[John Rogers]

I was able to get through the US Navy as a nuclear operator for a bit over 20 years before I retired due to health reasons. Here are some things to think about while worrying about the plants in Japan.
- The design of the fuel area is such that the heated water goes up (natural as heat rises) but then the pipes turn downward to get to the bottom of the steam generators so now the hot water is going down.
- After some of the heat is removed by the steam generators, the colder water now has to climb back to the reactor vessel so that is also against natural flow. This is why they have to move the coolant with pumps as there is NO natural circulation. The US Navy built some reactors that would be able to self cool and they were on submarines but large carriers and civilian power plants are not self cooling.

- The temp inside is less than the pressure so the coolant stays as liquid, I.E. for 500 degree coolant that can make 1000# steam the pressure is kept at 2000# or so. Now if the coolant recirculating pumps stop, generally the reactor scrams (rods drop) but for many hours there is heat built up in the fuel area due to residual radiation so in this case with no circulation the pressure will go up!

- Pressure build up will happen very quickly since the water (coolant) is acting like a solid and expands as it gets hotter. The old (now decommissioned) GE power plants on ships like the CGN25 would be pressure tested to 150% operating pressure or 3000# and then all bets are off if the pipes and welds would hold! So how to keep pressure and temps down, generally by bleeding off some steam which made cold slugs in the coolant pipes or hopefully trying to get the recirculating pumps running and it appears this is not happening in Japan. They did have power, alternate power, backup generators and even batteries but they all are under water I guess so no pumps.

- Generally pump systems such as the Navy used had a set of very high pressure pumps which were used first, then a set of massive low pressure high capacity pumps to try to food the reactor vessel when pressures dropped and they suctioned from the ships fresh water tanks and finally from the sea using the fire pumps and fire main system. This all need power though.......

- So to help keep pressure down, steam is vented from the reactor side but since there are no pumps to keep putting water in as it is vented off, pretty soon there will be steam bubbles in the core are and when temps get so high, water will just bounce off the fuel plates, like on a hot iron, but much worse. Even flooding with fresh or sea water will not cool the fuel and it will probably melt towards the bottom of the vessel.

- If that happens the Uranium and zirconium will actually catch fire and melt through the steel pressure vessel and on into the ground where it will eventually stop when the earth, acting as a large enough heat sink will cool it off. The explosions happen when the Hydrogen gas mixes with some O2 and then things will rupture. Has this ever happened, yes, even BEFORE the Chernobyl disaster when some fuel assemblies overheated and melted through the containment vessel on the Chalk river in Canada and burned for months before it was out out by covering it with sand!

- Will this affect us, yes as the upper atmosphere comes from west to east and back when China was doing nuclear testing above ground, we would get contamination on our feet and have to "decon" before we went into the reactor buildings for work! Will it be monitored, I sure hope so, at least for the kids we have?!