Atmospheric nuclear testing

Fossil fuel emissions alter the isotopic composition of atmospheric carbon, since they contain no C and are depleted in C. Releasing radiocarbon-free CO2 to the atmosphere dilutes the atmospheric C content, 3delding lower C/C ratios ("the Suess effect"). From 1850 to 1954 the C/C ratio in the atmosphere decreased by 2.0 to 2.5% (Fig. 11-23) (Suess, 1965 Stuiver and Quay, 1981). Then, this downward trend in C was disrupted by a series of atmospheric nuclear tests. Many large fission explosions set off by the United States with high emission of neutrons took place in 1958 in the atmosphere and the Soviet Union held extensive tests during... 

Am levels reflect resuspension of dust contamination at the WIPP site and not background 241Am levels. Present background levels result from past atmospheric nuclear testing and would be fairly uniform throughout the northern hemisphere. 

Irwin Goodwin. Fallout of Atmospheric Nuclear Tests in 1950s and 1960s Exposed More People to Iodine-131 than Chernobyl Accident. Physics Today. 50 (Sept. 1997) 54-55. 

Caribou in northern Quebec contained up to 1129 Bq 137Cs/kg muscle FW in 1986/87, but only 10 to 15% of this amount originated from Chernobyl the remainder is attributed to fallout from earlier atmospheric nuclear tests (Crete et al. 1990). The maximum concentration of 137Cs in meat of caribou (Rangifer tarandus granti) from the Alaskan Porcupine herd after the Chernobyl accident did not exceed 232 Bq/kg FW, and this is substantially below the recommended level of 2260 Bq 137Cs/kg FW (Allaye-Chan et al. 1990). Radiocesium transfer in an Alaskan lichen-reindeer-wolf (Canis lupus) food chain has been estimated. If reindeer forage contained 100 Bq/kg DW in lichens and 5 Bq/kg DW in vascular plants, the maximum winter concentrations — at an effective half-life of 8.2 years in lichens and 2.0 years in vascular plants — were estimated at 20 Bq/kg FW in reindeer-caribou skeletal muscle and 24 Bq/kg FW in wolf muscle (Holleman et al. 1990). 

Similarly, Fig. 13.12 shows the percentage deviation in regionally averaged stratospheric ozone for North America, Europe, and the Far East after variations due to the solar cycle, seasonal variations, the QBO, and atmospheric nuclear tests were subtracted out. Negative deviations are consistently seen in recent years, suggesting a long-term trend on top of the natural variability (Stolarski et al., 1992). 

Fallout from Atmospheric Nuclear Tests—Impact on Science and... 

Plutonium has been released into the environment primarily by atmospheric nuclear testing and at nuclear facilities that produce plutonium or store nuclear waste that contains plutonium. The plutonium isotopes of interest are shown in Fig. 15.1. 

Many measurements were made throughout the world during the period of atmospheric nuclear testing, and much is known of the release, dispersion, and deposition of radionuclides and the doses resulting from this practice. Exposures of the world population have been evaluated by the United Nations Scientific Committee on the Effects of Atomic Radiation. From this information the deposition and doses from individual tests or from a specific test series may be inferred. 

Most of the test sites for atmospheric nuclear testing were located in the northern hemisphere. The tests of France in the Pacific and of the United Kingdom in Australia were, with few exceptions, the only ones conducted in the southern hemisphere. Several tests of the United States were at or very near the equator, and from that location the injection of debris occurred to both hemispheres. The hemispheric partitioning of fission yields is shown in Table 10.5 140 Mt was injected into the atmosphere of the northern hemisphere, mostly into the stratosphere, and 18 Mt was injected into the atmosphere of the southern hemisphere. 

Environmental and human consequences of atmospheric nuclear tests have been recently summarised, see Shapiro (1998). 

A total of 41 atmospheric nuclear tests were conducted in the open air between July 1966 and September 1974, 37 at Mururoa Atoll and four at Fangataufa Atoll, and 137 underground nuclear tests took place deep below the surface of the atolls between June 1975 and January 1996, 127 at Mururoa Atoll and ten at Fangataufa Atoll. 

French atmospheric nuclear tests and safety trials at Mururoa and Fangataufa Atolls ... 

The atmospheric tests The radioactive material resulting from the atmospheric tests is essentially all residual material from the four barge tests there was very little local fallout from the explosion of any device suspended from a balloon, since the fireball did not touch the surface and radioactive material was drawn up into the atmosphere. Most of the residual material is plutonium found in the lagoon sediments immediately underneath where the barge tests were conducted, remains of the nuclear cores of the test devices. There is also present in the environment of the atolls global fallout from atmospheric nuclear tests conducted by other states, mainly in the Northern Hemisphere. 

The atmospheric nuclear tests which took place at the Mururoa Lagoon between 1966 and 1974 did not produce significant fallout on the emerged part of the atoll. The tests (three carried out on a barge) only affected the sediments at the bottom of the lagoon, especially in the area directly under the barge. In contrast, a few safety air tests that took place between 1966 and 1974 in the northern part of the atoll (between the Colette Motu and the Denise area) resulted in localised plutonium deposition on the coral bedrock. 

The terrestrial sampling and surveillance campaign was focused on Mururoa and Fangataufa atolls but at the time of the atmospheric nuclear testing, there was also some deposition of radionuclides on neighbouring islands, most notably at Tureia Atoll. Levels of activity were therefore measured at Tureia Atoll in order to calculate present dose rates for the inhabitants. 

Several kilograms of plutonium resulting from the atmospheric nuclear tests carried out at the atolls remain in sediments under the lagoon of each atoll. Some of the plutonium in the sediments of the Mururoa Atoll lagoon came from the atmospheric safety trials. 

Shapiro, C.S. (ed.). Atmospheric Nuclear Tests Environmental and Human Consequences. NATO ASI Series 2, Environment 35. Proc. Workshop, Vienna, Austria, Jan. 1994. Springer-Verlag, New York, 1998, 280 pp. 

Sample Pretreatment. Water samples are acidified with nitric acid immediately after collection to inhibit hydrolytic loss of trace elements and then filtered to remove suspended solids. Surface water samples frequently contain suspended soil from runoff water. This soil contains some transuranium nuclides, particularly plutonium, from fallout of previous atmospheric nuclear tests. The amount of suspended soil in water may be substantial under certain conditions. This pretreatment is used to obtain the concentration of the soluble transuranium elements. The filtered residue can be analyzed if desired. 

The present world-wide average annual effective dose due to inhalation exposure to plutonium and americium produced in atmospheric nuclear testing was estimated to be 38 rSv, or about 25% of the contribution of all radionuclides to the total dose from testing (UNSCEAR 2000). 

TABLE 22.2. Radionuclides released in atmospheric nuclear testing (UNSCEAR2000)... 

Rocky Mt. US/1972-1974 Deer 740-11000 Atmospheric nuclear test Markham etal., (1983)... 

Samples that contain approximately 10 radionuclides with intermediate to long (1 day-1 year) half-lives. This mix is found when monitoring distant locations for recent fallout from atmospheric nuclear tests and effluent from waste tanks and stacks at operating nuclear power plants. A subcategory is samples that contain natural radionuclides with half-lives in this range as progeny in terrestrial decay chains and cosmic-ray-produced radionuclides. 

Linus C. Pauling picketing the White House as part of a mass demonstration opposing the resumption of atmospheric nuclear tests. Pauling won the 1954 Nobel Prize in chemistry and the 1963 Nobel Peace Prize. (NARA AIP Emilio Segrfe Visual Archives)... 

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