Decay period

Abklingzeit,/. decay period, abklopfen, v.t. beat beat off, knock off scale off (Med.) percuss, abklbren, v.t. boil out (for redyeing). abkoalleUt v.t. go off, explode. — v.t. fire off. abkneifen, v.t. pinch off, nip off. abknicken, v.t. bend (sharply) crack or snap off. 

Following a decay period of at least 15 hrs, the 1,524 MeV 7-photopeak of 42K is counted for 40 min with a Ge-U solid state detector and a 4096-channel analyzer. This more sophisticated counting system is necessary to obtain the required resolution, since with a Na iodide detector, the 1,524 MeV peak of 42 K overlaps with the 1.369 MeV 7-peak of the 24Na decay spectrum... 

Fig. 1. Generalized a—time plot summarizing characteristic kinetic behaviour observed for isothermal decompositions of solids. There are wide variations in the relative significance of the various stages (distinguished by letter in the diagram). Some stages may be negligible or absent, many reactions of solids are deceleratory throughout. A, initial reaction (often deceleratory) B, induction period C, acceleratory period D, point of inflection at maximum rate (in some reactions there is an appreciable period of constant rate) E, deceleratory (or decay) period and F, completion of reaction.

We shall now examine the behavior of a fairly large sample of 10,000 cells using the same conditions as mentioned above. Again, use a single 5000 iteration run. (Check to see how many of the 10,000 starting A ingredients have ended up in the C states. Lengthen the run if too many have not completed then-decays after 5000 iterations.) Determine cpf, tf, and tp for this sample and compare these values with the deterministic values. For the lifetimes Xf and Tp, plot ln(A or B) versus time for the first 70% of each decay period and determine the decay rates k from the slopes. The lifetimes are the inverses of the slopes, r = k. 

Enclosed fires may exhibit fire growth characteristics as shown in Figure 5-5. Unlike gaseous or liquid fuels, there may be a considerable fire growth period in which temperatures and overall heat release is low and the fire is localized. As the fire becomes fully developed, the entire room volume can become engulfed in flames, finally, as air is depleted or fuel is consumed, a decay period occurs. In many cases, an enclosure fire will be starved for air ("ventilation-limited"), and the available airflow becomes the limiting factor for the fuelburning rate. 

It is further stated by Reitzner in Ref 37b, p 13f, that Arrhenius simplification does not take into account that a large number of expls follow an autocatalytic reaction mechanism, fn the case of the inorganic azides, for example, the metal is considered to be the autocatalyst. The pressure-time curves for such autocatalytic reactions are characterized by an induction period, followed by acceleratory and decay periods. 

The radioactive isotopes of most concern in high level waste (HLW) and their estimated toxicities after several decay periods are given in Table I. These data are largely taken from Wallace ( 1) supplemental estimates from calculations based on ORIGEN code information(2) are included. Other isotopes of the transuranic elements 2U5,2it6,2U7cm),... 

The irradiated coal ash sample with zinc and cadmium carriers is fused with sodium hydroxide. The melt in 2N HC1 solution is loaded onto a Dowex 1 anion exchange column (CT form). The column is rinsed with 2N HC1, and cadmium and zinc are simultaneously eluted with distilled water. The activity of the eluate caused by the 0.438 MeV y-ray of 13.8-hr 69mZn is counted immediately, and after a one-week decay period cadmium is measured by the 0.530 MeV y-ray activity of 54-hr 115Cd. 

The analysis scheme for the 10 evaluation samples used two aliquots ( 25 cm2 of filter paper/aliquot). One aliquot was encapsulated in polyethylene and irradiated in a polyethylene rabbit for 5 min in a thermal neutron flux of approximately 1014 n/cm2/sec. This sample was counted at decay times of 5 min, 30 min, and 24 hrs. The other aliquot was encapsulated in high purity synthetic quartz and irradiated in an aluminum rabbit 12-24 hrs. These samples were counted twice, after decay periods of 10 days and 3 wks. Sample counting equipment included one 4096-channel y-ray spectrometer and a Ge(Li) detector. 

Figures 4 and 5 also indicate that a decay period of approximately 25-30 days reduces the intermediate-lived radionuclides such as 24Na, 140La, and 82Br to insignificant activity levels without seriously affecting the ability to measure the remaining isotopes of interest. The second count is then conducted for 100-1000 min on a Ge(Li) or anticoincidence shielded Ge(Li) spectrometer (28) and provides concentrations for Ag, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Ni, Rb, Sb, Sc, Se, Sr, Ta, Tb, Th, and Zn.

The information in Figure 9 can be used to estimate the amount of data that must be collected. For example, if k = 103s-1, the ratio of the background-to-signal counts is equal to 1.0, the reaction is to be followed for three decay periods (t = 3/fc ), and a relative error of 0.05 is desired. 

When two such surfaces approach each other, layer after layer is squeezed out of the closing gap (Fig. 6.12). Density fluctuations and the specific interactions then cause an exponentially decaying periodic force the periodic length corresponds to the thickness of each layer. Such forces were termed solvation forces because they are a consequence of the adsorption of solvent molecules to solid surfaces [168], Periodic solvation forces across confined liquids were first predicted by computer simulations and theory [168-171], In this case, however, the experimental proof came only few years afterwards using the surface forces apparatus [172,173]. Solvation forces are not only an important factor in the stability of dispersions. They are also important for analyzing the structure of confined liquids. 

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