Cladding surface

Tritium co-deposition with eroded carbon, during the D-T phase, is anticipated to be the dominant tritium retention mechanism in ITER even if the use of carbon is limited to the divertor strike plates. Retention by implantation and bulk diffusion at the Be-clad surfaces of the first wall and W-clad surfaces of the divertor are expected to rapidly reach saturation, or to marginally contribute to the in-vessel tritium-uptake [95,96], In addition, adsorption of tritium at the inner surfaces of the porous CFC of the vertical target is expected to be very small (few g-T) and adsorbed tritium is not expected to significantly diffuse into the carbon matrix because the temperature of the majority of the bulk CFC will be significantly below 1200 K (Table 12.4). 

When it was estabhshed via calculations that the temperature on cladding surface imder dry storage did not certainly exceed the admissible value, a decision was made on water removal from cooling ponds. 

In the present studies an Inspection philosophy has been adopted which concentrates on the problems of Inspecting the Inlet nozzle-to-vessel weld for radial and circumferential flaws from the Inner clad surface of the vessel and nozzle bore. This situation reflects the pre-service and in-service Inspection condition for which access to the outer surface may be possible only under exceptional circumstances. 

In order to study the effect of heat transfer surface condition on the fuel element cladding temperature, one fuel element mock-up with polished cladding surface and the others with the rough surface were used. 

RPV integrity, particularly during PTS transients. Because of this need, the as-clad surfaces were sometimes ground or buffed as required to provide acceptable surfaces for non-destructive examination (NDE).The roughness of the cladding surface may be a factor in the abihty to examine the inside surface of the RPV wall. 

Clad is not observed to form any ordered structures on Pt(hkl) surfaces, in contrast with Brad on Pt(lll) - see Sect. 4.1.4.1.3). Furthermore, the potential dependence surface coverage by Clad cannot be discerned from RRDE measurements. As a consequence, it is difficult to find the relationship between the activity of the ORR and the potential dependence of Clad surface coverage/structures. To get... 

The location of maximum clad surface temperature, z, can be determined by the condition... 

Axial variation of coolant, cladding surface, and fuel element center temperatures. 

In Figure 22.28, the axial distribution of coolant, cladding surface, and fuel element center temperatures are illustrated. Maximum temperatures for coolant, clad, and the fuel occur above the mid plane. The effect of the coolant is to shift upward the radial temperatures along the rod. 

Amey, M, D. H, Johnson, P. A. V. Improved chemistry Key to reduce occupational radiation exposure in water-cooled reactors. Nucler Europe Worldscan X, 34-36 (1990) Anthoni, S., Ridoux, P, Chevalier, C. Evaluation of corrosion products in a pressurized water reactor during shutdown. Proc. 5. BNES Conf. Water Chemistry of Nuclear Reactor Systems. Bournemouth, UK, 1989, Vol. 2, p. 35-39 Antipov, S. A., Dranenko, V. V., Konkov, V. F., Sokolov, I. B., Khaikovskij, A. A. Influence of fuel clad surface on performance under operational and accident conditions. Report... 

Thus, it can be concluded that the temperature-dependence and kinetics of tellurium volatilization from the oxide fuel itself is comparable to that of iodine and cesium, but that this element is retained in the reactor core by reaction with metallic Zircaloy as a result, the extent of tellurium release from the fuel rod depends strongly on the degree of Zircaloy oxidation. If this oxidation starts exclusively from the outside of the cladding, then tellurium retention would be terminated not earlier than after almost complete oxidation of the cladding material if, however, the oxidation proceeds on both cladding surfaces (inner and outer surface), then an oxide layer of a minimum thickness would be sufllcient to prevent or to retard the progress of the Zr-Te reaction. From this behavior as a starting point for the calculation of tellurium release in the course of an accident it can be assumed that... 

Maximum cladding surface temperature of core fuel pin... 

Plant Maximum cladding surface temperature of core fuel pin (°C) Fission product gas volume per pin (cm ) ... 

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