Environmental Effects of the Kiwi-TNT Effluent: a Review and Evaluation

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LOS ALAMOS SCIENTIFIC LABORATORY University of Ca Iifornia LOS AMOS, NEW MEXICO Report written: January 1968 Report distributed: April 1968 Environmental Effects of the Kiwi-TNT Effluent: A Review and Evaluation

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11. The Experimental Plan IV. The Reactor Eruption V. The Recovered Debris VI. Proximate Nuclear Radiation 3leasurementc VII. The Cloud Growth and Ascent VIII. The Cloud Wake The Radiological Composition of the Cloud The Impact on the Neighborhood

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The K i w i Transient Nuclear Test (Kiwi-TNT) \vas a controlled excursion in which reactivity was inserted into a nuclear rocket engine prototype fast enough to vaporize a significant portion of the reactor core. The test studied the neutronic behavior of the reactor and the environmental effects of the radioactive materials released. This report discusses in detail only the determination of environmental effects. The test was conducted at the Nuclear Rocket Development Station. Jackass Flats, Nevada. on Janu ap 12. 1965. a t 1058 PST. The LOSAlamos Scientific Laboratory collected environnienlal data from the test point to apIir-osiniately 50 miles do\Yn\vind. The U.S. Public Health Service monitored the neighborhood and collected milk samples in scuthem Nevada and California to beyond 2000 miles do\vnivind. The course of the effluent cloud was tracked b y aircraft from the U. S. Public Health Service and EG&G. From j to 207; of the reactor core \vas vaporized. with approximatel\- 6 i y ; of the products from about 3 >( IO?'' fissions released to the effluent cloud. Radiation effects from the cloitd pawge \Yere less than predicted in the pretest safety evaluation report. The maximum off-site. integrated. whole-body exposure was 5 . 7 mrad about 15 miles from the test point. No fresh fission products \yere detected in any of the milk samples.

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The principal concern of this report is to summarize and interpret all available data concerning the environmental effects of the KiLvi Transient Nuclear Test (Kiwi-TNT). In addition to data obtained by the Los Alamos Scientific Laboratory (LASL', . the report includes summaries of data collected by other participating agencies. notably the U. S. Public Health Service can World Airways. Inc. This report collects under a single cover all the significant information about the environmental effects. Pertinent data and figures from referenced works are reproduced in this report to enable the reader to understand the overall interpretation of environmental effects. Some of the origmal reports received only limited distribution and their availability \vi11 decrease with time; the interested reader is referred to the source reports for fuller ireatment of sampling. measurement. and analytical techniques and for details of the neutronics and mechanical aspects of the experiment. The Kiwi Transient Nuclear Test (KiwiTNT) \vas a controlled power excursion in which reactivity was inserted into a nuclear rocket engine prototype at an unusually high rate calculated to vaporize a significant portion of the reactor core. The objectives of t h i s simulated reactor accident were to examine the material and neutronic behavior of the reactor and to study the effects of the radiation and radioactive maThe reactor. including the core and pressurc vessel. was. with few exceptions. a typical. late model Kini-B4. The nozzle was replaced with a mirror apparatus that permitted high-speed photography of the core top during the test. Coolant supply piping the reactor shell was rewas used. A point wdwliy of emphasis is that to achieve a reactivity insertion rate sufficient to vaporize a significant fraction of the core. the control rod mechanisms were modified to rotate at approximately 100 times the normal rate. The reactor core is extremely refractory. designed for normal operation above 2,OOO"C. Even in normal operation. the core materials are incandescent. and any abnormal operation that causes structural damage, so that core materials are expelled from the reactor by the exhausted coolant. produces a shower of sparks. In early tests. before many structural problems were solved. some fuel elements broke and were ejected from the nozzle with the exhaust gases. This spectacle resembled a Roman candle. Therefore, in an experiment of the KiLvi-TNT type. it waq a1)parent that the released vapor would be incandescent Except for the pressure vessel normally used with a Kii\i reactor. the core w a s ulishielded and uncontained. therefore. all vaporized and pulverized matenals \vould be immediately released before any appreciable cooling could ta he A few months before the test. the bect neutronic~ estimates indicated that the excursion nould produce approsimately 9 Y lozo fissions. ized. ascuming that the carbon vapor \vas monoatomic. and \vould release the products from a p - proximately 4 i< 10'" fissions. A felv day; before the test. these estimates were revised to approsimatell- 3604, of the core 1-aporized and i5& of the fission products released, or the products from fission-product inventory in the reactor a t the time of the test. As discussed later. the excursion produced 3.1 X 10"' fissions. 5 to 2006 of the bon vapor). and approsimately 67% of the f i \ - sion products were released in the effluent cloud. sec; an estimated 1% was kinetic enerp. Normal runs of this type of reactor produced a maximum of about 5 X 10; IIIY-sec, of energy. Details of the neutronics and mechanical a s - pects of the experiment are given in References

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If. THE EXPERIMENTAL PLAN The test was conducted at the Nuclear Flats, on January 12, 1965, at 1058 PST. Figure 1 shows the topography of the test point and downwind terrain out to approximately 50 miles. Jackass Flats and the Amargosa Desert form a flat plain, bordered by mountains, which slopes gently down to the southwest for about 30 miles from the test point. Death Valley, California. is approximately 50 miles from the test point. The LASL sampling array covered this entire area; the more distant stations are also shown in Fig. 1. The weather requirements for the test were northeasterly winds in excess of 5 mph blowing toward 244" 2 20", neutral to slightly unstable vertical temperature profile. nearly clear skies, and a reasonable certainty of persistence of these conditions to ensure that the effluent cloud would traverse the entire instrumented array. For cloud sampling, LASL trailer-mounted equipment was located at approximately IO" intervals between 180 and 270" on arcs at 4.000, 8,000. and 16.000 ft. and at 6, 12, 25. and 50 miles from the test point. A typical sampling trailer contains an engine-driven generator, one or more high-volume air samplers with filter paper and charcoal cartridges as collection media, a cascade impactor for particle size measurement, and a set of cycling. high-volume samplers with filter paper collectors for timing cloud passage. The trailers are radio-equipped so that sampling equipment may be started and stopped remotely. Resin-coated trays for the collection of deposited activity were placed on stands near the trailers at each sampling location. Stations for collecting cloud deposition activity and reactor&ebris extended from 100 to 2,000 f t from the test Poipt. Collectors for particles and , fragments of Mylar film on special frames, which also held large sheets of x-ray film for autoradiography of collected particles. After the event, the Mylar film was examined visually and microscopically to characterize the collected particles. The autoradiographs helped to distinguish the radioactive particles from desert dust. Specially mounted groups of microscope slides were placed with the Mylar films to provide samples for microscopic examination and analysis. Approximately half of these close-range stations also contained large. 4 X 4 f t funnel-shaped hoppers to collect fragments large enough to separate by sieving. To activity deposition. resin-coated trays identical to those used at the extended range stations were placed at 5" intervals around the reactor a t distances of 500, 1.000, and 2.000 ft. The test point was on a railroad culvert damming a wash approximately 500 ft wide and 30 ft deep. Thus. many of the short-range stations were at levels below the reactor. The Southwestern Radiological Health Laboratory (SWRHL) of the USPHS provided offsite radiation surveillance by aerial tracking of the effluent cloud, monitoring radiation dosage of the off-site population, and collecting environmental samples in southern Nevada and California. Twelve gro~indmonitoring teams equipped with portable instruments tracked the cloud passage. Dose-rate r .cording instruments were placed at eight downwind locations bracketing the anticipated path of the effluent cloud. Film badges were issued to 157 people in Lathrop Wells. Amargosa Desert. and Death Valley. Forty-five routine air samplers were operated in Nevada, Utah, Arizona. and California. supplemented by 18 samplers at anticipated downwind locations. All these highvolume air samplers were equipped with filter papers and charcoal cartridges. An Air Force U3-A aircraft carrying two USPHS monitors tracked the reactor effluent and assisted in positioning ground monitors. Two other PHS aircraft containing sampling equip ment were used in cloud tracking. although their primary purpose was to determine cloud size and Following the test. 74 milk samples were collected from two ranches in the AmargGa Desert and from 14 locations in southern California. The milk sampling program continued for approximately a week. Vegetation samples were obtained at most milk sampling locations; attempts were made to make these representative of the cows' feed but the forage samples were taken primarily as early indicators of areas of milk contamination rather than to yield cow intake-excretion data.s An aircraft of the Nevada Aerial Trackhg System, manned by EG&G personne1, tracked the effluent cloud from Death Valley over the Los Angeles area and terminated contact over the Neutron and gamma radiation measurements

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Fig. 1. Topography out to 60 miles downwind fmm teet point ahowing instrumented array on extended arcs.

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were obtained by LASL by methods used in other Kiwi reactor tests. Neutron integral fluxes and doses were determined by threshold detectors concomplemented by gold and sulfur activation detectors.' Ganlma doses were measured by gammasensitive glass dosimeters and by dosimetry films. Combinations of these detectors were positioned near the reactor to measure the prompt radiation. Dosimetry films were placed at all cloud sampling stations downwind to indicate gamma doses from the radioactive effluent cloud and subsetectors with remote readout equipment were placed around the test point, but concentrated downwind, out to 8.000 ft. Although the doserate instruments were inadequate to measure prompt radiation. they were useful in determining the decay of activity deposited around the test For several days after the test, radiation surveys of the area were made by monitors from LASL and the Radiation Services of Pan American World Airways, Inc.; isodose rate contours were made from these hand-he!d instrument surveys to follow the decay of the deposited activity. During decontamination of the test point area. recovered reactor fragments were placed in containers marked to indicate where they were found. After all locatable fragments had been recovered. they were sorted by size distribution and The material in thiq chapter is largely from the Kiwi-TNT Reactor Test" by hlueller and The weather at the time of the test fulfilled the desired conditions in every respect: it was clear. windy, and mild. The winds were northeasterly at all levels, ranging from 14 to 27 knots. Persistent northeasterly winds were the result of a surface high-pressure cell centered wer eastern Oregon. South of this high, a'fairly strong pressure gradient over Nevada helped prevent surface winds from turning toward the northeast, as frequently results from daytime surface solar heating. In addition, a 'pressure ridge over the Pacific Northwest, combined with a weak low off Baja California, produced the desired northeasterly winds over NRDS. Synoptic charts of these conditions are shown in F'g.2. weather station a few minutes after run time. and in the hnargosa Desert at about the time of cloud amval, were similar. The lapse rate was unstable near the surface, nearly neutral up to approximately 9,000 ft MSL. and more stable above that height. These temperature profiles are shown in Fig. 3. Upper-air data for Jackass Flats and the Amargosa Desert shortly after the test are listed in stations near the test point for several hours before and after the test. Fallout hodographs made from these data and plotted from the test point using Jackass Flats data for 1100 PST,and from Lathrop Wells using its 1115 PST data are shown in Fig. 4. Air trajectories plotted from these and other mind data for 5.000. 7.000, and 9,000 ft MSI, are shown in Fig. 5 . The theoretical trajectories of the lower levels correspond well with actual trajectories constructed from aircraft tracking data. as can be seen by comparing Fig. 5 with Figs. 52 and 53. The small amount of shear in the lower winds (approximately 10" up to 2.500 ft above the surface) led one to expect a narrow cloud and deposition sector, with a centerline bearing of 215". At higher altitudes the shear increased to about 25", and a centerline bearing of 220" was suggested. These expectations were consistent with the cloud and deposition patterns constructed from sampling data, as discussed in leased from the NRDS weather station at 1035 and 1133 PST on the day of the run. wer%tracked from the Lathrop Wells radar station and were first contacted approximately 6 miles from the release point. They were inflated to fly at 5,000 to 6,000 ft MSL, but considerable fluctuation in height occurred because of up- and downdrafts. The tracks of the tetroons plotted in Fig. 6 have been shifted about 2 miles to the west to simulate a release from the test point. This is considered to be valid because wind soundings from various stations in the area were similar at this time. The tracks were similar for about 15 miles south of the test point. Both balloons traveled this distance in about 40 minutes. Beyond this distance the tracks diverge, but both tetroons remained over areas where radioactive material from the effluent cloud was collected by ground-level samplers.

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SURFACE ANALYSIS SECOND STANDARD LEVEL STREAMLINES 7000 FOOT MSL STREAMLINES 9000 FOOT MSL STREAMLINES Fig. 2. M de or ol ~ c dconditions at loo0 PST,January 12, 1965.

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Fig. 4. 1100 PST NRDS and 1115 PST Lathrop Wells hodographs, January 12,1965.

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Height Wind Pressure Temperature Dew Point Humidity Amargosa Farm Road. 1200 PST,1/12/65

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IV. THE REACTOR ERUPTION The material in this chapter is largely from the sense that it was a violent disruption and dispersion of an originally intact object. It blew up in an unusual fashion resembling neither a typical nuclear detonation nor most types of chemical explosions. To give a better understanding of the eruption. its characteristics will be compared to those of more common explosions. The deflagration accompanying the KiwiTNT excursion was the result of rapid vaporization of part of the carbon-uranium-carbide core. The pressure vs. time relationships in the KiwiTNT event were unusual, but not unique. They are most nearly approximated by the explosion of black powder, one of the few explosive materials that acts by exothermic chemical reaction of physically mixed reactants rather than by exothermic decomposition of a chemical compound. The Kiwi-TNT energy release was physical in origin rather than chemical, however. The v a p r - ization OCCUR^ too fast for the resultant gas …