In Search of a Critical Moment

1970 film, with transcript

Catalog description: This film tells the story of the Zero Power Plutonium Reactor (ZPPR), which was a special test reactor in Idaho designed to supply information essential to the development of economic fast-breeder, central-station, nuclear-power plants. The film shows the construction of the ZPPR by the Argonne National Laboratory, its many safety features, plutonium handling and storage, the computer that analyzes the data obtained by the reactor, and the fuel loading and attainment of reactor criticality.

This is film 88308 in our catalog.

Show transcript
00:00 This focusing charge is for the convenience of the projectionist to set the focus and sound
00:25 levels for this film. Following this image the screen will go black and the
00:31 film will begin in five seconds.
00:55 During the next 30 years, man will consume more than three times the energy consumed
01:09 since time began.
01:20 every ten years, this country's electrical power needs double.
01:37 The burden of producing this energy is now carried almost entirely by the burning of
01:43 of naturally occurring fossil fuels such as coal, oil, and gas.
01:58 As these fuels are used up, America's power industry
02:03 must be carried more and more by nuclear energy, which
02:07 could generate half of all the electricity used in this country by the year 2000.
02:19 These energy demands place increased emphasis
02:22 upon the design and testing of advanced nuclear reactors
02:27 to improve the economics of large central station power plants.
02:33 The majority of all civilian power reactors in use today
02:38 burn uranium-235 in a slow neutron reactor.
02:46 To depend solely upon fissionable uranium as a fuel source would place significant limits
02:52 upon our future nuclear fuel reserves.
02:57 To overcome this limitation, the Atomic Energy Commission has placed high priority on the
03:03 development of fast breeder reactors that produce or breed more fuel than they consume.
03:16 This breeding capability in fast reactors would give us virtually an unlimited source
03:22 of nuclear fuel.
03:32 But between the idea and the reality lies a vast sea of technical and research problems.
03:40 And for the last 20 years, nuclear scientists have huddled in the Idaho desert in search
03:48 of a critical moment.
04:00 This is the Upper Snake River Plain in Idaho, formed over 10,000 years ago by the convulsion
04:08 of large molten flows of lava.
04:18 The first white men to range over this country were fur trappers, fast on the search for
04:24 beaver and elk.
04:28 In the early 1800s, large cattle herds were pushed across this area to eastern markets.
04:36 The high buttes were early landmarks to men seeking gold.
04:46 Under this broad expanse of 900 square miles of open desert, large tracks of lava rock
04:53 randomly outcropped here and there to remind us of their volcanic origin.
05:02 During World War II, this desolate plain was used for gunnery practice by the Navy.
05:08 And in 1949, the atom came into this desert and built the largest, most advanced nuclear
05:17 reactor testing station in the world.
05:23 The knowledge of tomorrow's reactors comes from research carried out today.
05:30 In the 20 years since its inception, 45 experimental reactors have been built in this testing complex.
05:41 Many of the totems of proven technology on commercial reactors have come from research
05:46 performed at this station.
05:53 One of the first reactors built here was experimental breeder reactor number one, which demonstrated
06:00 the feasibility of fast breeder systems in December 1951.
06:06 Now a National Historical Monument, EBR1 was the first reactor to generate electricity.
06:15 It contributed important data on the physics and kinetics of reactors and their fuels and
06:21 demonstrated the feasibility of using liquid metal as a coolant.
06:27 The lessons from EBR 1 were anchor points which led to the construction of experimental
06:33 breeder reactor number two in 1961.
06:39 This is the principal facility for irradiating fuel samples and structural materials in the
06:45 liquid metal fast breeder reactor program.
06:50 To achieve the technology and control so necessary for the experimental method, a series of research
06:58 machines have been developed to study advanced core designs.
07:04 Let's take a look at a fast reactor core.
07:08 To approximate the composition, configuration, and performance of this hypothetical core,
07:15 core halves are gradually built up on a rugged platform in a horizontal plane.
07:22 The matrices are loaded on two separate tables, one stationary and the other movable.
07:35 After each progressive fuel loading, the tables are remotely drawn together to test the critical
07:43 assembly.
07:46 The final criticality, or self-sustaining chain reaction, is reached by the slow insertion
07:53 of fuel-bearing control rods driven into each half of the core.
08:00 When enough neutrons are available to initiate the fission of fuel atoms, the assembly becomes
08:07 self-sustaining and a wide range of nuclear data is recorded.
08:20 The first split table machine was built in 1955, prompted by the complete lack of experimental
08:26 information on fast reactor systems.
08:32 These low-power machines achieve and maintain a self-sustaining chain reaction without producing
08:40 a significant amount of power, less than 100 watts.
08:51 These test reactors discover in a matter of months what non-test reactors take years of
08:57 operation to discover.
09:00 They can investigate specific reactors on a realistic scale, predict reactor performance,
09:08 and operate at higher power densities than slow neutron reactors.
09:16 Since they can tolerate a greater buildup of fission products, they hold the most promise
09:22 for economic power production.
09:29 To be competitive, the next family of fast-power reactors fueled with high-cost plutonium must
09:36 generate at least 1,000 megawatts.
09:40 It is therefore necessary to define many of the physical, chemical, nuclear and irradiation
09:46 properties of the plutonium.
09:50 Its use can only be meaningful in fast breeder reactors.
09:56 Plutonium will dramatically affect power economics in the fuel cycle and will contribute to efforts
10:02 of doubling the inventory of fissionable material in 10 to 20 years.
10:26 This is the Zero Power Plutonium Reactor, a three and three quarter million dollar Mayan
10:32 temple dedicated to exploring the frontiers of fast reactor physics.
10:41 Experiments with this reactor will permit the construction of larger, more sophisticated
10:46 power stations and will contribute information on how to multiply the world's supply of
10:53 reactor fuel. ZPPR is a tool capable of studying large plutonium-fueled fast
11:03 reactors, producing 1,000 megawatts of electrical power. It is the only facility
11:10 with this capability. Its design is a sharp departure from previous
11:17 containment designs.
11:23 The facility is divided into two general areas, an underground mound area and a large support wing.
11:36 The mound area is made up of a deep layer of compacted earth, which covers a 50-foot circular reactor cell,
11:44 A fuel storage vault where the plutonium is stored.
11:51 An equipment room and access and escape tunnels leading from the reactor cell.
11:59 The support wing contains the reactor control room and office and other necessary facilities
12:05 for the operation and maintenance of the reactor.
12:17 The construction of ZPP-R, the fourth such argon split-table reactor, began in August
12:24 of 1966.
12:27 Heavily reinforced concrete was used to build the walls and floor of the reactor, forming
12:32 a circular room 50 feet in diameter to form a solid foundation for the reactor
12:42 cell and to ensure it against possible damage from earthquakes. Steel pilings
12:48 were driven deep into the underlying lava bed. A uniquely designed cell roof
12:59 was fabricated to provide backup safety containment for the reactor.
13:05 An intricate web of steel cables knitted together to form a free-swinging hammock
13:11 was lined with several layers of overlapping wire mesh.
13:18 This hammock, designed to support a 16-foot-thick bed of sand and gravel,
13:24 will retain any possible energy release
13:27 from the combustion of large masses of plutonium.
13:35 The containment roof was supplemented by a circular array of highly efficient filters
13:41 to prevent any significant release of fission products.
13:45 All installations were completed by the end of 1968
13:57 and the reactor was ready to be loaded
14:00 for the march to criticality.
14:15 During reactor startup and operation, the reactor cell is separated from the outside environment by a series of blast and seal doors.
14:27 This separation precaution ensures complete safety when the reactor is operating.
14:38 There are many fundamental differences between fast reactors and their thermal counterparts.
14:45 In a fast reactor, there is no reason to slow down the neutrons.
14:50 We can eliminate the moderator and reduce the core size.
14:55 In thermal cores, the reactor is contained in a pressure vessel.
15:01 In a fast reactor, with the use of liquid sodium as coolant,
15:06 the containment problems are dramatically reduced.
15:10 The fast core is unmoderated and compact.
15:15 consisting only of an assembly of fissionable fuel, structural material, and coolant.
15:22 By operating at higher temperatures, we achieve a better efficiency in converting heat to electricity.
15:38 The recipes, or fuel strategies, for mocking up fast core are drawn up and loaded in this workroom.
15:45 Before being loaded into the reactor, the fuel is inspected in these negative pressure glove boxes.
15:57 Fifteen hundred kilograms of the plutonium fuel, valued at 64 and one half million dollars, are stored in these bins.
16:09 When pushed to 3,000 kilograms, this inventory will represent the largest mass of plutonium
16:19 employed in any single critical facility. Because it is a prolific spontaneous emitter of neutrons,
16:27 the plutonium is stored in small lots in these concrete blocks, which act as radiation shielding.
16:35 It is clad in stainless steel plates and stored in airtight canisters.
16:44 The initial experiments will be performed with volumes of 2,000 liters, demonstrating
16:50 reactors in the three to 400 megawatt range.
16:55 Future cores will exceed 6,000 liters, simulating reactors generating electrical power for a
17:01 city of a million people. ZPPR can accommodate essentially any power reactor core, be it
17:11 a metal, oxide, or carbide fueled core. By using metal fuel, the combinations assembled
17:20 in this test reactor core are extensive. To build the core design, stainless steel tubes
17:28 or fuel drawers are manually loaded in these glove boxes.
17:35 These mock-up fuels are in the form of small plates, and their interchangeability makes
17:41 this machine a very flexible experimental tool.
17:47 The individual fuel drawers, perforated to reduce density, contain a specific combination
17:54 of fissionable, structural, and coolant materials,
17:57 such as blanket material, metallic sodium, carbon, and depleted uranium.
18:09 After complete checks, they are transported to the reactor cell
18:14 through a 50-foot conveyor tube.
18:24 The core halves are loaded by stacking the fuel into separate rectangular lattices that
18:34 are formed by cast steel knees.
18:37 The lattices are held in position by I-beams bolted to the knees for stabilization.
18:47 After they are loaded into the reactor matrix assembly, the drawers are again checked.
19:01 For safety and convenience, the loading is performed from a seven foot wide platform,
19:07 which is retracted when the tables are drawn together.
19:12 The tops of the tables are at the same elevation as the main floor of the cell.
19:19 The entire assembly rests upon a thick slab of reinforced concrete anchored in a four-foot
19:25 pin.
19:28 The movable table travels on roller bearings and is driven through the 84-inch separation
19:34 by three different speed closure motors.
19:39 Each table is designed to support 120 tons.
19:44 When they are closed, they form a single matrix
19:47 10 feet square and 8 feet deep.
19:51 When larger cores are to be simulated, the matrix will be extended to 14 feet square.
19:57 Although operated at less than 100 watts of power, supplementary radiation shielding is
20:13 provided by large retractable personnel shields which can be positioned in front of each half
20:20 of the reactor.
20:38 All control aspects of the reactor are performed in this room.
20:43 This interlocking console monitors the reactor during startup and operation.
20:52 The reactor is controlled by safety and fuel-bearing control rods, which can be driven into each
20:58 matrix.
21:02 Duplicate instrumentation has been installed to provide malfunctioning backup.
21:13 ZPPR will measure the effects of sodium loss, core temperature on the system's reactivity,
21:24 and produce accurate definition of the neutron spectrum for the core under study.
21:31 This broad range of nuclear analysis will predict the behavior and economy of future
21:37 breeder reactors.
21:40 To respond to this data, these instruments will channel the information to a digital
21:45 computer which will automatically collect and process the data.
21:51 The computer will also be used to control experiments whenever practical.
22:02 These new techniques will eliminate the past need for frequent reactor shutdown to study
22:08 core performance.
22:16 The search for the critical mass in ZPP-R began on March 27, 1969.
22:25 The plutonium fuel was constantly inspected to ensure against contamination during storage.
22:36 Repeated checks and verifications were made to ensure that the fuel drawers were correctly
22:41 collated and loaded into the reactor in proper sequence.
22:46 The core halves were repeatedly drawn together and the data plotted on the critical approach
23:07 curve.
23:13 The daily loading followed an habitual schedule, checking the operation of the counters, loading
23:20 the fuel drawers, placing the fuel into the reactor, moving the tables together, plotting
23:29 the critical approach curve.
23:33 After 16 days of loading, the core contained 340 kilograms of plutonium.
23:43 approach curve suggested less than 20 more kilograms for the reactor to go
23:49 critical. On the morning of April 18th, the 17th day of loading, the instrument
23:57 normalization is made. The decision? Add 12.1 kilograms to the core. Total
24:06 inventory, 352.81 kilograms.
24:13 The tables are again brought together.
24:39 The loading does not achieve criticality.
24:43 In the afternoon, another loading, this time 4.53 kilograms of plutonium.
25:02 Total fuel load, now 357.34 kilograms.
25:12 final checks and once again the control room vigil begins
26:12 At 325 on April 18th, 1969, ZPPR became critical with a plutonium mass of 357.34 kilograms.
26:38 Its baptism into the field of fast reactor physics was now history.
26:45 This march to criticality for ZPPR was merely the first step in its day-to-day research
26:50 existence in the liquid metal fast breeder reactor program.
26:56 Its future performance will contribute vital information for the eventual construction
27:02 of plutonium-fueled fast breeder power reactors.
27:07 When perfected, these perpetual energy machines will serve us not in terms of decades, but
27:15 in terms of centuries. This criticality in the Idaho desert has been one more test along
27:23 the experimental road of fast reactor physics. There are many more to come.