Plutonium -- most toxic known --???

[js_dukelow@ccmail.pnl.gov (James S Jr Dukelow)]

On Wed, 1 Oct 1997 17:12:34 "Theodore S Bohn"<BST@inel.gov> wrote:
> Subject: Re: Radio-Phobia

> PLUTONIUM - Ever since plutonium was branded, "The most toxic substance 
> on earth," the fear of millions (especially the radio-phobic) is 
> triggered at even the mention of plutonium for any technical 
> application.  I understand that there are many substances that are much 
> more toxic than plutonium. Has there ever been a non-technical, user 
> friendly explanation to the public by a creditable nuclear professional 
> putting the harmful properties of plutonium into perspective with the 
> other harmful substances on earth that the public usually don't fear? 
> Silence on this subject by nuclear professionals (us) will only 
> continue to reinforce this label as being true!  I would like to see a 
> treatise of this sort be the subject of a 20-20 or 60 Minutes program 
> to reduce this fear if the public would believe it. 

In the middle of a recent exchange of messages with another subscriber 
to FOODSAFE, a food safety mailing list, I received the following 
gratuitous, but gentle, jab.

> As an aside, what do you risk analysts at DOE think of the idea of moving 
> all toxic radioactive waste to the New Mexico desert for containment? Of 
> course you know that: 1) plutonium is heat and environmentally stable; 2) 
> plutonium is MORE toxic than botulinum toxin; 3) any containers will always 
> degrade due to long-term radiactive damage. ?:}.

I gave the following semi-technical response:

> This is sort of off-topic for FOODSAFE, so I will try to be brief.  
> Nobody is proposing to move all toxic radioactive waste to New Mexico.  
> By Dukelow's First Law, everything's got to be somewhere, including the 
> 200-300 tons of plutonium the U.S., Russian, and others have 
> manufactured since 1944.  Essentially, you can leave it in bombs, burn 
> it in reactors, or put it "away" somewhere.  The "politically correct" 
> choice at present is disposal in a geologic repository. 
> 
> There are two repositories planned.  WIPP in New Mexico and Yucca 
> Mountain in Nevada.  WIPP is essentially ready to operate and is 
> intended to store waste from various DOE facilities (but not the bomb 
> material, itself; the decision what to do with it is still open).  Yucca 
> Mountain is a long way from operation and is intended to store 
> commercial reactor waste.  One of the ways in which plutonium is 
> environmentally stable is that in most of its chemical forms it tends to 
> grab on to soil/rock components and stay where it is rather than moving 
> with groundwater.  In addition, WIPP is sited in the middle of a thick 
> bed of salt 2000 feet down.  Since salt is highly soluble in water, the 
> existence of the thick bed is taken as evidence that this location has 
> not been subject to significant groundwater flow for several tens of 
> millions of years.  There is no mechanism other than groundwater that 
> offers a plausible pathway for bringing waste stored 2000 feet down at 
> WIPP back to the surface environment in the foreseeable future. 
> 
> Plutonium is widely believed to be the most toxic poison known, but 
> there is no evidence to support that belief.  The LD50 for botulinum 
> toxin is 1 nanogram per kg body weight (or 70 nanograms for a 70 kg 
> man).  The allowable yearly occupational intake for workers exposed to 
> Pu-239 is 200 Bequerels (1 Bq = one radioactive decay event per second) 
> for inhalation and 200,000 Bq for ingestion.  To put these numbers in 
> perspective, our 70 kg man is walking around with about 4500 Bq of 
> potassium-40 and another 1000 Bq of rubidium-87 in his body. The Pu-239 
> ingestion number is most appropriate if our concern is material stored 
> in a geologic repository, but let's use the inhalation number instead.  
> At a specific activity for Pu-239 of 2.3 billion Bq per g, 200 Bq 
> corresponds to 87 nanograms of Pu-239 or 1.25 ng/kg body weight.  The 
> corresponding number for ingestion of Pu-239 is 1.25 micrograms/kg body 
> weight.  The difference is that with 1 ng/kg of botulinum toxin, half of 
> you are dead right now and with 1.25 ng/kg of Pu-239, you have been 
> exposed to a hypothetical hazard (its existence depends on whether the 
> linear no-threshold hypothesis of cancer induction is true -- a point 
> about which there is considerable scientific discussion at present) that 
> has about a 1 in 200 chance of killing you in 20-30 years. 
> 
> Dr. ********'s point about waste containers degrading is well taken, but 
> safety of the waste disposal does not solely depend on the integrity of 
> waste containers.  Most waste is imbedded in or integrated into a waste 
> form that is resistant to degradation -- frequently, vitrification of 
> the waste.  Then the waste form is put into a container that is designed 
> to resist degradation.  Finally, the waste form/container is emplaced in 
> a repository location that is chosen and designed to offer additional 
> barriers and delays to the return of the waste to the surface 
> environment.  I make a point of this because this type of defense in 
> depth also seems appropriate to the E. coli problem and should be 
> incorporated into the HACCP process.  Measures should be taken on the 
> farms, at the slaughterhouses, in the processing plants, in supermarkets 
> and butcher shops, and in the kitchens, each of them providing a barrier 
> against the eventual delivery of an infective dose of E. coli to the 
> consumer.  That way, the safety of the consumer doesn't depend on any 
> one barrier. 
> 

I would be pleased with corrections or other suggested improvements to 
the presentation of these issues.

Interestingly, my response generated no "flames" and one supportive 
comment from a professor involved with drinking water safety issues, 
noting that water treatment facilities routinely implemented defense-
in-depth approaches to drinking water safety. 

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA

js_dukelow@pnl.gov

These comments are mine (and Theodore Bohn's and Dr. ********'s) and 
have not been reviewed and/or approved by my management or by the U.S. 
Department of Energy