a reactor may be taken offline safely in a relatively short period of time and other fairy talesgreenspun.com : LUSENET : Electric Utilities and Y2K : One Thread
the best minds accept the statement by the nrc that the nuclear plants may be shut down safely in a short period of time, and i say... so what?
what does that mean? the plants may be shut down safely? when? when it is too damn late?
what type of situation is going to arise that would call for the nrc to take a nuke down quickly and safely... a problem? well, i put forth the position that at that point in time it may be too late.
here is how tmi was turned off... 8 seconds after the feedwater valves failed to work... so what? what good did it do? the reactor was shut down but the problems persisted.
this from the president's commission report at the tmia website
In the parlance of the electric power industry, a "trip" means a piece of machinery stops operating. A series of feedwater system pumps supplying water to TMI-2's steam generators tripped on the morning of March 28, 1979. The nuclear plant was operating at 97 percent power at the time. The first pump trip occurred at 36 seconds after 4:00 a.m. When the pumps stopped, the flow of water to the steam generators stopped. With no feedwater being added, there soon would be no steam, so the plant's safety system automatically shut down the steam turbine and the electric generator it powered. The incident at Three Mile Island was 2 seconds old.
the production of steam is a critical function of a nuclear reactor. Not only does steam run the generator to produce electricity but also, as steam is produced, it removes some of the intense heat that the reactor water carries.
When the feedwater flow stopped, the temperature of the reactor coolant increased.The rapidly heating water expanded. The pressurizer level (the level of the water inside the pressurizer tank) rose and the steam in the top of the tank compressed. Pressure inside the pressurizer built to 2,255 pounds per square inch, 100 psi more than normal. Then a valve atop the pressurizer, called a pilot-operated relief valve, or PORV, opened -- as it was designed to do - - and steam and water began flowing out of the reactor coolant system through a drain pipe to a tank on the floor of the containment building. Pressure continued to rise, however, and 8 seconds after the first pump tripped, TMI-2's reactor--as it was designed to do-- scrammed: its control rods automatically dropped down into the reactor core to halt its nuclear fission.
Less than a second later, the heat generated by fission was essentially zero. But, as in any nuclear reactor, the decaying radioactive materials left from the fission process continued to heat the reactor coolant water. This heat was a small fraction --just 6 percent -- of that released during fission, but it was still substantial and had to be removed to keep the core from overheating. When the pumps that normally supply the steam generator with water shut down, three emergency feedwater pumps automatically started. Fourteen seconds into the accident, an operator in TMI-2's control room noted the emergency feed pumps were running. He did *NOT* notice two lights that told him a valve was closed on each of the two emergency feedwater lines and thus no water could reach the steam generators. One light was covered by a yellow maintenance tag. No one knows why the second light was missed.
now, what do we have so far? a] a feedwater pump stops, malfunctions...whatever.
b] no feedwater no steam, steam turbine and generator shut down.
c] no steam sufficient heat is not being removed.
d] no feedwater temperature of the reactor coolant increased.
e]high temperature of the reactor coolant caused the water to expand and steam to be compressed.
f]pressure rose, valve opened, steam and water poured out.
g]pressure continued to build so reactor scrammed -- its control rods automatically dropped down into the reactor core to halt its nuclear fission. now is it considered off? i certainly hope not... things were just starting to happen. does someone want to explain this to me?
what concerns me is what would require a reactor to be taken offline quickly. if it is what i think it is we are indeed in deep yogurt.
for years the nrc maintained the position that the electrical grid *must* be stable to insure the safety of the nukes... now we need the nukes to keep the grid stable.
but, not to worry, if need be we can take a nuke down quickly and safely.
-- Anonymous, July 10, 1999
First, I'm with you in being concerned about the nukes not being able to properly shut down if the power fails on the grid, or if compound problems create a scenario similar to the TMI incident, or for that matter, Chernobyl, where they just plain lost control of it on manual. While I have no doubt that many, even most, nukes can be shutdown without incident, there are bound to be a few bad mistakes.
Second, I think we are preaching to the choir about this matter. I strongly believe that the decision has been made at the highest level of the government to keep them running, even though it is risky. The potential problem of a grid collapse due to not enough generator capacity at the rollover time is probably being viewed as far more serious than a nuke shutdown incident. I think risk management is going on here, and while we know that a nasty situation would ensue from a runaway nuke, an equally or worse nasty situation would develop if major cities, or military bases, lost their power. Risk management. War is hell. Either way people die.
-- Anonymous, July 10, 1999
Can someone either confirm or dismiss this situation? If a nuclear plant is safely shut down, and the diesel generators are successful in keeping the cooling waters circulating, the power grid is still needed to restart the plant? So, if sufficent offsite power is not available, the nuclear plant is out of service?
-- Anonymous, July 10, 1999
It's pretty simple actually. Think of it this way if they botch the shutdown in any way really bad things happen fast.
I have to say I think Gordon is 100% right on this one. However, I disagree with the administrations approach on this one. A shutdown would be a known entity, a bird in the hand (albeit an ugly vulture) whereas the nuke situation may eventually result in the same scenario as a grid shutdown PLUS a nuclear disaster. In taking this approach the admin is probably factoring in at least one booboo. They look at casualty estimates all the time during wartime, this would be no different. The problem here will be what they call "collateral damage". Loosely translated, that means "lots of dead bubbas".
Unfortunately bubba don't read anything but the National Enquirer and People magazine, so he has no idea that his life is being gambled.
I'm grateful to the members of this forum for helping me to understand all of these issues from both sides so that I can make my own decisions. We are extremely fortunate to have this pool of information from both sides. I know I'll be at least 350 miles from the nearest Nuke come New Years. I've an aversion to being collateral.
-- Anonymous, July 11, 1999
I am glad to "happen" on this discussion (Thanks to a friend sending this link) --you folks are chewing some of most important questions clouding New Year. We at NIRS -- Nuclear Information & Resource Service http://www.nirs.org submitted three official "petitions for rulemaking" to NRC last December. They are posted on our site -- but in a nutshell asked for 1) a criteria of Y2K compliance in order for the regulator to judge the reactors, including a strict requirement of testing reactor systems -- both computers and chips and having those tests validated (NRC has none of these); 2) drills with Y2K scenarios for worker and emergency responder training at every reactor; 3) and maybe most important, certification that the diesel generators are working, have 60 days fuel and the fuel pools are hooked to them also for back-up cooling, we also call for additional back-up power for cooling systems.
To date the NRC has not responded. It is clear from their actions that they have already rejected our petitions, but cannot afford the bad press that an official rejection would bring.
Did you know that their contingency plan is to allow the on-site inspector to issue exemptions from any license requirement that the operator needs in order to maintain "operability."
It is insane to think that we need the 19% that nukes provide on a weekend that is likely to be 50% demand or less. Nukes are net 18% because uranium enrichment is the largest singe electrical user -- sucking a full 1% of the juice. So let's take what the Japanese are calling a WORLD ATOMIC SAFETY HOLIDAY -- Y2K WASH is their campaign...they are the first country with nuclear power to greet the New Year. Their government's policy is to follow the US policy -- but our policy is to watch the nukes across the time zones and respond...so the Japanese concerned citizens "get it" -- they are being treated as a nuclear Guinea Pig by the US, AGAIN.
The back-up power issue is in my mind completely mismanaged by both the industry and the NRC. We have been tracking diesel generator problems at these sites, and they are regular and on-going. The tests required is to start them up for 1/2 hour once a month. If they are needed, how long will they have to run? Estimates on how long active cooling is needed run from several months to 5 years...how much fuel do they keep on site? One week. How long would a Y2K caused outage last? It is cheap to add a robust, reliable -- ideally renewable energy source just to run the on-site cooling and monitoring equipment. Most people do not understand that a nuke cannot power itself -- at least in the US. Renewable sources such as solar and wind turbines coupled with battery reservoirs would not require refueling and is a beautiful image of transition out of the era of poisoned power. Even fuel cells or combustible gas turbines would be more efficient and more reliable than diesel generators.
I very much doubt that there will be coast to coast black-out. Fo rone thing, the system West of the Rockies is completely independent of the grid to the East -- so John Koskinen gets off easy when he says the grid is fine we won't have a national back-out. He is willing to say we may have local and regional black-outs. It just so happens that the oldest and most vulnerable Eastern grid has 3/4 of the US reactors in it. I maintain that a planned, temporary -- say 12 hour black-out in areas like Chicago and SC where there is little other juice would be better than the irreversible and permanent sacrifce not only of lives, but air and water and land that a major Chernobyl-style reactor accident causes.
FYI recent reanalysis of Three Mile Island health data shows that actual doses were in some cases 600 -- 900 times higher than previously reported, and there were excess cancers in Harrisburg attributable to the accident. (Steve Wing, et al 1994)
We should remember that there are 433 reactors in the world. Multiple reactor accidents would have global consequences.
I do think we have a chance still to impact these policy decisions. There will be a G-8 meeting on Y2K in Berlin in early September. If we each network whatever connections we have to people who can influence such a meeting...and get it out there that highly radioactive assets are not worth a whole lot, then maybe those who can pick up the phone and make that one call to that office at the top will do so.
Why in July do you accept one or more melt-downs in January. Better Active Today Than Radioactive Tomorrow!
So, we need to have these systems completely remediated adn tested for Y2K compliance whether they are on-line or off, exactly because of what others have written here. Then we need them off-line at least for the roll-over. Keep it simple folks. There may be huge electrical fluctuations -- so lets just focus on keeping each core cooled and not melting down. And we need back-up power that is reliabel and not limited to just a few days. If we can do this, we stand a good chance of avoiding any big problem. There are very few countries where the nukes have to stay on line to keep the grid up.
-- Anonymous, July 13, 1999
Bravo, many thanks for an eloquent/educational post with much to consider.
(The cooling issue - there seem to be quite a few variables involved... Isn't sadly notable how the CRUCIAL back-up possibilities of wind&solar finally make themselves fully apparent!!
//But it is difficult to believe that the Japanese will make their decisions based on this country's. The only "Guinea Pigs" on this planet - are ALL of us at the mercy of a economic/world government system that's been controlled by big oil interests, etc. ...that should have been doing so much more with solar & wind all along.
//No nukes in Eastern Australia or NZ?? Lucky them.)
-- Anonymous, July 13, 1999