Neptunium decay products

The chemistry of neptunium (jjNp) is somewhat similar to that of uranium (gjU) and plutonium (g4Pu), which immediately precede and follow it in the actinide series on the periodic table. The discovery of neptunium provided a solution to a puzzle as to the missing decay products of the thorium decay series, in which all the elements have mass numbers evenly divisible by four the elements in the uranium series have mass numbers divisible by four with a remainder of two. The actinium series elements have mass numbers divisible by four with a remainder of three. It was not until the neptunium series was discovered that a decay series with a mass number divisible by four and a remainder of one was found. The neptunium decay series proceeds as follows, starting with the isotope plutonium-241 Pu-24l—> Am-24l Np-237 Pa-233 U-233 Th-229 Ra-225 Ac-225 Fr-221 At-217 Bi-213 Ti-209 Pb-209 Bi-209. 

In the above analysis we have neglected the plutonium decay products and their associated hazards. All of Pu, Pu and Pu decay to much longer lived and less hazardous uranium isotopes. However, Pu (originally present to 1% in reactor plutonium) decays through Ra, and Pu (originally present to 12%) decays through Both radium and neptunium are of high radio-... 

After the discovery of uranium radioactivity by Henri Becquerel in 1896, uranium ores were used primarily as a source of radioactive decay products such as Ra. With the discovery of nuclear fission by Otto Hahn and Fritz Strassman in 1938, uranium became extremely important as a source of nuclear energy. Hahn and Strassman made the experimental discovery Lise Meitner and Otto Frisch provided the theoretical explanation. Enrichment of the spontaneous fissioning isotope U in uranium targets led to the development of the atomic bomb, and subsequently to the production of nuclear-generated electrical power. There are considerable amounts of uranium in nuclear waste throughout the world, see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendelevium Neptunium Nobelium Plutonium Protactinium Rutherfordium Thorium. 

Two searches were thus to proceed simultaneously. Seaborg s team would follow one especially intense alpha emitter it had identified in the hope of demonstrating that it was an isotope of 94, chemically different from all other known elements. At the same time, Segrd and Seaborg would produce neptunium 239 in quantity, look for its decay product (which ought to be 94 ) and attempt to measure that substance s fissibility. 

Analysis of the nuclide content of the plume over Finland suggests that the Soviet estimate of the neptunium emission may be too big by a factor of about 3 (T.Raunemaa, private communication, 1987). There is a suggestion that Np-239 was released slowly over some days and partly in the form of one of the decay products (G.Lewis, private communication, 1988). 

The first transuranium element, number 93, was discovered in 1939 by Edwin M. McMillan (1907-1991) at the University of California while he was investigating the fission of uranium. He named it neptunium for the planet Neptune. In 1941, element 94, plutonium, was identified as a beta-decay product of neptunium ... 

Smoke detectors contain a small amount of americium-241. Its decay product is neptunium-237. Identify the emission from americium-241. 

At one time, neptunium s entire existence was synthesized by man. Sometime later, in the mid-twentieth century, it was discovered that a very small amount is naturally produced in uranium ore through the actions of neutrons produced by the decay of uranium in the ore pitchblende. Even so, a great deal more neptunium is artificially produced every year than ever did or does exist in nature. Neptunium is recovered as a by-product of the commercial production of plutonium in nuclear reactors. It can also be synthesized by bombarding uranium-238 with neutrons, resulting in the production of neptunium-239, an isotope of neptunium with a half-life of 2.3565 days. 

Synthesis of plutonium in significant quantities requires a sufficiently long reactor fuel irradiation period. Uranium, plutonium, and the fission products obtained after neutron irradiation are removed from the reactor and stored under water for several weeks. During such cooling periods most neptunium-239 initially formed from uranium and present in the mixture transforms to plutonium-239. Also, the highly radioactive fission products, such as xenon-133 and iodine-131 continue to decay during this period. 

By using neutron and positive-ion bombardment, scientists have been able to extend the periodic table. Prior to 1940 the heaviest known element was uranium (Z = 92). However, in 1940 neptunium (Z = 93) was produced by neutron bombardment of The process initially gives 292U, which then decays to Np by /3-particle production ... 

Neptunium-237 Np-237 has two production routes. The first is rapid /3 decay of U-237 produced by nuclear reactions in the fuel. The second route is /3 decay of Pu-241 to Am-241, which decays losing an a particle to Np-237. This second route will lead to the in-growth of Np-237 in the waste during storage. Np-237 will only be present in waste contaminated with actinides. This is demonstrated by the waste streams that were found to exceed the GQ level. They were IX resin and sludge from BWA and SPF eontents from HPA. Adequate estimates of Np-237 can be made by ratio to Cs-137 determined by FISPIN in the first instance and then refined by taking account of the accumulation and chemistry of other transuranics already measured. At higher concentrations, it can also be measured by y spectrometry of the short-... 

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