Naval Research Laboratory Reactor

1958 film, with transcript

Catalog description: The film presents a guided tour through the Naval Research Laboratory's research reactor facility in Washington, DC. All visible components are pictured and described; composition of fuel elements, core assembly, and methods of exposing samples are explained by animation.

This is film 88192 in our catalog.

Show transcript
00:00 Washington, D.C. is the home of the United States Naval Research Laboratory.
00:27 The laboratory was founded in 1923 upon the recommendation of a special naval board of consultants headed by Thomas A. Edison.
00:37 Here, some 3,000 scientists, engineers, and supporting personnel are engaged in applied and basic research in the physical sciences.
00:46 In the field of radio astronomy, this 50-foot radio telescope has been used to measure the temperature of the planets Mars and Venus.
00:59 Intensive work has been carried out in upper atmosphere research, culminating in the launching of Earth's satellites.
01:06 In the field of nuclear physics, a variety of instruments is used, including a 6-million-volt
01:20 proton Van de Graaff, a 20-million-electron-volt Betatron, and two Cockcroft-Walton accelerators.
01:30 Right in 1952, laboratory scientists planned another tool, a nuclear research reactor.
01:41 They decided on a pool type reactor, modified to incorporate a thermal column and beam ports.
01:53 The design consists of a pool, a movable bridge from which the core is suspended at a depth
02:01 of 16 feet out in the pool or in a graphite-walled niche where the shielding is penetrated by
02:10 beam ports.
02:14 Through these ports, beams of radiation stream to the experimental area outside the shield.
02:23 A thermal column provides the source of thermal neutrons.
02:28 Pneumatic rabbit systems are used to irradiate samples for short times.
02:34 The reactor consists of a core,
02:38 detectors, and control rods.
02:43 In the pool, the 150,000 gallons of water surrounding the core serves as an
02:49 effective radiation shield.
02:52 additional concrete shielding eight feet thick is provided around the niche.
03:00 Construction began in 1955 in one end of an existing warehouse.
03:07 With the exception of the building modifications and the concrete construction,
03:12 all design and fabrication were performed by laboratory personnel.
03:17 Fuel elements were obtained from the Oak Ridge National Laboratory.
03:24 On September 17, 1956, the reactor was brought to criticality.
03:32 Operation is presently limited by license agreement with the Atomic Energy Commission
03:37 to 100 kilowatts.
03:41 Before entering the reactor area, all visitors are required to register and to receive radiation
03:48 badges.
03:51 All possible measures are taken to protect the health and safety of personnel.
03:59 The reactor pool is 40 feet long, 26 feet and 20 feet deep.
04:09 The instrument bridge is in the foreground.
04:13 And beyond it is the reactor bridge, from which the reactor core is suspended.
04:23 A fuel element is placed on the loading elevator.
04:27 Lead shields at the top of the element reduce the gamma radiation in the vertical direction.
04:34 Each element consists of two aluminum side pieces containing 18 thin uranium-aluminum
04:41 plates.
04:44 The fuel portion of each plate is a sheet of uranium-aluminum alloy, 20 mils thick.
04:52 The fuel is 90% enriched uranium-235.
04:58 Twenty mil aluminum cladding protects the fuel from corrosion and contains the fission
05:03 fragments. Water rising by natural convection between the fuel plates
05:09 removes the fission heat. Natural convection cooling is adequate to
05:15 several hundred kilowatts. At higher power, forceful coolant will be used. A
05:23 complete fuel element contains about 140 grams of uranium-235. Loading of the
05:32 core begins by lowering new elements into the pool. The core is assembled by
05:39 coupling on to the fuel elements with a long handling tool and transferring
05:44 these elements underwater to a grid positioning plate. In the pool where
05:49 water is the sole reflecting medium it takes about 3,400 grams of uranium to
05:56 form a critical mass. In the niche where three sides of the core are reflected by
06:02 graphite, only 2,700 grams are required. The individual elements are positioned
06:10 into a rectangular array.
06:22 The final element completes a core configuration in which the uranium mass
06:27 slightly exceeds that required for criticality.
06:39 The position and history of every element is recorded.
06:46 The geometry of the core can be changed to meet experimental requirements.
06:51 Six detectors are used to obtain all pertinent information about the power level and its rate of change.
07:00 The power level of the core is adjusted by neutron-absorbing control rods.
07:09 Here is a core with four rods in position.
07:13 Three of these are safety rods containing boron carbide.
07:17 The fission rate and accompanying radiation increase as the stainless steel control rod is withdrawn.
07:25 The three safety rods are suspended by electromagnets.
07:29 For reactor shutdown, or scram, the rods are released and dropped into the core.
07:38 An unshielded core would, of course, emit intense radiation over a wide area.
07:44 The water around the core serves as a radiation shield.
07:53 The reactor system now consists of a core in a large pool of water, control rods and
08:01 their drive mechanisms, a control room and detectors near the core to measure the level
08:13 neutron and gamma radiation. A view of the entire reactor area is available to
08:23 the operator at the control console. An array of indicators is in front of the
08:29 console. Alarms and indicators on the console provide warning of trouble. They
08:38 They indicate both the nature and location of the malfunction.
08:43 Each warning alarm must be acknowledged.
08:48 Here a chart drive was not turned on.
09:03 After the safety check is completed, the reactor is started up.
09:08 The operator actuates a switch to withdraw the safety rods.
09:13 Their positions are indicated on the console in centimeters.
09:25 After careful monitoring, the control rod is withdrawn.
09:33 As the reactor is started, the increasing count rate from a fission chamber is observed.
09:41 The period channel indication is a measure of the rate of increase.
09:45 Too fast a period results in an automatic reactor shutdown.
09:51 Too high a power level also results in a scram.
09:55 The power level is displayed on a linear scale.
10:03 And also on a logarithmic scale.
10:06 Twenty minutes are required to raise the power to 100 kilowatts.
10:12 At about 1 kilowatt, the characteristic blue glow of the Cherenkov radiation surrounding
10:18 the core becomes visible.
10:48 The operator can shut down the system manually at any time.
11:18 As a safety measure, all persons entering the experimental floor must signal the control operator,
11:25 who opens access doors by means of electrically operated locks.
11:35 The main experimental area of the reactor facility is used for neutron beam research.
11:43 Seven beam ports, which penetrate the thick shielding at the front face of the pool,
11:48 allow direct beams of neutrons to be used for research.
11:54 At this beam port, a neutron diffraction experiment is in progress.
12:00 A single crystal spectrometer is being used
12:03 to study the magnetic structure of nickel oxide.
12:09 At the adjoining port, a similar diffraction experiment
12:13 is in progress on powder samples such as iron oxide.
12:18 The investigator is using magnetic scattering of neutrons to locate the
12:23 lattice vacancies in the material. The neutron beam is directed by a collimator
12:30 onto the sample mounted on a goniometer. The sample can be rotated either
12:38 manually or by a servo motor. The large horizontal cylinder is a borated
12:44 paraffin shield surrounding a boron trifluoride counter. A third diffraction
12:53 apparatus is shown here. It is used to study the structure of single crystals.
13:00 The sample can be oriented with respect to the neutron beam. The detector arm can
13:08 be rotated through 175 degrees of arc.
13:14 Here a neutron crystal spectrometer uses Bragg reflections from a beryllium crystal to obtain
13:20 mono-energetic neutrons.
13:23 It is being calibrated with known resonances of indium.
13:28 The reactor beam port is out of sight behind stacks of paraffin shielding blocks.
13:35 Two indium foils are being rotated sequentially into the beam.
13:41 The desired neutron energy is selected by automatically positioning the spectrometer
13:47 arm at an accurately known angle.
13:51 The apparatus can be used for measurements of slow neutron resonances but is here being
13:57 employed as a source of monochromatic neutrons for the study of capture gamma ray spectra.
14:08 A different type of experiment is shown in this apparatus for investigating
14:12 the interaction of polarized neutrons with polarized nuclear samples.
14:19 The neutrons are polarized and given the orientation desired by transmission through
14:24 magnetize iron. The nuclear samples are polarized by reducing the temperature to
14:31 near one one hundredth of a degree absolute and then applying a strong
14:36 magnetic field. Here at the vertical axis to the thermal column, a physicist checks
14:47 the thermal neutron response of an experimental proportional counter filled
14:52 with boron trimethyl gas also on the balcony is the control center of the
15:01 pneumatic rabbit system here material to be irradiated is being inserted into the
15:08 rabbit system the system is used to transport samples to a point near the
15:17 reactor core where they are exposed for a predetermined time to radiation and
15:22 then sent to an outlet near a laboratory counting room. Here the rabbit is removed
15:30 from the pneumatic system, placed in a mechanical uncapping device,
15:47 and the sample taken out.
16:04 The activation of the sample is measured in a shielded, well-type scintillation counter.
16:17 The scientist observes the decay of the activity as displayed by an automatic printout scaler.
16:32 Samples can also be irradiated in the pool.
16:38 Set into the rear wall of the pool are the hand-operated doors of water lock type transfer
16:44 leading to the adjoining hot cell facility.
16:53 The irradiated samples can be moved underwater into the transfer ports.
17:07 The port door is then cranked closed and the water lock is drained.
17:15 The hot cell is designed for killer-curie level activities.
17:24 Adjacent to it is the radiation laboratory or manipulator room.
17:39 From this room operators can look into the hot cell.
17:44 Seen through the window, the inner gate of the water lock opens.
17:53 The window consists of one-inch thick glass plates set three feet apart with an aqueous
17:59 solution of zinc bromide in between.
18:13 The sample holder is withdrawn by a direct coupled manipulator.
18:17 A power-driven electromechanical manipulator is also available for handling heavy objects.
19:13 This, then, is the Naval Research Laboratory's latest addition to its family of investigative tools for nuclear experimentation.
19:34 It was designed and built primarily for the conduct of basic research, and findings are
19:42 made available to the public through the open literature of science.