A new nuclear option ?

[kowalskil@alpha.montclair.edu]

Do you remember a plenary talk at Spokane (AAPT Summer meeting, 1995) devoted 
to a nuclear waste disposal idea? The proposed solution was to send the high 
level waste to the sun. This triggered my interest and I started to learn 
about methods of dealing with nuclear waste. At the next Winter AAPT meeting 
I will outline what I learned (see Announcer, December 1996, page 42). A more 
extensive presentation is planned for the Summer meeting at Denver, if the 
proposal is approved.

In my opinion the most interesting method is the destruction of radioactive 
waste (such as spent reactor fuel) in a hybrid machine (accelerator-reactor).
The most undesirable components of waste, according to recent blueprints 
(from the leading labs in U.S., Europe and Japan), can be transmutted into 
stable, or relatively short-lived radioactive, atoms. The practicality of 
this approach has been discussed at several recent conferences. I learned 
about hybrid machines while on sabbatical in France last year and I am 
eager to share what I know.

The purpose of this long message is to outline what I am going to say at
Phoenix. It is for those who may be interested but not able to attend my 
talk (at the AC session). The physics of the new technology is relatively 
simple and, in my opinion, can be made meaningfull to our students. 

I WILL BE HAPPY TO GIVE TALKS ON THE SUBJECT IF YOU INVITE ME AND ONLY COVER 
MY EXPENSES. (AS A SENIOR CITIZEN I CAN NOW TRAVEL ANYWHERE IN THE CONTINENTAL 
US, CANADA AND MEXICO FOR $125 ONE WAY; TWICE AS MUCH TO ALASKA AND HAWAI). 
I WILL HAVE NO CLASSES ON THURSDAYS AND FRIDAYS NEXT SEMESTER.

       kowalskiL@alpha.montclair.edu    Upper Montclair, New Jersey

  ------------   Skip the rest unless you are interested.   ----------
                ------------------------------------------

Let me quote from a reference (BASIS AND OBJECTIVES OF THE LOS ALAMOS ADTT 
PROJECT, by Charles Bowman, presented at the International Conference in Las 
Vegas, 1994). A list of my references can be found in the last Announcer. 

> It has become increasingly difficult to convince a comunity to become a
> host to a nation's single site for storage of waste which many consider to 
> be the nation's most dangerous. The fact that the waste remains dangerous
> for many tens of thousands of years exacerbates these concerns. ....
 
> The world therefore is in desperate need for an acceptably priced
> inexpensive and safe alternative to the geologic storage concept. In 
> the U.S. commercial nuclear waste is accumulating at reactor sites and 
> the defense site clean-up effort is struggling to understand what will 
> happen to the plutonium and other high level waste which will be 
> gathered together after the clean up has been completed. The Los Alamos
> National Laboratory along with a rapidly developing national and 
> international community has therefore been studying Accelerator Driven
> Transmutation Technology (ADTT) as a possible means of destruction of
> this nuclear waste and of generating nuclear power by systems which do
> not generate the most dangerous components of this waste and which 
> concurrently destroy their own waste. If the full capability of the
> ADTT systems can be realized at acceptable cost, geologic storage of
> defense and commercial waste would not be required.

[The next two paragraphs call for some background in nuclear technology. 
Square brackets contain my insertions.]

> To understand the value of the accelerator more clearly, consider a system 
> containing U-233 fuel which undergoes fission with 92% probability upon 
> absorbing of one thermal neutron and which releases 200 MeV per fission.
> Assume further that no neutrons are released in fission. The 100,000 MeV
> released by 500 such fission events [500*200=100,000] would be converted
> with 42% efficiency [state of the art] to 42,000 MeV of electric energy.
> The accelerator [to be designed for a current as large as  0.1A] would
> convert this with 45% efficiency to 18,900 MeV of proton beam power if
> all the electric power were fed back to the accelerator. For a proton
> energy of 800 MeV, the accelerator would produce 18,900/800=23.6 protons.
> At a conversion rate of 25 neutrons per proton which probably can be
> achieved [in a thick target situated inside the reactor], a total of 
> 23.6*25=900 neutrons per 500 fissions is possible. Upon absorption, 92% 
> of these neutrons would lead to fission of 543 nuclei of U-233. 

> Comparing this number with the original 500 fission events, we can see 
> that an accelerator-linked chain reaction is possible even if no neutrons 
> were emitted from fission! Of course instead of no neutrons per fission
> 2.49 neutrons are produced per fission of a U-233 nucleus so that 
> altogether one has 590+500*2.49=1835 neutrons per 500 fissions. This is
> an increase in the effective number of neutrons per fission from 2.49
> to 3.67 if all of the electric power from the target-blanket were fed
> back to the accelerator. This is an increase of more than one neutron per
> fission and is an enormous increase in the number of neutrons per fission
> available to a nuclear system designer. The latter figure is far more
> neutrons than are required to maintain the fission process and to breed
> the U-233 from the thorium, so that only a small portion of the electric
> power must be consumed by the accelerator.
   
> [The rest of electricity can be delivered to the grid. This is the "safe 
> energy production" variant of the ADDT machine. The reactor is subcritical 
> and a run-away chain reaction, as in Chernobyl, is impossible. In the 
> "nuclear incineration" variant the overproduced neutrons will be used to
> transmute radioactive waste through nuclear reactions. A hybrid system 
> variant in which the energy production and transmutation of waste take 
> place at the same time can also be constructed. Safe nuclear power plants
> able to destroy troublesome components of their own radioactive waste are
> highly desirable. The Nobel prize laureate, Carlo Rubia, and his large
> team at CERN, are designing such system. Did you know that, according to
> the 1994 data, there are 340 nuclear reactors in the world and that they 
> produce 24% all electricity? In France 75% of electricity is nuclear.]