Japan Earthquake: nuclear plants

fusefiz

| http://www.nytimes.com/2011/03/26/wo...pagewanted=all

A senior nuclear executive who insisted on anonymity but has broad contacts in Japan said that there was a long vertical crack running down the side of the reactor vessel itself. The crack runs down below the water level in the reactor and has been leaking fluids and gases, he said.

The severity of the radiation burns to the injured workers are consistent with contamination by water that had been in contact with damaged fuel rods, the executive said.

“There is a definite, definite crack in the vessel — it’s up and down and it’s large,” he said. “The problem with cracks is they do not get smaller.”

But Michael Friedlander, a former nuclear power plant operator in the United States, said that the presence of radioactive cobalt and molybdenum in water samples taken from the basement of the turbine building raised the possibility of a very different leak.

Both materials typically occur not because of fission but because of routine corrosion in a reactor and its associated piping over the course of many years of use, he said.

The aggressive use of saltwater to cool the reactor and its storage pool for spent fuel may mean that more of these highly radioactive corrosion materials will be dislodged and contaminate the area in the days to come, posing further hazards to repair workers, Mr. Friedlander added. Whichever explanation is accurate, the contamination of the water in the basement of the turbine building poses a real challenge for efforts to bring crucial cooling pumps and other equipment back online.

“They can’t even figure out how to get that out, it’s so hot” in terms of radioactivity, the senior nuclear executive said.

(Published: March 25, 2011)

AntonL

Agree - maybe an administrator should do some censoring and delete inappropriate posts - should be seriously considered

tyroman

@TCups

I have read every post in this thread and have seen no reply to your "Primary Containment explosion" theory which addresses the following:

There is no question in my mind that Hydrogen escaping from the SFP's (or by some path out of the reactor core) could (and did) explode once it mixed with relatively dry air above the SPFs. However, I believe there would be insufficient Oxygen available within the Primary Containment for a Hydrogen explosion to occur there for the following reasons.

Consider the reaction which produces the Hydrogen;

Zr + 2 H2O = ZrO2 + 2 H2

In this reaction, all of the Oxygen in a water molecule is "fixed" on the surface of the fuel cladding in the form of zirconium oxide.

When Hydrogen burns (explodes), there is one molecule of Oxygen for each molecule of Hydrogen;

2 H2 + O2 ---> 2 H2O

The only other source for Oxygen within the RPV / Primary Containment might be the release of air entrained or dissolved in the cooling seawater or Oxygen released directly from the core via radiolysis of the surrounding water/steam.

The radiolysis source is questionable since it occurs at twice the temp of a redox reaction (between water and zirconium) and the heat source in the core is decay heat not fission generated.

The seawater source is more problematic...

Flamable/explosive gases such as Hydrogen have something called UEL or Upper Explosive Limit.

See;
[http://en.wikipedia.org/wiki/Flammability_limit]

"Upper Explosive Limit (UEL): Highest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat). Concentrations higher than UEL are "too rich" to burn."

From the table at the same link, Hydrogen's UEL in % by volume of air is 75%. Air is composed of about 21% by volume Oxygen. I expect that these figures are at STP for dry air and would need to be adjusted for the temperature and pressure in the Primary Containment. Additionally, the presence of steam in the same space as the Hydrogen and Oxygen inhibits their reaction. Thus, when the Hydrogen mixes with relatively dry air above the SPFs it can explode... but perhaps not while it is within the steamy Primary Containment.

Maybe one of our Nuclear Engineers can address your theory from this perspective.

.

Reno Deano

More than likely TEPCOs saltwater injection was via the reactor feed system which begins in the Turbine Bldg. There may have been a back flow at some time (on 2-3 inches of water) during the set up and change over. If they created a direct patch to either the Reactor Vessel or the Dry Well, then they also created a return path from those points. Just a plumber's theory.

jensjakob

Background reading: The Chernobyl Record - background, radiation theory, facts:
http://www.scribd.com/doc/40414231/Chernobyl-Record

Joe Neubarth

We see hundreds of people on this forum trying to put together the pieces of the puzzle that are the bits of the information that have been released. It is a shame that in this crisis they are not being more transparent.

|Fred

On the 25th at 03:13AM JST there was a press conference open to the international press as it was translated in English, Unfortunately very few reporter were there, and the stream that I was watching cut off after 6 minutes.. (too boring for the cameraman I guess -_- )

None the less I toke a few screen grab, the topic was the design of the BWR used in fukushima , specification , and way of predicted leaking of the RCV under pressure.

Shame they did not record the full conference, we might have glance a few more informations

The BWR Mark 1 made by GE used in Fukushima is the enhanced one with a bigger drywell (on the right)

Design spec
Leakage ref to the containment vessel

Bolted top with flange allowing leakage

Astronuc

Ouch! Crack(s) in the RPV is a problem. At this point though, the drywell should be flooded to the extent possible.

Co and Mo (and Tc-99) would come from activated corrosion products, which is normal. Usually, these products are filtered from the water (condensate polishers), or they deposit on the fuel. This does not indicate fuel failure (cladding breach).

The release of Xe, Kr, Cs, I, . . . isotopes would be expected from failed fuel rods, but that could mean small or tight leaks. These elements are gaseous or volatile, so they readily come out of failed fuel.

The indication of Ce-144 is a more serious indication of breached fuel. If Np-239 was measured in the water, that too would indicate fuel washout.

I also just realized that the cladding is probably liner (barrier) cladding, and it's possible that breached cladding could split open through reaction (oxidation of the liner) with the coolant, especially if the cladding temperature approached operational temperatures. I'm not sure that anyone has done an experiment on BWR fuel degradation in seawater, so this is likely uncharted territory.

|Fred

here are the result of the water analysis found in the basement of the Turbine unit 1 ( source nisa)

jensjakob

"Drywell head is predicted to unseat at 27 psig" (page 5, upper part)
http://www.osti.gov/bridge/purl.cove...630475-EX87x5/

"Just a few square inches are enough to relieve pressure"
"Due to the large surface of the drywell head, leaks are easy"

If that is true - then there is a SERIOUS flaw in the BWR 1 (and otherrrs?) design - and a quite plausible documentation for TCups theory.


Found also this detail diagram of drywell head fastening:
http://www.ansn.org/Documents/Traini...92,17,Example: BWR Drywell Head Seal

Joe Neubarth

Just like there were lots of examples of past accidents included in my reactor training days, there will be lot of learnings garnered from what has happened in Japan. Doctorates will be written on those learnings.

timeasterday

The shape on the right reminds me of an earlier photo showing a round hole atop some "whiskey distillery" shaped object.

PietKuip

Chlorine-38 has a 37 minutes half-life- Where could it come from? Neutron activation of the brine??

KateB

Looks like it is common in BWR's, and that you are correct, NaCl impurities in water.

http://www.nap.edu/openbook.php?record_id=9263&page=116

M. Bachmeier

Kate are we looking at unlikely chemistry. This case is unprecedented, with ocean water and uncounted types of impurities potentially interacting with isotopes?

Joe Neubarth

No, they do not know more than I do. Look at the photos. They are just spraying the hose into the air hoping to get some of the water in the building over the reactor and also in the general direction of the expended fuel rod pools. That was not a genius decision.

Also, a helicopter need not fly over the reactor site for more than a few seconds to hook a hose to a girder if the hook is already attached to the hose. long tending lines could have been attached to the end of the hose in one way or another. That would have been a lot more effective than trying to shoot water into the air in proximity to the reactor building.

M. Bachmeier

Joe do you know how difficult it would be to coordinate what your suggesting.