|Question 1:||What role in the Chernobyl' emergency did play experiment? Whether there was a cause of accident?|
In any way it is impossible to consider experiment as a cause of accident. If slow down test of turbine-generator was carried out exact in conformity with the program the accident on ChNPP on 26th of April 1986 year would not occur. And on the contrary, such accident on reactor RBMK could happens during any other moment without any experiment at certain coincidence of circumstances as its reason has been put in a design and the physics of the reactor.
Another matter that there is a question, what for in general is it necessary a slow down of TG.And if it is a mode stipulated by design, why it did not check on all blocks with ÐÁÌÊ at their commissioning?
|Question 2:||Which is the authenticity of the emergency data, given on the site, from where are they?|
All these data are taken from the primary information, registered by the regular sensors of the system of monitoring and control, and had at VNIIAES’s disposal. The authenticity of primary information is not subject to doubt, and therefore one should speak not about its authenticity, but only about the precision of registration (and about errors with its reading that is theoretically possible).
The precision of registration (with respect to time) depends on the type of recorder (and of its tuning) and is different for different data. Data, which were recorded only with the register diagrams (or written in the operational journals), were registered with the temporal resolution of about 1 min. These are, for example, the reactor power and position of the [AR] rods. The data, recorded on the magnetic tape by the system DREG of computational the integrated system of monitoring and control [SCALA], have resolution of 1-2 s. There are also given the data, recorded on the tape of light-beam oscillographs which were specially established for carry out the test of TG slow-down. These data are registered with the resolution respect to time less than 0.1 s.
A precision of registration of 1 min is sufficient for analysis of the slow processes which were proceeding prior to the beginning of slow-down (to the 1:23: 00), but it is insufficient for the analysis of the parameters variation during the TG slow-down, for this is necessary the information from DREG. But this is also insufficient for the emergency process proper, which was begun since the pushing of SCRAM button and only oscilograms of slow-down have a temporal resolution, sufficient for the analysis of processes afterward the 1:23: 40. As to errors at perusal of the primary information, such are still not found. That information completely coincides in all three organizations IAE (Kurchatov institute), NIKIET and VNIIAES, read it and participated in the investigation of emergency. All published actual data (including present site, and the books of N.V.Karpan and of A.S.Djatlov) coincides also.
But there is one important remark. No attempt was made in VNIIAES to decipher the record of reactor power and of [AR] rods position in the time of three-four recent minutes (afterward the 1:20: 00). They supposed, that it is impossible to do this for the data, which were registered with the temporal resolution of 1 min but must be known each second. The graph, which is given on the site, and the data given in the book of Karpan coinciding with it (as well as data given in other publications), all this is the result “of the interpretation” which is carried out in IAE. It is taken (as it is obvious in all other publications also) from the report of Soviet experts to IAEA in August 1986 [Y2].
|Question 3:||Why was pressed the button of emergency protection system? What situation was right before this?|
The reason on which the SCRAM button was pressed at 1:23:40 as well as that why it has not been pressed on 35 ñåê earlier simultaneously since the beginning of the slow-down test, authentically is not ascertained. On this score there can be only different assumptions (details see here). It is possible to say firm only one according to the sense of the program of slow-down testing experiment, it had to pass on the damped reactor..
|Question 4:||What moment of time can be considered as the beginning of emergency, and which at this moment did occur?|
There is a precise concept - “initial event of emergency”. Such initial event in the case of Chernobyl' emergency according to the data, fixed on the magnetic tape of the system of the centralized control SCALA, was the pushing of the knob of reactor scram system [AZ-5] (EPS-5) in the 1:23: 39, 26.04.1986. Immediately after this (during three seconds) the power of reactor sharply and uncontrollably grew with further catastrophic consequences. Such things became possible because of the erroneous construction of control rods and errors in the calculations of physical characteristics with the design of reactor. In the specific operating mode, which was realized during the execution of the run-down test program, the work of emergency protection system could instead of the damping of reactor cause its uncontrollable acceleration. The international advisory group of the IAEA experts, specially created for the analysis of causes for Chernobyl' emergency, considers this scenario of emergency most probable ([M2], p. 17, 82) .
The chief designer of reactor is not agreeable with this. In his opinion, the initial event (or as it is expressed, the beginning) of emergency it appeared: non-shut down of reactor after fall down of the power at 0:28, and instead of this raising the power of reactor again to (now reduced) value ([E21], p. 547) . In this case the button EPS-5 has to the emergency of no relation, and it is absolutely unimportant, when it was pressed ([E21], p. 578) .
The official point of view to the reasons for emergency, presented by the group of the USSR experts at the conference in the IAEA in 1986 ([Y2], p. 309, 311) is less categorical in the description of the events of emergency, and pushing of the knob EPS-5 is present in the enumeration of these events. However, this is not the initial event of emergency, but it was vice versa the reaction of personnel to the already begun increase in the power. Initial event, as it appears from the expert’s report, became closing turbine’s SAV, i.e. the beginning of run-down test of the turbogenerator (however, there are no words themselves “initial event” in the text of report).
|Question 5:||If the initial event of Chernobyl accident, this is the actuation of emergency protection system, then why it did not occur earlier? Indeed thus far on the reactors RBMK the SCRAM actuated of thousands of times.|
So that the Chernobyl' emergency would occur, emergency protection system must operate during the simultaneous extremely improbable combination of conditions. If the probability of this confluence of circumstances make 0,01%, then even thousands of the SCRAM actuation do not make the probability of such emergency sufficient large in order to be surprised at that, why it earlier did not happen. The crude estimates of probability can be made simply enough.
|Question 6:||Why nothing they do write about the trial on Chernobyl emergency? What was there? Whether indeed this information is secret until now?|
The trial of the declared culprits of Chernobyl emergency was closed for the general public. All data on the investigation of emergency and its reasons were still secret at that moment they were declassified only in 1990. It is possible only to guess, why are secret the materials of criminal case until now. Operational personnel were declared guilty prior and out of any trial. But that that is possible to slander under the veil of secrecy, it cannot be defended in the normal law court. If to declassify the materials of the trial, then unavoidably it is necessary to review this case, but nobody wants it.
Without looking at any secrets, something about this trial is known from the recollections of participants and from the records, which they keep. Analyzing these materials the trial picture can be imagined clearly enough (for more details, see here).
|Question 7:||Did appear the explosion of reactor on Chernobyl AES in 1986 a nuclear explosion or this was some another explosion?|
In the Chernobyl' emergency the explosive processes of different physical nature could appear. There are only three realistic hypotheses, if we reject the fantastic (ball lightning, magnetic monopoles) and conspiratory versions of emergency, such as the different kind of diversion, secret experiences on the production of weapons plutonium or explosion as a result of the remote action of the new type of weapon (geotectonic, bundle and so on). 1) The explosion of hydrogen, which is generated as a result of radiolysis of water during reactor operating. 2) Explosion of nuclear nature as a result of runaway of the nuclear fission reaction of uranium. 3) Steam explosion (explosion of reactor as vessel, which is under the large internal pressure of vapor).The version of the explosion of hydrogen chronologically the first, it was rejected as impossible one. There was not enough quantity of hydrogen that necessary for such explosion and it could not be generated. Steam explosion, undoubtedly, occurred at the initial stage of the destruction of reactor, its energy it could be sufficient even in order to destroy the building of power unit. But this explosion in no way explains the formation of the radioactive cloud, which covered the half of Europe and which contained uranium and plutonium.
There was or there was not nuclear explosion in the Chernobyl emergency, this is to a considerable degree a question of terminology. Unambiguously it is possible to say that there was incontrollable runaway of reactor power, and this is the same physical process as with the nuclear blast (dropped in Hiroshima in 1945.). But these two explosions differ by three orders by the scale of released energy, time within which it was isolated, temperature and pressure, which in this case arose. And such huge distinction in scales results not only to quantitative, but also to qualitative distinction in character, the mechanism of process proceeding and the destructions caused by it.
All this gives cause to many researchers of Chernobyl emergency to indicate that there was no nuclear explosion, as such, but there was the thermal explosion of nuclear origin. Such explosions, on three-four some more smaller order occurred, happened, on research nuclear reactors (and other nuclear objects), and there it have received this name. With this low scale of the phenomenon, when only the negligible part of the fissionable material enters into the nuclear reaction, this nuclear reaction can be simply considered external heat source for the remaining substance, which fills the volume, in which it occurs.
On exact terminology a thermal explosion, is explosion caused by prompt release of heat from an external source in some small volume. A classical example - explosion of a fine wire caused by strong impulse of an electric current passed through it.
|Question 8:||What are the proofs, that Chernobyl accident proceeded in two phases and what is the basic difference of one from another?|
Certainly there are no proofs, but there is the common sense, which indicates that the emergency process is divided by natural manner into two phases: 1) prior to the initiation of the destruction of the reactor tecnological channels (TC) and 2) after its destruction. While this destruction did not yet begin reactor preserves its structural and geometric integrity, all its systems function in accordance with their design possibilities, and the proceeding emergency process does not exceed the scope of the so-called design based emergencies.
If this it did not follow the destruction of the sufficiently large number of channels, then reactor would be finally shut down by emergency protection system, and everything would come to an end only by this first stage of emergency.
There is detailed recording of the parameters of this emergency process both by the regular instruments at CRU and by the additional means of registration. This process is sufficiently representatively and repeatedly simulated by calculation (also on the simulators). Emergency process has begun from that a large positive reactivity has been brought in the reactor, both by the emergency protection system itself (because of the incorrect construction of rods) and due to the large positive steam effect of reactivity. It occurs (locally) a sharp increase of energy release and the destruction of shells of fuel element.
The second stage of emergency begins from mass destruction of TC and as the consequence of the practically full dehydration of reactor. But this in turn causes reactor runaway on the prompt neutrons that brings all those destruction, which consequences we now observe.
How destruction of first several channels has passed in their mass destruction, how particularly there was a dehydration of the reactor and its further destruction, what accompanying physical and chemical processes with the release of energy thus proceeded? It is all very difficult to simulate if it is possible at all, and in this respect there are different hypotheses. The second stage of accident, unlike the first, probably for ever remains a subject for discussions.
|Question 9:||What is the danger in boiling of coolant at an input in the reactor core, it indeed nevertheless does boil in the reactor channels?|
In itself boiling of the coolant at an input in the reactor core, where it further all the same will boil, should not be dangerous of course. But in the situation of Chernobyl emergency boiling or almost boiling at the input represented large danger because it strongly increased a positive steam component of power reactivity coefficient. And it made positive all full power effect, which is inadmissible for reasons of nuclear safety. Two special features of the Chernobyl situation led to this behavior of power reactivity coefficient: 1) the work of reactor at the low power 200 MW and 2) the splash of neutron field in the lower part of the reactor created by work of emergency protection system (when pushing SCRAM button). Details are presented here, but briefly the essence of the matter is such.
1) The magnitude of the steam effect of reactivity is proportional (other conditions being equal) to a difference in the average (on the core) density of steam-water mixture from the initial water density. This difference grows with increase in reactor power, but it is nonlinear, the greater the power the dependence weaker. And by that, the reactivity coefficient (increase in the reactivity per unit of an increase in power) with the greater (initial) power of reactor is less, and it is considerably more with the small power.
2 Contribution of density change to the reactivity in each section throughout the height of reactor core is proportional to the square of relative (with respect to average on the core) neutron flux in this section. With the distribution of the neutron flux uniform along the height this property of the effects of reactivity in no way is manifested, and the local effect of reactivity does not depend on the overall level of the neutron flux. Another matter if is a splash of neutron flux into some of small region on the height of the core, then in this place local effect sharply grows and gives the noticeable contribution to an increase in the general effect of reactivity.
All this occurred in the case of Chernobyl' emergency. If coolant boiling begins exactly in that place on the height of the reactor core, where there is a splash of the neutron flux, then steam component of the power effect of reactivity sharply grows, and the action of emergency protection system on the bringing of the positive reactivity, which initiated this splash of power, many times increased.
|Question 10:||What particularly infringements of Nuclear Safety Regulations for NPP (NSR-04-74) and General Safety Provisions (GSP-82) have been made in reactor RBMK-1000 at its creation and introduction into operation.|
There are no doubts that any fundamental principles of creation of the reactor for the nuclear power station have been broken. Such reactor should not blow up under no circumstances, but it has blown up. Another matter is who is guilty in this infringement: the creators of reactor, who did not satisfy the requirement of regulations and provisions on the safety, or the creators of these regulations so written it that formally anything disrupting, it is possible to make a dangerously explosive reactor. Or someone third is guilty, who made so, that regulations were written by creators of reactors themselves for the already taken solutions in construction and physics of reactor. Without going into all this casuistry let us look to the assigned question from the common positions of the common sense.
Reactor in no way can blow up, if it has negative full power reactivity coefficient. Reactor RBMK-1000 (model 1986) had it positive in some operating modes. Whether the Chief designer had the right to make such reactor according to NSR or had no? Represent, in accordance with the point 3.2.2 NSR he had, but in this case he must ......... much that is what to make. And here he has made it or not, appears not so simply to find out it. Only the low court can cope with that matter, but the court was not engaged in such questions. The inspector of [Gosatomnadzor] Yadrikhinskiy, and together with him all [Gosatomnadzor] (from 1991 year) consider that “has not made”, and it seems that they correctly consider so. But after all they are not a court, and the Chief designer itself considers that he has made all that was required.
Here the second. For prevention of uncontrollable runaway of the reactor, for whatever reason such danger would not arise, each reactor has an emergency protection system which reliably shuts down the reactor (immediately terminates the nuclear chain reaction of fission) when any emergencies. There is an especial term for describing this indispensable feature of any nuclear reactor – SCRAM. In reactor (model 1986) emergency protection system instead of shut down the reactor put it runaway in certain situations (as has occurred on 4th unit of ChNPP). Whether such emergency protection by infringement of NSR is? A question on mine is rhetorical. There are many points in NSR from which follows that emergency protection of the reactor should be normal so not such what it was on 4th unit of ChNPP, and to these points refer also [Jadrihinsky] and [Gosatomnadzor]. But there is no any point in NSR directly demanding that emergency protection brought only negative reactance and no any positive. Using such Emergency Protective System (EPS), the Chief designer makes “innocent eyes” and does not see anything especial in that that protection instead of shut down the reactor put it runaway, naming this property of the protection system by hastily invented scientific term: positive scram-effect.
|Question 11:||Whether there was the emergency on LNPP in 1975 a harbinger of accident on ChNPP in 1986? If yes, then why this experience has not been considered?|
Yes, accident of 1975, is a harbinger of accident 1986. The same lacks of the reactor physics and of the control rods design are the reasons of both accidents. But they behaved variously in both these cases. In case of Chernobyl emergency "the trailer effect" on rods has became apparent directly by that, at attempt to stop the reactor (on termination of works) emergency protection of the reactor has brought positive reactivity instead of the negative. It has occurred because of synchronous movement of almost all rods from the top position. Uncontrollable power acceleration which it is impossible to stop as it was caused by emergency protection system itself has begun. The high positive steam reactivity coefficient has transformed this process into runaway on prompt neutrons with all consequences following from here.
In the case of Leningrad emergency “the trailer effect” caused chaos in control of reactor at the attempt to lift the power. And when, at last, it managed to be made, there was a crisis of heat exchange in a number of channels because of strong non-uniformity of distribution of energy release on the reactor core, and there were corresponding destructions.
According to the results of the investigation of emergency, was carried out a number of measures. The system of local automatic control of reactor power (LAC) was introduced, the total of cores with 179 to 211 was increased, enrichment of uranium from 1,8 % to 2,0 % was raised, etc. But all these actions have been directed exclusively on struggle against internal instability of a neutron field in the reactor core. And even introduction in regulations of restriction on minimum ORM in 15 rods pursued this aim. About any trailer effect on rods and its influence on efficiency of emergency protection there was no speech.
There is a question. The Chief designer and the scientific manager could not or have not wanted deeply, to the end to understand that chaos and imagine to what catastrophic consequences can to result dangerous "features" of a design and physics of the reactor, or what? Probably, this question for ever remains now without the answer.
|Question 12:||What resemblance of emergency 1982 ã on 1st unit of ChAES with emergency 1986 ã on 4th unit, whether was it the “second call”?|
On September, 9th 1982 ã on the unit ¹ 1 at take out of planned maintenance there was a destruction of one of technological channels on the power in 20 % from nominal, and in such condition the reactor has worked more than 20 minutes. As a result of accident there was a considerable release of radioactivity into the environment, the reactor has demanded serious repair and year has left almost on that it again to put out on a total power. And various competent bodies still for a long time were engaged in confidential correspondence concerning radioactive contamination of neighboring territory.
One resemblance at these two accidents undoubtedly is, with only one difference. This resemblance is pack of lies for true concealment. In 1986 ã emergency consequences were too catastrophic, and about causes of accident it was not possible to hide the objective data. Eventually, though and not completely, but the truth all the same has triumphed. It was not in 1982 ã, and a cavalry swoop of the Chief designer at investigation of causes of accident hot on the trial, so remained its basic and unique version. And here in what it consists.
The maintenance personnel on the reactor power of 700 ÌW (thermal) closes the Stop and Adjastment Valve (SAV) on an input in the channel and by that, cutting off water flow, leaves it without cooling. They do it quite consciously and without the permission of Shift Supervisor of the Unit (SSU), without informing the Senior Reactor Control Engineer(SRCE).
Otherwise it is impossible to name such actions except as diversion. Nevertheless criminal case upon this accident it has not been got, and guilty have got off light. That is fabulousness, and no more to say. To whom details are interesting, look here
|Question 13:||Why by slowdown of 4 MCPs the flow rate on others, not being slowdown MCPs, did not vary, after all the common drop of pressure thus changed?|
Really, when two centrifugal pumps are parallel included in the same circulating circuit they create one common drop of pressure (pressure). And if the speed of rotation of impeller (because of the decrease consumed of power) decreases by one of these pumps, then the common flow of the pumped through liquid decreases, and accordingly decreases the pressure required for this purpose. But then according to the pump characteristic curve which remained invariable at the pump which has not changed the speed of rotation, the flow through this pump should increase. However, we of it do not see in the presented actual data (fig. 13)
And the matter is following. In real circuit (MFCC), parallel work of circulating pumps MCP is not described by such simple hydraulic scheme as it is stated above. Actually MFCC, this is not one circuit, but some parallel circulating circuits having one common point – separator drum which sets the general level of pressure, but pressure differentials are formed on each circuit their. Transverse (hydraulic) connections certainly exist, and these circulating circuits (according to the number of MCPs) are not completely independent from each other. But these connections are not continuous. Details are stated here
|Question 14:||What role in Chernobyl accident was played by switching-off MCP? When and why they were cut off?|
Switching-off MCP in this emergency does not play any special role. First, switching-off MCP does not mean the instant termination of the flow, MCP by inertia continues to pump water within a minute, for this purpose in its design the massive flywheel is specially provided. For a few seconds, which lasted the emergency process in the reactor, nothing essential with the flow because of (electrical) turning off MCP occur it can.
Secondly, even if instantly the water flow through these 4 MCPs also has completely stopped, remained 4 it is quite enough to cool the reactor on 70 %-s' power, and before accident capacity was no more than 7 % of nominal power.
And, at last, the most important thing, MCP were turned-off, when emergency process of uncontrollable runaway of the reactor power went already at full speed. Their switching-off could not be at the bottom in any way, and could be only a consequence of this process.Own emergency protection has evidently switched-off it after at an exit of pumps has arisen high counterpressure from outside the reactor core and the flow from running-out MCPs has fallen practically to zero.
Stir round switching-off MCP, it not that other, as the gamble pursuing only one aim: to hang up as much as possible doubts round initial event of accident – pushing of the button of emergency protection, having displaced for this moment of time also switching-off MCPs (as it becomes, it is in detail shown here).
|Question 15:||What concrete regulations infringement has allowed operational personnel thyself, and what role it has played in the emergency?|
First of all, it is necessary to distinguish two different concepts: infringement of regulations of operation and wrong (or erroneous) actions of the operational personnel. Wrong actions in case of Chernobyl failure undoubtedly were also the fatal role have played (without them the reactor would not blow up). Whether but there were infringements of TR (Technical Regulations)?
Normally, at good TR and the other operational documentation made on its basis, such question should not to arise. There can not be wrong actions at regulations strict keeping. But if this question arises, then to be investigated is necessary not so much in the actions of operation, as in the documentation. But if such question arises, it is necessary to understand not so much operation actions, how many in the documentation.
It is necessary to consider as wrong actions work on low power of the reactor at the large coolant flow and the control rods completely taken out of reactor core (almost all, including [USP]). In such condition dangerous defects of physics and a reactor design were catastrophically showed. With it almost all researchers of Chernobyl failure agree. As to regulations infringements here such unity is not present. Charges of operators in infringement of TR total from 2 – 3 infringements to one-and-a-half ten, depending on "enthusiasm" of accusers. Here so differently it is possible it appears to read the operational documentation. And what was to the operational personnel it to execute?
Most in detail the actions of NPP personnel are analyzed in the report) of commission of [SCSSINP] (State Committee for the Supervision and Safety in Industry and Nuclear Power) which has been included as the appendix I in the report INSAG-7 of 1991 on Chernobyl accident made by IAEA international experts [M2]. This analysis revealed only 4 disturbances of regulations, of which only one influenced appearance and flow of emergency, and even then in a certain not quite usual sense. The regulations of operation that was in low then, did not forbid reactor work at small level of power and connection of all 8 MCPs (the flow through them was limited only). And such parameter as ORM, made decisive impact on emergency occurrence, has not been given properly as a safety-significant parameter.
|Question 16:||Did contribute delay at the level of power to 50% creation of conditions for the appearance of emergency?|
One of the main conditions of the appearance of emergency was the work of reactor with the small operational reactivity margin (ORM). The basic contribution to the decrease of ORM gives the xenon poisoning, whose depth is determined by the regime of passage by the power from the initial level 3100 MW up to final 200 mW. However strange it is, this process of poisoning is any in detail analyzed not in one of the origin sources on the investigation of Chernobyl' emergency, but it is mentioned in them all as the basic factor, which contributed to the appearance of emergency. From the fact that is there said, is created impression, that delay at the level of power 50% and subsequent downfall to zero led to too deep a poisoning, that also created prerequisites for the emergency. However, this idea is deeply erroneous, and in reality all was quite the contrary. Delay at power 50% did not increase, but it decreased the depth of poisoning, and the power downfall with the subsequent output to the level 200 MW in no way affected the value of poisoning in comparison with simple reduction in the power up to the level 200 MW without any downfall.
It is another matter that because of this delay of experiment after multihour waiting they passed from day to night shift , and in this sense delay can be considered the negative (human) factor, which contributed to the creation of conditions for the emergency.