Originally Posted by alnorth:
I don't want to be a completely unfair nuclear homer, so I will admit that the situation in these spent fuel rod pools is a concern. They have the potential to emit far less radiation than the troubled reactors, but they are more dangerous because at least the reactors are encased in concrete. If the water in these pools burn out, then you've got still-warm and still-dangerous fuel rods completely exposed to the environment. If the area is evacuated several kilometers that still wont mean anything to anyone, but they really need to get those pools under control.
Turn on CNN: Anderson Cooper got his finger on the pulse... [Reply]
Originally Posted by 'Hamas' Jenkins:
That's a whole lot of words to put into my mouth. What I was speaking of was the long term effects of prolonged exposure, even a minuscule amount over a period of time.
There was a prolonged study done of over 300,000 workers at the Hanford site that was abruptly defunded whenever the initial results of the study were published. The reason was that the stated "safe doses" were anything but, and the DOE and the subcontractors who ran the facility, namely GE, didn't want to assume culpability for it.
fair enough, my apologies, but your intent wasn't clear. The damage was small and we've learned quite a bit since then. [Reply]
Originally Posted by alnorth:
Quick reality check, after some quick research. I'm not a nuclear expert, but this info is readily available through reliable sources.
First, radiation is usually measured in Sieverts (Sv) 1 full Sv = 1,000 mSv = 1 million microSv. Radiation exposure is also often measured in Sieverts per hour, or Sv/h, mSv/h, microSv/h
There are generally two hazards to radiation exposure. 1) Dying quickly due to acute radiation exposure 2) Dying within 5-30 years due to cancer caused by radiation.
Fatal acute radiation exposure (resulting in death within days or weeks) = roughly 1 full Sv/h for 5 hours, or more than 6 Sv/day. (Apparently the threshold for having any immediate symptoms at all is about 0.25 Sv/day. If you get less than 0.25 Sv/day, you wont even feel nausea, but might have some increased cancer risk)
Estimated cancer risk from radiation = about an extra 5% per full Sv per year, but if you pick up less than 100 mSv in a year, the research seems to indicate that doesn't increase your chances. (So, at 100 mSv in a year, you have about a half percent chance of getting cancer from that radiation exposure)
Exposure examples
Eating a banana = 0.1 microSv
chest CT scan = 6-18 mSv
background radiation most people experience just walking around = 3 mSv/year
Total exposure by the average American = about 6 mSv/year = 6,000 microSv/year
Total additional exposure that could be expected by people on the west coast if the reactors in Japan all dramatically explode in a firey ball of death (which is extremely unlikely): maybe another 1 or 2 microSv
Exposure faced by the workers currently risking their lives in the Japanese facility: well, the absolute peak was briefly about 400 mSv/h, but it seems to mostly be about 8 or 9 mSv/hr. Of course, if it melts down and if the concrete container also fails, those workers could get a fatal acute dose within minutes depending on where they are.
Current exposure at the gate to the facility at the Japanese reactors = 0.6 mSv/hr
Exposure in Tokyo = seems to be about 2 microSv/hr
Total exposure if you lived within the 30 km evacuation radius of Chernobyl when it blew up and didn't leave for a few weeks = varies depending on where in that radius you mostly lived, but the accumulated dose for people who were near but weren't at the disaster usually seemed to max out at about 150 mSv.
Originally Posted by alnorth:
Those fuel rod pools aside (seriously, get some water-dropping helicopters if you have to, they aren't that hot and this shouldn't be hard), here's the likely worst-case scenario.
This one reactor melts down. The concrete container holds long enough for the nuclear fuel to be safely encased. Beyond a mile or so, the radiation is not much. After a few days, the radiation is next to nothing even when you stand right next to the facility. This company pays for an expensive cleanup operation. A few workers from the nuclear power plant get cancer and die after a few decades. The world moves on, no one is really hurt. Some silly americans continue to panic over something that isn't as dangerous as coal power.
Originally Posted by alnorth:
we've learned quite a bit since then.
Yes, we have:
HAZARDS OF BOILING WATER REACTORS IN THE UNITED STATES
BACKGROUND
Of the 110 operational nuclear power reactors in the United States, thirty-five are boiling water reactors (BWR). General Electric is the sole designer and manufacturer of BWRs in the United States. The BWR's distinguishing feature is that the reactor vessel serves as the boiler for the nuclear steam supply system. The steam is generated in the reactor vessel by the controlled fissioning of enriched uranium fuel which passes directly to the turbogenerator to generate electricity.
LACK OF CONTAINMENT INTEGRITY DURING A NUCLEAR ACCIDENT
The purpose of a reactor containment system is to create a barrier against the release of radioactivity generated during nuclear power operations from certain "design basis" accidents, such as increased pressure from a single pipe break. It is important to understand that nuclear power plants are not required by the Nuclear Regulatory Commission (NRC) to remain intact as a barrier to all possible accidents or "non-design basis" accidents, such as the melting of reactor fuel. All nuclear reactors can have accidents which can exceed the design basis of their containment.
But even basic questions about the the GE containment design remain unanswered and its integrity in serious doubt. For example, eighteen of these BWRs use a smaller GE Mark I pressure suppression containment conceived as a cost-saving alternative to the larger reinforced concrete containments marketed by competitors. A large inverted light-bulb-shaped steel structure called "the drywell" is constructed of a steel liner and a concrete drywell shield wall enclosing the reactor vessel. The atmosphere of the drywell is connected through large diameter pipes to a large hollow doughnut-shaped pressure suppression pool called "the torus", or wetwell, which is half-filled with water. In the event of a loss-of-coolant-accident (LOCA), steam would be released into the drywell and directed underwater in the torus where it is supposed to condense, thus suppressing a pressure buildup in the containment.
However, as early as 1972, Dr. Stephen Hanuaer, an Atomic Energy Commission safety official, recommended that the pressure suppression system be discontinued and any further designs not be accepted for construction permits. Shortly thereafter, three General Electric nuclear engineers publicly resigned their prestigious positions citing dangerous shortcomings in the GE design.
An NRC analysis of the potential failure of the Mark I under accident conditions concluded in a 1985 report that Mark I failure within the first few hours following core melt would appear rather likely."
In 1986, Harold Denton, then the NRC's top safety official, told an industry trade group that the "Mark I containment, especially being smaller with lower design pressure, in spite of the suppression pool, if you look at the WASH 1400 safety study, you'll find something like a 90% probability of that containment failing." In order to protect the Mark I containment from a total rupture it was determined necessary to vent any high pressure buildup. As a result, an industry workgroup designed and installed the "direct torus vent system" at all Mark I reactors. Operated from the control room, the vent is a reinforced pipe installed in the torus and designed to release radioactive high pressure steam generated in a severe accident by allowing the unfiltered release directly to the atmosphere through the 300 foot vent stack. Reactor operators now have the option by direct action to expose the public and the environment to unknown amounts of harmful radiation in order to "save containment." As a result of GE's design deficiency, the original idea for a passive containment system has been dangerously compromised and given over to human control with all its associated risks of error and technical failure.
DETERIORATION OF BWR SYSTEMS AND COMPONENTS
It is becoming increasingly clear that the aging of reactor components poses serious economic and safety risks at BWRs. A report by NRC published in 1993 confirmed that age-related degradation in BWRs will damage or destroy many vital safety-related components inside the reactor vessel before the forty year license expires. The NRC report states "Failure of internals could create conditions that may challenge the integrity the reactor primary containment systems." The study looked at major components in the reactor vessel and found that safety-related parts were vulnerable to failure as the result of the deterioration of susceptible materials (Type 304 stainless steel ) due to chronic radiation exposure, heat, fatigue, and corrosive chemistry. One such safety-related component is the core shroud and it is also an indicator of cracking in other vital components through the reactor made of the same material.
Core Shroud Cracking
The core shroud is a large stainless steel cylinder of circumferentially welded plates surrounding the reactor fuel core. The shroud provides for the core geometry of the fuel bundles. It is integral to providing a refloodable compartment in the event of a loss-of-coolant-accident. Extensive cracking of circumferential welds on the core shroud has been discovered in a growing number of U.S. and foreign BWRs. A lateral shift along circumferential cracks at the welds by as little as 1/8 inch can result in the misalignment of the fuel and the inability to insert the control rods coupled with loss of fuel core cooling capability. This scenario can result in a core melt accident. A German utility operating a GE BWR where extensive core shroud cracking was identified estimated the cost of replacement at $65 million dollars. The Wuergassen reactor, Germany's oldest boiling water reactor, was closed in 1995 after wary German nuclear regulators rejected a plan to repair rather than replace the reactor's cracked core shroud.
Rather than address the central issue of age related deterioration, U.S. BWR operators now opt for a dangerous piecemeal approach of patching cracking parts at least cost but increased risk.
Originally Posted by 'Hamas' Jenkins:
This study was done in the 1980s, not the 1950's.
The incompetent water pollution from the government was done in the 50's. At least according to my quick research, I remembered seeing that it peaked in 1954 or something like that. I presumed that the study focused on people.
Either way, it remains that we've learned a thing or two since the 50's and the 80's, and the fatality scoreboard is still a few thousand for nuclear and a hell of a lot more for coal. [Reply]
Originally Posted by alnorth:
Those fuel rod pools aside (seriously, get some water-dropping helicopters if you have to, they aren't that hot and this shouldn't be hard), here's the likely worst-case scenario.
This one reactor melts down. The concrete container holds long enough for the nuclear fuel to be safely encased. Beyond a mile or so, the radiation is not much. After a few days, the radiation is next to nothing even when you stand right next to the facility. This company pays for an expensive cleanup operation. A few workers from the nuclear power plant get cancer and die after a few decades. The world moves on, no one is really hurt. Some silly americans continue to panic over something that isn't as dangerous as coal power.
the fuel rod pools are not open to the atmosphere, they are in a containment area, and therefore cannot be replenished by helicopter.
And concrete or not, if those reactors melt down, they will LITERALLY melt through anything in the way - steel, concrete, kryptonite. That is the real hazard. [Reply]
It will never stop being hilarious to me that we demand absolute zero-death perfection but we blithely shrug our shoulders when tens or hundreds of thousands die due to coal power.
It all comes back to our caveman brain. We can understand rocks burning and we can accept the harm of dirty air, but nuclear power is frightening voodoo magic. [Reply]
