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Hundreds Still Live In The 'Exclusion Zone' Around Chernobyl (bbc.com)
This weekend the BBC reports on the site of the Chernobyl nuclear plant explosion -- where "robotic cranes are dismantling 33-year-old, radioactive wreckage" -- investigating an area of more than 4,000 square kilometres [2,485 square miles] that's been abandoned since 1986. "That could be about to change..."
An anonymous reader summarizes their report: "Every community within a 30km radius [18.9 miles] of the plant was evacuated and abandoned; no one was allowed to return here to live." Yet the BBC visits a tiny community of 15 who reclaimed their homes in 1986 -- part of a population of 200 "self-settlers" deep in the exclusion zone, "an ageing population cut off from the rest of the country.... Almost every family forced to leave here was given an apartment in a nearby town or city. For Maria and her [88-year-old] mother, though, this cottage, with the garden wrapped around it, was home. They refused to abandon it. 'We weren't allowed to come back, but I followed my mum.'"
Parts of the exclusion zone in Ukraine and Belarus have become "a post-human nature reserve", home to prowling wolves and dozens of wild horses. Yet Professor Jim Smith from the UK's University of Portsmouth explains that "Most of the area of the exclusion zone gives rise to lower radiation dose rates than many areas of natural radioactivity worldwide." In fact, the abandoned nuclear-worker city of Pripyat was recently deemed safe to visit for short periods, "and has now become one of Ukraine's most talked about tourist attractions. An estimated 60,000 people visited the exclusion zone last year, keen to witness the dramatic decay."
And beyond the 18.9-mile line is Narodichi, a town of more than 2,500 people, where people "were quietly allowed to return home a few months after the disaster." Still considered an officially contaminated district -- and still in the "exclusion zone" -- it's a semi-abandoned area where all agriculture is banned, and the land can't be developed. 130 children attend Narodichi's kindergarten, but the kindergarten manager says half their parents are unemployed, "because there is nowhere to work." One of the least-contaminated areas in the exclusion zone, "Three decades of research have concluded that much of it is safe - for food to be grown and for the land to be developed." The BBC argues that "Fear of radiation could actually be hurting the people...far more than the radiation itself. "
An anonymous reader summarizes their report: "Every community within a 30km radius [18.9 miles] of the plant was evacuated and abandoned; no one was allowed to return here to live." Yet the BBC visits a tiny community of 15 who reclaimed their homes in 1986 -- part of a population of 200 "self-settlers" deep in the exclusion zone, "an ageing population cut off from the rest of the country.... Almost every family forced to leave here was given an apartment in a nearby town or city. For Maria and her [88-year-old] mother, though, this cottage, with the garden wrapped around it, was home. They refused to abandon it. 'We weren't allowed to come back, but I followed my mum.'"
Parts of the exclusion zone in Ukraine and Belarus have become "a post-human nature reserve", home to prowling wolves and dozens of wild horses. Yet Professor Jim Smith from the UK's University of Portsmouth explains that "Most of the area of the exclusion zone gives rise to lower radiation dose rates than many areas of natural radioactivity worldwide." In fact, the abandoned nuclear-worker city of Pripyat was recently deemed safe to visit for short periods, "and has now become one of Ukraine's most talked about tourist attractions. An estimated 60,000 people visited the exclusion zone last year, keen to witness the dramatic decay."
And beyond the 18.9-mile line is Narodichi, a town of more than 2,500 people, where people "were quietly allowed to return home a few months after the disaster." Still considered an officially contaminated district -- and still in the "exclusion zone" -- it's a semi-abandoned area where all agriculture is banned, and the land can't be developed. 130 children attend Narodichi's kindergarten, but the kindergarten manager says half their parents are unemployed, "because there is nowhere to work." One of the least-contaminated areas in the exclusion zone, "Three decades of research have concluded that much of it is safe - for food to be grown and for the land to be developed." The BBC argues that "Fear of radiation could actually be hurting the people...far more than the radiation itself. "
Is that a joke? I have to assume it is. Hiroshima ground zero is marked with a fairly small plaque on a boring standard Japanese side-street next to apartment buildings, businesses and restaurants. The one in Nagasaki is a small park with apartment buildings and a busy street about 150' away.
The design of the plant at Chernobyl used a positive void coefficient. Basically, when the cooling water starts to boil (creating voids in the water), that increases the rate of nuclear fission. No western nuclear plant was ever designed like this because of how stupidly dangerous it is. All western nuclear plants use a negative void coefficient - the cooling water boiling slows down the rate of fission. An accident like Chernobyl could never happen at a western plant. The Soviets were trying to get energy for as cheap as possible and cut all sorts of corners designing their plants, including using a positive void coefficient .
Chernobyl began as a test where they intentionally shut down the automatic safety systems, then didn't react in time when the rate of fissioning began to go out of control. Due to the positive void coefficient design, once the boiling water began boiling, the heat generation began to increase exponentially. The fuel vaporized and exploded, blowing the reactor and containment building apart, and throwing radioactive debris and vapor into the atmosphere and countryside.
The accident at Three Mile Island was actually pretty similar in terms of buildup. They shut down a bunch of safety systems for a test, then didn't monitor the instrument readings closely enough (or more likely, the people monitoring them weren't trained well enough to understand what the readings meant - Homer Simpson as incompetent nuclear plant operator is actually a reference to TMI). The temperature went up, the cooling water boiled, and the fissioning stopped. The increased temperature was enough to melt the fuel rods, turning the reactor into useless slag. But it was all contained within the steel pressure vessel exactly like designed (there's a second reinforced concrete containment vessel around the pressure vessel in case it fails). The concern at the time was that a reaction between the fuel rod cladding and water had created hydrogen gas at sufficient pressure to crack both containment vessels, so they evacuated around the plant out of an abundance of \caution. But it turned out not to have been a concern as the hydrogen vented. It's a tiny molecule so can permeate through things that are designed to contain water and radioactive materials. (It's the reason the buildings at Fukushima blew apart. There's supposed to be a vent or fan which exhausts hydrogen into the atmosphere, but apparently that wasn't working at Fukushima so it built up until it reacted with atmospheric oxygen in an explosion that blew apart the exterior building. It did not affect the pressure vessel or the concrete containment vessel.)
The comparison I like to draw when people point to Chernobyl as an example of problems with nuclear power is Banqio. The worst power generation-related accident in history was actually the failure of a series of hydroelectric dams. During intense rain, a series of earthen dams used to hold water for generation at a hydroelectric power plant failed. The resulting flood and devastation killed about 170,000 people, destroyed nearly 6 million buildings, and left 11 million people homeless. But no western country uses earthen dams for hydroelectric power. So citing Banqio as an example of why hydroelectric power is dangerous and shouldn't be used, is like citing Chernobyl as an example of why nuclear power is dangerous and shouldn't be used. They're both irrelevant outside of the Communist bloc, since the rest of the world never did anything so stupidly dangerous.
Actually, at the time of the explosion, the operators were doing things FAR from standard, and in fact, the precipitating event was an operation explicitly prohibited under any circumstances in order to do something they weren't supposed to attempt.
More specifically, they were SUPPOSED to bring the reactor down to a low output and stabilize it there, then scram the reactor to see if residual steam and inertia in the system would provide sufficient power to safely shut it down. In order to do the test, several safeties were disabled.
The test was supposed to happen during the day shift, but high power demands meant they had to wait. This left the less experienced night crew to carry out the test. They probably should have postponed, but that would anger the (seriously dysfunctional) upper management.
First stem, they reduced power, but they reduced it too much. So they tried to bring power back up to the starting condition but the reactor wouldn't do it. This shouldn't have been a surprise, when reactor power is reduced by a large amount, the production of neutron absorbing poisons temporarily outstrips their "burn off" from excess neutrons. Rather than wait the prescribed 24-48 hours for the poisons to decay, they decided to attempt to burn off the poisons by withdrawing more control rods (a prohibited procedure)
Still having no success, they eventually withdrew ALL of the control rods (an absolutely forbidden procedure) leaving the reactor in a VERY unstable condition. In fact, it was primed for a runaway positive feedback. As power output started rising rapidly, they attempted to drive the conntrol rods back in, but it wasn't possible to do it fast enough, so the reactor went to many times it's maximum rating and then part of the core exploded (a flash steam explosion, not a nuclear explosion) and much of the core was ejected through the top of the reactor.
So it was an inherently dangerous reactor design, disabled safeties, and undertrained and inexperienced operators doing all the don'ts that resulted in the disaster.
The reactor's design was a big contributor as well. For one, it had a positive void coefficient. Meaning if the coolant formed a void, power output would increase. Reactor designs approved in the rest of the world tend to have a negative void coefficient. The control rods were (for some odd reason) carbon tipped, meaning that the first few feet of the rod INCREASE output by improving moderation. It had no actual containment building, just standard industrial sheet metal.