RE: TEPCO admits Fukushima Daiichi Unit 1 core completely melted down

Fri, 20 Mar 2015 21:19:59 -0700 

 

 

From: [email protected] 
[mailto:[email protected]] On Behalf Of meekerdb
Sent: Friday, March 20, 2015 5:20 PM
To: [email protected]
Subject: Re: TEPCO admits Fukushima Daiichi Unit 1 core completely melted down

 

On 3/20/2015 10:43 AM, 'Chris de Morsella' via Everything List wrote:

 

 

From: [email protected] 
[mailto:[email protected]] On Behalf Of Telmo Menezes
Sent: Friday, March 20, 2015 10:32 AM
To: [email protected]
Subject: Re: TEPCO admits Fukushima Daiichi Unit 1 core completely melted down

 

 

 

On Fri, Mar 20, 2015 at 6:20 PM, 'Chris de Morsella' via Everything List 
<[email protected]> wrote:

http://www.beyondnuclear.org/japan/2015/3/19/tepco-admits-fukushima-daiichi-unit-1-core-completely-melted.html

 

Just in case anybody wanted to pretend that the Fukushima disaster is behind 
us; here is this piece of bad news, based on recent telemetry using muon 
detectors for imaging the reactor vessels. The core of reactor units 1 appears 
to have melted through both the reactor itself and the outer containment 
structure. This is also the likely situation for units 2 and 3 as well. A total 
meltdown is not a good scenario – and that is a huge understatement.

 

It sounds bad for sure.

What can the consequences be?

 

They cannot be good, that is for sure. If the cores of units 1,2, and 3 have 
melted all the way through the outer containment structures that implies that 
the radioactive materials that had been contained in those cores has now 
migrated into the ground beneath these units. I would imagine that the 
intensely hot corium, at first melted down in a tendril like manner forming a 
branching structure until it becomes diluted with enough melted rock to 
decrease the intense temperatures. At some point – I would imagine – it would 
become dilute enough so that it no longer is above the temperature required to 
melt rock and at this point it will become fixed into the sub surface geology 
beneath those plants. 

As ground water comes into contact with this highly radioactive materials, it 
will continuously leach some of the content and transport this radioactive 
material elsewhere, including into the Pacific ocean and underlying aquifers.

I believe that this is the prime motivation for the – desperate – attempt to 
create a sub-surface wall of frozen ice around the affected area to try to 
contain this radioactive hell within the ice wall so that it does not migrate 
into the larger surrounding environment.

I have no idea how one could go about trying to remediate this; how would one 
go after the concentrated tendrils of dilute corium that has become frozen in 
place in the surrounding rock matrix. A first step would be to get a better 
idea of the 3-dimensional sub-surface distribution of the highly radioactive 
material, in order to at least begin to get an idea of the scope of the problem.

-Chris


I'd guess the best solution is: Don't mess with it and see that nobody else 
messes with it. Just keep monitoring food and water.  The corium should all be 
solidified into a glassy mass by now and not very susceptible to dissolution in 
water.

 

I agree the branching like glassy mass of the corium/rock mix is probably best 
left in place. However I also believe that it is incumbent – and this is a long 
haul effort of many decades and perhaps centuries – to isolate the very hot 
sub-surface glassified branching structures of solidified corium melt/rock mix 
from the larger environment. As you noted glass is not *very* susceptible to 
dissolution in water. However glass is not immune to leeching what is contained 
within the glass mass – slowly – into water that it comes into contact with. 
Water is an excellent solvent. 

The ice wall though flawed is a necessary first start. Apparently this reactor 
complex had been sited over an area with substantial subterranean water 
migration going on, not the best place to put a reactor over (nor was it wise 
to site it in a tsunami zone either). The ice wall’s aim is to form a barrier 
that diverts the flow of water around the Fukushima complex. If they can also 
clear – using hardened robots, because there is some very hot debris still 
covering the site and especially within the damaged structures themselves – if 
they can clear away all debris and cover the surface with impermeable covering 
in order divert runoff away from the site. And they then pump away the water 
table from below the hot zone; then this hot zone could in principal become 
isolated from water, which is the major carrier of stuff in our environment.. 
and hence largely isolated form the rest of Earth’s living systems and 
biosphere. A wall made of ice is an emergency measure. Eventually they will 
need to trench and trench very deeply around the hot zone and back fill those 
trenches with something very impermeable like compressed bentonite; perhaps 
even well injecting high pressure concrete mixes into even deeper areas beneath 
the trench in order to get the barrier to intersect even deep zones of water 
movement. 

This is a massive engineering undertaking! Many times the mass of the great 
pyramids will need to be moved. Which is why getting the best picture of where 
the radioactive stuff has ended up is important so that the job can be 
correctly scoped and only what is absolutely necessary can be walled in from 
the rest of the earth.

If the hot areas can be kept from contact with water they will remain 
contained, and for as long as they are kept out of contact with moving water 
will continue to remain contained within the surrounding mass of earth and rock.

Chris



Brent

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