Inside the Chernobyl Unit 4 control room

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The following is the third installment of a new series of editorials which will communicate portions of my recent trip to the Chernobyl nuclear power plant (Read the first installment herethe second installment herethe third installment here, the fourth installment here, and a bonus installment about the animals at Fukushima Daiichi and Chernobyl here).  

When I visited the Chernobyl nuclear power plant in September, I was aware that we would be visiting the Sarcophagus and the Unit 4 control room.  Once we had arrived at the site however, we began to hear rumor that maybe we wouldn’t be able to access the control room due to some worker activities inside of the structure that would hinder our access to some areas.

That is just the nature of working at an extremely contaminated place like Chernobyl, it is impossible to predict what the on-site worker conditions will be like in the future, things can pop up which require immediate attention and may alter day-to-day activities.

After coming face-to-face with the Sarcophagus on our first day on-site, while inspecting the new confinement structure under construction at the nuclear power plant, we didn’t see much of the Unit 4 structure while we visited other areas of the site the second day.  On Wednesday evening we first learned that we would be visiting Unit 4 after all, and a few of us stayed up late into the night preparing to make the most of the time that we would have available in the structure.

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The next morning a thick layer of fog hovered low over the city of Slavutich.  We walked through the tall pine trees in the park, past a beautiful bronze statue of a father, mother and child, on the way to the station to take the train to the nuclear power plant.  The fog was so thick that we couldn’t see the train until it appeared abruptly nearly at the station.

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Once we had boarded and taken our seats, we met Irina Kovbich, the head of the Information Department at the Chernobyl nuclear power plant.  During the train ride, the fog precluded us from seeing outside of the train windows, so we were left to our thoughts and conversations during the 45 minute trip to the power plant.

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Once we arrived at the plant, passed through security, and were accepted onto the site we made our way to the bright blue sanitorium building, where workers change in and out of protective gear to enter critical areas at the plant.  The sanitorium also provides decontamination showers, medical staff, dosimetry, and meeting areas for workers.

We were taken inside to change out of our clothes and gear, men went one way to a small room with lockers – women went another way to the ladies locker room.

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Inside of the first room we took off our clothes and stored whatever gear we were not taking into Unit 4 in lockers.  We changed into small cotton robes and sandals and carried our items with us.

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The workers led us into a second room where we were given a light cotton undershirt, pants, and socks.  We were also given a heavier cotton jacket and matching pants which we put on over the undergarments, a canvas head covering, gloves, boots and a hard hat.

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After we put on our clothes and arranged the gear we wanted to take into Unit 4, we grabbed our boots and walked downstairs to get assigned a disposable mask and second dosimeter that would allow us to monitor our exposures in the more contaminated areas of the site.

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Inside of the sanitorium workers employ the “clean line” principle.  In the downstairs lobby where workers enter and exit the building there is a line with benches.  Workers are not allowed to wear boots or shoes inside of the building over the clean line.

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Looking out the window, we could see the top of the Sarcophagus and ventilation stack peeking above the building across the street.

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After donning our gear and putting our boots and masks on we made our way onto the site  from the south and entered the clean road between the new confinement structure on our left and the Sarcophagus and turbine building on our right.

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By the time we reached the site the sun had risen and was shining down brightly from above, the fog had lifted, leaving us with perfect conditions for taking photos and videos of the site.

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We paused at the entrance to the clean road and surveyed the site.

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High above our heads workers were suspended on work platforms by cranes as they worked on the new confinement structure.

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Large cranes positioned inside and outside of the new structure under construction were installing and testing the panels on the east side of the structure that will be lowered in place after it is moved in place over the Sarcophagus in the years to come.

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A blue and green dump truck rumbled past us and parked next to the new confinement structure, it was covered in radiation signage indicating that it was used to move materials around.  As soon as the vehicle came to rest a dosimetrist ran up and began surveying the materials.

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The site today is very similar to many other construction sites but it also happens to be heavily contaminated and has high ambient gamma radiation levels emanating from the melted nuclear fuel in the sarcophagus.

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There are piles of materials and pipes and heavy equipment moving about.

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Workers help guide cranes move heavy loads,  survey areas for new structures, and climb up and down the scaffolding erected along the western wall of the Sarcophagus.

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There are posters hanging throughout the site, to remind workers to be safe, to check their harnesses, etc. – but my favorite was the Simpsons-themed shielding poster.

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Bright orange plastic fencing outlines the clean path areas workers pass through on their way about the site.

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Our boots crunched along gravel paths as we walked to the southwest corner of the turbine building and headed north towards one of the entrances which would take us to the control room.

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Workers are still working to repair the portion of the roof of the turbine building that collapsed in 2013.  We were told that initially, the plan was to leave the turbine building roof – because it would just be covered by the new confinement structure once it was moved in place anyways, but the international outcry caused them to commit the manpower and resources to repairing the turbine building roof in the interim.

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We walked up a set of concrete steps to reach the northern side of the turbine building where our entrance was located.

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White cranes were moving large sections of concrete walls for structures that are being constructed near the Sarcophagus.

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As we approached the entrance we passed underneath an awning made of aluminum sheets and passed by a small bench where some workers were seated as they watched us climb up to the structure.

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Once we had entered the building we clicked on our flashlights and headlamps and lined up to enter the hallways to access the control room.

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The hallways were dimly lit and the paint was slowly peeling off of the concrete walls.

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We ascended a narrow concrete stairwell as we navigated the winding twisting hallways to our destination.  It became hard to remember exactly how we had travelled the farther we went, we passed through countless doors and access hatches.

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I was almost caught by surprise when we passed through one door and found ourselves in a tight room and as our eyes adjusted we began to make out the control panels and indicators of the control room.

The control room has changed quite a bit in the last thirty years.  Portions of the control room ceiling have been removed, exposing the concrete beams hanging above our heads.

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I vividly remember standing in the Unit 4 control room, just trying to take in the surroundings and considering what it must have been like on that fateful night. I was surrounded on all sides by a sea of dials, indicators, and actuators.

In April 1986, operators in this room were running an experiment which would help them determine how much electricity would be generated while the turbine was running down.  The rundown was supposed to occur with the reactor operating between 700-1,000 megawatts per hour.  During the experiment, operators had trouble maintaining power levels, the reactor power dipped below 30 MW and fell into the iodine pit.  The reactor was entering dangerous waters now and becoming evermore difficult to control.  The operators didn’t want to increase power after it had fallen, but a special supervisor was on duty because of the test named Anatoly Stepanovich Dyatlov who ordered the operators to increase the reactor power levels –  Dyatlov argued that the experiment could not be allowed to fail just because the operators were having problems and accused them of ruining the test.

Three of the men in the room, Aleksandr Fyodorovich Akimov, Leonid Toptunov, and Boris Stolyarchuk attempted to manually control the reactor by adjusting the steam pressure and water level, but were unable to keep the water in the fuel channels from boiling and steam from being generated – which led to a surge of power in the reactor.  When Toptunov noticed the power increase he warned Akimov.  Akimov briefly hesitated, then pressed the emergency power reduction system button (A-Z) which was designed to drop the control rods into the reactor and stop the nuclear chain reaction.  No one in the room at the time could’ve have guessed in their wildest dreams what sequence of events would be set into motion by that action.  After the button was pressed and the control rods began to insert, the reactivity in the reactor accelerated out of control, leading to a prompt neutron power surge that was beyond control and completely destroyed the reactor.

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Our liaison with the power plant, Stanislav, indicated to us the control panel that held the A-Z button, which once fatally pushed, attempted to lower the control rods into the core and sealed the fate of the Chernobyl Unit 4 reactor.

The control rods were graphite tipped.  Akmiov hit the A-Z button at the same time as steam was building up in the reactor causing a rise in reactivity and when the rods began to insert they displaced some of water in the core but did nothing to slow the nuclear reaction.  The control rods began to drop, but almost immediately stopped.  They never fully inserted partly because of the forces inside of the reactor and the destruction of the fuel channels – therefore they only displaced some of the water in the reactor (which was moderating the reaction) and did nothing to stem the increase of reactivity.  Once operators realized that they could not get the control rods to insert they also realized that they had completely lost control of all ability to stop the chain reaction in the core.

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Only a handful of the servo-indicators remain in the panel, but they still show that the control rods were never fully inserted into the core.

When Akimov realized that the control rods had not fully inserted he yelled out, “The reactor’s out of control!” and began attempting alternative methods trying to insert the control rods which would bring the reactor back under control, but he was unsuccessful.  Akimov and Toptunov, like many others, would later die from the radiation exposure they received that night.  With the tips of the control rods displacing some coolant water, combined with the rising temperature and boiling of the coolant water, and the lack of enough absorbing rods to slow the multiplication of neutrons in the reactor – the reaction ran out of control.

Loud banging noises began emanating from the Central Hall housing the reactor and the floor in the control room began to shake.

Inside of the reactor, water levels continued to drop, steam formation intensified, fuel assemblies began to fail and the fuel channels began to fall apart.  The pressure in the reactor increased by 15 atmospheres per second and prevented the flow of water into the core altogether – which instead began to fill up with a mixture of radioactive gases, including hydrogen and oxygen.

Within seconds at least two powerful explosions ripped through the reactor and destroyed the reactor building spreading contamination around the site and into the environment.

One analogy is that the reactor was like a car travelling down the road at 60 miles per hour approaching a stop, but as soon as the operators hit the brake (the A-Z button) to bring the car to a stop the car starts to accelerate instead of brake and speeds up until it blows up.  The operators had done what they had been instructed to do, they had tried to bring the nuclear reaction under control, but their actions unwittingly led to disaster.

Men like Akimov and Toptunov would die without knowing why the reactor blew up.  Only after the accident would it be discovered that the flaw that caused the power surge that occurred after the tips of the control rods inserted was known to some senior engineers and designers but was never fully investigated and communicated to the operators of RBMK reactors.

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One can only imagine the conditions the operators were trying to work under after the explosion while the panels and indicators were lighting up like a Christmas tree and the ground was heaving and shaking with the force of the runaway reaction in the reactor.

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The control room is silent now, it seems like even the air is quiet, and our flashlights provided the strongest source of light. For some time I just stood there, camera in my hand, but all I could do was contemplate.

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Dust was heavy in the air and clung to the rusting control panels.  Many of the components in the control room have been salvaged for use in the control rooms of the other 3 reactors at the site.

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After a while we began inspecting around the control room monitoring the radiation levels and looking for hotspots of contamination.

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We succeeded in finding several areas with alpha and beta contamination and located a few hotspots, the hottest of which was located behind the control room indicating panels in a corner.  After spending another twenty minutes monitoring the radiation levels in the control room we exited back into the blue hallways of the upper floors, traversed back down the stairwells and hallways back to the exit.

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As we exited the building we walked past three large sheets of lead and a concrete ALARA box, both of which can be used by workers to lower exposures from the gamma shine coming from the nuclear fuel in the Sarcophagus.

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We found that standing with the lead between us and the structure cut the dose rate from the gamma shine in half.

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We walked a little farther up and down the clean road monitoring the radiation levels.

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From our vantage point we could see the large yellow gantry that will remove the roof panels of the Sarcophagus someday and workers assembling the inner panels of the new confinement structure.

After we returned to the Sanitorium we went through the reverse process that we had taken when we had gotten geared up for our trip to the Sarcophagus.  After putting our clothes back on we exited the Sanitorium and went up on the roof for the best view of the Unit 4 Sarcophagus facing the west side of the structure.

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The top of the Sanitorium will offer the best view of the new confinement structure being moved over the Sarcophagus in a few years.  From this vantage point we could see the Western and Southern walls of the Sarcophagus and the roof.

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Piles of debris could still be observed just west of the new confinement structure.  To the northwest we could see the tops of the remnants of the buildings of the City of Pripyat, which we would be visiting very soon.

Stay tuned as this series of articles will be continued in Part 4.  

Chernobyl Series

Part 1 – Experiencing the Chernobyl nuclear power plant

Part 2 – Visiting the Chernobyl site and the Unit 2 control room

Part 3 – Inside the Chernobyl Unit 4 control room

Part 4 – Pripyat: City for the Future, City of the Past

Bonus Coverage – The Animals at Fukushima Daiichi and Chernobyl

All images courtesy of Carl Willis, Heidi Baumgartner, Lucas Hixson, and the Chernobyl Nuclear Power Plant

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