David Lokbaum, a former engineer of the first block of U.S. nuclear power plants, "Browns Ferry," and now the employee of "the Union of Concerned Scientists" — an organization known for its criticism of nuclear energy — has a blog, which publishes stories about incidents and other non-standard cases, and with whom he his comrades had to face over the years in the nuclear industry.
Moon crash — 1982
The morning of February 27, 1982 almost 30 minutes for the block number 1 nuclear power plant, "San Onofre" in California remained without cooling for HVAC systems and other containment systems important to safety.
For these cooling systems have been provided on the block are two independent loops. Each of them has been designed in such a way as to be able to single-handedly ensure that under normal conditions and during design basis accidents HVAC heat sink assemblies in the reactor hall and around the containment, as well as motors emergency diesel generators and other equipment important to safety.
One of the loops is constantly at work, while the second is in warm-standby state, or is under maintenance. Recently, just happened to "San Onofre." A team of technicians intended to inspect and repair the pump in the back loop.
At nuclear power plants, "San Onofre" process water is drawn from the Pacific Ocean, where then is discharged after use. Pumps in the two cooling loops, referred to in the story, stand in the building of BNS, built right on the shore.
Renovation began with the fact that technology otbaltili pump from the base and raised his cock for inspection. In the floor of the building, of course, a hole in the place where the state has to stand on the pump.
Lifting the pump valve
Much to the surprise of technicians, through a hole in the building flowed water. To put it bluntly, in the building of a pumping station began flooding. The water was coming up, as long as not risen to five feet above the floor. As it later investigation showed that this marker is exactly consistent with the level of ocean water outside the building LBP.
Operators in the control room did not have a clue as to what's going on at the pumping station. However, they drew attention to the fluctuations of the value of the current to the motor of the second (working) pump and disconnect it from harm's way. No wonder there is no current in the race — the second pump was in the same building as the first, and likewise fell victim to floods.
Thus, the block was no emergency cooling despite project provided two independent loops. The pump is one of the loops hung suspended from a crane, and the second pump was turned off the remote control room for his own safety.
Staff who was on the BNS, started a fight with the flood. They launched a portable pump and started to pump water into the Pacific Ocean, arriving on the same station from the Pacific Ocean. At first, the success of these actions had not. Through the hole in the floor with water flowed clearly faster than it can evacuate the premises.
Realizing that he is opposed to the law of physics of the communicating vessels, vehicles made the only right decision.
They tried to plug the hole, putting in place a crane to remove the pump. Partially succeeded, and flood went better. He coped with the primary task, technology took care of the safety of the station, connecting to one of the loops of the reserve (third) pump.
The total period during which the unit remained without emergency cooling was 24 minutes. Return to the work of the first full-time pump failed after more than 4 hours after its shutdown. What is needed in the end to do with the pump number 2, played a role in this story and the perpetrator, and the gag is left covered with darkness trade secrets.
When all was over, began debriefing. The Commission found that the man who planned the work on the pump number 2 made a mistake and miscalculated the time of high tide and low tide. The whole operation to remove the pump and return it to the place was to be held during the low tide, when the water level in the ocean below the floor in the BNS. In fact, everything happened exactly the opposite.
Who is responsible for what happens on Earth tides? The gravitational field of Earth's natural satellite. So, who should be punished for the incident at "San Onofre-1" 02/27/1982? Of course, the Moon …
It is always better to think first, and only then do. Disassembled flood incident started because of a manifest error of planning. But suppose the tide would be calculated correctly. Even in this case, the risk remained. Suppose technology could linger with repair the pump and not have time to put it in place in time.
Even the best plan is to be a backup plan. Removal of the pump unit on the BNS number 1 nuclear power plant, "San Onofre" created a potential threat of flooding, and the required measures that would prevent or easy to deal with threats to the building of ocean water pumping station.
The moral of the story is this — in the nuclear industry always keep on hand a plan "B". Otherwise, your best plan of attack in the world will turn to the fact most infamous instructions on how to get directly to the largest number of simultaneous ambushes.
And three stories and three morals from David Lokbauma
October 20, 1986 Inspector of the Nuclear Regulatory Commission (NRC) issued a U.S. warrant holders of two nuclear power plants in the state of Minnesota — «Monticello» and «Prairie Island». A precept required to prohibit operators control room to listen to music in the workplace of the radios.
In fact, this story began even earlier. In February 1981, NRC has addressed to all owners of nuclear power plants in the United States showing — music in the control room is not the place. Regulators have found that listening to the radio can distract operators from their work.
In August 1985, the owners of the two stations have notified the Commission of Minnesota — the highest pleasure, it is done and all the radios removed from the control room. Regulators chose not to believe the owners of a word. As it turned out, for good reason. Inspector who visited the stations Atomnadzor seen with my own ears — radios have not gone away.
The Commission went on principle. But operators responded in kind. International Brotherhood of Electrical — union, defending the interests of the nuclear industry — filed a complaint with the arbitration. The ban on radio, it said, has a bad effect on the morale of the operators. Arbitration in any case decided — give back their nuclear scientists to music!
The next move was for the regulators. To business joined the highest ranks of NRC. In Minnesota, the rebellious one by one flew inspectors, experts and psychologists with stories about the dangers of music for nuclear safety.
Director of NRC inspections personally gave the March 6, 1987 affidavit in which all depict the threat that lurks for nuclear power in modern music. Specific examples, however, he forgot to bring.
In the end, regulators have won, and the music was banned. Staff NPP «Monticello», every year the music gets from the NRC for his work mark "excellent" after the ban rolled off the mark "good" and he could not go back to dozapretnym indicators.
What is the moral of the music of the war in Minnesota? The reader may think: "For all these guys toiled foolishness, blowing case, which is not worth a damn."
Cleaning — a delicate matter
June 17, 1970 is now closed nuclear power plant operator «LaCrosse» in Wisconsin decided to clean the control panel. At home, he wiped the dust cloth, and it is not surprising that just as he decided to go and in the workplace.
No, nothing exploded and melted. Fumbling with a cloth on the console, the operator just switched one of the tumblers, and instantly triggered automatic protection. By counting the losses from downtime, disgruntled owners released a statement: "Gentlemen! Clean the remote control room at least a brush, not a rag! ".
It is not known whether he knew about the incident in Wisconsin operator of nuclear power plants «Waterford» in Louisiana. But October 25, 1992 in the hands of the rag he did not take. Instead, he used the most effective tool for cleaning surfaces, advertises in all the magazines for housewives.
Means really been effective. The report describes the NRC subsequent events as follows: "Two hours later, a cleaning substance called bonding with each other 16 plastic switch systems related to security, thereby making the switches inoperative." Among them, by the way, were the switches ECCS system.
In one research reactor in Florida is not wiped with a cloth panel and means for housewives are not sprayed. It is possible that there is not cleaned it at all, and grateful for decades served as a control operators faithfully. But the trouble lay in wait on the other side.
The research reactor — no power plant. There's all different. The cooling system is powered from the city's water supply. From the same branch pipe departed for the bathroom.
Very clever system of monitoring the state of the reactor taken all the necessary for the salvation of entrusted property from the accident. If the flow of cooling water fell, the system dumped rods AZ.
Research reactors run by the experimenters, people with a particular mindset. It only took them five automatic shutdowns to detect a correlation — the system resets the pins after flushing the toilet water in the service.
What we can do? Redesign the system of control is not possible, to lay new pipes — expensive. Such a solution was found — on the door of a toilet, an inscription, "Lord! Do not rinse water when the reactor is working! ".
But in the restroom no overview window with views of the reactor hall. From now on, all working at the reactor had to learn quickly on circumstantial evidence to determine whether the unit to safely shut down or criticized, because it depended on the solution to the question "does not wash off or wash off."
Moral of the story about cleaning even easier than in the history of music. The institutes and MTC, in lectures and classes at the gym, future nuclear scientists are taught the basics of reactor control. But life is richer than any training course. Unit nuclear power plant or research reactor is a complex and comprehensive system of relationships, understanding that only comes with time and experience.
Hot Night in Georgia
Night of May 15, 1985 at the plant «Hatch» in Georgia has stood dry and hot. Exhausted staff dreamed of rain. Who knows, maybe that's why the team, pushed for a standard inspection of the equipment unit, damaged one of the auxiliary piping system.
Leaked pipeline has been associated with the maintenance of fire safety systems for ventilation and air conditioning (HVAC) unit. In other words, the water was taken out in case of fire, activated carbon filters in the system HVAC.
HVAC system designers have been very prudent people. In no case did not want to allow the unit to fire. One of them embedded design solutions provided for the following — if the water pressure in the main pipe drops below the set point, then automatically turns the sprinkler system, which proceeds to extinguish the fire on the filters, regardless of whether is it really they are on.
Operators in the control room rather quickly determined that there is no fire, and manually disabled the sprinkler system. But the night in the state of Georgia has been dry and hot …
HVAC system designers have been very prudent people. In no case did not want to be allowed to accumulate in the ventilation system to the water, as this would threaten the corroded wall ducts. They organized drainage holes through which water was poured into the tanks for disposal. The project has passed all tests and examinations, and no one has thought of a simple question — what would happen if the drain holes clogged?
Of course, that dry hot night in Georgia holes were clogged.
Water trapped in the ventilation system to extinguish the fire of a false, searched out and found it evenly over the remote control room. While the operators were recovering from a sudden shower, the water has short-circuited part of the electric equipment console.
Developers remote control room were people very prudent. They provided everything, including the earthquake, but not the situation when the console will pour water on top of a bucket. The effect came out awesome.
In the BWR, each of the four steam in which steam coming from the reactor to the turbine provided with two or three safety valves labeled Safety / Relief Valve. They are opened to discharge steam, if the pressure in the reactor becomes too high.
After a short circuit on the remote, the valve is opened, closed, opened, closed, opened, closed, and finally opened and remained open. By the way, in BWR steam is discharged into the cold water, and it is considered one of the protective measures in case of major accidents. Open valve led to the fact that the water began to heat up, and the protection of the reactor from the accident has gone down.
Short-circuit system also suffered «High pressure coolant injection» (HPCI) — a system that triggers an accident and poured into a large volume of the active zone of cold water. It should be added that the other system operates like «Reactor core isolation cooling» (RCIC) was at that time off for other reasons.
To the credit of the operators, they are not confused and thrown rods AZ. The water level in the reactor was maintained pumps that move the flow of steam from the reactor. After resetting, AZ, worked valves and pumps are cut off from their driving force. In the end, the cooling of the reactor blanked provided only feeble pumps in the cooling line drive control rods. Fortunately, it was enough to avoid serious consequences.
At the debriefing, of course, got repairmen, protknuvshim auxiliary piping. But the share of accusations must obtain and forward-looking designers, their decisions have created the conditions for the manifestation of the domino effect of dry hot night in the State of Georgia.
The moral of the third story turns quite simple. Unit nuclear power plant is a complex and comprehensive system of relationships, each element of which design is very prudent people.
The main thing in this case — to understand what they actually provided