Krypton isotope

Kuroda, P. K., Sherill, R. D. (1977) Xenon and krypton isotope anomalies in the Besner Mine, Ontario, thucolite. Geochem. J., 11, 9-19. 

Pepin, R. O., Becker, R. H., Rider, P. E. (1995) Xenon and krypton isotopes in extraterrestrial regolith soils and in the solar wind. Geochim. Cosmochim. Acta, 59, 4997-5022. 

Rocholl, A., Heusser, E., Kirsten, T., Oehm, J., Richter, H. (1996) A noble gas profile across a Hawaiian mantle xenolith Mantle-derived cognate and accidental noble gas components and evidence for anomalous krypton isotopes. Geochim. Cosmochim. Acta, 60, 4773-83. 

Young, B. G., Thode, H. G. (1960) Absolute yields of the xenon and krypton isotopes in U238 spontaneous fission. Canad. J. Phys., 38, 1-9. 

Clayton D. D. and Ward R. A. (1978) s-Process smdies xenon and krypton isotopic abundances. Astrophys. J. 224, 1000-1006. 

Limitations, (i) As with other radionuclide-based ages, the terrestrial age of the sample must be known, (ii) Concentrations of Kr are quite low in most meteorites, typically just 5 X 10 atomg in chondrites. For this reason, Kr measurements are still scarce and their uncertainties can be relatively large, often —20%. (iii) Production rates for krypton isotopes may vary with the abundances of rubidium, yttrium, and zirconium relative to strontium. It should be understood that the original basis for the calculation of Pgi/Fgs was a set of relative cross-section measurements for the production of krypton from silver (Marti, 1967). 

As all known lunar meteorites are finds (and therefore have nonzero terrestrial ages), we need at least four measured quantities to determine the four parameters of a simple one-stage history. Similarly, for a simple two-stage history, we need at least six measured quantities. Typically the data set available comprises He, Ne, Ne, Ar, C1, A1, and e. Occasionally we may have other information— the concentrations of spallo-genic krypton isotopes, spallogenic xenon isotopes, " Ca, and Mn, the densities of nuclear tracks (tracks/unit area), and the concentrations of certain isotopes produced by thermal neutrons, e.g., Ar (from C1) and Gd. 

There are various terrestrial reservoirs that have distinct volatile characteristics. Data from midocean ridge basalts (MORBs) characterize the underlying convecting upper mantle, and are described here without any assumptions about the depth of this reservoir. Other mantle reservoirs are sampled by ocean island basalts (OIBs) and may represent a significant fraction of the mantle (Chapter 2.06). Note that significant krypton isotopic variations due to radiogenic additions are neither expected nor observed, and there are no isotopic fractionation observed between any terrestrial noble gas reservoirs. Therefore, no constraints on mantle degassing can be obtained from krypton, and so krypton is not discussed further. Comparison between terrestrial and solar system krypton is discussed in Chapter 4.12. 

Figure 3 Krypton isotopes in solar system volatile reservoirs, plotted as %o deviations of the ratio to Kr, and normalized to the ratio in terrestrial air (Basford et al., 1973). The heavy solar Kr cruve represents a smooth fit to the measrued solar-wind isotope ratios. Measured SW-Kr from Wieler and Barn" (1994) and Pepin et al. (1995) Mars Kr from Pepin (1991) carbonaceous chondrite Kr from Krummenacher et al. (1962), Eugster et al. (1967), and Marti (1967) (Pepin and Porcelli, 2002) (reproduced by permission of the Mineralogical Society of America from Rev. Mineral.

The preferred method of disposal of radioactive krypton isotopes, after being separated from other volatile fission products, is by dumping at sea as the compressed gas, confined in steel cylinders. According to a report by Bryant and Jones the cumulative quantities of Kr and in the environment by the year 2000 are such that these nuclides will pose no significant health problem. 

Kr, a 10-year half-life krypton isotope, is currently released from reprocessing plants to the atmosphere. There will probably be no urgent need in terms of radiation dose to the local population to retain Kr. However, in view of a worldwide accumulation of Kr in the atmosphere, krypton recovery from reprocessing plants is required or will be required in the near future. 

It was clear from the time of the first fission product studies that the mass spectrometer would eventually be used in separation problems, mass identification, and isotope abundance measurements. However, the early work on fission products involved very small samples of material and only radiochemical methods were considered sensitive enough to identify and follow the radioactive isotopes. In 1945, Thode and Graham (104) succeeded in obtaining mass spectrograms of the xenon and krypton isotopes formed in the thermal neutron fission of U23B. 

The relative abundances of the xenon and krypton isotopes obtained with these samples provide the best relative yields of mass chains ending in these isotopes for the thermal neutron fission of U236. Table I gives this... 

Fission Product Xenon and Krypton Isotope Abundances for Uranium Irradiated in NR.X Thermal Column ... 

Fission yields of the stable and long-lived isotopes of xenon, cesium, barium, cerium, neodymium, samarium, krypton, rubidium, strontium, zirconium, molybdenum, ruthenium, have been measured mass spectro-metrically for the thermal neutron fission of U23B (40, 61, 90), U233 (4, SI, 61, 82, 100), and Pu239 (32, 61, 66, 124). In addition, the relative yields of the xenon and krypton isotopes produced in the fast neutron fission (fission spectrum neutrons) of U238 and Th232 (64, US) have been determined. 

The total number of atoms of each fission product xenon and krypton isotope in the mineral sample was determined by means of mass spectrom-... 

Recently, absolute yields of Mo" and several iodine isotopes from spontaneous fission of U238 determined by radiochemical methods were reported by Parker and Kuroda (89) and Ashizawa and Kuroda (5). These yields, along with the absolute yields of the xenon and krypton isotopes obtained... 

Table 3a. Neon, argon and krypton isotopic composition of martian atmosphere. 

Martian krypton also differs isotopically from terrestrial krypton. For most krypton isotopes, the Martian atmospheric ratios are indistinguishable from those of the solar wind, within the uncertainties in our knowledge of the two compositions, or perhaps isotopically fractionated in the opposite direction from terrestrial krypton (Garrison and Bogard 1998 see Fig. 4). Meanwhile, Kr and Kr are elevated in most samples of shergottite glass, presumably reflecting neutron capture on Br and Br, respectively. Whether this occurred within the rock or is a feature of the Martian atmosphere remains to be determined. 

Figure 4. Krypton isotopic composition of various measurements of the Martian atmosphere (represented by the Pepin Mars composition (Pepin 1991) and the 1550°C extraction from glass 8A of BETA 79001 (Garrison and Bogard 1998)) and the terrestrial atmosphere, compared to measured solar wind Kr (Pepin et al. 1995). Deviations are given in percent. The BETA 79001, 8A glass appears to be fractionated in favor of the lighter isotopes by as much as 1%/amu, while the Pepin Mars composition is virtually identical to the solar wind. The terrestrial atmosphere, on the other hand, is fractionated in favor of the heavier isotopes. For more detailed discussion (and plots) see Garrison and Bogard...

Krypton isotopes in oceanic basalts have not been very diagnostic of mantle processes. The Kr isotopic composition of oceanic basalts is typically the same as modem... 

There are no reports of krypton isotope anomalies in arc-related terrains— the small number of krypton isotopic analyses (e.g., Patterson et al. 1994) reveal only atmospheric-like ratios. For the most part, the situation is similar for xenon—atmospheric-like ratios dominate the few analyses reported. An exception is found in the work of Nakai et al. (1997) which reports two samples from the vicinity of Mt. Etna with enrichments in both Xe and Xe relative to air. The anomalies are correlated such that they appear to reflect mixing between air and an enriched source with a xenon isotope signature similar to MORE. 

Finally, we note that deviations from atmospheric-like krypton isotope ratios have not been found for any back-arc basin however, there are two reports of anomalous xenon isotope variations for the Mariana Trough. Ikeda et al. (1998) found coupled " Xe/ °Xe and Xe/ °Xe deviations from air—similar to those found in MORE, whereas Sano et al. (1998a) reported only Xe excesses (relative to Xe). These signatures reinforce the idea that the mantle wedge is the principal source of volatiles in the Mariana Trough particularly where circumstances limit the amount of atmosphere-derived contributions. At all other localities, only atmospheric-like xenon isotope ratios have been found. 

Sabu DD (1971) On mass-yield of xenon and krypton isotopes in the spontaneous fission uranium. J Inorg Nucl Chem 33 1509-113... 

Young BG, Thode HG (1960) Absolute yields of xenon and krypton isotopes in spontaneous fission. Can J Phys 38 1-10... 

Ludin AI, Lehmann BE (1995) High-resolution diode-laser spectroscopy on a fast beam of metastable atoms for detecting very rare krypton isotopes. Appl Phys B61 461-465 Maloszewski P, Zuber A (1982) Determining the turnover time of ground water systems with the aid of environmental tracers, I. Models and their apphcability. J Hydrol 57 207-231... 

The release of xenon and krypton isotopes at the time of the Windscale accident was not directly measured, but because 4 days intervened between shutdown of the reactor and commencement of the graphite fire during low power running and because most xenon and krypton isotopes have a short radioactive half-life, this component of the activity released would have been small. It is notable that although a search was made for plutonium contamination of the environment after the release, none in fact was found. 

It is essential for steady and safe operation of a sodium cooled fast reactor to limit the coolant and cover gas impurities to prevent corrosion of reactor component materials and to reduce radiation dose by corrosion products (CPs). Therefore, impurity concentrations of both coolant sodium and cover gas argon were measured during the duty cycle operation and annual inspection period. The sodium impurity data include oxygen, hydrogen, nitrogen, chloride, tritium, metal elements and radioactive ° Ag, Na, Xs. The cover gas impurity data include O2, N2, CO, CO2, H2, CH4, He, H and radioactive xenon and krypton isotopes. 

Similar equations can be derived for fu/Kr ages calculated from the concentration of and mass yield of suitable krypton isotopes such as Kr. 

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