Activity of radionuclide

In this expression A(i) is the specific activity of radionuclide i, A(i) (r = 1) is the specific activity of nuclide i at r = 1, r is the radius of a debris particle, and mis a number between 0 and 1. A value of m = 0 implies that the activity is proportional to the volume of the particles. Such a volume dependence results for nuclides which combine with the matrix material in the cooling fireball and applies to the so-called refractory chains, such as the 95-, 11-, and 147-chains. A value of m = 1 or a surface-... 

The specific activities of radionuclides in debris from ground surface bursts are generally complicated functions of the particle size, in accordance with the composite nature of the debris. 

The specific activities of radionuclides in samples from surface burst debris are not necessarily unique functions of the particle size. The uniqueness is determined by the degree of mixing in the cloud, and is, therefore, expected to be a function of the time elapsed between the shot time and the sampling time. 

Using the Methodic Guides [5] trough an assigned value a, for volumetric activity of / radionuclide in water and a specified human exposure time tj via path j the radiation dose Dij through this path due to water contamination by the indicated nuclide can be calculated via the following formulae ... 

TABLE 3. Specific activity of radionuclides in bottom sediments and algae at Atomflof enterprise water area, 1998 (Bq/kg, dry weight)... 

Absolute activities of radionuclides may also be determined by coincidence measurements, provided that the decay scheme is relatively simple, e.g. only one f transition followed immediately by emission of one or more y-ray photons. The principles of the use of coincidence circuits are discussed in the following section. 

Pulsed research reactors, such as reactors of the Triga type, are especially designed for production and investigation of short-lived radionuclides. In these reactors the neutron flux is increased for about 10 ms to about 10 cm s by taking out the control rods (section 11.5). Due to the negative temperature coefficient of the zirconium hydride moderator, the outburst of power causes a sudden decrease of the moderator properties and shutting off of the reactor. After several minutes the effects have vanished and a new pulse can be started. The activities of radionuclides of various half-lives obtained with pulsed reactors are compared in Table 12.2 with those produced at constant neutron flux densities. The table shows that pulsed reactors are useful for production and investigation of radionuclides with half-lives < 10 s. 

Table 12.2. Activities of radionuclides of various half-lives obtained in pulsed reactors of the Triga type compared with those obtained at constant flux densities (activities in MBq/g for (t = 1 barn, if = 1 and Af = 100)...

In the absence of stable isotopes, the specific activity of radionuclides is given by... 

The introduction of NIREX GQs for packaging and disposal of ILW has resulted in the need to analyse or calculate the specific activities of radionuclides that had not been important historically. This paper identifies those nuclides that are likely to exceed the GQ in a range of Magnox waste streams and considers whether adequate procedures exist for all. For those... 

Assinder et al. (1985) reported that the behaviour of radionuclides in the Esk Estuary was determined by its physical characteristics and by its location close to the Sellafield discharge point. Relatively high specific activities of radionuclides in the dissolved phases of waters were encountered. They found that sediment reworked from earlier deposits within the estuary formed a major part of the sediment load of the tidal waters and therefore provided a significant part of the total activity of the particulate phase. The temporal and spatial variation of the total water activity for radionuclides such as Pu follows the pattern for suspended sediment concentration whereas, for conservative radionuclides (e.g. Cs), the... 

Gamma spectroscopy is a radiochemical measurement method that allows identification and quantitative determination of activity of radionuclides, which emit gamma radiation or x-rays. The equipment used in gamma spectroscopy includes an energy-sensitive radiation detector, such as semiconductors, scintillators or proportional counters, and a multichannel analyzer. The energies and the photon yields are characteristic for specific nuclides. 

C8d = specific activity of radionuclide per gram at depth d in core C80 = specific activity of radionuclide at surface p = penetration coefficient... 

TABLE 1. Specific activity of radionuclides in Stereocaulon vesuvianum from slopes of Mt. Vesuvius (Bq kg 1 dry weight). 

Radioanalytical chemistry is devoted to analyzing samples for their radionuclide content. For this purpose, the strategies of identifying and purifying the radioelements of interest by chemical methods, and of identifying and measuring the disintegration rate ( activity ) of radionuclides by nuclear methods, are combined. Radioanalytical chemistry can be considered to be a specialty in the subdiscipline of nuclear and radiochemistry. 

During the period 1986-97, a complex for HLW vitrification on the basis of two EP-500 ceramic melters were operated at the Mayak power unit (Fig. 1). For six years exploitation of a ceramic melter EP-500/lp, under conditions of remote operation, about 12,500 m liquid HLW were transferred into glass-type matrices based on phosphate glass (Table 1). The total activity of radionuclides incorporated in glass is 285 million Ci on P-emitters and 2.5 million Ci on a-emitters [1]. 

Table II. 1 Half-life and specific activity of radionuclides. 259...

C(j) is the activity of radionuclide j as other than special form material, and A O) is the A2 value for radionuclide j. 

---