Sodium Handling at Argonne National Laboratory - American

Sodium Handling at Argonne National Laboratory F. A. S M I T H

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 2, 2015 | http://pubs.acs.org Publication Date: January 1, 1957 | doi: 10.1021/ba-1957-0019.ch006

Box 2 9 9 , A r g o n n e N a t i o n a l L a b o r a t o r y , Lemont, III.

Sodium, used as a heat transfer fluid, can most effectively remove heat from a fast breeder reactor. Development work on sodium handling at Argonne National Laboratory in 1945 led to the first turbine-electric power from nuclear energy in 1951. This paper presents the engineering mock-up of the experimental breeder reactor II and illustrates associated pumps, valves, and instrumentation. The past year's successful operation of the EBR-II mock-up has demonstrated that sodium technology is adequate for the job. Properly used, sodium may be the key to the problem of really using the elusive atom.

I H E Reactor E n g i n e e r i n g D i v i s i o n of the A r g o n n e N a t i o n a l L a b o r a t o r y is c u r r e n t l y w o r k i n g o n the design of a s o d i u m - c o o l e d fast reactor. F i g u r e 1 shows the c o m p l e x i t y of equipment that must r e m a i n compatible w i t h , a n d operate i n s o d i u m at temperatures r a n g i n g f r o m 580° to 900 °F. F r o m the aspect of s o d i u m h a n d l i n g as a p p l i e d to the design w o r k o n this reactor, the u n i q u e features are important. T h e e x p e r i m e n t a l breeder reactor ( E B R - I I ) is conceived as a n entire p r i m a r y reactor system contained i n a single vessel; the core, p u m p , heat exchanger, a n d f u e l h a n d l i n g equipment are a l l c o n tained i n a single tank containing 80,000 gallons of sodium. A v a r i e t y of safety considerations m a k e this p a r t i c u l a r arrangement i n h e r e n t l y m o r e safe t h a n the i n d i v i d u a l component type reactor, such as M o d e l E B R - I . T h e most obvious advantage of a s o d i u m submerged or flooded reactor is that the large v o l u m e of s o d i u m i n the container vessel c a n handle, b y n a t u r a l convection, emergency s h u t d o w n cooling requirements i n case of p u m p failure. A l s o , a leak i n the radioactive p r i m a r y p l u m b i n g to a n d f r o m the reactor is not serious. T h e flooded s o d i u m cooled E B R - I I reactor design s i m p l y keeps a l l of the radioactive s o d i u m i n a single tank. H o w e v e r , the s o d i u m technology i n the design of this type of plant is m o r e c o m p l e x t h a n for E B R - I . A p u m p must r u n s u b m e r g e d beneath s o d i u m ; pressure gages, flowmeters, f u e l loading, a n d u n l o a d i n g gadgets m u s t o p e r a t e i n h o t s o d i u m . T o demonstrate that s o d i u m technology has a d v a n c e d to a point w h e r e such a reactor m i g h t actually be built, a scale m o d e l has been b u i l t w i t h m a n y of the engineering problems p e r t a i n i n g to s o d i u m incorporated into a n operating unit.

Initial Filling EBR-II Model Storage Tank T h e i n i t i a l l o a d i n g of s o d i u m was into a 5000-gallon storage tank, w h e r e it was " c o l d t r a p p e d " a n d then p u m p e d into the reactor m o d e l tank. 42

In HANDLING AND USES OF THE ALKALI METALS; Advances in Chemistry; American Chemical Society: Washington, DC, 1957.


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Figure 1. EBR-II w o r k i n g m o d e l

E v e r y effort was made to m a i n t a i n h i g h s o d i u m p u r i t y d u r i n g i n i t i a l filling. T h e s o d i u m was filtered a n d argon gas was b l a n k e t e d into 55-gallon steel d r u m s b y the vendor. F o r convenience i n e m p t y i n g the d r u m s a n d ultimate disposal of e m p t y containers, the d r u m s were s u p p l i e d w i t h a gasketed a n d r e m o v a b l e head, a n d w i t h a thermocouple w e l l cast into the center of each b a r r e l . A n i m p o r t a n t step i n the transfer of s o d i u m f r o m the vendor's container into the c h a r g i n g tank is the exact m a n n e r of c o u p l i n g a rather a w k w a r d 55-gallon d r u m to a 125-gallon fixed c h a r g i n g tank. A s s h o w n i n F i g u r e 2, a 1-inch v a l v e d pipe extension, a, at the bottom of the b a r r e l slides t h r o u g h a T e f l o n - p a c k e d c o m pression nut, c, a n d 2 - i n c h gate v a l v e , b, m o u n t e d o n the c h a r g i n g tank. T h i s simple slip connection eliminates a bellows assembly a n d / o r flanges that w o u l d have to be made u p a n d b r o k e n for each b a r r e l . T h e sequence of filling was as follows ( F i g u r e 3) : E a c h b a r r e l is preheated to 175°F. a n d then positioned b y a n electric hoist above the c h a r g i n g tank. T h e 1-inch b a r r e l extension assembly is l o w e r e d t h r o u g h the compression nut, c, a n d the nut is tightened h a n d tight. T h e 2 - i n c h gate v a l v e , b, is opened a n d the b a r r e l is gently l o w e r e d to rest o n the top stand a n d is r e a d y for c h a r g i n g . D u r i n g this positioning, the 1-inch v a l v e , a, remains closed. T h e b a r r e l is heated w i t h a b e l l - j a r heater assembly of 2 0 - k w . capacity. T h e s o l i d - l i q u i d phase is reached i n about 30 minutes. T h e compression nut, c, a n d gate v a l v e , b, are heated w i t h a q u i c k - w r a p , E l e c t r o t h e r m a l heating tape. E a c h b a r r e l is fitted w i t h a n i n t e r n a l thermocouple a n d the temperature is r e c o r d e d o n a



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Figure 2. Sodium unloading arrangement

6000 GAL. DUMP-STORAGE TANK

VALVE© SODIUM TRANSFER AND VA1.VIN0 SECUENCE TO COLO TRAP STORAGE TANK : OPEN VALVES 2.4,6, AND 7 ONLY TO COLO TRAP REACTOR MOOEL TANK : OPEN VALVES 2,3,5, AND 7 ONLY TO FILL REACTOR MOOEL TANK

OPEN VALVES 2,4,3, AND 7 ONLY

TO EMPTY REACTOR MOOEL TANK : OPEN VALVES 2.3,6.AND 7 ONLY

125 GAL. CHARGING TANK

Figure 3. Schematic of sodium transfer system for EBR-II model



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B r o w n strip chart recorder. W h e n the temperature is observed to rise s h a r p l y f r o m 210° to 250°F., the heating m a n t l e is t u r n e d off, the 1-inch gate v a l v e is opened, a n d m o l t e n s o d i u m drains b y g r a v i t y into the charge tank. Inert gas is m a i n t a i n e d at equalized pressure b y a " q u i c k m a k e a n d b r e a k " flare tube connecti n g the top of the charge tank to the top of the s o d i u m b a r r e l . N i n e t y - s e v e n b a r rels of s o d i u m were charged i n this m a n n e r without difficulty.


Pumps T h e p u m p chosen for the m o d e l tank is a direct current, electromagnetic p u m p capable of p u m p i n g 1000 gallons at 15 pounds per square i n c h . Before the c o m pleted p u m p was installed i n the m o d e l tank, a test loop was b u i l t ( F i g u r e 4) a n d the p u m p was r u n " u n c a n n e d " for h e a d - c a p a c i t y curves. F r o m the s o d i u m t e c h nology viewpoint, the p u m p operates considerably better submerged i n the m o d e l tank. T h e p r a c t i c a l p r o b l e m of getting a l l t r a p p e d inert gas out of the test loop was responsible for lower flow rates t h a n are possible i n the m o d e l tank, w h e r e the suction side of this p u m p takes s o d i u m f r o m the bottom of a 5000-gallon r e s e r v o i r that is free f r o m t r a p p e d gas. T h i s p u m p has operated for 1000 test hours w i t h no maintenance, no seals to replace, no a u x i l i a r y cooling, a n d no failures. O t h e r smaller p u m p s are used i n the m o d e l t a n k system. F i g u r e 5 shows the p u m p tube as made u p for a c o l d t r a p p u m p . T h i s little p u m p operates o n 750 °F. s o d i u m a n d transfers s o d i u m f r o m the m o d e l t a n k to a cold trap a n d b a c k to the m o d e l tank ( F i g u r e 3). It has operated for 7000 hours without attention of a n y k i n d . F i g u r e 6 shows a n A l l i s - C h a l m e r s canned rotor fluid b e a r i n g p u m p that circulates coolant for m a i n t a i n i n g a AT across the c o l d t r a p itself. T h i s p u m p has operated v e r y w e l l at temperatures of 300 °F., where the p u m p is deliberately placed i n the cold e n d of the heat transfer system. T o supplement the design of the m a n n e r of j o i n i n g h i g h direct c u r r e n t c o n ductors (30,000 amperes direct current, 200,000 amperes) to t h i n - w a l l e d direct c u r r e n t p u m p tubes, a s m a l l test p u m p a n d loop has been b u i l t . T h e design of the bus b a r c a r r y i n g direct c u r r e n t to the t h i n tube is a u n i q u e application of l i q u i d metal. F i g u r e 7 shows details of a l i q u i d m e t a l b o n d e d copper bus bar. A s m a l l p u m p b u i l t i n this m a n n e r has p u m p e d s o d i u m for 3400 hours at 8 0 0 ° C . H i g h

Figure 4.

1000-gallon-per-minute test facility for direct current sodium pump


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temperature was used to subject the u n i q u e joint to severe temperature to determ i n e the corrosion effect of the N a K o n the " c a n n e d " copper bus bar. T h r e e failures of p u m p tubes have o c c u r r e d b u t no f a i l u r e of the bus connector. T h i s indicates that the m a n n e r of attaching a v e r y large piece of copper to a v e r y t h i n stainless steel p u m p tube is at least as good as, i f not better, t h a n the tube itself. O p e r a t i o n of the loop to test bus b a r connections has also demonstrated satisfactory operation of pressure gage a n d a n electromagnetic flowmeter at 8 0 0 ° C . ( F i g u r e 8). In a n effort to a r r i v e at a more conventional type of p u m p for the secondary s o d i u m - s t e a m system of the E B R - I I plant, a large 3800 g a l l o n - p e r - m i n u t e m e c h a n ical p u m p was tested w i t h sodium. F i g u r e 9 shows the magnitude of a 12-inch s o d i u m test facility for this p u m p test. T h i s test was of short d u r a t i o n , as after o n l y seconds of operation the rotor seized. Disassembly has s h o w n that a leak c o u l d have exited where, d u r i n g earlier water tests, water could pass t h r o u g h a v e r y s m a l l crack i n the magnet lift assembly a n d could have r e m a i n e d there u p u n t i l s o d i u m was charged into the p u m p . A reaction between water a n d s o d i u m c o u l d have p r o duced the type of damage shown b y F i g u r e 10. B l a c k e n e d m i c a indicates these are reasonable assumptions, because m i c a i m m e r s e d i n s o d i u m without moisture p r e s ent does not carbonize. S o here is a n i l l u s t r a t i o n of the " i m p o s s i b l e " things that c a n h a p p e n w i t h the a p p l i c a t i o n of s o d i u m to a f a i r l y complicated piece of m a c h i n ery. T h i s p a r t i c u l a r w e l d e d area was not checked w i t h a h e l i u m mass spectrometer as it should have been.

Model Tank Instrumentation PRESSURE. M o o r e N u l l m a t e r pressure transmitters measure the pressure drop of the reactor core ( F i g u r e 11). T h e application of s u b m e r g i n g this type of pressure transmitter is n e w i n s o d i u m techniques, b u t is s t r a i g h t f o r w a r d . F i g u r e 12 shows a close-up of a M o o r e pressure transmitter used i n a more conventional i n s t a l l a tion. T o adapt this instrument to s o d i u m submerged operations, a stainless steel liner is w e l d e d a r o u n d the entire pressure transmitter, as indicated b y F i g u r e 11. T h e air supply lines to this transmitter are stainless steel t u b i n g inside the reactor tank, coppr lines outside the tank. A bellows seal at the top of the pressure t r a n s mitter w e l l makes a gas-tight expansion joint for the stainless steel air lines. In case of a w e l d failure, s o d i u m w o u l d rise to the operating l e v e l of s o d i u m i n the tank. S i n c e the space the a i r lines occupy is filled w i t h argon gas, there w o u l d be no oxide contamination, as the bellows is still the final seal between s o d i u m a n d the outside atmosphere. O t h e r types of pressure gages are used i n other e x p e r i m e n t a l s o d i u m loops. H o w e v e r , to measure pressure at points of a system s u b -

Figure 5. Direct current e l e c t r o m a g n e t i c p u m p f o r c o l d t r a p o p e r a t i o n s A. E. Copper bus B. S S T c a n (0.020 wall) a r o u n d copper bus C . N a outlet D. Compression gasket S S T c a n to copper bus F . W e l d e d S S T c a n (0.020 wall) G . N a inlet (2-inch, SCH.40 pipe)




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Figure 6. A l l i s - C h a ! m e r s c a n n e d motor f l u i d bearing pump

Figure 7. Direct current e l e c t r o m a g n e t i c p u m p in o p e r a t i o n a t 8 0 0 ° C . (1472°F.)

m e r g e d i n s o d i u m , t h e M c o r e p r e s s u r e t r a n s m i t t e r is u s e d b e c a u s e o f i t s a b i l i t y to s t a n d h i g h t e m p e r a t u r e s w i t h a n e g l i g i b l e c a l i b r a t i o n c o r r e c t i o n f o r c h a n g e s i n s o d i u m t e m p e r a t u r e . G e n e r a l l a b o r a t o r y u s e o f 14 M o o r e Dressure t r a n s m i t t e r s h a s b e e n 100% s u c c e s s f u l . T h e f i r s t o f t h e s e , p u r c h a s e d 7 y e a r s a g o , i s s t i l l i n o p e r a t i o n . A t t e m p e r a t u r e s u p t o 1100°F. t h e p r e s s u r e - s e n s i n g b e l l o w s h a v e n e v e r f a i l e d . T h i s i n s t r u m e n t a p p e a r s t o b e so r e l i a b l e t h a t t h e r e i s n o p r o v i s i o n f o r removing a n d replacing the pressure transmitters. FLOW INDICATION. A n e l e c t r o m a g n e t i c flow m e t e r i s u s e d o n t h e p r i m a r y h e a t r e m o v a l s y s t e m o f t h e s u b m e r g e d E B R - I I r e a c t o r m o d e l . F i g u r e 11 s c h e m a t i c a l l y s h o w s t h e m a n n e r o f j a c k e t i n g t h e t w o e l e c t r o d e s o f t h e flowmeter t o b r i n g t h e m t h r o u g h t h e s o d i u m a n d t o p of t h e reactor t a n k . T h e p e r m a n e n t m a g n e t is s u r r o u n d e d b y s o d i u m . T h e electrodes a r e canned w i t h a t h i n stainless steel sleeve concentric w i t h the 4 - i n c h s o d i u m pipe. Inside the stainless steel c a n a n d s a n d American Chemical Society Library In HANDLING AND USES 1 1 5 5 OF 1 5 THE t h S tALKALI . . N.W. METALS; Advances in Chemistry; American Washington, DC, 1957. W a s h Chemical i n g t o n . Society: D.C. 20O36

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Figure 8. Sodium test facility at 800°C.

Figure 9.

Twelve-inch sodium test facility for 3800-gallon-per-minute

pump


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Figure 10. Magnet lift assembly after sodium test

Figure 11. Primary sodium system EBR-II w o r k i n g

model

w i c h e d between two sheets of h i g h grade m i c a are the two electrodes of the flowmeter. These leads are brought t h r o u g h a 1-inch pipe, w h i c h is then w e l d e d to the jacket and t h r o u g h the reactor top shield, as F i g u r e 23 illustrates. T o demonstrate the technical feasibility of this p a r t i c u l a r arrangement for a flowmeter, the entire assembly of magnet a n d canned pipe containing insulated leads was fabricated into a s m a l l box filled w i t h sodium. T h e entire assembly was then calibrated i n the test loop that was b u i l t to test the 1000 gallons per m i n u t e , direct c u r r e n t p u m p ( F i g u r e 4). T h e c a l i b r a t i o n was made against an orifice using conventional techniques. T h e results of the calibrations, plus 9 months of o p e r a tion, h a v e demonstrated that the electromagnetic flowmeter is i d e a l l y suited for s o d i u m s u b m e r g e d operation; hot s o d i u m has no effect on the permanent magnets at 750°F.; the insulation of the leads is adequate; and there is no maintenance. T h u s , no p r o v i s i o n must be made for future r e m o v a l of this instrument. A n o t h e r important application of an electromagnetic flowmeter is i n the e x t e r n a l s o d i u m line f r o m the m o d e l tank to the d u m p storage systems. A L e e d s & N o r t h r u p direct c u r r e n t amplifier, M o d e l 9835-B, is used to a m p l i f y the flowmeter signal to d r i v e a B r o w n 0 to 4 - m v . recorder to any desired amplitude for a g i v e n flow rate. T h i s technique is v e r y convenient to m a i n t a i n a flow rate of 1 to 2 gallons per minute for the cold trap operation w h i c h follows the s o d i u m charging.


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T h i s same technique enabled personnel engaged i n the i n i t i a l s o d i u m b a r r e l c h a r g i n g operation to see a large indication of flow o n a c i r c u l a r chart recorder. T h e electromagnetic p u m p flow was m a i n t a i n e d constant for each transfer o p e r a t i o n ; therefore, operators calibrated the flowmeter b y discharging a k n o w n 50gallon v o l u m e of s o d i u m i n a k n o w n recorded time. T h e flow rate established as convenient for c h a r g i n g s o d i u m was 10 gallons p e r minute. CONTINUOUS SODIUM LEVEL INDICATION. T h e s o d i u m l e v e l indicator used o n the m o d e l tank is shown i n F i g u r e 13. It is a solenoid I f inches i n outside diameter a n d 5 feet long, made of a c l o s e - w o u n d coil of two layers of N o . 14 glass insulated w i r e on a n i r o n core. E a c h t u r n of the coil is separately w r a p p e d w i t h glass cloth. It operates o n the p r i n c i p l e that the effective impedance of a transformer p r i m a r y decreases as the c u r r e n t i n the secondary increases. I n this application the solenoid is the transformer " p r i m a r y , " a n d the external s o d i u m separated f r o m the solenoid b y a t h i n - w a l l e d stainless steel tube, closed b y a lower e n d , is the transformer "secondary." T h e calibration c u r v e is influenced b y the temperature of the sodium. T h i s continuous l e v e l indicator i n application o n m o d e l systems does not have to be calibrated for a l l temperatures; one is calibrated at operating temperature of the storage tank ( 3 0 0 ° F . ) , a n d another such coil is calibrated at 600 °F. for the average temperature of the m o d e l tank. T h e advantage of this type of l e v e l i n d i c a t i o n is no seal or entrance into the sodium. T h e disadvantage or l i m i t a t i o n i n the use of this sensing device is the ultimate temperature the coil c a n stand. A m a x i m u m temperature of 900 °F. has been achieved w i t h V i t r o t e x w i r e .

Figure 12. M o o r e N u l l m a t e r s o d i u m pressure t r a n s m i t t e r a n d control valve positimer Figure 1 3 . S o d i u m level i n d i c a t o r


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SMITH—SODIUM HANDLING MANUALLY OPERATED ELECTRONIC

SODIUM LEVEL PROBE.

T h e l e v e l probe,

shown

in


F i g u r e 14, has been i n use at A N L for 4 years. F o r most e x p e r i m e n t a l equipment, this unit has replaced spark p l u g probes, as w e l l as the f a m i l i a r w e l d i n g r o d placed t h r o u g h a r u b b e r stopper. T h i s type of probe is installed i n the E B R - I I m o d e l tank to supplement the continuous sodium l e v e l solenoid. It is, i n fact, a n electronic modification of the continuous l e v e l indicator. T h e electronic circuit has been developed b y the A r g o n n e Electronics D i v i s i o n . Instead of a l o n g solenoid, the coil has been s h o r t ened to 1 i n c h . T h e diameter of the coil has been r e d u c e d f r o m I f inches to f i n c h , m a k i n g it more adaptable to s m a l l l i q u i d m e t a l systems w h e r e expansion tanks are 2 to 4 inches i n diameter. A h i g h frequency electronic bridge c i r c u i t is used for the l e v e l probe coil. W h e n the probe coil is m a n u a l l y l o w e r e d i n its " w e l l " t h r o u g h the s u r r o u n d i n g s o d i u m l e v e l , the b r i d g e change or unbalance is amplified a n d a n indicator light changes f r o m " o u t " (of sodium) to " i n " (into s o d i u m ) . A 0 to 30-μ&. meter gives a v i s u a l indication of a change. T h i s meter gives a swing of 8 to 15-μΆ., about a 100% increase i n current, w h i l e the probe c o i l passes t h r o u g h the s o d i u m l e v e l . T h e electronic circuit is m o u n t e d on a portable relay r a c k . I n this m a n n e r , one power s u p p l y c a n service a n u m b e r of l i q u i d metals operations. I n general, this device is most useful i n filling a closed system to a k n o w n l e v e l . A n i m p o r t a n t accessory for the electronic probe is a s m a l l , completely w e l d e d c y l i n d e r of pipe h a l f filled w i t h s o d i u m a n d h a v i n g a 1-inch w e l l or " t h i m b l e " for the probe. U s i n g this portable c y l i n d e r as a test tank of k n o w n l e v e l , one c a n q u i c k l y balance the electronic circuit for proper operation. HEATING OF SYSTEM PIPING. H e a t i n g of the s o d i u m system p i p i n g ( 2 - i n c h type 347 S S ) is accomplished w i t h G e n e r a l E l e c t r i c N o . 20 N i c h r o m e heating cable

Figure 14. Portable sodium level test probe with test container



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w i t h a metallic sheath. C o n s i d e r a t i o n has been g i v e n to the integrity of the e x ternal pipe heaters. E x p e r i e n c e has shown that 3.0 amperes is a reasonable c u r rent for this type of heating cable. T h i s c u r r e n t has been reduced, further, to 1.5 amperes per circuit to increase heater life to a m a x i m u m . H e a t i n g cable w i n d i n g s are spaced about 2 inches apart i n 50-foot coil lengths. K a y l o i n s u l a t i o n 2J inches thick is applied over the heating cable. E a c h heater circuit is i n s t r u m e n t e d w i t h a separate V a r i a c control separately fused. A c u r r e n t of 1.5 amperes per heater circuit has been sufficient to m a i n t a i n s o d i u m pipelines at 250°F. T h i s represents a power r e q u i r e m e n t of about 10 watts per foot of 2 - i n c h pipe. A n important feature of this installation is that a l l heaters are " o n " continuously. T h e r e is no temperature controller for line heaters or v a l v e heaters; control is m a n u a l . T h e r e have been no heater failures since the installation i n M a y 1955. T h e valves are deliberately r u n hotter than pipes by using 110-volt E l e c t r o t h e r m a l tape heaters at i u l l power of 350 watts per heater. T h e valves are, therefore, always hotter than the process p i p i n g a n d ensure no freeze-ups i n the v a l v e b e l lows by r e d u c i n g the possibility of oxide p l u g g i n g i n the r e g i o n of the v a l v e . A n o t h e r method of s o d i u m system heating is illustrated i n F i g u r e s 15 a n d 16. H e r e the basic 60-cycle, alternating current, eddy current i n d u c t i o n heating p r i n ciple has been b o r r o w e d f r o m the sodium m a n u f a c t u r i n g i n d u s t r y a n d a p p l i e d to a stainless steel reactor system. T h i s has been done b y c l a d d i n g the n o n m a g netic stainless steel w i t h | - i n c h steel plate. T h e steel plate is heated b y i n d u c t i o n , the stainless steel is heated b y conduction. T h i s loop has been heated to 4 0 0 ° F . b y i n d u c t i o n heat alone a n d adequately demonstrates that this m e t h o d c o u l d be a p p l i e d to a s o d i u m - c o o l e d reactor system. In a reactor, the heating is necessary o n l y for t h a w i n g s o d i u m at start up, so the operating expense of a s l i g h t l y less efficient heating system (as c o m p a r e d to resistance heaters) is not n e a r l y so i m portant as long neater life. Since the alternating c u r r e n t i n d u c t i o n heater is applied external to the insulation, heater life should be excellent. Induction heating has also been a p p l i e d to the E B R - I I m o d e l tank. F i g u r e 17 shows the finished heating coil w r a p p e d a r o u n d the m o d e l tank. T h i s p a r t i c u l a r installation is capable of heating 5000 gallons of s o d i u m up to 400 °F. on i n d u c t i o n heat alone. T o achieve the 750 °F. operating temperature for the E B R - I I model, C a l r o d s are i m m e r s e d i n the sodium. T h e s o d i u m - t o - a i r seal for the C a l r o d installation is a Swage lock fitting a r o u n d the C a l r o d .

Figure 15. Steel clad on 347 SS sodium facility before insulation and induction heating is applied




Figure 16. C o m p l e t e d a l t e r n a t i n g current i n d u c t i o n h e a t i n g a p p l i e d t o a s o d i u m test f a c i l i t y

F i g u r e 17. Induction h e a t i n g a p p l i e d t o EBR-II m o d e l t a n k


53

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VALVES. F i g u r e 18 shows one of the seven valves used i n the E B R - I I w o r k i n g m o d e l system. T h e u n i q u e features of these valves are bellows seal w i t h 10% bellows t r a v e l , spark p l u g probe to detect bellows f a i l u r e ; b a c k - u p p a c k i n g i n case of bellows f a i l u r e ; a n d a replaceable or r e m o v a b l e bellows assembly that permits disassembly of bellows f r o m v a l v e b o d y for cleaning. These valves are made u p f r o m stock parts a n d have been b u i l t i n the A N L shop. T h e r e have been no failures. A n o t h e r s o d i u m v a l v e of interest is a 14-inch bellows seal gate v a l v e ( F i g u r e 19). T h e v a l v e body is a standard C r a n e 14-inch steam v a l v e of alloy steel c o n struction. T h e bellows assembly is of A N L design a n d has been a d d e d to the v a l v e . A prototype of this v a l v e has been tested w i t h N a K (1000°F. temperature) without the bellows to determine p r e s s u r e - t e m p e r a t u r e conditions that are f a v orable for c o n v e n t i o n a l p a c k i n g materials that are to contain s o d i u m . F i g u r e 20 has been d e t e r m i n e d e x p e r i m e n t a l l y a n d shows that w i t h i n certain l i m i t s of p r e s s u r e - t e m p e r a t u r e , o r d i n a r y water valves are adequate for s o d i u m service. T h e smallest bellows seal v a l v e that has been adapted to s o d i u m service is a J - i n c h needle v a l v e used i n d r a w i n g off s m a l l quantities of s o d i u m into the oxide sample operation. T h i s v a l v e has operated at temperatures u p to 500 ° C .

Mechanical Components Operating in Sodium O n e of the major reasons for b u i l d i n g the E B R - I I m o d e l was to demonstrate that equipment c a n operate i n s o d i u m at 750 °F. F i g u r e 21 shows a s m a l l test

Figure 19. Fourteen-inch bellows seal sodium valve Figure 18. Two-inch bellows seal valve for sodium service


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facility for i m m e r s i n g a fuel assembly g r i p p i n g mechanism, a simple i c e - t o n g type of latch. T h i s test facility was initiated before the m o d e l system was b u i l t . T h e need f o r clean s o d i u m was v e r y c l e a r l y illustrated i n this simple test r i g . W h e n b r i c k s o d i u m w i t h oxide film was o r i g i n a l l y placed i n this system, the m e c h a n i s m d i d not operate. W i t h o u t t a k i n g the m e c h a n i s m apart, a n d without r e m o v i n g the i n i t i a l sodium, a second s o d i u m tank was added. Independent heaters were w r a p p e d o n each tank, a n d a t h e r m a l At loop was set u p ; the latch then operated as w e l l i n o x i d e - f r e e s o d i u m as it d i d i n hot h e l i u m gas.


Some consideration was g i v e n to the proposition that a s o d i u m facility c o u l d be b u i l t " c l e a n " a n d w o u l d r e m a i n clean. A rather large loop was m a d e u p of

0

122

212

302

TEMPERATURE,

392

482

F.

Figure 20. Pressure t e m p e r a t u r e criterion f o r successful s o d i u m v a l v e p a c k i n g

Figure 21. R o d g r i p p e r test f a c i l i t y


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A D V A N C E S IN

CHEMISTRY SERIES

S c h e d u l e 40, 347 S S , 4 - i n c h pipe, a 5 0 0 - g a l l o n - p e r - m i n u t e s o d i u m p u m p , a " c o r rosion test section," a n d a 35-gallon expansion tank. E a c h a n d e v e r y part was electropolished, pipe ends were taped dust-tight before w e l d i n g , inert arc gas back welds were made, a n d every effort was made to complete, i n the field, a c h e m i c a l l y clean sodium system. F i g u r e 22 shows the d i r t y sodium surface w h i c h resulted after clean sodium was filled into the loop. T h i s experience demonstrated v e r y conclusively the importance of being p r a c t i c a l i n sodium system construction.


F u r t h e r operation of the E B R - I I m o d e l system has demonstrated on a r e a s o n a b l y large scale that s o d i u m can be cleaned of s o d i u m oxide a n d dirt a n d that the m e c h a n i c a l components w i l l operate as designed. T h e E B R - I I m o d e l system was fabricated a n d instrumented b y m e n w e a r i n g o r d i n a r y shoes, w a l k i n g about a n d w o r k i n g o n the interior of the s o d i u m container, as e v i d e n c e d b y F i g u r e 23. T h e interior of this reactor m o d e l was cleaned u p w i t h an i n d u s t r i a l v a c u u m cleaner before being filled w i t h s o d i u m . B u t a c o l d trap has operated n e a r l y continuously for the past 9 months. A t no time has s o d i u m oxide or s o d i u m h a d a n y t h i n g to do w i t h a serious m a l f u n c t i o n of equipment. F o r p u r e l y m e c h a n i c a l reasons, items of equipment have been r e m o v e d , a n d F i g ure 24 shows evidence of a large quantity of s o d i u m oxide f o r m e d d u r i n g r e m o v a l of an equipment item. In spite of this severe oxide formation, the cold trap system is capable of r e m o v i n g this quantity of oxide i n a v e r y reasonable n u m b e r of hours. F i g u r e 25 shows a top v i e w of the Y o r k p a c k i n g used i n this c o l d trap. W i t h o u t cold t r a p p i n g , operation of the E B R - I I m o d e l w o u l d be impossible. T h e past year's operation of s o d i u m equipment at A N L has demonstrated that s o d i u m c a n be c h a r g e d w h e r e v e r we w i s h , p u m p e d , a n d its flow, temperature, l e v e l , a n d oxide content measured. E v e n t h r o u g h abuse a n d f o r m a t i o n of large quantities of s o d i u m oxide, the s o d i u m oxide c a n be r e m o v e d a n d the m e c h a n i c a l gadgets function "as designed." W o r k e r s i n the reactor business are i n d e e d f o r t u nate that A m e r i c a n i n d u s t r y , t h r o u g h a p p l i e d c h e m i c a l engineering, has made s o d i u m available i n quantity a n d i n e x p e n s i v e l y .

Figure 22. Sodium surface of "chemically clean" sodium test facility




Figure 23. Interior of EBR-II model tank during installation. Component in lower left-hand corner is " c a n n e d " electromagnetic flowmeter


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lure 24. Sodium oxide formed during removal of EBR-II component




Figure 25. EBR-II cold trap showing York packing


Sodium Handling at Argonne National Laboratory - American

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