reply to post by GullibleUnderlord
thanks for the input , i hope they do not return any of that used water
back into the sea
Sorry for the delay...
It will at some point go back into the groundwater or the air. it will probably contain some radiation signature when it does so. But right now that
is far preferable to a complete uncontrolled meltdown.
Let me try to explain the cooling system again....
The primary loop never exits the reactor building. That is the water inside the reactor which is pumped through a heat exchanger. This is also the
water whose level is being discussed when they say rods are uncovered. And it is the water which is highly radioactive, containing energetic neutrons
as well as some of the soluble fission products. It cannot be simply returned to the environment.
This primary loop is cooled by the secondary loop (sometimes referred to as the main steam lines). This water cycles through the heat exchanger, turns
to steam, drives the turbines that produce electricity, then routes through the cooling towers which act like a second huge condenser and cool the
steam back into water. This water is considered hazardous as well, but to a much lesser degree than the primary loop water. It is normally replenished
from an outside water source, such as a river or sea.
Primary water is supposed to be denatured and pure, in order to prevent radioactive impurities from accumulating as much in it, and to prevent
corrosion to the interior of the reactor vessel. During a meltdown, some of this water steams and raises the pressure inside the reactor until a
balance is obtained between pressure and temperature. As the temperature rises, more pressure builds, and vice-versa.
Surely, they are not running seawater through the reactor itself.... if they were, we would be seeing those huge plumes of smoke (steam). So that
means they are flooding either the heat exchangers or the building itself with seawater. The heat exchangers would be most probable, since they are
specifically designed to draw heat from the reactor. If they can keep enough water flowing fast enough through those heat exchangers, the water may
not all steam... it will depend on how hot the cooling water gets, which is a function of how fast it is being pushed through the heat exchangers and
how much heat is being transferred. If they are using a fast pumping through just the exchangers, which is probable, then hot water is indeed being
returned to the soil and ocean, but not highly radioactive water.
My concern, and the reason I am keeping up with this so much, is that there have been reports of both I-131 and Cs-135 outside the reactor
containment. These are fission products, and had to have formed inside the reactor itself, from fuel in the fuel rods. That means somehow, radiation
has escaped. Now, it may have been purposely vented (better than letting the reactor vessel crack wide open, but not much IMO) or it may have exited
from a pressure crack in the reactor vessel itself, which would be an even worse thing.
The real danger outside of Japan is that steam containing energetic neutrons could be emitted. Forget the cesium... it is low-level radiation. Forget
the iodine... it has a fairly short half-life. Forget the gamma radiation... it disappears almost instantaneously. It is the energetic neutrons that
could travel across the Pacific, absorbed into airborne water vapor. As of this time, there is no indication that dangerous amounts of
neutron-containing steam have been released.
The danger is that it is still possible if the reactors are not kept cool and contained.
To the poster who suggested just letting it melt down... uranium melts at about 3000°C, and a meltdown can create temperatures of over 6000°C. That
is far beyond the melting point of the reactor vessel itself, even above the melting point of most rocks. Allowed to run freely, a full reactor could
theoretically melt its way through the reactor vessel, venting all of its water supply as radioactive steam, through the concrete containment floor,
through the soil and bedrock, until it merged with magma in the mantle. This newly formed tube through the crust would be a perfect candidate for a
new, radioactive volcano. To quote Egon Spangler from Ghostbusters, "That would be a bad thing."
Now, my concern is that there may indeed be a pressure crack in the reactor vessel. Steel pressure vessels can crack in such a way as to release under
pressure but then close back up and seal themselves until the pressure rises again. Each time pressure is released, some radioactive steam will exit
the reactor, whether by relief valve or by pressure crack. The difference is that we (the operators) have control over the relief valves; we (they)
have no control over a pressure crack. A pressure crack can (probably will) develop into an open crack as well over time, giving an open vent to the
atmosphere and making it impossible to maintain water levels inside.
As long as the reactors are kept cool, the pressure will max out at an acceptable level that will not crack the reactor vessel. That is why all the
concern over the cooling, and that is why I am happy with the way Japan is handling this situation so far. They are doing everything possible to
maintain the reactor in a safely operating condition until the fuel can safely burn itself out... the only reasonable course of action at this point.
That is also why I am not overly worried at this point, just concerned.
I hope that was a little more understandable.