Three Mile Island react

Although the Three Mile Island incident of the 1970s and the Chernobyl disaster increased the awareness of radioactive gases in the atmosphere somewhat, radioactive xenon does not pose a significant health risk compared to other radioisotopes since it does not react with the environment and has a short half-life, hence it does not give the public much dose compared to other reactive radioisotopes such as Cs and Sr even though it is present in the air. 

In the Three Mile Island core meltdown, it is known that there was also a Zircaloy-water chemical reaction leading to a considerable release of hydrogen. However, the reactor circuit pressure relief and containment system there prevented damage with no significant fission product release to the atmosphere. There was no free oxygen in the vessel so that hydrogen did not react chemically. 

A technical superintendent at TMI-2 who arrived on the plant at 03 45, subsequently said I had the perception that we were in a very unusual situation, since I had never seen the pressurizer level increase and stay at a high value and, at the same time, the pressure staying low. They [the pressure and the level] had always behaved in the same way . As a consequence of the described evaluation errors the primary circuit continued to lose water for hours and in addition the automatic core cooling system, correctly activated, could not perform its function of fuel integrity protection. It is now known that if the block valve had been closed after one and half or two hours or if the operation of the HPI only had not been arrested, even without the closure of the valve, the Three Mile Island accident would have been no more than a modest nuisance of operation. For completeness of information it has to be added that the possibility of an accident of the type of TMI-2 had been foreseen by some experts. If these foresights had been confirmed by in-depth theoretical studies and possibly by experimental tests, their results, duly made known to interested people, would have enabled the TMI-2 operators to correctly diagnose the fault and react correctly. 

Without either spray droplets or flooded pathways, substantial fractions of radionuclides released from the degrading reactor fuel can be retained within the reactor coolant system. Results of some example calculation for radionuclide retention in the reactor coolant systems for various types of accidents are shown in Table III-l. The natural retention of radionuclide vapors oeeurs because the vapors either condense on surfaces or react with these surfaces. Depending on the surface temperature and the duration of its exposure to high temperature steam, the surface material is either ehromium oxide (Cr203) or iron oxide (Fe304 y). Both of these materials are expected to be reactive toward cesium-bearing vapours and strontium or barium vapors. Stainless steel lead screws above the core at Three Mile Island were found to have captured cesium by reaction with silica impurities in the steel. Metallic nickel inclusions in the oxide films on surfaces within the reactor coolant system are reactive toward tellurium whether it is in the metallic state or present as TeO or SnTe. 

Hydrogen detonation has become an important issue after the Three-Mile-Island accident. The hydrogen burning occurred approximately 10 hours into the accident. The steam reacting with the Zircaloy cladding and the oxidation of the overheated steel vessel interiors created large quantities of hydrogen. This can also occur due to interaction of the molten core. In order to predict the wall pressures due to such detonations, non-linear gas dynamics equations for the entire volume of the containment vessel have to be solved. In the current analysis of the Sizewell B containment vessel, it is assumed that the wall pressure... 

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