Chronology is a sequence of events with reference to their respective time of occurrence. It would appear very simple. It was with this in mind that the Chief Designer of the high-power pressure tube reactor (RBMK) provided the computation complex of the centralized control system SKALA with the diagnostic recording software DREG that was intended specially for tape recording of such chronology in case of emergencies and other fast transitory processes. However, nothing of the kind happened. Any question, however simple and clear, may turn into a complicated riddle if only it affects someone’s selfish interest.
We would like to remind you of the basic outline of this chronology. Until the time of 01:23:40 a.m. (as recorded by the DREG), when the EPS-5 button was pressed, the sequence of events is equally recognized by everyone, and does not call for any serious discussion. The only issue (related, to a large extent, to terminology) that has been discussed is whether the accident started before that time, or only after that. After pushing the EPS-5 button, the abnormal process in the reactor started developing rapidly. At 1:23:43, all measurement channels recorded alarm signals of exceeding maximum power and maximum power growth velocity; at the same, time, there were malfunction alarms of all those channels (that means both power and its growth velocity went off scale to such an extent that they could not even be measured). At 1:23:49, there were alarms "pressure growth in reactor space"(which means rupture of fuel channels), and "no voltage of 48 V" after that, there was a power outage (the reactor existed no more).
Analogue signals recorded by the DREG during the last 10 sec of the reactor’s life (readings of process control sensors) are shown in the tables (at the beginning of the page) and in the graph in Fig. 12-14.
The data recorded by the DREG provides clear evidence that the reactor has been exploded by its own emergency protection system. The starting point of the accident is pushing the EPS-5 button; it caused initial reactivity that brought about uncontrollable reactor runaway and everything that followed. Naturally, the Chief Designer is not happy about such a chronology; he wants the starting point of the accident to be shutdown of the Main Coolant Pumps (MCPs), stopping of coolant circulation, etc. – anything but the EPS-5 button. For that purpose, one needs first of all to shift back records of the MCP flow rate at the 47th second – and that’s what the Chief Designer did.
One would ask whether it is possible to shift back the time of recording at will. Well, it is. Start by spreading a rumor that the minimum event recording time-error of the DREG is 4 seconds, and, as a result, a 4-second shift is possible already. And if, in addition, you drop a delicate hint that, as a matter of fact, the DREG marks not the time of registration, but the time when data is recorded on tape, you will have vast opportunities for such a shift. Just avoid any direct and straightforward statements, and, what’s more, do not get involved into any detailed discussion of the DREG system operations and specific records related to the Chernobyl accident – otherwise, you might be exposed. Wait unit rumors and wild guesses become public knowledge, and after that, simply specify the necessary timing for the necessary event in any official documents you will publish.
Are you going to say that it’s impossible, and no one will believe you? No one will, indeed – unless you are the Chief Designer, who should better than anyone know the operations of his DREG system installed on his reactor. So even if someone fails to believe, they will have to respect this opinion.
Still, there remains a feeling of dissatisfaction, because we have shifted back the event arbitrarily – why by 4 seconds, instead of 3 or 5? It would be good to have some pretext in order to substantiate this shift. And, bingo, here’s the pretext.
During rundown tests of the turbine generator, light-beam oscillographs were used to record rundown data; that was another recording system, independent from the DREG (and featuring a very high resolution – less than 0.1 sec). Actually, the DREG system and the oscillographs recorded different events and parameters; however, oscillograms registered an event (a current surge in the outer circuit of the generator) that was interpreted as switch off of the MCP. It would be logical to assume that it happened simultaneously with the flow rate drop recorded by the DREG; if we carry out a time correlation (i.e., synchronize) the oscillogram and the DREG magnetic tape, we will learn the time of such flow rate drop with high accuracy.
For such a correlation, we need to have something that was recorded at the same time both by the DREG and by the light-beam oscilloscope. And there is such an event – it is the beginning of rundown. From the mechanical point of view, this means closing of the turbine Isolating and Control Valves (ICV) recorded by the DREG, while from the electrical point of view, this event means activation of the rundown unit recorded on oscillograms; this unit performs necessary switching in the circuits of the power generation unit. The ICV are closed by the turbine protection key from the turbine control board, and this is the time when rundown of the turbine generator starts. The rundown unit is turned on by the Naximal Design basis Accident (MDA) button installed on the safety board especially for rundown tests. Upon receiving this signal, the 6kV auxiliary power section (8RNA) is disconnected from the outside power circuit, and rundown of 4 MCP’s together with the turbine generator begins.
When G.P.Metlenko, technical supervisor of the test, commanded: "Oscillograph – start!", two operations were performed simultaneously: the Senior Engineer of Control of Turbine (SECT) turner the turbine protection key, and Mr.Lysyuk, Senior Foreman of the electrical shop, pushed the MDA button.
That’s the way it should have been, but was it? In other words, did the rundown of the turbine generator (start of which was recorded by the DREG) and the rundown of the MCP (start of which was recorded on the oscillogram) occur at the same time?
The alarm signal line from the ICV had been connected with the light-beam oscilloscope, but, as ill luck would have it, this alarm failed. Now, in order to synchronize the oscillogram with the DREG tape records, there is a dilemma: either we determine the time of the ICV closing on the basis of indirect indicators on the oscillograms, or we take it for gospel that the pushing of the MDA button and the closing of the ICV took place simultaneously, without trying to find anything on the oscillograms. If the MCP rundown started at the same time with the turbine generator (TG) rundown, then it does not matter – in that case, time records on the oscillogram of both deactivation of the 8RNA section and closing of the ICV should have matched. However, there was a mismatch of as much as 6.6 sec.
Was it possible that the MDA button was pushed with such a delay? Here’s the court evidence of G.V.Lysyuk.
"My understanding of Mr.Metlenko was that the first command would be «Oscilloscopes – start», and after that «push the MDA». But he only gave one command, and after that he just looked at me, saying nothing. And I pushed the button. There was a delay of 1-3 seconds, but I’m not going to argue with the readings of the oscillograph".
However, this is the pretext which one could use in order to shift the sequence of events.
All the events recorded on the oscillograms were transcribed during the first weeks after the accident(see. here), when it was still not clear what role the oscillograms would play in the investigation, and whether there would be any role for them at all. At the same time, the Chief Designer read this transcript and agreed with it. In accordance with this transcript "the theoretical reconstruction of the accident development process based on a mathematic model" was carried out for the fundamental report of the Soviet experts that was delivered at the IAEA in 1986.
True, there is no other transcript of the oscillograms – and there never was any. Therefore, correlation between the oscillograms and the DREG records is carried out (if at all) on the basis of that transcript. However, starting from a certain moment, the Chief Designer has been ignoring this correlation. Not that he has proposed any other correlation, but his behavior and his words suggest he takes it for an absolute fact that closing of the ICV and activation of the rundown unit happened simultaneously. That means that shutdown of the MCP and sharp decrease of flow rate occurred not at the 47th second, as recorded by the DREG, but at the 40th – 41st second, simultaneously with pushing the EPS-5 button.
It is difficult to substantiate such chronology, and those researchers of the accident that would like to seriously follow the position of the Chief Designer must be suffering from throes of composition and double consciousness.
On one hand, there is a detailed description of the events that took place within 45-47 seconds (e.g., see [K4], page 383), and everything is connected and reciprocal there. The MCP flow rate drop recorded at that time blends in perfectly with the general description of the accident (and shutdown of the MCP that followed afterwards looks quite logical). On the other hand, the Chief Designer insists that the MCP was switched off at the 40th – 41st second.
How can we reconcile the switching off and sharp decrease of flow rate 6 seconds before (and without any relation whatsoever to the current process) and the detailed description of the process in accordance with the chronology?
What king of switching off was that – the same one, but with a different time correlation, or were there two different instances? Neither statement can be justified by normal logic. Between the 39th and the 43rd seconds, the DREG recorded no data regarding flow rate, and one is free to dream up anything that might have happened at the 41st second (and then, miraculously, recovered, only to kick the bucket again in 6 seconds).
Certainly, the Chief Designer cannot manipulate with the real facts, and he has to respect them. But the rest of the former USSR’s scientists and engineers can hardly feel at ease while the Chief Designer, with maniacal obstinacy, keeps shifting back the MCP switching off from the 47th second to the 41st one. This, for example, is how in 1991, 5 years after the Chernobyl accident, this event was skillfully described in the Soviet experts’ report for the IAEA ([M2], Annex II, pages 112-113, Tables II-III.)
"01: 23 : 04 a.m.: command "Oscillograph started" issued, isolating & control valves (ICV) of the turbine No.8 closed. Turbine rundown started. Time of operation of the RCP connected to the TG in rundown state was 36.2 sec according to the oscilloscope that was recording electrical parameters of the RCP. The DBA button was pushed*. The exact timing of pushing the button and activation of the oscilloscope is not available."
At first sight, this is simply some strange description of one of the chronological stages: the ICV’s were closed, and rundown started. Why all the other information? It would seem that the MCP should be dealt with in due time, so why mention them now? Here’s why.
In this document, the Chief Designer cannot make directly his favorite statement "MCP switched of at 01:23 :41 a.m.", since below it says that the switching off occurred at 01:23:47 a.m. (after all, this is a document of international importance, prepared by all the experts, not by the Chief Designer alone). So, he makes that statement in a veiled form.
What does that mean - "time of operation of the RCP was 36.2 sec"? This is the time from pushing the MDA until switching off of the RCP recorded by the oscillograph. But since this phrase follows the statement regarding closing the ICV and without any explanation, the impression is that this time is calculated from the moment of closing the ICV. This, however, means (taking into account the generally accepted correlation between the DREG records and the oscillograms) that the MCP switched off at 01:23:41 a.m. And in order to avoid any formal charges of manipulation, the MDA button is also mentioned below. The document just says, "The MDA button was pushed", and that’s that (ok, it’s pushed – what makes it important?). On the one hand, it is not known when it was pushed (according to the next phrase), and on the other hand (according to the note with the asterisk (*)), it must be pushed simultaneously with closing the ICV.
So, gentlemen, here’s a lesson of writing reports for the IAEA – learn from the best!.
5 years later, in 1996, when preparing the final report for the IAEA based on the results of the 10 year long
investigation of the Chernobyl accident [Ì3], the Chief Designer went to greater length. He insisted that, apart from setting forth the general accident analysis results (prepared by all the parties involved), each of those parties should be able to explain, addition, its own vision (without discussions with each other). And after that the question about the MCP (which of them shut down, and when), became absolutely obscure, or, on the contrary, absolutely clear (as, for example, for B.I.Gorbachev). He believes that all the 8 MCP switched off, four of them at the 41st second, and the other four – at the 47th second.
Finally, 20 years after the accident the Chief Designer published a monograph [ E2], where ( page 551 and page 578) the timing of the 4 MCP switching off was specified clearly and within the accuracy of 0.1 second:
MCP-14 at 01:23:39.9 a.m., MCP-24 at 01:23:40 a.m., MCP-13 at 01:23:40.5 a.m., and MCP-23 at 01:23:40.6 a.m. Such figures would be available only in case we assume that the DREG recorder the ICV closing time – 01:23:04 a.m. – with absolute accuracy (correct to centiseconds), and that the MDA button was pushed without any delay at precisely the same time. Of course, the Chief Designer’s book contains nothing but silence and obfuscation about it (see [E21] Manipulation No.5. MCP switching off).
So, it turns out that switching off of the MCP, a seemingly simple and well-recordable event, is quite a «thing-in-itself».
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