Pressurized Water Reactor Observations

In the period fi om October to December 2006, 14 crews of Swedish licensed pressurized water reactor (PWR) operators participated in an experiment performed in H AMMLAB (H Alden Man Machine L AB-oratory Braarud et al. 2007). All crews responded to two versions of a steam generator tube rupture (SGTR) scenario. These simulations constituted the empirical reference data for the International HRA Empirical Study (Lois et al. 2008). While the International HRA Empirical Study focuses on comparing observed performance in HAMMLAB simulator trials with HRA analyses predictions, the present paper concentrates on substantive issues of the observed crew performances namely, the interactions between crews, situations and procedures. 

Although the water and steam contain appreciable amounts of oxygen, carbon steels and stainless steels exhibit equivalent or superior corrosion resistance to that observed in pressurized water at the same temperatures. However, special problems do exist. Stainless steel fuel cladding has failed by SCC in boiler water reactors. 

P12-5f Safety Problem The following is an excerpt from Tfie Morning News, Wilmington, Delaware (August 3. 1977) "Investigators sift through the debris from blast in quest for the cause [that destroyed the new nitrous oxide plant). A company spokesman. said it appears more likely that the fatal] blast was caused by another gas—ammrmium nitrate—used to produce nitrous oxide. An 83 X (wt) ammonium nitrate and water solution is fed at 200 F to the CSTR operated at a temperature of about SIO F. Molten ammonium nitrate decomposes directly to produce gaseous nitrous oxide and steain. It is believed that pressure fluctuations were observed in the system and. as a result, the molten ammonium nitrate feed to the reactor may have been shut otf approximately 4 min prior to the explosion. 

At still higher temperatures, when sufficient oxygen is present, combustion and "hot" flames are observed the principal products are carbon oxides and water. Key variables that determine the reaction characteristics are fuel-to-oxidant ratio, pressure, reactor configuration and residence time, and the nature of the surface exposed to the reaction 2one. The chemistry of hot flames, which occur in the high temperature region, has been extensively discussed (60-62) (see Col ustion science and technology). 

The kinetics results of the batch reactor runs lead to the following qualitative observations At low CO pressures (less than about 1 atm) the catalysis appears to be first order in ruthenium over the range 0.018 M to 0.072 M and also in Pco as illustrated by the log Pco vs time plots of Fig. 2 and also shown by the method of initial rates. Changes in the sulfuric acid and water concentrations over the respective ranges 0.25 M to 2.0 M and 4 M to 12 M have relatively small effects on the catalysis rates, although the functionalities are complicated and show concave rate vs concentration curves with maximum rates... 

Bertole et al.u reported experiments on an unsupported Re-promoted cobalt catalyst. The experiments were done in a SSITKA setup, at 210 °C and pressures in the range 3-16.5 bar, using a 4 mm i.d. fixed bed reactor. The partial pressures of H2, CO and H20 in the feed were varied, and the deactivation, effect on activity, selectivity and intrinsic activity (SSITKA) were studied. The direct observation of the kinetic effect of the water on the activity was difficult due to deactivation. However, the authors discuss kinetic effects of water after correcting for deactivation. The results are summarized in Table 1, the table showing the ratio between the results obtained with added water in the feed divided by the same result in a dry experiment. The column headings refer to the actual experiments compared. It is evident that adding water leads to an increase in the overall rate constant kco. The authors also report the intrinsic pseudo first order rate-coefficient kc, where the overall rate of CO conversion rco = kc 6C and 0C is the coverage of active... 

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