Single-channel analyser

Working solutions (1 litre) which were 10 7 mol/1 in one of the elements to be studied were prepared by appropriate addition of the radioactive stock solutions to pH-adjusted artificial seawater. After the pH had been checked, 100 ml portions were transferred to the bottles to be tested. The filled bottles were shaken continuously and gently in an upright position, at room temperature and in the dark. At certain time intervals, ranging from 1 min to 28 d, 0.1 ml aliquots were taken. These aliquots were counted in a 3 x 3 in Nal (TI) well-type scintillation detector, coupled to a single-channel analyser with a window setting corresponding to the rays to be measured. 

A wide-ranging ground survey of Taranaki area was conducted by the Australian Radiation Laboratory (ARL) over the period 1984 to 1986. Field measurements employing thin sodium-iodide detectors and single-channel analysers were used to provide a qualitative indicator of plutonium (Cooper et al., 1985), and quantitative data were obtained by gamma-ray analyses of soil samples (Cooper et al., 1985 Bums et al.,... 

Figure 4.27 A single channel analyser with upper and lower discriminator levels defining a window ...

SINGLE CHANNEL ANALYSER (SCA) A device that produces a logic output pulse when an input pulse has a maximum that falls within a user-defined window. 

The angular correlation of the 2y-annihilation photons is measured with the system described in Figure 4.37. The annihilation photons are detected in coincidence by Nal scintillation counters, which are shielded from direct view of the source. The lead collimators in front of the detectors define the instrumental angular resolution (1 mrad). To archive counting rates, the detectors and slits are made as long as possible in the x-direction. The single-channel analyser (SCA) is tuned for 511 keV photons, and the device simply counts the coincidence pulses as a function of the angle 0z. 

This S/N ratio obviously depends on the detector energy resolution, the setting of the single channel analyser and on the radiation source spectrum. It is this last point that concern us. 

The limiting flow velocities for each diameter and P/D are determined so that the cladding surface temperature reaches the limiting value with given MLHGR of 39 kW/m. Then, degree of FIV is evaluated from those flow velocities. All the evaluations are conducted by single channel analyses. 

The core design procedure consists of two parts, nuclear design and thermal-hydraulic analysis. The former is based on the fine-mesh multi-group neutron diffusion solution. The latter is based on single channel analyses for the average and hot channels of all the fuel assemblies. This approach is the same as that in the Super LWR design. 

The nuclear design limits and the nuclear performance are examined in the nuclear design part, while the core outlet temperature and MCST are examined in the single channel analyses. Detailed descriptions for each part are discussed below. 

The peak values of the cladding surface temperatures in each seed assembly are shown in Fig. 7.41. The MCST throughout the equilibrium cycle, calculated by the single channel analyses, is 643°C. The local power distribution within an assembly is taken into account, but heterogeneity of the subchannels is not considered. The maximum cladding surface temperature is calculated again by subchannel analyses in Sect. 7.6. 

Table 7.29 [26] shows the fuel rod design results. The fuel rod diameter and P/D are 7.0 mm and 1.16, respectively. The rod arrangements in the seed and blanket assemblies are the same as those of the 1,000 MWe class design as shown in Fig. 7.57 [26]. The fuel loading pattern and flow distribution design are shown in Fig. 7.58 [26]. The distributions of the MCST calculated by single channel analyses and subchannel analyses are shown in Fig. 7.59 [26]. The highest value is kept well below the criterion of 650°C by modifying the subchannel shapes as introduced in Sect. 7.6. The core design results are summarized in Table 7.30 [26]. Based on the reference core design, two important performances are improved in Sects. 7.8.2 and 7.8.3.

---