William Hannum

Dr. Hannum retired after more than 40 years in nuclear power development, stretching from design and analysis of the Shippingport reactor to the Integral Fast Reactor.  He earned his BA in physics at Princeton and his MS and PhD in nuclear physics at Yale.  He has held key management positions with the U. S. Department of Energy (DOE),  in reactor physics , reactor safety, and as Deputy Manager of the Idaho Operations Office.  He served as Deputy Director General of the OECD Nuclear Energy Agency, Paris, France; Chairman of the TVA Nuclear Safety Review Boards, and Director of the West Valley (high level nuclear waste processing and D&D) Demonstration Project.  Dr. Hannum is a fellow of the American Nuclear Society, and has served as a consultant to the National Academy of Engineering on nuclear proliferation issues.

Preaching to the Choir


This paper presents no new science; the science behind what I have to say is all available.  This is not a paid promotion of any specific product or design, but an appeal for all of us in the nuclear community to recognize that we need to get on with the practical matter of addressing immediate needs, and put aside the thrill of searching for something that is different, and perhaps a little more sexy.  Members of the Choir: We need to be singing from the same song book.

The context of my remarks is that we need additional electrical capacity in this country and around the world, to support a healthy, growing economy. The energy needs of the U.S., or of the wider world, will not be met without nuclear power, and lots of it, and we need it now.  That means we need to get on with building standardized light-water cooled reactors (LWRs).

If we are going to have lots of LWRs, we need to have a plan for the used fuel.

That, in turn, means a Yucca Mountain type repository - or - recycle.

I’ll not spend much time on the Yucca Mountain approach, except to note:
There is a popular belief that global warming (or is it cooling - I’ve been around long enough to hear both scare stories) will destroy the earth’s environment within 20 years if we don’t stop burning fossil fuels, and you know we won’t do that;
Within 50 years an earthquake will send much of California into the ocean;
Within 500 years an asteroid will destroy the earth;
And what is really scary, in about 100,000 years, some leakage from Yucca Mountain might add a bit to the background radiation in a small town in southern Utah. Call me insensitive, but in 100,000 years, for all I know, Martians may be living in Utah, and they may enjoy a little extra radiation.
BUT, politics is politics, and Yucca Mountain is dead, at least for now.  Thus, we need to take a hard look at alternatives.

If it were established policy to:

  • Build 100 large LWRs within the nest 20 years;
  • Store the used fuel for 100 years;

And if we had:

  • A practical way to dispose of excess weapons materials;
  • An effective approach to strengthen non-proliferation;

We could approach this problem with full academic leisure.  Since each of these propositions is questionable at best, we have no choice but to look seriously and urgently at Option B: Recycle.

Characteristics of Recycle

I have summarized the key features of three basic fuel cycles in Table 1: once-through; PUREX reprocessing; and pyrometallurgical electrochemistry, as regards wastes, resource efficiency, and proliferation.

First: Waste management. 

The major waste stream for the once-through approach is used fuel.  Fuel elements of questionable integrity, perhaps encased in copper or another metal, are sealed in one or more layers of stainless steel or some other high-integrity container, and buried in impervious rock, salt, sea bed, or otherwise isolated from the biosphere for an interminable time.  The same container and geology must keep the material from the biosphere during all time phases, including the period when the waste generates significant heat, and then continuing into perpetuity. 

We must also deal with excess weapons materials, defense wastes, depleted uranium from the enrichment process, and mill tailings.

Technically, all this is quite feasible, but politically it is an albatross.  Yucca Mountain has been a challenge, and it is now time to start characterizing an Eastern repository, presumably in Vermont.  It could be politically challenging.

If we go to PUREX reprocessing (as the French are doing), the waste disposal story is the same except for one major difference.  The processed waste form, borosilicate glass or a stable ceramic, can readily be shown to provide containment for the radioactive materials during the entire heat-generating phase.  This simplifies the analysis, if not the politics. 

With the pyro-metallurgical process, essentially all of the long lived material is recycled, so by the end of the cooling period (several hundred years), the radioactivity of the waste is essentially gone.  Two exceptions may be noted: For geologic disposal, there have been questions about retaining a very long-lived isotope of iodine (I-129), and one of technetium (Tc-99).  Again, the pyro-process offers ready solutions for these problems.  Each is easily separated from the other wastes.  In particular, Tc is collected with the noble metals where it can be alloyed to form an extremely stable waste form, or, if necessary, separated and transmuted.  It then becomes both technically simpler and politically feasible to license suitable sites for disposal of material that truly is wastes: that which has a hazard life of a few centuries, and the minor quantities of unrecoverable long-lived wastes .

With pyro-processing, the excess weapons materials, defense wastes, depleted uranium from the enrichment process, and mill tailings, are no longer wastes.  These materials are ideal fuel for the fast reactor.  In addition, there will be no need for enrichment for the recycling fast reactor, so there will be no new depleted uranium, and no need for mining for centuries while we use up existing stocks.

Resource utilization:

For this audience, I do not need to belabor the resource factor: going from less than 1 % utilization of the uranium to essentially 100 %.


The safeguards issue is a bit more subtle.  In Table 1, I have labeled each of the proliferation materials issues as to whether there is a potential for mis-use by:

  • Terrorist groups (T), who might be satisfied with a single device, even if a dud;
  • Rogue nations (R), who might wish to have a few reasonably effective weapons;
  • Wannabe nuclear weapons states (N), who would wish to have an arsenal of weapons.

Excess weapons material is clearly the biggest threat, because with this, a terrorist or rogue nation could easily produce a device or devices.  The second biggest concern is enrichment capability, because with that, weapons materials can be produced from relatively easily obtained natural uranium.  PUREX type reprocessing is next, because, coupled with selected used fuel, this offers a path to weapons material. 

I list Material in use last, because without a PUREX type processing facility, it is not a proliferation concern, and in use, it is immediately subject to effective safeguarding. 
The once-through fuel cycle has all these concerns.  PUREX recycle has not only these concerns, but also involves commerce in separated plutonium (albeit, much of which is unsuitable for effective nuclear weapons).  The PUREX fuel cycle is clearly only suitable for established nuclear-weapons states with excess weapons material, and who employ rigid physical security.

With advanced recycle technology using fast reactors, each of these areas of concern is reduced or simplified.  Excess weapons materials and much of the defense waste can readily and efficiently denatured in a fast reactor.  Depleted uranium, and used LWR fuel become the raw materials to fuel the recycling fast reactor. 

Perhaps most significantly, in a mature-recycling economy, there is no need to enrich the uranium.  Existing facilities are sufficient to service a substantial increase in the current fleet of LWRs during their entire lifetime.  And clearly, there will be no need for further PUREX reprocessing capacity.  Any new construction of facilities for enrichment or for PUREX reprocessing becomes prima facie evidence of an intent to proliferate.

The Path Forward

There are four parts to a mature nuclear recycling program:

1.    Recovery of actinides from used LWR fuel.  It may be useful to get started on this.  We know at least one way it can be done: with a modified PUREX type chemical separation.  This technology is suitable for use with rigid physical safeguards, comparable to those used in PUREX facilities in nuclear weapons states.  Electro-chemical processes that would facilitate safeguarding may be feasible alternatives.

2.    A fast reactor or reactors.  We know how to build these, and there is no need to wait for an optimum design, but we do need one or more fast reactors to demonstrate the use of recycled fuel.

3.    A recycle facility.  This is the critical path, in that the technology has been demonstrated only on a pilot scale.  It is necessary to show its commercial viability.

4.    Packaging of wastes.  Since the quantities are small (approximately one tonne per GW year - electrical), and various waste forms are feasible, this aspect can be demonstrated later.

We who are familiar with what has been accomplished in the development of advanced recycle technologies believe all of this to be a straightforward, technologically proven undertaking, but this is a hard sell to skeptics and anti-nuclear zealots without a relatively large-scale demonstration.

On the outside, there are a number of individuals who are spending a lot of time, effort, and a lot of their own money promoting recycle.     There is even a not-for-profit web site promoting recycle.

Meanwhile, DOE is constrained by political correctness, and the Laboratories are waiting to see what will be funded by DOE.


We need a relatively large-scale demonstration to show the practicality of recycling used nuclear fuel in a fast reactor, and we need it now

What will demonstrating the practical feasibility of advanced recycle accomplish?

Will this meet our energy demands?  Not for the near term, but it will facilitate the building of many LWRs by resolving the Yucca Mountain dilemma, and it will point the way to inexhaustible energy.

Will this eliminate the need for a nuclear waste disposal site?  No.  Such a facility will still be needed for some defense wastes and certain long lived materials.  But it will dramatically reduce both the magnitude of the problem, and the difficulty of assuring the safety of such a site.

Will this secure nuclear weapons-usable materials?  Not by itself, but it will be a valuable component of this effort.

Will this achieve non-proliferation goals?  Not by itself, but it will help by providing some near term options, and will serve as a basis for negotiating a more secure future.

We need more nuclear power now; that means LWRs.  We need lots of it; that means standardized designs.  And we need to demonstrate advanced nuclear recycle.  This is a modest step, but it will allow us to move forward.  The alternative is continued stagnation.

Table 1


Characteristics of Three Basic Fuel Cycles





PUREX reprocessing




Used Fuel

Excess weapons mtl

Defense wastes


Mill tailings

Used Fuel

Excess weapons mtl

Defense wastes


Mill tailings

Fission products

Resource Utilization

< 1 %

~ 1 %

~ 100 %



Excess weapons mtl (T,R)

Used Fuel (R,N)

Enrichment (R,N)


Material in use



Excess weapons mtl (T,R)

Used Fuel (R,N)

Enrichment (R,N)


Separated Pu (T,R,N)

Material in use



Material in use




N: Wannabe nuclear weapons states

R: Rogue nations

T: Terrorist groups