Wednesday, August 14, 2013

#Fukushima I Nuke Plant: Alpha Nuclides Found in Condensed Water from Reactor 3's PCV Gas Control System


As the sudden and renewed media attention (latest I found today was from Bloomberg News, informing the readers about that "300 tons of water laced with radioactive particles") is being focused on contaminated water (highly contaminated water in the underground trenches, low-contamination water in the observation holes along the embankment which is a reclaimed land along the ocean) at Fukushima I Nuclear Power Plant, there are other curious surveys and examinations being done at the plant, without any media attention.

The probe of Reactor 2's Containment Vessel into the pedestal area is one. Here, I think, is another.

On August 12, 2013, TEPCO announced the result of the alpha-nuclide analysis of condensed water from the gas control system of Reactors 1, 2 and 3. I believe this is the first time that TEPCO has ever tested alpha nuclides in gas/condensed water coming out of any Containment Vessel.

All-alpha was not detected in the condensed water from the gas control system of Reactors 1 and 2, but there was a small amount of all-alpha, max 0.19 Bq/cm3 (cubic centimeter) detected from the condensed water from the gas control system of Reactor 3.

Reactor 3 was using MOX-fuel with extra plutonium as part of fuel when it was shut down on March 11, 2011. 32 MOX-fuel assemblies were installed in the fuel core when Reactor 3 was restarted in October 2010 after a scheduled maintenance.

From TEPCO's handout for the press in English, 8/12/2013:

Sampling Results (All α) of Condensed Water at Unit 1-3 PCV Gas Control System (the Entrance of HEPA Filter) in Fukushima Daiichi Nuclear Power Station



TEPCO had done the nuclide analysis for condensed water for gamma nuclides (including radioactive cesium) back in June, and there was no statistical difference between the reactors.

Even though TEPCO hasn't identified which alpha nuclides were found in the condensed water from the Reactor 3 gas control system, it seems the company suspects the contamination of Reactor 3 building may be different from that of other reactor buildings, which may pose problems in the future decontamination work.

TEPCO has been injecting nitrogen gas into the Primary Containment Vessels of Reactors 1, 2 and 3 to prevent the concentration of hydrogen gas. The gas control system with HEPA filter has been installed to treat the gas being pushed out of the PCV, and there are particulate filters and charcoal filters to collect radioactive materials in the gas. There are also drains to collect condensed water.

The nitrogen injection system and the gas control system of Reactor 3 were installed in July 2011, with TEPCO workers and affiliate company workers getting 5.34 millisieverts radiation for 9-minute work. The hose for the nitrogen injection had to be installed in the area with 55 millisieverts/hour radiation.

(There are several, curious loose ends about Reactor 3. I'm writing a post for my record.)

6 comments:

Anonymous said...

Maybe you can figure out what the arrows in the upper part of the drawing mean. If they are showing unrestricted venting, like Unit 3's steam, then what is the makeup of the freely venting radioactivity? Same as the samples found before filtering?

Anonymous said...

Reuters has a longish news piece on the removal of fuel assemblies at unit 4 which is supposed to start this November. Kind of scary given Tepco track record.

Beppe

Vyse Legendaire said...

Interesting finds there.

arevamirpal::laprimavera said...

Anon at the top, yes the dust sampling of air above the reactor buildings are about the same as at the gas management filters for radioactive cesium, order of 1.0E-5 or 1.0E-6 to ND. As far as radioactive cesium goes, the gas inside the CV is very "clean".

Beppe, TEPCO may be slightly better at removing fuel assemblies, because that is part of what a nuclear plant operator does normally in normal times. They have zero experience in civil engineering, other than picking the cheapest general contractors to do the job.

Anonymous said...

Primavera-san
if Tepco were good at its job it would do inspections at the prescribed intervals at its npps, it would take measures to prevent earthquakes from stopping its npps for years (KK, Fuku2) or destroy them altogether (Fuku1).
Besides, the fuel removal this time is not business as usual: the machine used to move the fuel used to know the position of the rods down to the millimiter and now the have debris in the pool and they even dropped a 400kg beam into the pool, if I recall correctly.
Quite not the usual procedure.
Google for reuters gundersen november to read the details.

arevamirpal::laprimavera said...

400 kg debris dropped in Reactor 3 SFP. They fished it out, I think.

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