Thermonuclear test

Figure 3. Twilight lithium enhancements at Saskatoon during the Soviet thermonuclear tests of Sept. I-Noo. 4,1961 (37)...

Starting with the atmospheric thermonuclear tests, tritium concentration in the Northern Hemisphere has increased considerably above the natural background of approximately 10 pCi/liter of water (5). Since the cessation of these tests, environmental tritium concentrations have decreased gradually. Tritium is, however, produced in every nuclear reactor to some extent as a product of fission (1) or the activation of deuterium. In particular, reactors with heavy water as the moderator or cooling agent produce a large amount of tritium. Inasmuch as no... 

Table 2.3 shows the estimated releases of 90Sr, 131I, 137Cs and 144Ce in the Nevada tests, the thermonuclear tests (H tests), the 1957 Windscale accident, the 1957 accident at a separation plant in the Urals... 

Begemann Libby (1957) estimated that 1.1 kg of T was released to atmosphere for each megatonne (MT) thermonuclear explosion. The tests between 1954 and 1963 had a fusion yield of 320 MT. Allowing for radioactive decay, the global inventory in 1963, including tritium in the atmosphere, groundwater and oceans, was about 330 kg. French and Chinese thermonuclear tests between 1968 and 1977 may have added another 20-30 kg. In 1972, by which time most of the pre-1963 tritium had returned to the earth s surface, a world-wide survey of oceanic waters gave a total of 164 kg (Ostlund Fine, 1979). Corrected for radioactive decay, this is equivalent to an inventory of 270 kg in 1963. 

Most of the T from atmospheric tests is formed as HTO. Presumably, the heat of the fireball ensures oxidation. Ehhalt (1966) noted an increase in the atmospheric HT before the series of large thermonuclear tests in 1962 and 1963, but observed no increases correlated with individual tests. Mason Ostlund (1979) analysed samples of stratospheric air after the Chinese tests of November 1976 and observed a big increase in HTO but not in HT. HT may, however, be released following underground tests. 

Tritium is also formed as a product of ternary fission in power reactors. Yields in thermal fission of 235U and 239Pu are about 1 x 10-4 and 1.5 x 10 4 respectively (NCRP, 1979). Most of the tritium is retained in the fuel, but some may be released to atmosphere as HTO during reprocessing. At present, no fuel is reprocessed in the USA. The NCRP (1979) report included speculative estimates that reprocessing in Europe, excluding the USSR, may release 0.4 kg a-1. This is small compared with the release in atmospheric thermonuclear tests. 

The first US thermonuclear bomb was detonated near the ground at Bikini atoll in 1954, and much surface material was incorporated into the fireball, but most US and USSR thermonuclear tests were conducted at altitude, and relatively small amounts of material were vapourised. Consequently small particles were formed on condensation, and these have become attached to the general stratospheric aerosol (Harley, 1980). 

Fm, which undergoes spontaneous fission (ti = 0.38 ms). This point can be passed in two ways. One is to utilize a more intense neutron flux than can be obtained in a reactor, in the form of a thermonuclear explosion, so that a product such as undergoes further neutron absorption before fission can occur. Here, in the synthesis of Fmin Tvy Mike , the world s first thermonuclear test, atEniwetok atoll on 1st November 1952, the initial product of multiple neutron capture, underwent a whole series of rapid decays, yielding Fm. 

Because of greatly contrasting low tritium levels before thermonuclear tests and because of the distinct peak tritium levels that occurred in the atmosphere during 1962-1965, tritium has been used as an environmental tracer in the studies on surface water budgets, groundwater age and flow velocities, groundwater recharge, and dispersion and diffusion in aquifers. A 1989 study detailed the distribution of tritium... 

The radioactive isotopes C1 and 1 behave conservatively in the hydrological system and are important tools for studying salinization processes. Since 1952, atmospheric thermonuclear testing... 

Such ideas spurred the quest to produce still heavier elements in subsequent thermonuclear tests. Indeed, the rather long-lived nuclide Fm (half-life Tin = 100 days) was detected in later nuclear tests, indicating capture of at least 19 neutrons in uranium. However, attempts to produce and detect still heavier elements in underground nuclear tests conducted at the Nevada Test Site all failed, thus dashing hopes that heavier long-lived elements could be produced via this multiple neutron-capture process that, as it had been postulated, might... 

Schematic diagram of production of heavy uranium isotopes by successive neutron captures in followed by their subsequent beta-decay to spontaneously fissioning or alpha-decaying nuclides. Mass chains detected in debris from the Mike thermonuclear test are shown...

Hoffman, D.C. Production of heavy elements in a recent Los Alamos thermonuclear test. Alt. Fys. 36, 533-537 (1966)... 

---