[link to www.cnic.jp]

[snip]


The ‘simulation analysis’ deception technique


It seems to me that an LOCA occurred due to pipe damage; large amounts of steam blew out into the containment vessel (drywell) heading toward the suppression chamber, but due to the hydrodynamic loads and the ‘sloshing’ at the time of the earthquake, the structures were damaged and the pressure suppression mechanism was lost. As a result, steam volume was not reduced through condensation, and thus the pressure in the containment vessel rose to 0.74 MPa (about 7.4 atm), and this is the answer to the ‘greatest puzzle of the 1F 1 accident.’

Meanwhile, on Sunday, 15 May, TEPCO held an emergency press conference to explain that, as a result of a ‘simulation analysis,’ 1F 1 had experienced a ‘meltdown’ (by this term TEPCO apparently meant that molten fuel rods had fallen to the bottom of the reactor) at quite an early stage.

TEPCO did not really need to explain this as it had already become quite obvious to many people that a meltdown had occurred, but perhaps because this was the moment when TEPCO at last ‘formally’ recognized the fact, this meltdown press conference is still accepted by the general public in a positive and favorable light. In fact, it was clearly a TEPCO ‘trap,’ and most people walked straight into it. In a simulation analysis, you can get any result you want simply by altering the conditions of the analysis (i.e. the input data). However, most people were so surprised by TEPCO’s admission of the so-called ‘high-speed meltdown’ that almost no one thought to ask about the simulation analysis conditions.

Once again, the greatest puzzle of the 1F 1 accident sequence was why the containment vessel pressure rose to 0.74 MPa (about 7.4 atm). TEPCO must naturally have thought at first that it was an LOCA. They probably wondered about what sorts of things could happen to cause the containment vessel pressure to rise to 0.74 MPa. The Mark-I containment vessel’s ‘unresolved safety issue’ must have passed through the analyst’s mind. Certainly, the ‘sloshing’ problem at the time of the earthquake must also have passed through his mind. However, TEPCO would not wish to take up these matters in the simulation analysis, because that would then make an issue out of ‘earthquakes.’ If this were to be presented in a simulation, the ten Mark-I containment vessels still being used in Japan (excluding those used in 1F 1-5) would immediately become a ‘big problem.’

The TEPCO simulation analysis considered no impact from the earthquake. So how did TEPCO manage to arrange for the simulation to achieve the ‘abnormal’ containment vessel pressure rise? Figures 3 and 4 give the answer. Looking at Figure 3, the reactor water level drops precipitously (because the input conditions are set for it to do that, but I will not go into the details here). In this case the fuel rods very quickly melt down. In fact, looking at Figure 4, you can see that it says ‘RPV (reactor pressure vessel) damage’ at about 15 hours after the earthquake struck. That is, a meltdown occurred and a hole opened up ‘somewhere’ in the RPV.

As a result, as the meltdown proceeded in the RPV, the high temperature, high pressure gas blasted violently out through that hole into the containment vessel. Thus the containment vessel pressure rose rapidly (Fig. 4). This is TEPCO’s ‘simulation analysis’ deception technique.

This is nothing but a ‘voodoo simulation’ in which the earthquake issue is cleverly ignored using the smokescreen of the high-speed meltdown. The undeniable gap between the actual measured values for the reactor water level and the result of the simulation is the very piece of evidence that is needed to see through this disgraceful deception.

Mitsuhiko Tanaka (Science writer; ex-RPV designer)