The Chernobyl Exclusion Zone 'I Physically Felt the Radioactivity'

The Chernobyl disaster happened over two decades ago, but its effects continue to be as present as ever. German photographer Rüdiger Lubricht spent months documenting what has been left behind in the exclusion zone which now surrounds the stricken reactor. In an interview with seen.by, he talks about his experiences.

Question: Mr. Lubricht, do you remember the final days of April, 1986?


Lubricht: Not very well, to be honest. My children were very young, so my wife and I were of course quite concerned. But at the time, I didn't see the intensity of the catastrophe to the same degree I do today.

Question: How long have you been working on your Chernobyl project?

Lubricht: For six years. During my stay in Ukraine and Belarus, I could never stay in the Chernobyl exclusion zone for longer than a week, for health reasons. Travelling around the huge area also took up a lot of the time; I had to drive for thousands of kilometers in order to find victims in evacuated villages that aren't even on maps anymore. Often, there are just a couple of houses left, hidden in the forest. Many villages were levelled to the ground immediately following the disaster.

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He says at the bottom, "I have already taken portraits of 10 of them , and hope to photograph 50 altogether. Their stories are crazy. I had originally intended to do 6 portraits a day, but I just can't manage it. I listen to their stories until I just can't take it anymore."

It reminds me of the toll on the first responders at Ground Zero, for whom nothing is also being done.

godforsaken tomb of a place and did their best to seal it off.

Words cannot express.

Makes you feel real smug and safe about nuclear energy, don't it?
:scared:

1) positive void coefficient reactors (i.e as water steams the nuclear reactors SPEEDS UP which produces more heat -> more steam -> more reactions.... etc)
2) no containment structure.... they thought they were too expensive. A containment structure would have contained Chernobyl meltdown
3) keep the reactor running despite aging and failing infrastructure.

1 + 2 + 3 = Chernobyl Exclusion Zone

Reactor 4 went online in 1983 and 1986 was when the chain reaction grew out of control. Was this reactor considered "aging" after only three years?

Don

It was growing very difficult to acquire backup parts, training, equipment, and other resources. Even nuclear fuel was getting difficult to acquire consistently resulting in reactors being run at a burnup rate they were never designed for.

A major element of the disaster was the operators wanted to test a safety procedure during shutdown. As they began to shutdown the reactor in the morning another (non nuclear) plant failed under the increased load. Given the critical need for energy (grid running at well over rated capacity due to aging infrastructure) the power distriubtion operator pleaded with Chernobyl plant to delay reactor shutdown which they did.

The problem is they day shift which was well trained in the new safety procedure was replaced by night shift which was unaware of the procedure and a new procedure was tried for the first time with an inexperienced crew in the middle of night.


However the reactor design was the most dangerous aspect.

http://en.wikipedia.org/wiki/Chernobyl_disaster#Causes


* The reactor had a dangerously large positive void coefficient. The void coefficient is a measurement of how the reactor responds to increased steam formation in the water coolant. Most other reactor designs have a negative coefficient, i.e. they attempt to decrease the heat output in the presence of an increase of the vapor phase in the reactor, because if the coolant contains steam bubbles, fewer neutrons are slowed down. Faster neutrons are less likely to split uranium atoms, so the reactor produces less power (a negative feed-back). Chernobyl's RBMK reactor, however, used solid graphite as a neutron moderator to slow down the neutrons, and the water in it, on the contrary, acts like a harmful neutron absorber. Thus neutrons are slowed down even if steam bubbles form in the water. Furthermore, because steam absorbs neutrons much less readily than water, increasing in the intensity of vaporization means that more neutrons are able to split uranium atoms, increasing the reactor's power output. This makes the RBMK design very unstable at low power levels, and prone to suddenly increasing energy production to a dangerous level. This behavior is counter-intuitive, and this property of the reactor was unknown to the crew.

* A more significant flaw was in the design of the control rods that are inserted into the reactor to slow down the reaction. In the RBMK reactor design, the lower part of the control rods was made of graphite and was 1.3 meters shorter than necessary and in the space beneath them were hollow channels filled with water. The upper part of the rod—the truly functional part which absorbs the neutrons and thereby halts the reaction—was made of boron carbide. With this design, when the rods are inserted into the reactor from the uppermost position, initially the graphite parts displace some coolant. This greatly increases the rate of the fission reaction, since graphite (in the RBMK) is a more potent neutron moderator (absorbs far fewer neutrons than the boiling light water). Thus for the first few seconds of control rod activation, reactor power output is increased, rather than reduced as desired. This behavior is counter-intuitive and was not known to the reactor operators.

Soviet reactors designs are inherently unstable. They can never be safe on a long enough timescale. It is like a cowboy riding a bull and it requires constant attention and proper response to avoid a disaster.

Western reactors have always operated on a principle of layered passive safety:
1) NEGATIVE VOID COEFFICIENT. As reactor heats up steams if formed which slows the reactor down reducing heat output
2) Gravity lowered control rods. Control rods require both a constant signal from control room and electrical power to remain up. Any failure (operator death, explosion, loss of power) will results in the electromagnets failing and control rods lower by gravity. Relying on two natural forces rather than human intervention.
3) Nuclear poison. Reactor has nuclear poison usually gadolinium nitrate is held back by heat activated seals under extreme pressure. If heat in coolant water rises in bursts the seals flooding reactor with poison. The high neutron cross section absorbs large amounts of neutrons reducing rate of fission.

These 3 systems ensure a reactor will halt even without human response. However that is only part of the safety system. Even scrammed a reactor will put out a "small" percentage of heat, usually 1%-3% in decay heat. Now when you consider a reactor may have 3000MW of heat ouput even 3% is a massive amount of heat which much be gotten rid of or the core will melt. Most of the safety systems in Western reactor designs deal with this problem. Cooling the reactor under adverse conditions (loss of pressure, loss of electrical = pumping power). Once again a layer safety system is used.

Lastly the containment structure can't prevent a core event but it can contain the damage. Cleaning up a core that has melted when the containment structure holds would be a massive and complex operation likely running into hundreds of billions of dollars. Still that pales in comparison to Chernobyl where a lack of containment structure allowed radioactive material to be spread of hundreds of kms.

To somebody totally untrained in these matters, as I am, it sounds as if you were there.

The incident has been heavily studied to improve US safety standards & protocols.
As someone with a degree in physics the underlying physics in the catastrophe are also interesting to me just as a naval catastrophe (Titanic) would be interesting to a Naval Captain.

The greatest thing we can take from Chernobyl is to learn from those mistakes. While Western Reactors don't share the flaws in the Soviet design Western humans are just as failable as Soviet ones. :) Any design which relies on quick reaction, skill, or intuition of operations is doomed to failure. Reactors run 24/7/365 for 80+ years and there are 500 of them on the planet (and likely to grow in next decade) so statistically speaking you will eventually encounter an operator who isn't as skilled or has slower reaction. Given a long enough timescale any system like that will fail.

So we need to design reactors from the view that a critical event will occur AND all humans may be dead (or worse alive to do the WRONG thing). Such a system should be able to shut down the reactor either with no human intervention or incorrect human response.

BTW: I no longer work for nuclear power industry however I do believe nuclear power is the only power source that can replace fossil fuels in our lifetime.

brought in to help test the area. She seems healthy so far. She was not one of the first responders though so no doubt she was provided with protective gear etc. She married one of our group when she met him in France.

If we insist upon using nuclear fission to generate electric power, the buildings and other safeguards are absolutely necessary. If Three Mile Island didn't have a containment building, these pictures could very well have been of Harrisburg and Philadelphia.

1) not building positive void reactors. Western reactors are negative void which means that steam actually slows down the reaction speed as water (in denser liquid form) moderates (slows down) neutrons to allow fission.
2) not using graphite in reactors. Graphite burns when exposed to oxygen & high heat. It burns extremely hot. The burning of graphite is what spread most of the radioactive material
3) not using BWR. BWR have control rods raised from the bottom. PWR has control rods lowered from top. Electromagnets stop working without power so in a power failure the control rods lower automatically by gravity
4) not design reactors without a containment structure. Western reactors containment structure can withstand a core failure and the associated pressures involved
5) no rely on a single safety system. Western reactors rely on passive safety. negative void reaction, gravity lowered control rods, containment structure, pressure activated nuclear poison, and gravity fed cooling water can all operating with no human operator and no electricity using the forces of physics to slow and cool the reactor.

It was only a matter of time before a Soviet reactor had a core failure. The likelihood was on the probability of one in 10,000 reactor years. Given the Soviets had 200 reactors that means about one in 50 years.

Existing Western Gen II reactors are rated with an average of one "core event" every 100,000 years. Given ~500 Western reactors in operation that is about one event worldwide every 200 years.

Western Gen III+ reactors like the AP1000 that are being built now are rated with likelihood of a "core event" much lower with an average of one event every 20 to 300 million years (depending on design).

The reactor vessel head on Toledo Edison's Davis-Besse reactor had internally corroded so much that all that was left was less than 1/2 inch of buckled stainless steel. We came that close to another TMI with another Babcock & Wilcox POS. Imagine if the pressure had gotten through that stainless.

We need to start looking at shutdown and possible replacements for many of these older plants, IMHO.

That is the just reactor vessel. Surrounding the reactor vessel was the containment structure. This consists of 18"-24" of steel alloy and then surrounded by 10ft on reinforced concrete.
Even IF the reactor vessel had failed the molten core would have been contained by the containment structure. There is a secondary and tertiary system to cool the damaged reactor inside the containment vessel.

Of course better designs are possible so I do agree with shutting down older plants in favor of new plants. The AP1000 for example can cool a core breach even with no electrical power using natural forces of convection & recirculation. The Emergency Cooling System on the AP1000 is called Passive Core Cooling System (PCCS) because it can cool even a ruptured reactor vessel entirely without a single watt of electricity and even if no human operator is alive on site.

The problem is that for last 20 years anti-nukers have made it virtually impossible to replace plants so existing plants will be used longer. However if the first 4 AP1000 are built ontime and on schedule in China in next couple years that may change.

;-)

The reactor could have failed, but the containment would have more than likely held.

I far prefer the Canadian CANDU reactors. China just signed a big agreement with AECL for construction of multiple CANDU reactors.

The fuel, fuel rods, supporting structure, containment rods, and assorted material inside the reactor partially melted together however the pressure was never breached.



The release of radiation in TMI was not the result of a reactor breach.

Gradual release of radiation from the containment building, as at TMI-2, with a very long wait until anyone could get into the building to survey the damage.

I wonder if TMI-1 has the same vessel head erosion problem as Davis-Besse. It is a Babcock & Wilcox of similar design.

Radiation was released by TMI due to a stuck open valve.

A pump failed in TMI and the reactor scammed however decay heat still needs to be removed.
Three backup pumps activated to cool the reactor however due to a violation of operating procedures a valve had been closed for maintenance to pumps. It took 6 minutes to get manual valve open.

During that time steam built up in reactor and a relief valve opened to release pressure. <- this is 100% of radiation from TMI came from and was well before the core melted.

What damaged the core was that relief valve didn't close so when pumps came online the coolant was pumped out of the reactor through the stuck open relief valve. At TMI two key insturments were missing
a) there was no way to know directly if the core was covered in water
b) no way to know the relief valve hadn't closed

During the time it took to discover these mistakes the reactor overheated and partially melted however it is important to note the release of radiation was NOT from the melted core. If it had then the accident would have been much worse.

The gas that escaped the relief valve was about 13 million curies. The radioactivity of the core was on the order of 10 billion curies.

The plant as economic entity would be over. It would never generate a single kwh or power again. There was a rush at Chernobyl because one the core was hot, it was burning, and it was venting into the atmosphere. None of that will exist if the core is contained by the containment structure.

So the first thing you do is wait. Monitor and come up with a plan. The containment structure has multiple "airlock" type entrances for persons and heavy equipment.

Most of the "radioactive gas" will not be radioactive gas. It will be radioactive fallout suspended in air and/or steam. True radioactive gases can occur (namely xenon) but they are relatively harmless most being beta emitters and having short half life. The radioactive fallout inside the containment building is of more danger but with time it will settle into cooling water which fills the bottom 1/3 of the containment building.

Many of the isotopes have very short lived half lives. Iodine-131 (a very bad one for humans) has half life of 8 days. So after 8 days radioactivity is cut in half. Half of the I-131 decays into Xe-131 which is no radioactive. 8 days later (16 total) it is down to 25%. So after a year that is 45 half lives and 1/20 trillionth of the radioactive I-131 remains.

So once enough time has passed (to allow decay of short lived isotopes, cooling of reactor which takes about 30 days, and fallout to settle) you will need to remove all the waste. If you wait a year the radioactive output of the waste will have be reduced by a factor of 10 (10% remains). If you wait a decade it will be reduced by a factor of 100 (only 1%) remains. However past that waiting won't do much more good. To reduce radioactive output by another factor of 10 (0.1% remaining) will take another 100 years. Another 10x factor would take 1000 years. Beyond that it slows down considerably. So likely you would want to wait at least 1 year and preferably 10 years to reduce output to a safe(r) level.

The contaminated coolant water can be evaporated slowly to separate the slightly radioactive H20 with the more radioactive material settled in it. The sediment can be casked up along with any solid waste. The damaged reactor will also be casked up. Then entire containment structure can be thoroughly decontaminated, dried, sealed, and eventually returned to a greenfield status.

With an intact containment structure the greatest asset is time.

What happens when wind farm produces say 100MW but the grid demands 120MW? Blackouts?

What people fail to realize is that despite the fact that you pay a flat rate for electricity ($0.11 kwh in VA) that isn't how it is produced.

Demand varies constantly. Right now on a particular grid it might be 4800 MW, in an hour it might be 4200 MW, tomorrow at noon it might be 6200 MW.

So is supply (powerplants) exceed demand which plants produces the power.

Well nuclear plants have very low per unit costs and high fixed costs so they must run as close to 24/7/365 as possible. They tend to bid very low like $0.003 per kwh.

Other baseline plants (coal) might outbid nuclear slightly $0.035. They get a little more per kwh but the risk not running 24/7. Given coal has a fixed cost per ton they can't bid quite as low without selling power at a loss.

Now peaking plants often run <50% of the time. So they bid much higher $0.05-$0.09 per kwh. When demand is low they lose the auction and don't run. When demand is high they win and provide power (at double to triple the cost of nuclear plants).

Solar & wind can compete with peaking plants. Given they have no fuel requirements they can underbid peaking plants. They are a long long long long long long way away from being able to replace baseline power.

However due to the large range in wholesale power prices solar, wind, and other renewable can take 90% of the peaking plant market. Now due to the fact that they are variable peaking plants will still be needed to constantly load balance the output with demand.

If Carbon tax was added to fossil fuels likely within a decade wind & solar could replace natural gas and coal completely (except for peaking to balance supply with demand).

However economics isn't the only issue.

Electricity is a unique commodity. It can't be easily or cheaply stored in large quantities, customers can't wait for it (turn on lights and get a notice you will have power in 7-10 minutes), demand varies constantly making supply very difficult. Also supply must at all times exceed demand or we get brownouts.

The unique nature of electricity means we can't go past about 30%-40% variable power sources (like wind & solar) without some unique soluations. Now even 30%-40% renewable power would be a major accomplishment but 100% wind & solar is a pipedream.

None of this means I am anti-renewable. I am 100% pro renewable but not everything is a nail (solar being the hammer). Adressing any future energy requirements will likely require a combination of solutions. Until someone figures out a way to replace basload (not peaking) power with solar/wind/tidal that means nuclear, hydro or geothermal.

I know solar panels can't replace everything but it can put a dent in power delivery outside the home.

Currently <1% of US electrical production is by Solar. I hope in my lifetime that becomes 10% - 15%. If we can do that it will be a major achievement.

:thumbsup: