[ RadSafe ] Fw: Fw: Radioactive contamination of the ocean

Tue Apr 5 03:58:48 CDT 2011

Burying it in the sediment (silt) will normally mean it is scraped off and accumulated in the accretion wedge - it is never subducted. The environment you are burying into will be subject to heating, much stress through shearing and faulting as the material is scraped.

To get it truly subducted, you need to get it into the subducting slab - deep enough so it is not "scraped off" during subduction.

At subduction zones, the water is ~4km deep, the silt is of variable depth and the crust is ~7km thick. Drilling into this is cold, dense slab under this amount of overburden is a formidable task.

As the slab is buried, it is heated - 1200C is achievable, and as the rock melts/deforms, anything buried in it will be subject to stress and heating. Partial melting will bring material from the slab to the surface in island arc volcanoes.

So about doing it differently - bury it close to the spreading ridge, the water is ~2.5km deep, there is minimal silt and the crust is slightly thicker and less hard. If you were to do this in the Pacific, you could have 400Ma before the waste is subducted and then re-erupted in the island arc. The drawback is the length of time corrosive seawater has to attack the burial chamber and the fact the slab contracts over time (due to cooling).

Or alternatively, bury it centrally within a continental mass - away from spreading ridges, subduction zones, known faults, mantle plumes (causing rifting such as the rift valley in Africa) and hotspot volcanism. Continents are generally stable, are thick regions of the crust having low heat flow. Central Australia, North America and the northern regions of Africa are stable and likely to remain so for a long time.

The 3rd option is a surface repository where material can be retrieved and moved should the security/integrity of the repository become compromised with time. I'm sure someone suggested Fort Knox as a possible location, plenty of security there.

Mind you, to paraphrase our banks when selling financial services "Past performance is no guarantee of future performance".

Dave Richardson

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike (DOH)
Sent: 05 April 2011 00:18
To: Jerry Cohen; The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] Fw: Fw: Radioactive contamination of the ocean

Yeah, but engineering a delivery system that bury the waste a hundred meters deep in the sediment in a subduction zone would be really cool.

----- Forwarded Message ----
From: Jerry Cohen <jjc105 at yahoo.com>
To: "Neil, David M" <neildm at id.doe.gov>
Sent: Wed, March 30, 2011 3:04:48 PM
Subject: Re: [ RadSafe ] Fw: Radioactive contamination of the ocean

That's nice, but subduction is unecessary. All that is needed is depth and
distance. Nature will take care of the rest. There is a lot of water in the
oceans!

________________________________
From: "Neil, David M" <neildm at id.doe.gov>
To: Jerry Cohen <jjcohen at prodigy.net>; "radsafe at agni.phys.iit.edu"
<radsafe at agni.phys.iit.edu>
Sent: Tue, March 29, 2011 10:54:49 AM
Subject: RE: [ RadSafe ] Fw: Radioactive contamination of the ocean

Actually, the subduction zones where that would be effective tend to have
islands along the edge of the over-riding plate.  Or continents.

Dave Neil

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