Reassessing the frequency of partial core melt accidents

[kristopher]

Reassessing the frequency of partial core melt accidents
April 27th, 2011 by Thomas B. Cochran, National Ressources Defense Council

There have been enough partial core-melt accidents that we can ask whether the operational nuclear power plants throughout the world are safe enough as a group.

12 nuclear power reactors have experienced fuel-damage or partial core-melt accidents: The Sodium Reactor Experiment (SRE), Stationary Low-Power Reactor No. 1 (SL-1), Enrico Fermi Reactor-1, Chapelcross-2, St. Laurent A-1 and A-2, Three Mile Island-2, Chernobyl-4, Greifswald-5 and Fukushima Daiichi-1, -2 and -3. (see Table 1 in paper). Eleven of these (all except SL-1) produced electricity and were connected to the grid during some period of their operation, and all are now permanently shut down. In assessing the historical core melt frequency among nuclear power reactors, the number counted depends on how the issue is framed. SL-1 is excluded because it was an experimental reactor, and the design was abandoned after the accident. Although it was the first U.S. reactor to supply electricity to the grid, the SRE could be excluded because it was primarily a research reactor. Chapelcross-2 and St. Laurent A1 and A2 were dual use military reactors, producing plutonium for weapons and electricity for civilian use. From the data available to this author it is unclear whether any fuel actually melted in Greifswald-5. In five cases then, i.e., SRE, Chapelcross-2, St. Laurent A1 and A2, and Greifswald-5, the fuel melt or damage did not result in immediate closure of the plant; rather the damage was repaired and the reactor was restarted.

Worldwide, there have been 137 nuclear power plants that have been shut down after becoming operational with a total generating capacity of about 40,000 MWe and 2,835 reactor-years of cumulative operation (1). Thus, one in twelve <137/11 = 12.5> or fourteen shut down power reactors experienced some form of fuel damage during their operation. Of the power reactors that have been shut down one in 23 <137/6 = 22.8> were shut down as a direct consequence of partial core melt accidents; one for every 500 reactor-years <2,835/6 = 472.5> of operation. Only about seven of eight giga-watts (GW) <40,000-5,250.5)/40,000 = 0.87≈ 7/8> of nuclear power plant capacity have been closed without experiences a fuel damage accident. One out of 13 GW <40,000/3,011 = 13.3> of nuclear power plant capacity have been closed as a direct result of a fuel melting accident.

Worldwide, there have been 582 nuclear power reactors that have operated approximately 14,400 reactor-years (1). Thus, to date, the historical frequency of core-melt accidents is about one in 1,300 reactor-years <14,400/11 = 1,309>, or excluding SRE, about one in 1,400 reactor-years...

http://www.energypolicyblog.com/2011/04/27/reassessing-the-frequency-of-partial-core-melt-accidents/


- 12 nuclear power reactors have experienced fuel-damage or partial core-melt accidents: The Sodium Reactor Experiment (SRE), Stationary Low-Power Reactor No. 1 (SL-1), Enrico Fermi Reactor-1, Chapelcross-2, St. Laurent A-1 and A-2, Three Mile Island-2, Chernobyl-4, Greifswald-5 and Fukushima Daiichi-1, -2 and -3. (see Table 1 in paper).


- Eleven of these (all except SL-1) produced electricity and were connected to the grid during some period of their operation, and all are now permanently shut down.


- In assessing the historical core melt frequency among nuclear power reactors, the number counted depends on how the issue is framed. SL-1 is excluded because it was an experimental reactor, and the design was abandoned after the accident. Although it was the first U.S. reactor to supply electricity to the grid, the SRE could be excluded because it was primarily a research reactor. Chapelcross-2 and St. Laurent A1 and A2 were dual use military reactors, producing plutonium for weapons and electricity for civilian use.


- From the data available to this author it is unclear whether any fuel actually melted in Greifswald-5.


- In five cases then, i.e., SRE, Chapelcross-2, St. Laurent A1 and A2, and Greifswald-5, the fuel melt or damage did not result in immediate closure of the plant; rather the damage was repaired and the reactor was restarted.


- Worldwide, there have been 137 nuclear power plants that have been shut down after becoming operational with a total generating capacity of about 40,000 MWe and 2,835 reactor-years of cumulative operation (1).


- Thus, one in twelve ... or fourteen ... shut down power reactors experienced some form of fuel damage during their operation.


- Of the power reactors that have been shut down one in 23 ... were shut down as a direct consequence of partial core melt accidents; one for every 500 reactor-years ... of operation.


- Only about seven of eight giga-watts (GW) ... of nuclear power plant capacity have been closed without experiences a fuel damage accident.


- One out of 13 GW ... of nuclear power plant capacity have been closed as a direct result of a fuel melting accident.


- Worldwide, there have been 582 nuclear power reactors that have operated approximately 14,400 reactor-years. Thus, to date, the historical frequency of core-melt accidents is about one in 1,300 reactor-years ..., or excluding SRE, about one in 1,400 reactor-years...

[mackdaddy]

1. So 7 to 8 times more Core-Melt accidents than predicted for operation??

In looking over the article at the link it seems that the NRC was predicting an "acceptable" occurrence of core-melt in about 1 occurrence of 10,000 reactor-years of operation. But, their best estimate (eliminating several other melt incidences at "non-electricity producing plants") is 1 in 1400 reactor years of operation. Ie SEVEN TIMES the predicted rate of Core-Melt.

All of the exclusions of partial melts and other accidents from their calculations is troubling too. These were OK because they were only partial melt downs and they could repair the plant?

Maybe all these nuclear experts and execs should prove how safe this is an have to live within a mile downwind of a reactor.

[kristopher]

2. That seems to be an accurate reading, yes.

The actual performance of reactors should be having far more weight than the PRAs but it looks like it is going to take a couple of more "Oooopses" before the industry loses its cachet with the regulators.

[bananas]

3. I should really spend some time on this...

but I've concluded that costs are the #1 block to nuclear energy.
Yes there are a whole sh*tl**d of other problems with nuclear energy,
but if they can't even justify it on near-term costs,
it's f*ck*ng dead in the water,
so why should I spend any more time on this?

edit to add: I originally said,
"why should I spend any more time on this?"
but what I really meant was,
"why should I waste any more time on this?"

I'm not being rhetorical.
I'm kind of pissed off that I've wasted so much time this far.

[kristopher]

4. Because they have a strategy to get around the cost issue

Simply legislate their construction in the State Houses. Yes some of them will go bankrupt, but with federal loan guarantees and CWIP financing to build them the investors walk away whole, the taxpayers get the shaft and the nuclear industry sells their electricity at a price that reflects none of the cost of construction - thereby undercutting any effort to move away from centralized thermal generation.


It isn't over until it is over.