Annuli, corrosion rate

Results obtained with loop experiments with 0.04 m UO2SO4 solution (F.,-2-10 and L-2-17) are illustrated by the curves in Fig. 5-17 [59]. A portion of line B from Fig. 5-16 is included in Fig. 5-17 for comparison. Corrosion rates for channel specimens in this solution are greater at the same power density than those for specimens in 0.17 m UO2SO4 solutions. The. shape of the curve through the channel data is also different. As will be discussed later, these channel data may l>e interpreted in terms of a beneficial effect of solution velocity on corrosion. The approximate locations of. specimens in the channel with respect to the power density to which the specimen was cxpo.sed and the average velocity of solution at the specimen are indicated in Fig. 5-17. The annulus specimens, which were exposed at low. solution velocities, corroded at higher rates than the channel specimens. 

Silverman [21] derived velocity correlations between a rotating cylinder (mO, pipe flow (m2), annulus flow (1/3), and an impinging jet (wall jet region only, 1/4), as listed in Table 2. These equations assume that the appropriate transformations are to be made on the basis of equal mass-transfer rates for the different geometries. Silverman [21] also explored the case where the equality of surface shear stress is the appropriate criterion, on the basis that the equality of the shear stress will ensure the same corrosion processes for the various geometries. We stress that the equations listed in Table 2 must be used with great caution because they are based on the... 

Continuous injection of corrosion inhibitors is practiced in once-through systems where slugs or batch treatment cannot be distributed evenly through the fluid. This method is used for water supplies, oil field injection water, once-through cooling water, open annulus oil or gas weUs, and gas lift wells. Liquid inhibitors are injected with a chanical injection pump. These pumps are extremely reliable and require little maintenance. Most chemical injection pumps can be adjusted to deliver at the desire injection rate (Chen et al. 2010). 

The release rate will now become complex as the circles merge an approximation can be made by simplifying the geometry to form an annulus as shown in Figure 13. Corrosion and activation product release can then continue inward and outward at 0.019 mm-a until the BeO reflector or the corrosion attacking inward from the edge of the structure are reached. 

By the year 2180, fission products and actinides from the damaged and undamaged reactor cores join the release stream and the total release rate is of the order of 5 GBq-a. By the year 3000, the rise in release rate of the SNF and thermal shields of the reactors, caused by the expanding circles of corrosion exceeds the fall due to decay, and the release rate rises until the year 5200 when the ECTs merge to form an annulus. The release rate then varies as the shields external to the ECTs corrode away by the year 6800 and the left board SG loses all its SNF by the year 7500. By this stage, the release rate has fallen to 0.07 GBq a. ... 

Note Stages are pumped at maximum matrix rate, without diversion, even in long zones. Acid must first be spotted with coiled tubing, then pumped through the annulus at a high rate.The following acid additives are required corrosion inhibitor, iron control agent, and surfactant. 

---