Flux peak

Experimental data from Bech Nielsen s study is shown in Fig. 6 and Fig. 7. The data show that implanted 2H is found predominantly in bond-center sites. This qualitative conclusion can be drawn immediately from the raw channeling data, especially the 111 planar scans, and does not depend on the details of the model used to subsequently analyze the data in greater detail. Si—Si bonds run perpendicularly across the 111 planar channel. At zero tilt, a strong flux peak of planar channeled ions is focused on the bond centered site and causes the peak seen in the data at this angle. However, back-bonded sites are hidden in the wall of this channel, which is unusually thick and consists of two planes of atoms close together. Thus, the ion flux near the back-bonded sites is low when the tilt angle is small, hence the dip in nuclear reaction yield calculated for this site. Bech Nielsen (1988) found that this data pointed to there being a minority of the 2H... 

The experimental data show that most of the deuterium atoms in the samples examined occupy bond-center sites. The attribution of this site comes both from the observation of a flux peak in the 111 plane (Fig. 11), and of a dip in the (110) axial channel (Fig. 12), together with the channeling simulations shown in Fig. 9 and Fig. 10. Just as in the case of FI-implanted silicon, the qualitative observation of a flux peak in the 111 planar data rules out any possibility of a back-bonded site for the 2H, although some calculations of the B—H structure have suggested this site. The data were analyzed on the assumption that they could be fitted by a combination of a small number of sites of high symmetry. First, the excess hydrogen, i.e., the part of the hydrogen concentration in Fig. 8... 

Bech Nielsen et a/. s experimental channeling data for the (100) axial channels is shown in Fig. 14. Together with 111 planar data, which showed a pronounced flux peak, these data clearly indicate a near bond-center site for the 2H. According to Bech Nielsen s analysis, the best fit to the data was obtained with 87% of the 2H atoms in the sample assigned to near BC sites and the rest to T sites. However, the attribution of the minority component could be influenced by radiation effects during the analysis, as will be discussed later. 

Incident sunlight is partially absorbed by minerals on an asteroid s surface, and the fraction of light that is reflected can vary as a function of wavelength. Spectrophotometric studies of asteroids have been carried out for decades. Asteroid reflectance spectra have been compared to the spectra of meteorites measured in the laboratory (Fig. 11.3), providing a way to link some kinds of meteorites to possible parent bodies. Most measurements are made at visible wavelengths ranging from 0.4 to 1.0 pm, because the illuminating solar flux peaks... 

ErH2 -> Er). Then diffusion may be considered as relatively fast and therefore ordinary differential equations are sufficient. This significantly simplifies solving the inverse problems of parameter identification. Although models with fast diffusion may also correspond to the low-temperature flux peak atoms of H easily diffuse in ErH2 (may be, even easier than in Er even at higher temperatures). 

Salt rejections by the NS-300 membrane toward synthetic seawater improved as the isophthalamide content of the barrier layer increased. Surprisingly, membrane flux peaked rather than simply declining as a function of increasing isophthalamide content. This is illustrated by the data in Table II. Maximum water permeability characteristics were found at an approximate copolymer ratio of 67 percent isophthalic and 33 percent trimesic groups. The differences in the magnesium sulfate versus sodium chloride rejection appear to be due to the anionically charged nature of the membrane barrier layer, which is rich in carboxylate groups. 

Scatter refueling. Flux peaking can be reduced by a different method of partial batch replacement, called scatter refueling, which is illustrated by Fig. 3.8. In this method, fuel is... 

For larger reactors with hi bumup, however, out-in fueling leads to too great a depression in the flux and power density at the center of the reactor. This may be seen from the lower half of Fig. 3.9, which shows the power density calculated by Westinghouse [Dl ] for three-zone out-in fueling of a 1000-MWe PWR, with a core 6.5 ft in radius, operated at a burnup of 24,000 MWd/MT. At the begiiming of a cycle, the flux peaks heavily in the outside zone, and the peak-to-average radial power density ratio is 2.0. The reason for this poor... 

The nonuniformity of heat flux around mbe is described by the circumferential flux factor, which is the ratio of peak flux to average flux. Peak flux determines the maximum TWT. The peak flux is typically 1.5-1.8 times the average for a single-fired heater, while it is 1.2 times the average for a double-fired heater. That explains why the double-fired heater has longer run length as it has lower flux rate and hence lower TWT than the single-fired heater. 

This result might also be anticipated on physical grounds, for, if the maximum flux is indeed large, a minimum energy loss is equivalent to a minimum control time at fluxes less than the maximum. The Fo trajectory cuts across the top of a zero flux peak to reach the desired flux maximum trajectory in less time and with less waste of nuclear energy. 

Provision of natural uranium fuel pellets at the pellet stack ends to reduce end-flux peaking. 

What fuel configuration is specified by Technical Specifications to prevent flux peaking in a... 

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