquid metal circulates by thermal convection rather than by pumping. The cold legs run about 1000° F., and the hot ones 2100e F. A great many runs of several hundred hours have been made in loops of this type.

The ultimate aim of the liquid metal research, together with that on thermionic generators—which produce electricity directly from a diode sur­rounded by hot cesium vapor—is to develop fast reactors suitable for space. The main object is to cut down weight in the reactor. By using a fast, rather than a thermal neutron reactor, the need for bulky moderator is elimi­nated. Lithium metal is a light, effi­cient heat transfer medium. By plac­ing a small thermionic generator in each fuel element, the need for boilers and other bulky equipment for conver­sion of heat into electricity disappears.

So far, Martin has conceptually de­signed a 60-kw. reactor system, a 300-kw. system, and is developing a conceptual design of a 2000-kw. sys­tem. The company expects these re­actors to be veiy useful in the space program during 1970 to 1975.

Foxboro Adds Digital Systems

Company forms digital division, will use RCA electronic equipment on a nonexclusive basis

Foxboro has formed a new digital sys­tems division which will design and make automation systems for industrial process control. The move gives Fox­boro complete in-house capability to engineer and manufacture integrated digital and analog systems for both measurement and control.

The digital systems division will call Natick, Mass., its home. Richard W. Sonnenfeldt, formerly with Radio Corporation of America at Natick, moves next door to head Foxboro's new division.

Coinciclentally, RCA will provide Foxboro with some of the equipment which it will need for its new, inte­grated systems. Principally, Foxboro will use, on a nonexclusive basis, RCA computers made at Van Nuys, Calif., and West Palm Reach, Fla. Also in­cluded will be RCA's industrial data transmission link.

Three-Year Program. Until three years ago, Foxboro concentrated on mechanical, pneumatic, and electronic analog-type industrial instruments. Then, realizing the major role that electronic data processing could play in industrial telemetry and remote su­pervisory control, it formed a systems team to study specific industrial ap­plications for digital computers and allied equipment. Out of these stud­ies came the entry into the digital field.

The next step came last year when Foxboro bought Waugh Engineering of Van Nuys, Calif. Waugh broad­ened Foxboro's capabilities with such systems as fully automatic blending control.

At its Natick plant, the new division is cranking up to make input-output equipment, including analog-to-digital converters and other equipment used in the interfaces between process in­struments and computers. Foxboro has already outfitted the division with experienced programers and systems project teams. Now it's training its service people to handle the completed installations.

The chemical industry has been Foxboro's best customer, responsible for about a third of its S54 million sales in 1960. Rut for the digital systems division, the prime target—for the moment, at least—will be the power plant field.

44 C & E N M A R C H 12, 1962