PRODUCTION
Hanford System —A First Hanford heat recovery system will b e first in U. S. t o use heat made in plutonium production LOS ANGELES.—Successful operation of the Hanford heat recovery system will mark the first useful recovery in the U. S. of waste heat from the plutonium production process. Installed at AEC's Richland, Wash., plant, operated by General Electric, the system will recover more than 50 million B.t.u. per hour of heat released when U035 fissions to yield plutonium. This heat formerly left the plant unused with waste reactor cooling water. Sterling E . Nelson of GE described the Hanford system before the 1955 Nuclear Engineering Conference, sponsored here by the Departments of Engineeri n g and University Extension, University of California. A shell and tube heat exchanger with 7 2 0 0 square feet of heat transfer surface will recover the 5 0 million B.t.u. from 10,000 gallons per minute of waste process water, according to Nelson. Stainless steel is used in the shell, admiralty brass in the tubes. Process water will enter the heat exchanger tubes at about 150° F, and will leave at 140° F; it will be circulated by a 10,000 gallon per minute centrifugal pump. Heat will be transferred to 5850 gallons per minute of 34% (by weight) ethylene glycol solution which will enter the exchanger shell at 120 e F. T h e system will carry 30,000 gallons of ethylene glycol in all, and will retain useful heat about 4 5 minutes. Glycol solution is used instead of plain water to avoid freezing. Warm glycol solution will be pumped to heating coils where it will warm 168,000 cubic feet per min-ite of outside air to 72° F. This air will heat and ventilate the large reactor building in which the heating coils are located; the tremendous quantity of air is needed to sweep from the reactor building the small amounts of radioactive gases which tend to accumulate if inside air is recirculated. Radiation is not expected to trouble the Hanford system, says Nelson, although certain precautions will be taken. The secondary circulating loop, for instance, will operate under 25 p.s.i. positive pressure; should tube leakage develop in the heat exchanger, therefore, glycol solution will enter the radioactive waste process water in the tubes rather than become contaminated itself. Intense gamma radiation will break ethylene glycol down to yield 2240
formaldehyde, but under system conditions a measurable amount of formaldehyde should not form for about 100 years of operation, and even if some did form it would not harm the system. After the Hanford heat recovery system is amortized, it i s expected to save annually at least $59,000 in plant operating cost. Amortization will take from 2.3 to 7.5 years, depending upon the accuracy of certain design assumptions. The heat to be recovered is only a fraction of that produced in making plutonium, But is still enough to heat more than 1000 average size homes continuously under winter conditions. All equipment in the system is standard, as are the operating principles involved. The Hanford system is noteworthy, says Nelson, not because it has unique features but because it is a simple and satisfactory adaptation of atomic energy to a peaceful use. Compact Reactor. Space, weight, and primary (radioactive) coolant needs of a nuclear power plant could be reduced considerably by placing the reactor proper inside a cylindrical heat exchanger. E. A. Luebke and L. B. Vandenberg of General Electric propose a design of this type in which the primary coolant is liquid metal, sodium in this case. The advantage of using liquid metal is that the heat exchanger
can incorporate a thermoelectric coolant pump, thus further improving the design's compactness. In the Luebke-Vandenberg design, primary sodium coolant and secondary water coolant flow in parallel tubes. Chromel-constantan thermocouple strips are placed between the hot and cold tubes, and the interstices are filled with copper and molten sodium which reduce thermal and electrical resistance. Current generated in the thermocouple strips flows between iron pole pieces on the sides of the heat exchanger and connected across the bottom of the exchanger, thus creating a strong magnetic field which pumps the sodium coolant through the reactor. Design flow rate is 600O gallons per minute of sodium. This thermoelectric pump, say Luebke and Vandenberg, is self-regulating. Increased reactor heat output causes a rise in sodium temperature which in turn increases the pumping action on the sodium by increasing the thermoelectric temperature gradient. Increased turbine demand (in a steam generating reactor) has the same effect for the same reason. Liquid metal flow control can also be achieved by introducing appropriate electrical resistances into the system o r by adjusting reluctance across the open end of the magnetic circuit. T h e low efficiency of thermoelectric generators ( 1 to 5% ) is not important in this application since the unused energy (in the form of heat) does fulfill its primary function—generating steam to operate the turbine.
Producing Stronger Plasties A study conducted by GE's locomotive and car equipment department is designed to develop better transportation equipment from glass reinforced plastics. Here strands of pure glass roving are fed through a locater screen prior to resin dip. After impregnation and baking, these strands will be stronger than an equal weight of steel
CHEMICAL
AND
ENGINEERING
NEWS
