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Home Dr. William Hannum

Lessons from Fukushima for Future Nuclear Power Plants

22 March 2011


On 11 March 2011, a massive earthquake hit Japan.  The six reactors at Fukushima-Dai-ichi suffered ground accelerations somewhat in excess of design specification.  It appears that all of the critical plant equipment survived the earthquake without serious damage, and safety systems performed as designed.  The following tsunami, however, carried the fuel tanks for the emergency diesels out to sea, and compromised the battery backup systems.  All off-site power was lost, and power sufficient operate the pumps that provide cooling of the reactors and the used-fuel pools remained unavailable for over a week.  Heroic efforts by the TEPCo operators limited the radiological release.  A massive recovery operation will begin as soon as they succeed in restoring the shutdown cooling systems.

It is important to put the consequences of this event in context.  This was not a disaster (the earthquake and tsunami were disasters).  This was not an accident; the plant experienced a natural event (“Act of God” in insurance parlance) far beyond what it was designed for.  Based on the evidence available today, it can be stated with confidence that no one will have suffered any identifiable radiation-related heath effects from this event.  A few of the operators may have received a high enough dose of radiation to have a slight statistical increase in their long term risk of developing cancer, but I would place the number at no more than 10 to 50.  None of the reports suggest that any person will have received a dose approaching one Seivert, which would imply immediate health effects.

Read more about Fukushima's lessons for future nuclear power plants


Safeguarding the Nuclear Fuel Cycle

by William H. Hannum

Abstract and Summary

The purpose of this essay is to compare the safeguards challenges presented by two nuclear recycle approaches, relative to the current U. S. approach of a once-through fuel cycle.  If these nuclear fuel cycles are evaluated solely on the basis of the safeguards needed, one finds the following:

PUREX recycle offers no safeguarding advantage over the once-through fuel cycle.  Beyond that, this approach presents a significant concern over handling of separated plutonium in the power plant environment.  Since chemically pure Pu is inherent in the PUREX process, safeguards inspections must be highly intrusive.

Adding recycling fast reactors with pyroprocessing (“PYRO”) to an existing fleet of LWRs absorbs all of the plutonium produced by LWRs.  There will be no inventories of plutonium other than what is in active use. PYRO is a new class of facility requiring safeguards, but batch-process inventory controls, coupled with a simple mechanical layout, will make the inspectors’ job more straightforward than for a PUREX facility.  The facility for recovering usable material from used LWR fuel may require safeguards similar in approach to those in PUREX facilities, but no separated plutonium will be involved.  If plutonium were to be diverted from a PYRO facility or from the LWR recovery facility, it would be useless (for weapons use) without further processing in an otherwise unneeded PUREX type of facility. 

Realistically, a full transition to recycling fast reactors is a process that will take decades.  However, if all the LWRs were retired and replaced with recycling fast reactors, in addition to the above advantages, there would be no further need for uranium enrichment.

Read more about fuel cycle comparisons


Nuclear Recycle

Canadian Nuclear Society
29th Annual Conference
2 June 2008


Sensible recycling of used nuclear fuel will allow nuclear power to satisfy the early dream of environmentally responsible, essentially unlimited energy at a reasonable cost. This will require a multiple-pass nuclear fuel cycle.  Technologies for recycling used nuclear fuel are available that will resolve the most challenging nuclear waste issues and will significantly simplify the task of controlling the potential for weapons proliferation.   A major effort is needed to build prototype facilities for processing used fuel from today’s nuclear power plants, to recover material for use in fast reactors.  As these technologies are being developed and implemented, many additional nuclear power plants based on today's single-pass nuclear fuel cycle will be needed to meet near term demands for energy.


This is an exciting time to be involved in the nuclear power business.  Existing nuclear power plants are operating very well.  They are largely paid off, and are running flat-out, minting money.  Generating companies can see the need for additional base-load capacity, and there are no real competitors to nuclear power to fill this need.  But there are doubts and challenges on the horizon.

Read more...


Advanced Recycle - Why Now?

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.

Read more...



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.