Krypton nuclides

Krypton-85 has been used for over 25 years to measure the density of paper as it is amanufactured. The total weight of paper can be controlled to a very accurate degree by the use of krypton 85 and other radioactive nuclides. The common name for such a device is a beta gague that can measure the thickness of a material. 

The abundances of krypton and xenon are determined exclusively from nucleosynthesis theory. They can be interpolated from the abundances of neighboring elements based on the observation that abundances of odd-mass-number nuclides vary smoothly with increasing mass numbers (Suess and Urey, 1956). The regular behavior of the s-process also provides a constraint (see Chapter 3). In a mature -process, the relative abundances of the stable nuclides are governed by the inverse of their neutron-capture cross-sections. Isotopes with large cross-sections have low abundance because they are easily destroyed, while the abundances of those with small cross-sections build up. Thus, one can estimate the abundances of krypton and xenon from the abundances of. v-only isotopes of neighboring elements (selenium, bromine, rubidium and strontium for krypton tellurium, iodine, cesium, and barium for xenon). 

The chemical properties of the radiation source. When a radioactive nuclide is ingested into the body, its effectiveness in causing damage depends on its residence time. For example, f Kr and gSr are both /3-particle producers. However, since krypton is chemically inert, it passes through the body quickly and does not have much time to do damage. Strontium, being chemically similar to calcium, can collect in bones, where it may cause leukemia and bone cancer. 

The prior presence of " Pu, the only transura-nic nuclide known to have been present in the early solar system, can be inferred from its spontaneous-fission decay branch, through production of fission tracks and, more diagnostically, by production of fission xenon and krypton. The identification of " Pu as the fissioning nuclide present in meteorites is unambiguous, since the meteoritic fission spectrum is distinct from that of but consistent with that of artificial " Pu (Alexander et al, 1971). The demonstration of the existence of " Pu in the solar system reinforced the requirement (from the presence of I) of a relatively short time between stellar nucleosynthesis and solar-system formation and made it incontrovertible, since while it might be possible to make in some models of early solar system development, the rapid capture of multiple neutrons (the r-process) needed to synthesize Pu could not plausibly be supposed to have happened in the solar system. 

Physicians can assess a patient s lung function with the help of krypton-81. What is this nuclide s atomic number and mass number Flow many protons and how many neutrons are in the nucleus of each atom Write two other ways to represent this nuclide. 

The periodic table shows us that the atomic number for krypton is 36, so each krypton atom has 36 protons. The number following the element name in krypton-81 is this nuclide s mass number. The difference between the mass number (the sum of the numbers of protons and neutrons) and the atomic number (the number of protons) is equal to the number of neutrons, so krypton-81 has 45 neutrons (81 - 36). atomic number = 36 mass number = 81 36 protons and 45 neutrons 36Kr iKr... 

The development of more sensitive ways to measure levels of radioactive substances has allowed scientists to take advantage of the decay of nuclides other than carbon-14. For example, chlorine-36 can be used to date ground water, marine sediments can be dated by measuring levels of beryllium-11 and aluminum-26, and krypton-81 has been used to estimate the age of glacial ice. 

Your cardiovascular system can be assessed using krypton-79, wbicb shifts to a more stable nuclide by electron capture. Write an equation that describes tbis change. 

It takes 3 half-lives for a radioactive nuclide to decay to Vi of its original amount (Vi xViX Vi). Therefore, it will take 103.5 hours (104 hours to three significant figures) for krypton-79 to decrease to Vs of what was originally there. 

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. 

These early spectrograms shown in Figs. 4 and 5 were obtained with a 180° gas-type mass spectrometer, using fission gas samples of 0.1 to 1 mm3 in volume at N.T.P. (105). The importance of this method of investigating fission products was immediately recognized. Stable and long-lived isotopes of xenon and krypton which are end products of fission chains, were identified for the first time. Since these products were extracted from the uranium several years after the neutron irradiation and since the precursor nuclides were known to he all relatively short-lived, it could be assumed that the... 

In nuclear fission a heavy nuclide splits into two or more intermediate-sized fragments when struck in a particular way by a neutron. The fragments are called fission products. As the atom splits, it releases energy and two or three neutrons, each of which can cause another nuclear fission. The first instance of nuclear fission was reported in January 1939 by the German scientists Otto Hahn (1879-1968) and Fritz Strassmann (1902-1980). Detecting isotopes of barium, krypton, cerium, and lanthanum after bombarding uranium with neutrons led scientists to believe that the uranium nucleus had been split. 

The gases released from the primary coolant in the degasification system mainly contain the fission product noble gases which, with the sole exception of Kr, are comparatively short-lived nuclides. In order to prevent release to the environment, therefore, it is sufficient to store them for a certain time until these isotopes have decayed. In most of the US PWR plants as well as in the plants built by Frama-tome, gas decay tanks are used for this purpose. In the plants designed and built by Siemens/KWU, decay lines are employed which are equipped with a series of charcoal beds in which the noble gases are delayed relative to the carrier gas flow by a dynamic adsorption-desorption equilibrium. Under normal operation conditions, delay times on the order of 60 hours for the krypton isotopes and 60 days for the xenon isotopes are obtained, which are sufficiently long for nearly complete... 

Three researchers in Germany— Lise Meitner (1878-1968), Fritz Strassmann (1902-1980), and Otto Hahn (1879-1968)— repeated Fermi s experiments, and then performed careful chemical analysis of the products. What they found in the products— several elements lighter than uranium—would change the world forever. On January 6, 1939, Meitner, Strassmann, and Hahn reported that the neutron bombardment of uranium resulted in nuclear fission—the splitting of the uranium atom. The nucleus of the neutron-bombarded uranium atom had been split into barium, krypton, and other smaller products. They also determined that the process emits enormous amounts of energy. A nuclear equation for a fission reaction, showing how uranium breaks apart into the daughter nuclides, is shown here. 

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