Posted on 09/17/2010 2:07:48 PM PDT by epithermal
Whoever is the last one out of the reactor.
Concur. Thank you for pointing that out.
No, not really.
TMI’s core had already melted, and was in molten (lava-like) streams of mixed debr4is passing through the flow holes in the lower plate and re-solidifying against the walls and bottom of the core. (My former company modeled the 3d geometry of the remnants - so I'm more than familiar with the geometry.) Jane Fonda's famous quotes notwithstanding, it could not have melted through anything. Nor was it “pushed” towards criticality as in the Russian plant: There, they had been pulling rods to overcome the build up of natural poisons for hours to stay critical. (As pinted out above.)
At TMI, the reactor had already been shutdown, the rods were fully down and (stayed there - melting with the fuel around them). So the whole mass was simply heating up from residual heat, which will decrease with time.
The flattened, mixed mass of the TMI core, used fuel, fuel poisons, control rods, and support alloys around the fuel meant the mass was well below critical shape or construction, and it was, of course, rapidly cooling as flowed past the steel reactor vessel walls. The steel and stainless steel vessel walls, internal separator plates and wall shields and flow dividers were not threatened.
No way. The Chornobil (Ukrainian spelling) accident was a power excursion. The damage was caused by a rapid and uncontrollable rise in power as a result of the physics of the design (positive power feedback). Those kinds of transients occur over relatively short times (seconds to fractions of a second).
The TMI accident involved loss of coolant, not a power excursion. The damage was primarily thermal. Thermal events evolve much more slowly over time. You cannot have as rapid a release of energy as you have with a power transient. Thermal phenomena take time to occur, on the order of hours to tens of hours).
Nor were the radiological consequences comparable. In accident analysis there is something we call the source term. That is, how much radioactivity might be involved in a potential release. Because of the containment structure at TMI and other mitigating systems, the source term is much smaller than for an uncontained release, which is what we had at Chornobil.
Have you looked at Elena's site? It is extremely interesting. They lost quite a lot of people, territory, and equipment to that disaster.
Thank you very much for your information and explanation. I appreciate having an better understanding.
OK, thanks for being open and listening.
Yes, they did, it was very tragic, and very unnecessary. There was no reason they had to run that test the way they did.
Fermi recognized the danger of the positive feedback in graphite-moderated, water-cooled systems way back in the early days of reactor physics. He'd called them autocatalytic systems, meaning they could under some conditions burn themselves up. We had the uranium enrichment technology to make light water-moderated and cooled systems work, and history has borne out that it was the right choice from an inherent safety (negative void and temperature feedback) viewpoint.
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