The World Agency or the FSB Agency?
The World Agency or the FSB Agency?
Strange things are happening among the leaders of the "Nuclear Elite of the World", who have occupied the IAEA. Have the russians moved to more decisive action because they have the unconditional support of the IAEA head, with whom they hold the entire Agency hostage?
The last official update 167 of the IAEA is indicative for all of us. It turns out that the self-defense of a nuclear terrorist by placing mines at the Zapirizhzhya NPP and outside the plant perimeter is acceptable from the point of view of nuclear safety. Maybe in the next statement, the IAEA will offer to throw away those needless guidelines with the fundamental safety principles SSR-2/2 and SF-1, because the Agency is the FSB?
The very compelling question comes today: Is it safe to operate a nuclear power plant that was seized by a nuclear terrorist, who has mined the safety systems and their power sources, who has taken the operational personnel hostage and who is blackmailing the world with a nuclear catastrophe?
A simple answer is in the last update 167 of the IAEA: The safety of the nuclear power plant is at an acceptable level while the nuclear terrorist justifies it with “iron-concrete” documents and the Agency agrees with it.
The loss of the physical protection at the ZNPP, the capture of the ZNPP by nuclear terrorists from russia, who designs the nuclear facilities itself and knows how to maximally damage nuclear safety, - these are not toys, but quantitative indicators of a sharp increase by more than two orders of magnitude of the risk of damage to the core of each of the 6 reactors.
For those who support the technical policy of the IAEA and Mr. Grossi, please see the results of calculations made by Ukrainian accident risk analysts using the licensed codes of ZNPP PSA models, exactly with the tools for analysis accepted in the world.
All those 5 worthless principles of R. Grossi on nuclear surrender of the world to russia have absolutely nothing to do with NPP safety and testify to the complete degeneration of safety culture and blatant disregard for the principles of nuclear and radiation safety declared by the IAEA in relation to the peaceful use of nuclear energy...
Separately, attention should be paid to the fact that this model does not take into account the probable deterioration in the psychological state, stress of personnel in the combat conditions, as well as the resulting erroneous actions, which in turn can predictably significantly worsen the situation and lead to additional negative consequences.
I also emphasize that in order to analyze the risk of failures in war conditions, we took not the most difficult conditions for the impact of an explosion or fall of cruise missiles.
I understand that there will again show up the experts who have never performed such analyses before, but they already know that everything needs to be done differently, through other ways of influencing russia.
I hope that the IAEA will draw appropriate conclusions regarding Russia's attempts to destroy the very thing that is the source and quality of life of IAEA specialists...
When a criminal is not stopped by a decisive action, he goes further, he raises the stakes and acts even more audaciously.
Russia pretends that nothing is holding it back, and here they are already testing us and impotent institutions like IAEA and WENRA. Despite the military and political goals of the war, the ruzzians want to show the world that it is very dangerous to develop nuclear energy, because everyone is at risk.
Why this nuclear terror from the Russian Federation, what goals does the aggressor set and what does the gas station want to tell the world?
?Russian Federation wants to restrain the development of nuclear energy in the world, and build only its own nuclear industry, without having any reservations for this
What more terrible should ruzzia do that its fans in the IAEA wake up from their lethargic sleep and throw ruzzia out of all international institutions, prohibit ruzzia from spreading its nuclear technology around the world, stop all international projects for the construction of ruzzian nuclear power plants?
What tools do we have? Can we be heard by those who are able to influence the threats posed to mankind by the hybrid nuclear terror of the Russian Federation?
Persuading the Russian Federation is hopeless, because it encourages Russia to launch its cruise missiles, which then fly over critical infrastructure objects
Their trajectory ran precisely over the critical infrastructure of a NPP, where VVER-1000 nuclear reactors operate, and each contains 70 tons of enriched uranium. By the reactors, there is spent nuclear fuel stored in the spent nuclear fuel pools. The site has storage facilities with highly radioactive waste from processing of boron solutions, evaporated solutions of radioactive water and solid radioactive waste. At least 1,000 tons of diesel fuel are stored within the NPP site for emergency diesel generators of safety systems, which should provide power to the NPP in case of loss of external sources of the Ukrainian power grid.
Turbine halls with a turbine, generator and transformers operate in the conditions when any ingress of foreign objects from the outside, in particular those moving at speeds of more than 20 meters per second, can not only damage the equipment, but cause hydrogen explosions, oil burning and flooding, which will be catastrophic for the nuclear power plant under the war conditions.
What more can you wish for? The territory of the nuclear power plant is already mined, there is military equipment on the territory of the nuclear power plant and the Russian military dominates. The Russian military is setting up munitions warehouses in the premises and on the sites of the ZNPP warehouse, because they are sure that the Ukrainian military will not destroy them. On the approaches to the NPP, the Russian military is building defense lines, and from the territory of the city of Energodar, rocket salvo systems are striking towards the unoccupied territory on the right bank of the Dnipro River. Residents of the city and ZNPP workers are kidnapped, robbed, tortured, and killed.
A war within the nuclear power plant site, a war within a 30-kilometer zone around the nuclear power plant, the flight of cruise missiles and other military or other flying devices is dangerous and this is an understandable signal to anyone who dares to stand up in spite of ruzzia.
Everyone must understand that only ruzzia can develop nuclear energy field, because it will never attack its nuclear facilities. Sounds like absurdity. Though it is not absurd - this is the goal that ruzzia sets for itself, allowing only itself and those who will cooperate with it to develop nuclear energy, therefore, according to ruzzia, they should depend on its ability to influence the World through control of energy sources.
I am also categorical in favor of developing a peaceful atom because today it is the cleanest source of energy capable of restraining the chemical process of carbon dioxide formation in the planet's magnetosphere caused by aging of the Sun.
How many people there were willing to promote themselves on the fact that it is not necessary to carry out risk analyses for war conditions, so that, for God’s sake, the enemy and terrorists do not take advantage of this.
And in order for everyone to understand what risks Russia is juggling by laying the trajectories of its cruise missiles over the SUNPP site, I again return to those analytical tools that American specialists once provided to us and taught how to use and that were financed by the people of the United States of America. Only with such scientific and technical tools can we show the world nuclear community that ruzzia's contributions to the IAEA support budget have a very negative impact on IAEA specialists in order for them to do the job in a due, professional manner with responsibility to humanity.
Either we are able to resist this, or the Russian Federation will achieve its goals of changing the energy development of mankind only in favor of the Russian Federation and to the detriment of future generations of the Planet.
It was the war with the Russian Federation that made these adjustments to our nuclear consciousness of the further technological development of the industry. We must take this into account in the future, even if these threats disappear. At the same time, we are aware that ‘Black Swans’ with bombs and shells can also be a strategic weapon of hybrid influence on the consciousness of mankind.
The problem is that this is not Nashim Taleb's black swan. This is Shoigu-Gerasimov's "black hundred" with explosives, grenades, heavy weapons, and next to them are crazy specialists from Rosatom, who manage the steps of nuclear escalation as soon as the bunker moth needs it. These are the thirty Kadyrov tic-tokers from the third floor of LBK-1, who are being held to kill witnesses to the crime planned by the Black Hundreds and nuclear kind-of-surprises.
Complete loss of ZNPP physical protection and operation of ZNPP Unit 5 in the “hot shutdown” state would enable russia to use ZNPP Unit 5 as a tool of influence, due to the threat of emergency scenarios with severe consequences:
?The list of severe and any scenarios with core damage and radiation release will reduced by orders of magnitude if all ZNPP reactors are in the “Cold Shutdown” state.
All actions of Ukraine should be focused at immediate transfer of power unit 5 to the “Cold Shutdown” state. And if the suspension of the license does not give any positive result, then any technological means should be used to disable keeping ZNPP-5 in the “Hot Shutdown” state, and the power supply for ZNPP’s own needs from the russian power system.
?The position of the nuclear lawyer R. Grossi is nothing more than a cover for the actions of the state - a nuclear terrorist, which is trying to influence the course of the liberation of the territory of Ukraine by creating artificial nuclear threats due to violations of nuclear safety norms and rules, namely:
In order to imagine the scale of what Russia is planning, we present at your discretion quantitative probabilistic risk indicators that allow you to compare the safety of the pre-war and current state of nuclear power plants.
For some experts, such risk analyses is an uncceptable thing. They consider another way of resolving the safety issues.
Here, it goes about fundamentally different strategies: deal with a damage or violation that has already occurred, or - prevent them using the state-of-the-art tools for analysis, impact and change of the design basis.
In the first case, it is a possibility using “hands” and “eyes” to comprehend something that happened, give an assessment to this without further consequences and a single percentage mistake. And in the other case, predict and exclude the risk, even if it is something probable, but can be extremely dangerous, and might not be always obvious through the prism of normative pile-up and acquired experience.
However, for most experts this is only about what is asked in exams and not minted in the minds and practical space of use for managing the safety at the nuclear power plant. Therefore, in the events that took place at ZNPP, and which South Ukraine NPP managed to escape, the important are precisely those consequences that were avoided thanks to some miracle. I do not even want to hear that an attack is a less scary thing than an analysis of occurring something impossible.
The impossible in fact was a purposeful action on the part of the Russian Federation and “our”, unfortunately “compatriots”, who did not even realize the consequences of the fact that it was precisely them who could cause terrible things, the consequences of which are hard to predict
I do not accept any accusations that what I represent is not quite appropriate, that it is in the favor of the enemy, and is an instruction for terrorists, or even harm to safety. I do not think that there are many people who want to discuss this at a professional level, and not hide behind a pile of regulatory documents, and dive deep into the usual safety analyses that have long become real and cannot be discussed on the fingers.
?This work was performed in the first month of the war by the best specialists of Ukraine.
In the conditions of the war, which became a test for all Ukrainian world, having a hybrid nuclear threats induced by the Russian Federation by inflicting a military attack on the ZNPP site, we counted on timely and adequate assessments of nuclear risks by IAEA and other international nuclear institutions. Idle hopes - it was they who made weak and cowardly statements that are almost an excuse for further aggression by the Russian Federation, because, in their opinion, nothing happened to the nuclear safety of ZNPP, meaning there is nothing to talk about.
The Ukrainian specialists using operating and analytical models of probabilistic analysis of risks of damage to reactor cores, performed a quantitative analysis of the increase in risks for the ZNPP site during hostilities, and a similar analysis was carried out on the model for South Ukraine NPP as potentially vulnerable platform for Russian nuclear blackmail.
In general, these are precedent analyses, from the point of view of the World, as they have been performed in short terms and under the conditions of war. This is done in order to make a preliminary quantitative assessment of the actions of the Russian Federation through traditional tools for analyzing the risks of damage to the reactor core and radiation releases, so that it becomes clear to both specialists and citizens how dangerous, irresponsible and criminal the threat of military intervention in the operation of nuclear power plants is to humanity.
Yes, I see only one problem - the world’s gurus turned out to be simply fragile and helpless, especially when it was most needed, and this list includes IAEA, WENRA, as well as top officials of both SNRIU and NNEGC Energoatom. It was they who did not use all the potential that is at their disposal, all they did was thorough working out of the Russian agenda.
Such and similar analyses have already been performed by three independent analytical teams and on different models and with different tools. Deeper risk assessments are also being conducted, and this is done by the specialists who have been brought up and trained by the US nuclear community, who have helped us in the nuclear field for a long time, exactly using such analytical “Javelins”.
It is the aggressive actions of the Russian Federation at ZNPP site that are a challenge for a new direction in the development of analytical tools for assessing military and terrorist threats, as well as new natural disasters, which should be taken into account both in passive and active protection of nuclear facilities. This should be taken into account both at the design stage and at all stages of licensing and operation of new facilities, as well as at existing critical infrastructure facilities.
All this needs to be analyzed and taken into account right away. Otherwise, the risks cannot be considered in isolation from the modern development of the world, where military threats have come to the fore, completely crossing out all the achievements in the field of nuclear safety! And those who did not protect it all, now justify it at their level in a very false way, stating that nothing terrible happened, even during the attacks of ZNPP.
Therefore, I propose to have a look at what goals are the priorities for us with the perspective of safety. It is important how exactly the safety is physically perceived and evaluated in terms of technology indicators recognized by the world. Technology is acceptable only on the condition that the potential risks from it are less significant than the potential risks of loss of human life, compared with the integral potential threats to humanity in this space.
Using the example of Zaporizhzhya NPP, the Russian Federation will hinder the development of nuclear power plants on the Planet by imposing military risks
1.????????Object and Purpose
1.1?????The operating nuclear power plants (NPPs) of Ukraine.
1.2?????The modern safety analysis of power units of Zaporizhzhye NPP (ZNPP) was conducted for normal operating conditions and does not take into account the conduct of hostilities in close proximity to the ZNPP site.
1.3?????Using the existing probabilistic models, it is possible to perform certain analyses and make conclusions about potential negative consequences due to damage to NPP equipment and systems during hostilities and terrorist attacks.
2.????????Task
2.1?????To protect the Ukrainian nuclear power plants by using the modern analytical models of NPPs nuclear safety analysis, which with appropriate input data allow modeling of the catastrophic consequences of military intervention and combat operations from the Russian Federation’s side.
3.????????Capabilities of the tools
3.1?????Allows creation of information pressure on the Russian Federation and stop disinformation on the part of the Russian Federation about the allegedly peaceful nature of its military operations on the territory of nuclear facilities, such as the Zaporizhzhya NPP.
3.2?????Shows to the World’s nuclear and political community, that the tools for assessing the safety of nuclear power plants adopted in the world indicate the catastrophic consequences of military actions of the Russian Federation at nuclear facilities that we managed to avoid.
3.3?????Gives an opportunity to demand from the world community to act in accordance with the level of potential risks and protect the 30-kilometer zones of Ukrainian nuclear power plants, as well as to withdraw Russian troops from Ukraine's nuclear facilities.
4.???????Analytical and other impacts
4.1?????Risk assessment experts are one of the most experienced specialists in the safe operation and nuclear safety of NPPs.
4.2?????It is possible to have the most qualified and effective and unbiased information free from Russian influence for making managerial decisions on nuclear issues and reducing possible nuclear risks in the conditions of combat operations.
4.3?????Impact on the adoption of military and political decisions in a war.
5.???????Characteristics and properties
5.1?????The presented results and conclusions are the basis for real actions on the part of the country's leadership to achieve the goals of eliminating military threats in the activities of nuclear facilities, such as nuclear power plants.
5.2?????Allows, among other things, the world community to help operate not with the narratives of the Russian Federation, but with the use of recognized tools for analysis and the consequences of actions and threats.
5.3?????Allows consultions and lets the military-political leadership of the country act using the potential of analytical and professional support from the nuclear environment of the country and the world.
5.4?????Development of more flexible analytical tools, as well as procedures for protecting nuclear facilities in the face of hostilities and terrorist threats.
5.5?????To include in capital expenditures for the introduction of nuclear facilities components that relate to the sphere of physical and military protection of nuclear facilities, both existing and new ones.
5.6?????Development of international requirements and mechanisms for the collective protection of nuclear facilities in the world and rules for the conduct of hostilities, which should be prohibited, like proliferation of nuclear weapons.
6.????????Conclusions
6.1?????If we talk about the preliminary analysis results using the model, the expert conclusions are given at the end of the attachment “Probabilistic risk analysis of the nuclear safety of ZNPP against threats of a combat attack by the Russian armed forces”.
6.2?????If we talk about the military-political consequences, then this has already been stated in the previous sections.
6.3?????The tool is currently the only one that provides undeniable evidence of quantitative indicators of increased risks of damage to reactor cores.
6.4?????The work done is an extraordinary opportunity to capitalize on the actions of the military-political leadership of the country in conditions when even those who should have been worried about the problems of protecting nuclear facilities in the world, like the IAEA, did not do this, and not only because they are mainly dependent on the Russian Federation, but also because no one had a dialogue with us, with reliance on modern tools available for analyzing nuclear risks.
6.5 It is also an opportunity to draw the attention of the world's leading experts who prioritize nuclear safety of nuclear power plants, how irresponsibly the Russian Federation neglects the fundamental principles of safety, deliberately and defiantly creates high levels of nuclear threats in order to frighten and control humanity.
Georgiy Balakan
22.06.2023
Probabilistic risk assessment of Zaporizhzhye NPP safety due to threats from military attacks of the Russian armed forces
I.???????????General provisions
The current safety analysis for the power units of the Zaporizhzhye NPP (ZNPP) was performed for normal operating conditions and does not take into account the conduct of hostilities in close proximity to the ZNPP site. However, the existing probabilistic models make it possible to perform certain analyzes and make conclusions regarding the potential negative consequences due to damage to the equipment and systems of nuclear power plants during hostilities and terrorist acts.
A.????General approach (simplified):
·????????Identify vulnerable on-site objects/components that are important for safety (common-plant and for each power unit);
·????????Determine initiating events (IAs) that can occur in case of damage of these objects/components (and determine safety function that can degrade), for each power unit taking into account its current operational state;
·????????Develop accident scenarios and assess probabilistic risk indicators (CDF, CDP), postulating that the IE has already occurred;
·????????Assess the risk index (RI):
B.????For the events with occurred IEs, the index of possible risk is calculated using the following formula
RI = CDFevent/CDFbas*100, % ??????????????????????????????????????????????????????????????????????????????????(1)
where:
RI – index of possible risk due to the event;?
CDFevent – CDF due to the event under the analysis;?
CDFbas – CDF for all IEs for basic power unit configuration for the annual operating campaign (1/reactor*year);
C.??For the events without IEs but with safety function degradation, the index of possible risk is calculated using the following formula
IR = ((CDFbas*(tyr–tunav)/tyr+CDFevent*tunav/tyr)- CDFbas)/CDFbas*100, % (2)
where:
IR – index of possible risk due to the event;?
CDFevent – CDF for all IEs taking into account equipment failures due the event under the analysis;?
CDFbas – CDF for all IEs for basic power unit configuration for the annual operation campaign (1/reactor*year);
tyr – time of the year in hours;
tunav – time of equipment unavailability in hours.
In the assessment, tunav is taken as equal to 72 hours.?
The higher the risk index, the more attention should be paid to such an event.
Criteria of General Safety Regulations (GSR) for core damage frequency (CDF): 1Е-04 1/year, or 1.14Е-08 1/year
D.??Taking into account the territorial location of ZNPP structures and buildings, in accordance with the ZNPP Site General Layout,?GS 512-348/11-308 GP, the objects most vulnerable to shelling and destruction are:
D1??????Outdoor switchgears (ORU-750);
D2??????Standby diesel power stations (RDES):
·????????1RDES-1 S-S-W (south-south-west) from power unit #1 (01QV10);
·????????RDES-1 between power units #1 and #2 (01QV20, 02QV10, 01QV30);
·????????RDES-2 between power units #2 and #3 (02QV20, 03QV10, 02QV30);
·????????RDES-3 between power units #3 and #4 (03QV20, 04QV10, 03QV30);
·????????RDES-4 between power units #4 and #5 (04QV20, 05QV10, 04QV30);
·????????RDES-5 between power units #5 and #6 (05QV20, 06QV10, 05QV30);
·????????RDES-6 N-N-E (north-north-east) from power unit #6 (06QV20, 06QV30);
D3??????Common-plant diesel power station (ZRDES) for power units #5 and #6;
D4??????Cooling facilities (spray ponds):
·????????Spray pond of system I, power units #1 and #2;
·????????Spray pond of system II, power units #1 and #2;
·????????Spray pond of system III, power units #1 and #2
·????????Spray pond of system I, power units #3 and #4;
·????????Spray pond of system II, power units #3 and #4;
·????????Spray pond of system III, power units #3 and #4;
·????????Spray pond of system I, power unit #5;
·????????Spray pond of system II, power unit #5;
·????????Spray pond of system III, power unit #5;
·????????Spray pond of system I, power unit #6;
·????????Spray pond of system II, power unit #6;
·????????Spray pond of system III, power unit #6;
D5??????Plant pump stations (BNS-1, BNS-2, BNS-3, BNS-4, BNS-5, BNS-6);
D6??????Auxiliary building #1 and auxiliary building #2.
E.??Since these structures and buildings are located along the perimeter of the ZNPP site, they are primarily open to the damaging factors due to a direct hit, and when exposed to shock waves from potential explosions. Thus, even considering that, for example, spray ponds are physically separated for each safety system (SS) channel of a certain power unit or standby DGs of one power unit are located in different buildings of the RDES, the impact of the shock wave from the explosion can lead to the destruction of all cooling structures or buildings of the RDES that belong to a specific power unit..
The hitting of a projectile(s) or the impact of a explosion wave on the outdoor switchgear ORU-750 leads to the occurrence of IE: T1 “Loss of all normal power supply buses”. Recovery of ORU-750 within 24 hours as a result of such impacts is impossible.
The hitting of a projectile(s) or the impact of a explosion wave on the buildings of standby diesel power station (RDES) and common-plant standby diesel power station (ZRDES) do not lead directly to the occurrence of IE. The loss of standby DGs and common-plant standby DGs results in failure of the safety function “Power supply”, which in turn catastrophically increases the probability of destruction of the ZNPP reactor core in the event of occurred other IEs.
Destruction of the cooling structures as a result of projectile(s) hit or impact of a shock wave leads to the loss of the essential service water system and, accordingly, the occurrence of IE: T12 “Loss of essential service water system” or T7 “Loss of two trains of essential service water system”, depending on OS (operational state).
The destruction of unit pumping stations leads to failure of BNS pumps (circulating water and non-essential service water system). The loss of water flow in the system leads to a combination of IEs: T9 “Loss of non-essential service water system” and T32 “Failure of condensate-vacuum system”.
A qualitative analysis of ZNPP systems database showed that in the buildings #1 and #2 of the auxiliary building there is no equipment and system components, the failure of which caused by a projectile(s) hit or explosive wave can lead to IE and safety function (SF) degradation that are considered in PSA Level 1.
II.???Zaporizhzhye NPP Unit 1
As of March 21, 2022, the 1st power unit was in operational condition that combined fuel refueling operations, including fuel unloading and loading (Operational State OS-9 “Refueling”).
The probability assessment of the reactor core damage was performed using the ZNPP power unit #1 model, which takes into account the full range of accident initiating events for all tech specs states of the reactor plant and spent fuel pool, and was approved by the State Nuclear Regulatory Committee of Ukraine. This model was developed using the SAPHIRE code.
The core damage frequency for ZNPP Unit 1 in the event of internal IEs when the reactor is in OS-9: 6.32Е-07 1/year (7.21Е-11 1/hour).
Scenario А-1?“Loss of all normal power supply buses caused by damage of outdoor switchgear ORU-750”:
As a result of this scenario, the IE T1 “Loss of all normal power supply buses” is initiated. The core damage frequency (CDF) for ZNPP Unit 1 with the reactor facility in OS-9 and occurrence of IE T1 is 1.99Е-09 1/year. The frequency of IE T1 is 1.03Е-02 1/year. Postulating the occurrence of T1, the CDF (or conditional probability of core damage - CDP) for IE T1 in OS-9 is 1.93E-07 1/year.
The risk index as a result of the occurred event:?
RIА-1_1 = 9698% - in regard to CDF for IE T1 in OS-9.
RIА-1_2 = 30.54% - in regard to total CDF for internal IE in OS-9.
The CDF settled for 1 hour for OS-9 with implemented scenario A-1 is 2.20Е-11 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
?
Scenario B-1?“Failure of Safety Function “Power Supply” as a results of destruction of 1RDES-1 and RDES-1”:?
The core damage frequency for ZNPP Unit 1 in case of internal IEs when the reactor facility is in OS-9 and the scenario B-1 is implemented, considering the possibility of heat removal through the secondary circuit using SG mobile pump, will be 7.13E-03 1/year (in the base model for accident sequences with total loss of power, the possibility of removing heat through the secondary circuit using SG mobile pump was not taken into account, since the frequency of such accident sequences (AS)?was below 1.00E-8 1/year).
The risk index as a result of the event:?
RIB-1 = 9265%.
The CDF settled for 1 hour for OS-9 with implemented scenario B-1 is 8.13Е-07 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.
This scenario is quite conservative, but quite possible. However, the scenario with the destruction of one RDES building, for example RDES-1, will be more likely, which will lead to the failure of sections BW and BX. In this case, the CDF for OS-9 will be 2.46E-03 1/year (or 2.81E-07 1/hour, RI=3196%). The CDF increase in case of this scenario is shown in the diagram below.
Scenario V-1?“Damage of spray ponds”:
As a result of this scenario, the IE T7 “Loss of two trains of essential service water system” is initiated. The CDF for ZNPP Unit 1 with the reactor facility in OS-9 and occurrence of IE T7 is 1.29Е-11 1/year. The frequency of IE T7 is 8.89E-10 1/year. The CDP for IE T7 in OS-9 is 1.45E-02 1/year.
It should be noted that in the basic model for IE T7, when the reactor plant is in OS-9, only the possibility of heat removal through the secondary circuit using SG mobile pump is taken into account as regard to the mobile emergency response equipment. At the same time, there is also PRT mobile pump at ZNPP (was taken into account only for the PSA external events in the probabilistic model). For this scenario, the possibility of using both SG mobile pump and PRT mobile pump was taken into account. Thus, the CDF for ZNPP Unit 1 in the event of IE T7 when the reactor facility is in OS-9 in case of the implemented scenario V-1 will be 8.39Е-03 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIV-1_1 = 65038759689% - in regard to CDF for IE T7 in OS-9.
RIV-1_2 = 132753% - in regard to total CDF for internal IE in OS-9.
The CDF settled for 1 hour for OS-9 with implemented scenario V-1 is 9.57Е-07 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Scenario G-1?“Destruction of BNS-1 (unit pump station)”:
BNS destruction when the plant is in OS-9 does not result in IE.
Scenario D-1?“Damage of outdoor switchgear ORU-750 and destruction of 1RDES-1 and RDES-1”:
When the plant is in OS-9, the implementation of IE T1 “Loss of all normal power supply buses” with overlapped failure of the safety function SF “Power supply” results in core damage. But considering the possibility for heat removal via the secondary circuit using SG mobile pumps, the CDF in the scenario D-1 will be 1.59Е-02 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RID-1_1 = 798994974% - in regard to CDF for IE Т1 in OS-9.
RID-1_2 = 2515822% - in regard to total CDF for internal IE in OS-9.
The CDF settled for 1 hour for OS-9 with this implemented scenario is 1.81Е-06 1/hour.
Below is a diagram showing the CDF increase for ZNPP Unit 1, which is in OS-9 “Refueling” as of 21.03.2022, in case of hit by hostilities or impact of waves from potential explosions on the building of the ZNPP site
III.??ZNPP Unit 4 and Unit 2
As of March 21, 2022, the power units #4 and #2 were in an operational state (OS), in which the reactor thermal power is in the range from 100% to 40%, and the main technological parameters correspond to the operational limits for the state “Operating at power”.
The probability assessment of the reactor core damage was performed using the ZNPP power unit #4 model (compared to the probabilistic model of ZNPP power unit #2, it considers the possibility of using such mobile emergency response equipment at ZNPP as PRT mobile pump and mobile diesel generator), which takes into account the full range of accident initiating events for all tech specs states of the reactor facility and spent fuel pond (SFP), and is approved by the State Nuclear Regulatory Commission of Ukraine. This model was developed using the SAPHIRE code.
The core damage frequency for ZNPP Unit 4 in case of internal IEs when the plant is at the nominal power: is 1.30Е-06 1/year (1.48Е-10 1/hour).
Scenario А-2 “Loss of all normal power supply buses as a result of ORU-750 damage”:
As a result of this scenario, the IE T1 “Loss of all normal power supply buses as a result of ORU-750 damage” is initiated. The CDF for ZNPP Unit 4 with the reactor facility in OS-0 and occurrence of IE T1 constitutes 2.36Е-08 1/year. The frequency of occurring IE T1 is 3.37Е-02 1/year. When postulating the occurrence of T1, the CDF (CDP) for IE T1 in OS-0 is 7.00Е-07 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIА-2_1 = 2966% - in regard to CDF for IE T1 in OS-0.
RIА-2_2 = 53.85% - in regard to total CDF for internal IE in OS-0.
The CDF settled for 1 hour for OS-0 with implemented scenario A-2 is 7.99Е-11 1/hour.
?Scenario B-2?“Loss of SF “Power supply” as a result of RDES-3 and RDES-4 destruction”
The CDF for ZNPP Unit 4 in case of internal IEs when the plant is at nominal power for the scenario B-2 will be 1.43Е-05 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (2) and constitutes RIB-2 = 8.21% (tunav?is taken as equal to 72 hours in this scenario).
The CDF settled for 1 hour for OS-0 with implemented scenario B-2 is 1.63Е-9 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.
Scenario V-2?“Damage of spray ponds”:
As a result of this scenario, the IE T12“Loss of essential service water system” is initiated. The CDF for ZNPP Unit 4 with the reactor facility in OS-0 and occurrence of IE T12 is 7.21Е-11 1/year. The frequency of IE T12 is 1.26Е-8 1/year. The CDP for IE T12 in OS-0 is 5.72Е-03 1/year.
It should be noted that in the basic model for IE T12, when the reactor plant is in OS-0, only the possibility of heat removal through the secondary circuit using SG mobile pump is taken into account as regard to the mobile emergency response equipment. At the same time, there is also PRT mobile pump at ZNPP (was taken into account only for the PSA external events in the probabilistic model). For this scenario, the possibility of using both SG mobile pump and PRT mobile pump was taken into account. Thus, the CDF for ZNPP Unit 4 in the event of IE T12 when the reactor facility is in OS-0 in case of the implemented scenario V-2 will be 3.87Е-04 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIV-2_1 = 536754507% - in regard to CDF for IE T12 in OS-0.
RIV-2_2 = 29769% - in regard to total CDF for internal IE in OS-0.
The CDF settled for 1 hour for OS-0 with implemented scenario V-2 is 4.42Е-08 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.
Scenario G-2?“Destruction of BNS-4”:
When the plant is at nominal power operation, the destruction of BNS leads to occurrence of the combination of IE T9 “Loss of non-essential service water” and T32 “Failure of condensate-vacuum system”.
With the plant operation at nominal power and occurrence of IE T9 and T32, the CDF for ZNPP Unit 4 is (CDFТ32=4.12Е-11 1/year CDFТ9=0.00). The frequency of occurrence of IE T32 is 1.73Е-02 1/year, and IE Т9 is 3.01Е-08 1/year. The SDP for this scenario is 2.38Е-09 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIG-2_1 = 5776% - in regard to CDF for IE T9 and T32 in OS-0.
RIG-2_2 = 0.18% - in regard to total CDF for internal IE in OS-0.
The CDF settled for 1 hour for OS-0 with implemented scenario G-2 is 2.72Е-13 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Scenario D-2?“Damage of ORU-750 and destruction of RDES-3 and RDES-4”:
It should be noted that in the basic model for IE T1, when the reactor plant is in OS-0, only the possibility of heat removal through the secondary circuit using SG mobile pump is taken into account as regard to the mobile emergency response equipment. At the same time, there is also a possibility to use MDGS (mobile diesel generator station) to avoid core damage at ZNPP when the plant is at nominal power in case of total loss of power supply (was taken into account only for the PSA external events in the probabilistic model). For this scenario, the possible use of both the SG mobile pump and MDGS was considered. Thus, the CDF for ZNPP Unit 4 when the reactor facility is in OS-0 in case of the implemented scenario D-2 will be 1.29Е-03 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RID-2_1 = 5466101 % - in regard to CDF for IE T1 in OS-0.
RID-2_2 = 99230% - in regard to total CDF for internal IE in OS-0.
The CDF settled for 1 hour for OS-0 with implemented scenario D-2 is 1.47Е-07 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Below is a diagram showing the CDF increase for ZNPP Unit 4, which is in OS-0 "Operation at power" as of March 21, 2022, in the event of projectiles hit or waves impact from potential explosions on the ZNPP site buildings.
IV.?ZNPP Unit 3, Unit 5 and Unit 6
As of March 21, 2022, the power units #3, #5 and #6 were in cold standby. This operational state combines a time-stable cold shutdown condition without primary depressurization (OS-7 “Cold shutdown without primary depressurization”).
The probability assessment of the reactor core damage was performed using the ZNPP power unit #6 model (it considers the possibility of using such mobile emergency response equipment at ZNPP as PRT mobile pump and mobile diesel generator), which takes into account the full range of accident initiating events for all tech specs states of the reactor facility and spent fuel pond (SFP), and which was approved by the State Nuclear Regulatory Commission of Ukraine. This model was developed using the SAPHIRE code.
The core damage frequency for ZNPP Unit 6 in the event of internal IEs when the plant is in OS-7 will be 1.23Е-06 1/year (1.40Е-10 1/hour).
Scenario А-3?“Loss of all normal power supply buses as a result of ORU-750 damage”:
As a result of this scenario, the IE T1 “Loss of all normal power supply buses as a result of ORU-750 damage” is initiated. The CDF for ZNPP Unit 6 with the reactor facility in OS-7 and occurrence of IE T1 constitutes 2.36Е-08 1/year. The frequency of occurring IE T1 is 2.17Е-03 1/year. When postulating the occurrence of T1, the CDF (CDP) for IE T1 in OS-7 is 1.23Е-05 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIA-3_1 = 46240% - in regard to CDF for IE T1 in OS-7.
RIA-3_2 = 1000% - in regard to total CDF for internal IE in OS-7.
The CDF settled for one hour in case of implemented scenario is 1.40Е-09 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Scenario B-3?“Failure of Safety Function “Power supply” as a result of RDES-5 and RDES-6 destruction”:
The core damage frequency for ZNPP Unit 6 in case of internal IEs when the reactor facility is in OS-7 and the scenario B-3 is implemented, considering the possibility of heat removal through the secondary circuit using SG mobile pump, will be 3.19Е-03 1/year (in the base model for accident sequences with total loss of power, the possibility of removing heat through the secondary circuit using SG mobile pump was not taken into account, since the frequency of such accident sequences (AS)?was below 1.00E-8 1/year).
The index of possible risk as a result of the occurred event is calculated using the formula (2) and constitutes RIB-3 = 2129% (tunav?is taken as equal to 72 hours in this scenario).
RIB-1 = 9265%.
The CDF settled for 1 hour for OS-7 with implemented scenario B-3 is 3.64Е-07 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Scenario V-3?“Destruction of spray ponds”:
As a result of this scenario, the IE T7 “Loss of two trains of essential service water system” is initiated. The CDF for ZNPP Unit 6 with the reactor facility in OS-7 and occurrence of IE T7 is 1.25Е-10 1/year. The frequency of IE T7 is 1.88Е-10 1/year. The CDP for IE T7 in OS-7 is 6.65Е-01 1/year.
?It should be noted that in the basic model for IE T7, when the reactor plant is in OS-7, only the possibility of heat removal through the secondary circuit using SG mobile pump is taken into account as regard to the mobile emergency response equipment. At the same time, there is also PRT mobile pump at ZNPP (was taken into account only for the PSA external events in the probabilistic model). For this scenario, the possibility of using both SG mobile pump and PRT mobile pump was taken into account. Also, it was considered that the plant is in standby mode and not in the outage (the safety trains were not disabled for maintenance, accordingly). Thus, the CDF for ZNPP Unit 6 in the event of IE T7 when the reactor facility is in OS-7 in case of the implemented scenario V-3 will be 2.26Е-02 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RIV-3_1 = 18080000000 % - in regard to CDF for IE T7 in OS-7.
RIV-3_2 = 1837398 % - in regard to total CDF for internal IE in OS-7.
The CDF settled for 1 hour for OS-7 with implemented scenario V-3 is 2.58Е-06 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Scenario G-3?“Destruction of BNS-6”:
Destruction of BNS with the plant in OS-7 does not result in occurrence of IE.
Scenario D-3?“Damage of ORU-750 and destruction of RDES-5 and RDES-6”:
When the plant is in OS-7, the implementation of IE T1 “Loss of all normal power supply buses” with overlapped failure of the safety function SF “Power supply” results in core damage. But considering the possibility for heat removal via the secondary circuit using SG mobile pumps, the CDF in the scenario D-3 will be 1.33Е-02 1/year.
The index of possible risk as a result of the occurred event is calculated using the formula (1) and constitutes:?
RID-3_1 = 50000000% - in regard to CDF for IE Т1 in OS-7.
RID-3_2 = 1081300% - in regard to total CDF for internal IE in OS-7.
The CDF settled for 1 hour for OS-7 with this implemented scenario is 1.52Е-06 1/hour.
The CDF increase in case of implemented scenario is presented in the diagram below.?
Below is a diagram showing the CDF increase for ZNPP Unit 6, which is in OS-7 “Cold shutdown without primary depressurization” as of 21.03.2022, in case of hit by hostilities or impact of waves from potential explosions on the building of the ZNPP site.
V.??ZNPP Unit 4, risk assessment when shutting down the plant for outage (OS1÷OS15)
Additionally, for ZNPP Unit 4, the above scenarios were assessed for the case when the plant is transferred from OS-0 to other states (the values for OS-0 are given as reference ones).
The assessment results of CDF contribution for particular scenarios are given in the diagram below.
The assessment results of CDF total contribution for all scenarios are given in the diagram below
VI.?Assessment of the multi-risk ZNPP site
Within the framework of the IAEA’s MUPSA project “Probabilistic Safety Assessment (PSA) Benchmark for Multi-Unit/Multi-Reactor Sites” (https://www.iaea.org/projects/crp/i31031) in 2018-2021, the probabilistic models for PSA Levels 1 and 2 were developed for assessing the frequency of simultaneous fuel damage in several cores/SFP of ZNPP power units.
In MUPSA the calculations of damage frequency for more than one reactor core in an accident with the failure of all ESWS spray ponds (essential service water system) due to tornadoes (for the states of operation of all ZNPP power units at rated power) are given below. The CCDP curve in the diagram corresponds to the SBD with damage of ESWS spray ponds.
In addition, within the framework of MUPSA project, the estimation was made for conditional probability of the maximum accidental release as a result of fuel damage in the core and spent fuel pool of one ZNPP power unit in the event of failure of all ESWS ponds, which is 2.93E-04.
VII. Conclusions
Conduct of hostilities at the ZNPP site can lead to damage to vulnerable structures/systems that ensure the safe operation of power units in all operational states (rated and reduced power, cold shutdown and refueling states). As a result of damage to vulnerable structures/systems, there will be several initiating accidents and/or combinations of initiating events:
·????????Loss of all normal power supply buses;
·????????Loss of essential service water system;
·????????Loss of non-essential service water system;
·????????Failure of condensate-vacuum system.
In addition, degradation of safety function can occur with power supply both to one and several power unit at one and the same time.
To demonstrate the potential risk for each power unit, 4 conservative scenarios with the most devastating consequences were quantitatively assessed. For a complete, comprehensive assessment, it is necessary to consider several dozen scenarios, taking into account less conservative scenarios and a combination of impacts on several power units at the same time.
Current risk for scenarios due to hostilities (SDH)
Therefore:
1.????Scenarios with damage to the outdoor switchgear (ORU) alone will not lead to a violation of the safety regulation criterion on CDF for any of the power units.
2.????Scenarios with BNS damage have very little impact on the risk of core damage for any of the power units.
3.????In case of severe damage to all spray ponds, the probability of simultaneous multiple damage to the reactor core of several power units increases significantly.
4.????For six power units of ZNPP, the combination of simultaneous damage to two or three power units is the most probable. In addition, it is also possible to damage the fuel in the core and spent fuel pool of one power unit with the conditional probability of the integral large early release of radioactive substances exceeding the safety regulation criterion.
5.????The maximum risk index is observed for ZNPP power units in the refueling state.
6.?????The most risky operational state is OS-8 “Operation with drained primary circuit”.
For this OS “Operation with drained primary circuit”, it is impossible to arrange the heat removal through the secondary circuit to maintain the power unit in a safe end state.
7.????In OS-9 "Refueling" it is possible to arrange the heat removal through the secondary circuit by feeding the 1st SG from the emergency feedwater system or using the mobile pump station with subsequent SG draining.
8.?Other conclusions and recommendations are being processed and will be presented in more details in further calculation analyses of the modeled initiating events caused by military hostilities and terrorist acts of the Russian Federation.
Probabilistic risk analysis of the nuclear security of the SUNPP from threats of a combat attack by the Russian armed forces
Next, I want to present more risk analysis calculations specifically for the SUNPP site, conducted using the analytical model of VVER-1000 small series V-302 and V-338 reactors, which on April 16, 2022 were operated at full power, and three ruzzian cruise missiles flew over them in the direction of the city of Mykolayiv to kill Ukrainians.
The current safety analyses of SUNPP power units were carried out for normal (peaceful) operating conditions and do not consider the possibility of terrorist acts on the territory of the NPP. However, even on existing analytical models, it is possible to make certain analytical estimates and conclusions about the potential negative consequences due to damage to equipment and systems of nuclear power plants during military actions.
Assessing the territorial location of SUNPP facilities, the most vulnerable to shelling and destruction are:
·????????Open switchgears (ORU-150, 330 and ORU-750),
·????????Cooling facilities of power units (cooling towers and spray ponds) for the NPP safety systems,
·????????Backup diesel power plants (DGs standby power plant - RDES and, accordingly, DGs of safety systems located in these buildings, which ensure emergency power supply to the nuclear power plant.
Since these facilities are located along the perimeter of SUNPP power units and the site, they are primarily open both to damaging factors due to direct hits by cruise missiles or shells, and when exposed to shock waves from potential explosions.
The negative consequences can be exacerbated by damage to the mechanisms and systems of deaerator compartments and machine rooms of power units, which will lead to the loss of such safety functions as:
·????????Maintaining the coolant inventory in the primary side,
·????????Heat removal by the secondary circuit,
·????????Pressure control in the secondary circuit,
·????????Provision of power supply,
and this catastrophically increases the likelihood of damage to the reactor core of power units.
Therefore, based on the foregoing, when conducting an estimating calculation, the following were considered as one of the most dangerous real scenarios:
·????????Scenario A “Loss of plant’s off-site consumers”,
·????????Scenario B “Loss of backup diesel generators”,
·????????Scenario C “Combination of loss of diesel generators and off-site consumers”.
It is quite logical that with conduct of the full-scale hostilities, the implementation of “scenario C” is most likely.
The assessment of the core damage probability was made on the basis of SUNPP power unit 1 model, which takes into account the full range of initiating events for all tech specs states of the reactor facility and spent fuel pool.
This model is developed on the basis of Risk Spectrum PSA code. The use of a software product and a probabilistic model for conducting safety justification analyses has been agreed with the SNRIU.
At the same time, it should be taken into account that in the case of catastrophic scenarios, similar results will be valid for any of the three SUNPP power units.
?As the calculation results showed:
·????????In case of loss of off-site plant consumers, the probability of severe damage to the reactor core increases by 5 times (but the criteria of safety standards in this scenario will not be exceeded);
·????????In case of loss of standby diesel generators, the probability of damage to the reactor core as a result of an accident increases by 20 times (this will lead to exceeding the criteria established by the current standards in terms of the target safety indicators).
The evaluation of “Scenario C” shows a catastrophic increase in the frequency of damage to the reactor core in case of an accident, which numerically is 1000 times higher than the existing safety indicators of the power unit.
When scenarios “B” and “C” are implemented, the state of the power unit will be dangerous in fact (significantly exceeded safety standards) and the probability of catastrophic severe damage to the core of SUNPP power units is significant.
First of all, it is necessary to consider scenarios with occurrence of the initiating events (IE). If there is no IE, for example, a de-energization of 6 kV sections, then the loss of the DG will lead to nothing. However, their absence reduces redundancy of the safety function and leads to an increase in the total CDF.
Separately, attention should be paid to the fact that this model does not take into account the probable deterioration in the psychological state, stress of personnel in the combat conditions, as well as the resulting erroneous actions, which in turn can predictably significantly worsen the situation and lead to additional negative consequences.
I also emphasize that in order to analyze the risk of failures in war conditions, we took not the most difficult conditions for the impact of an explosion or fall of cruise missiles.
I understand that there will again show up the experts who have never performed such analyses before, but they already know that everything needs to be done differently, through other ways of influencing russia. But, Bucha showed that there are no boundaries for the abyss and ferocity. And what was done does not correspond in any way to their ideas about reality and especially about determinism in probabilistic safety analyses. I am only glad that they have never had anything to do with analytical calculations and models of nuclear power plants, on the basis of which these analyses are performed by the entire nuclear world. Therefore, it is important for me that we will still be able to reach out to those who understand the danger of ruzzia’s actions and understand it not from the pieces of paper of the IAEA regulatory requirements, which the leaders of these respected institutions forgot about, or maybe they themselves never believed in them…
Georgiy Bakakan
20.03.2022