Plutonium half-life determination

The order of reaction has an impact on the way of determining the time at which the reaction takes place, or conversely the degree of incident reaction at the time. The half-life of a reaction describes the time needed for half of the reactant to be depleted (think plutonium half-life in nuclear physics, which can be defined as a first-order reaction). In the case of reactions occurring during the flow, the degree of occurrence of the reaction depends on the speed of reaction and the way that the reactants have to proceed. Adequate factors (powers) of the Eq. 2.43 determined experimentally for selected reactions are given in Appendix A. 

The ratio of plutonium isotopes to 241 Am is often reported in monitoring studies as it is an important tool in dose assessment by enabling a determination of plutonium concentrations. 243Am is produced directly by the capture of two neutrons by 241 Am. The parent of241 Am is 241Pu, which constitutes about 12% of the 1% content of a typical spent fuel rod from a nuclear reactor, has a half-life of 14 years. Separation of... 

Am with a half-life of ti = 432 a has to be determined in waste and environmental samples by mass spectrometry. The determination of 238Pu (ti 88 a) at the trace level is difficult in the presence of uranium due to isobaric interference with 238 U+ in mass spectra measured by ICP-MS or LA-ICP-MS. Therefore the application of a sensitive and selective technique such as RIMS or AMS is advantageous. The determination of 238Pu for plutonium isotope analysis in irradiated... 

Microscopic samples were used to determine the half-life of the alpha decay of Pu to be (2.43 0.12) X 1 O yr compared to the current accepted value of 24,110yr. The isotopic sequence to plutonium, -I- neutron (immediate release of gamma energy... 

Mass spectrometry is used by some research laboratories to determine the concentration of each plutonium isotope, including the naturally-occurring plutonium-244. Mass spectrometry determines the number of atoms of a given mass number and, therefore, can measure the concentration of all of the plutonium isotopes, not only the alpha-particle emitters as in alpha spectrometry. Mass spectrometry is several orders of magnitude more sensitive than alpha spectrometry in determining the quantities of plutonium isotopes with long half-lives, which also tend to be the heavier isotopes. However, plutonium-238 is most accurately determined by alpha spectrometry (Bernhardt 1976) because of its relatively short half-life and the potential interferences from traces of uranium-238. 

The process of determining a permanent disposal solution involves social, political, economic, and technical issues that compete and coalesce to determine the specific end state. Characteristics that make permanent disposal of TRU and HLW complex include contamination with long-lived radionuclides (e.g., plutonium-239 has a half-life of approximately 24,000 years) and high concentrations of radioachvity. While less contentious, LLRW disposal also presents challenges, as discussed in Section 16.6. The discussion in this section is primarily applicable to TRU and HLW disposal. 

Transient effects When the reactor is suddenly shut down, removal ceases while decay of Pm continues with its 53.1 hour half life. The Sm concentration will then increase slightly (imperceptible in UWNR, about a 10% increase for a power reactor) until it reaches a maximum about two weeks after the shutdown. It would then remain at the new level until power operation is resumed to burn out to equilibrium level. Even the small increase in poisoning is not apparent, since a power reactor will also have a build-in of Plutonium from the decay (56.4 hour half live) of Np. The Sm defect is often included in the fuel reactivity curves used for ECP determinations. 

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