Nuclear disaster narrowly avoided in Sweden?

[Christophe]

Via the Sortir du Nucléaire network. To be taken with the usual precautions ...

Europe passed on the brink of the nuclear disaster on July 25, 2006 due to a short circuit that caused the blackout of a reactor at Forsmark in Sweden. According to the former manager of this plant, "This is the most dangerous event since Harrisburg and Chernobyl".

While the very serious failure of the Swedish reactor has hit the headlines in Europe, we have heard very little about it in France. The “Get Out of Nuclear” Network therefore sheds light on the most serious event linked to a nuclear reactor since the Chernobyl explosion, exactly 20 years ago.

On July 25 at the Forsmark nuclear power plant (Sweden) a short circuit in the power plant's external electrical network caused the loss of electrical power to reactor no. 1. The reactor was then stopped suddenly due to the power outage. All the screens in the control room went off simultaneously: the operators were left without the controls in front of an uncontrolled and uncontrollable reactor. One solution to avoid core meltdown: start up the four generators to supply electricity to the reactor cooling pumps. But none started spontaneously as it should have done as soon as a failure of the external power supply occurs. It looks like the generator batteries have been affected by the short circuit. Since the reactor could no longer dissipate its heat, it heated up, the water level in the primary circuit dropped by two meters and the pressure plummeted to 12 bars while it must remain at 70 bars.

(Uh it is not the opposite which occurs during a warm-up ??? a maybe it is because of the lack of pressure of the pumps? ...)

Under these conditions the major accident is only a matter of minutes. However, it will take 23 minutes for the team in place to finally manage to manually start two backup generators. 23 minutes during which the operators did not know if the reactor was really shut down and if their actions had the desired consequences [2]. Why did only two out of four generators finally start when the four generators were of the same design?

We still ignore it.

The following : http://www.sortirdunucleaire.org/index. ... page=index

[Chuwee]

Weird description of this incident .

Already I can't see a chain reaction "stopped all at once" unless the rise of the control bars and the automatic addition of boron have worked correctly. In this case, it is a simple "automatic reactor shutdown".
Assuming that they lose the primary and secondary pumps and that the reactor continues to operate, the pressure should have risen. With the reactor stopped, I doubt that it could have gone down to 12 bars without cooling (at 12 bars the water would have turned into vapor, the assemblies would no longer have been cooled and the core would have melted ... ).

In my opinion, this info is to be taken with tweezers ...

[Christophe]

Well this is what I thought (hence my remark), but since I am not a nuclear engineer I think that:

1) the 12 bars come from the rise in pressure of the vapor of the primary circuit ... or from the lowering of water (which has evaporated) by 2m from the heart ...

2) the value of 70 bars is the "normal" pressure from the circulation pumps ...

Good or not?

[Chuwee]

It is the circuit which is at 70 bars, it is an isobaric transformation between the secondary and the primary. The pumps are only there for recirculation. It seems to me that it must also be able to run without a thermosyphon pump for a while ...

For those who will read the full article

Even when a nuclear reactor does not produce electricity, it must continue to cool because nuclear fissions continue. For example, a 1300 MW reactor one month after shutdown still produces 6 MW of residual power.

The residual power is not due to chain reaction fissions, but mainly to all radioactive decay. There are however spontaneous fissions due to activation (very rare).

Once the process of melting the core began, the explosion of the reactor was likely to occur at any time [3].

[3] In particular due to the emission of hydrogen produced by the oxidation of zirconium from the claddings housing the fuel when the core melts

Why not but it seems to me that it takes oxygen to have an explosion right?


Without taking sides.
The emergency power supplies on the reps are 2 diesel groups per unit + one turbine per site. It seems to me that there are also inter-slice couplings.
The control clusters fall by gravity and do not have to go up mechanically as on the BWR and RBMK.

A peculiarity of PWRs and surely other channels is that when the temperature increases, the water is less dense therefore the neutrons are faster. They are too fast to create reactions. The reaction decreases, the temperature drops, the neutrons are therefore slowed down and therefore the reactivity increases ...

[nonoLeRobot]

It is also in the world among others:

http://www.lemonde.fr/web/article/0,1-0 ... 238,0.html

We don't have a lot of details but the incident would be level 2 on a scale of 1 to 7 (7 major accident). The network leaving nuclear power surely amplifies. It's a bit of his job and without that, I wouldn't have heard of it. It is still worrying that not 1 but 2 backup motors do not work. It is reassuring to see that even without them, there was still no bp.

[Christophe]

It is reassuring to see that even without them, there was still no bp.

I believe that in the case of Chernobyl it is 17 levels of security (in series) which were crossed ... And the Russian plants are far from having the same security as the French plants. Here it was just to say that safety is still a main factor in the design of a power plant ...

[Chuwee]

If you want information on the central French, a small MP is I will try to answer you (at worst, I will ask the question at work) ...

[Christophe]

If you want information on the central French, a small MP is I will try to answer you (at worst, I will ask the question at work) ...

Pkoi in MP? Debate us all in public! Ah shit it's confidential defense ...

[Chuwee]

This is not necessarily confidential defense.
It's just to avoid rotting the post

[Christophe]

This is not necessarily confidential defense.
It's just to avoid rotting the post

Ben should create one ... style: All your question about nuclear.

What do you think ?