Axial power

A proportion of the shaft power is used to overcome the bearing friction. This is allowed by using the mechanical efficiency. Thus, the required axial power is... 

B17. Bertoletti, S., Gaspari, G. P., Lombardi, C., and Zavattarelli, R., Critical heat flux data for fully developed flow of steam and water mixtures in round vertical tubes with non-uniform axial power distribution, CISE-R.74 (1963). 

Tong et al. 19-rod Uniform axial Power ramps in a Transient CHF can be... 

Single tube 12 ft long Nonuniform axial Power ramp at 150%/sec Flow coastdown by tripping the circulating pump CHF data... 

The worst operating condition in a common design practice consists of overly conservative assumptions on the hot-channel input. These assumptions must be realistically evaluated in a subchannel analysis by the help of in-core instrumentation measurements. In the early subchannel analysis codes, the core inlet flow conditions and the axial power distribution were preselected off-line, and the most conservative values were used as inputs to the code calculations. In more recent, improved codes, the operating margin is calculated on-line, and the hot-channel power distributions are calculated by using ex-core neutron detector signals for core control. Thus the state parameters (e.g., core power, core inlet temper-... 

In the case of uniform axial power distribution, Eq. (5-141) becomes... 

C-E Report, 1975, C-E Critical Heat Flux Correlation for C-E Fuel Assemblies with Standard Spacer Grids, Part I, Uniform Axial Power Distribution, CENPD-162, Combustion Engineering Co., Winsor, CT. (5)... 

Furnace atomisation plasma emission spectrometry (FAPES) this consists of an atmospheric pressure source combining a capacitively coupled radiofrequency helium plasma formed inside a graphite tube which contains an axial powered electrode. This miniplasma has rarely been used in analytical atomic spectrometry, probably because of the small number of users and a lack of information about its applications and capabilities [7]. 

Because of the presence of sleam voids in lire upper part of [he core, there is a natural characteristic for a BWR to have the axial power peak in the lower part of the core. During the early part of an operating cycle, bottom-entry control rods permit a partial reduction of this axial peaking by locating a larger fraction of the control rods in the lower part of the... 

Based on the comparison to MOX criticals shown in Fig. 5, it would appear that Surry BZ and TMI BZ are most consistent with the experimental measurements, and that only the Surry EF case would be considered as an outlying result. Sequoyah results are self-consistent and are relatively close to the results of the experimental cases, as is the North Anna result. Note that the Surry BZ case is closest to the fit to the zero-power MOX criticals, and that all full-power cases (Sequoyah BF, Sequoyah MF, and Surry EF) are more removed from the data. This trend indicates that perhaps aspects of full-power operation (e.g., nuclides present, temperature effects, axial power distributions, xenon distributions, etc.) are not being well represented in the KENO V.a models. 

The reflector is installed inside the reactor vessel and the heat generated in the reflector is cooled by sodium. The equivalent core diameter is 0.8m which satisfy negative void reactivity requirements. The reflector length is 1.5m and the reflector gradually moves up to control the reactivity leading to bum-up. The axial power distribution changes as shown in Fig. 3 according to the reflector position. 

Fig. 3 Axial Power Distribution as a Function of Reflector Position... 

Relative Axial Power Distribution for Equilibrium Cycle... 

The active core height has been chosen to allow a maximum power rating while assuring axial power shape stability to xenon oscillations over a normal burnup cycle. 

Figure 4.2-11 shows the axial power distribution for an equilibrium cycle. This distribution indicates 65 percent of the power in the top zone, 25 percent in the middle zone, and 10 percent in the bottom zone. This distribution is expected to minimize peak fuel temperatures. The selection of the active core height of ten fuel elements was made to yield a maximum power rating while maintaining an axial power shape that remains stable with burnup and stable to axial xenon transients. 

Preliminary analyses were made on the stability of the radial and axial power shapes to xenon-induced transients. The degree of damping, with time, of the resulting power oscillation was used to indicate the relative power stability of the core. The perturbations incorporated into these test calculations were much more severe than could be encountered in actual operation at power... 

RELATIVE AXIAL POWER DISTRIBUTION FOR EOUILIBRIUM CYCLE... 

Failures to this equipment can occur in the gamma thermometers or the signal conditioners, resulting in erroneous flux level readings. Because there are five strings of IFMUs, a failure in one or several detectors reduces the amount of data available to map the axial power offsets. These failures have no immediate effect on the plant operation. 

During plant operation, the in-vessel flux mapping units (IFMUs) are monitored at predetermined intervals to record the flux level at fixed axial positions, so that a core axial power offset can be determined. 

Axial Power Indicator (APD - Brown Recorder Roof Top Ratio (R.TR) Recorders 1 2 Power ENbdsi Monitor (PDM)... 

APSR AXIAL POWER SHAPING ROD ASSEMBLY cl TABLE 4.2-5... 

Ultimately, bundles can be removed from the channel during on-power refueling and reshuffled, and reinserted in any order. This axial shuffling provides nearly unlimited capability for shaping the axial power distribution, if necessary. Adjuster rods are located interstitially between fuel channels, in the low-pressure moderator. They flatten the power distribution with NUE fuel, a function not required with enriched fuel, and provide xenon-override capability. With an enriched fuel, the adjuster rods can be easily replaced, if desired, or even eliminated, providing further flexibility in accommodating advanced fuel cycles. 

Transition from the equilibrium natural uranium core to the mixed core would be particularly straightforward because the adjuster rods do not distort the axial power profile in the SEU-fueled channels. In those channels, the axial power profile evolves smoothly, with no significant power boosting at extended bumups. 

Figure XV-9 shows the averaged axial power profiles at several moments during the core lifetime. At the beginning of core life (BOC), a bare sub-critical core becomes critical by inserting reflectors to reduce the neutron leakage. The peak power is at a lower part of the core. As the core bums, the reflector is gradually lifted up to cover fresher fuel parts at the middle of core life (MOC). At the end of core life (EOC), the reflector is almost at the top of the core. Otherwise negative, the coolant density reactivity coefficient and the coolant void reactivity effect are approaching zero at the EOC.

---