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If a meltdown does occur, damage will depend on whether or not the reactor's containment structure holds. In the case that it does hold, the plant itself is FUB

by adbge 16y ago

If a meltdown does occur, damage will depend on whether or not the reactor's containment structure holds. In the case that it does hold, the plant itself is FUBAR'd but, otherwise, there isn't significant cause for concern. This would be analogous to the Three Mile Island accident -- in which a partial meltdown occurred but was successfully contained. If the containment structure is breached, the resulting fallout will be comparable to that of the Chernobyl disaster which, like most Soviet reactors, had no containment structure whatsoever. Wikipedia has a good article on the effects of the Chernobyl disaster: http://en.wikipedia.org/wiki/Chernobyl_disaster_effects http://en.wikipedia.org/wiki/Chernobyl_disaster_effects

wtallis 16y ago
Chernobyl was worse than just a meltdown. The graphite moderator caught fire and helped carry fallout into the atmosphere. This would not likely happen at Fukushima, as it is water-moderated, nor would the uranium fuel be able to catch fire as happened at Windscale, because modern reactors use uranium oxide instead of metallic uranium. In the event that containment is lost, there will still be contamination, but it probably couldn't be spread anywhere near as widely as the fallout from Chernobyl.
Ratfish 16y ago
Are the containment domes intact in Japan? Edit: found this on IAEA site: "Containment remains intact at Fukushima Daiichi Units 1, 2 and 3". It doesn't even mention the 4th, but does say the explosion occurred outside unit 1s primary containment dome. What does that mean? It's outer shield is wrecked?
- cnvogel 16y ago
  There's no containment dome. http://i.imgur.com/CckjP.jpg http://i.imgur.com/CckjP.jpg (X) The reactor is the red cylinder in the middle, the containment is the pear-shaped cavity it sits in, closed on top with the yellow hood and connected to that torus in the lowest-level which in case of an accident is supposed to condense the steam back into water, thereby removing heat from the containment. The part that's exploded is the flimsy metal "hut" on top of the concrete building. (X) from another HN comment I can no longer find, sorry, no attribution for who posted it initially
  - uvdiv 16y ago
    Original was NRC: "Reactor Concepts Manual | Boiling Water Reactor (BWR) Systems" http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf Here's one with labels: http://i.imgur.com/Oj4kg.png http://i.imgur.com/Oj4kg.png Magdi Ragheb, "Containment Structures" https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Containment%20Structures.pdf https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462...
- uvdiv 16y ago
  It doesn't even mention the 4th, There are six, and units 4,5,6 were already in a cold state before the tsunami (for maintenance); they're not involved. You could be thinking of Fukushima Daini, which has four reactors.
cnvogel 16y ago
That comparison is not correct. The chernobyl plant exploded because of a instantaneous power excursion to many times the rated maximum, and it contained a huge amount of Graphite (=Coal!) which caused a fire that dispersed a lot of fine-grained core material. The activity in the reactor core(s) in Japan right now should have decayed to a heat-output that is a few % of their rated power and, to make up some vivid comparison with the reality as we know it: The reactor core should look like what you get if a blacksmith puts glowing-hot iron (which in the reactor-case magically heats itself up constantly) in water, the resulting steam bubbles are what creates the increase in containment pressure. Even if there would be another hydrogen induced explosion there's no chance that even a tiny fraction of the amount of radioactive material set free in Chernobyl would be released to the environment.
jessedhillon 16y ago
The plant itself would not be FUBAR'd. As it stands, that reactor will never be brought back online, but the other units at the plant can still generate power. (This is assuming that containment at reactor 1 succeeds and that it would be safe for humans to be working at the plant.) This is what happened at Three Mile Island. Reactor 2 was taken offline and retired, but reactor 1 has continued operation. [1] [1] http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Current_status http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Curr...

by adbge 16y ago

wtallis 16y ago

Chernobyl was worse than just a meltdown. The graphite moderator caught fire and helped carry fallout into the atmosphere. This would not likely happen at Fukushima, as it is water-moderated, nor would the uranium fuel be able to catch fire as happened at Windscale, because modern reactors use uranium oxide instead of metallic uranium. In the event that containment is lost, there will still be contamination, but it probably couldn't be spread anywhere near as widely as the fallout from Chernobyl.

Ratfish 16y ago

Are the containment domes intact in Japan? Edit: found this on IAEA site: "Containment remains intact at Fukushima Daiichi Units 1, 2 and 3". It doesn't even mention the 4th, but does say the explosion occurred outside unit 1s primary containment dome. What does that mean? It's outer shield is wrecked?

cnvogel 16y ago
There's no containment dome. http://i.imgur.com/CckjP.jpg http://i.imgur.com/CckjP.jpg (X) The reactor is the red cylinder in the middle, the containment is the pear-shaped cavity it sits in, closed on top with the yellow hood and connected to that torus in the lowest-level which in case of an accident is supposed to condense the steam back into water, thereby removing heat from the containment. The part that's exploded is the flimsy metal "hut" on top of the concrete building. (X) from another HN comment I can no longer find, sorry, no attribution for who posted it initially
- uvdiv 16y ago
  Original was NRC: "Reactor Concepts Manual | Boiling Water Reactor (BWR) Systems" http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf Here's one with labels: http://i.imgur.com/Oj4kg.png http://i.imgur.com/Oj4kg.png Magdi Ragheb, "Containment Structures" https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Containment%20Structures.pdf https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462...
uvdiv 16y ago
It doesn't even mention the 4th, There are six, and units 4,5,6 were already in a cold state before the tsunami (for maintenance); they're not involved. You could be thinking of Fukushima Daini, which has four reactors.

cnvogel 16y ago

That comparison is not correct. The chernobyl plant exploded because of a instantaneous power excursion to many times the rated maximum, and it contained a huge amount of Graphite (=Coal!) which caused a fire that dispersed a lot of fine-grained core material. The activity in the reactor core(s) in Japan right now should have decayed to a heat-output that is a few % of their rated power and, to make up some vivid comparison with the reality as we know it: The reactor core should look like what you get if a blacksmith puts glowing-hot iron (which in the reactor-case magically heats itself up constantly) in water, the resulting steam bubbles are what creates the increase in containment pressure. Even if there would be another hydrogen induced explosion there's no chance that even a tiny fraction of the amount of radioactive material set free in Chernobyl would be released to the environment.

jessedhillon 16y ago

The plant itself would not be FUBAR'd. As it stands, that reactor will never be brought back online, but the other units at the plant can still generate power. (This is assuming that containment at reactor 1 succeeds and that it would be safe for humans to be working at the plant.) This is what happened at Three Mile Island. Reactor 2 was taken offline and retired, but reactor 1 has continued operation. [1] [1] http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Current_status http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Curr...