Fission, fusion et., les déchets nucléaires??

"Only because of..?"

Ci-après se trouve reproduit un article - présent dans la documentation reprise par Google, article de la rubrique "Green Inc." du New York Times, quotidien dont le moins qu'on puisse dire à propos de son orientation idéologique est que le thème directeur de la rubrique elle-même: 'Energy, the Environnement and the Bottom Line' (la Ligne de Fond) reflète des idéaux relativement proches de ceux, par exemple, du Figaro dans l'Hexagone.
La "Ligne de Fond" , et pourquoi pas le "plancher des vaches" , tant qu'ils y sont ?!
Il m'a semblé cependant intéressant de reprendre l'essentiel de cette page car l'info a suscité un échange instructif entre deux lecteurs avertis.

December 9, 2008, 12:20 PM
Fission, Fusion and Nuclear Waste

By MATTHEW L. WALD

graphics8.nytimes.com/images/blogs/greeninc/compact.pdf

Scientists at the University of Texas want to use a compact fusion reactor to deal with nuclear waste from fission. (Click image to see a larger diagram.)

Creating commercially useful power with fusion, in which small atoms are combined to produce energy, always seems to be decades away — and too costly. But physicists at the University of Texas at Austin have come up with a reactor design that would provide a second purpose for fusion: destroying long-lived nuclear waste arising from the splitting of atoms — or fission.

In a nutshell, the problem they sought to overcome goes something like this:

In a fission reactor — the only type of reactor currently operating commercially — uranium atoms are split by a bombardment of neutrons, releasing a lot of useable energy. But the process also generates nuclear waste, which is radioactive and has to be dealt with safely.

The problem is complicated further by the fact that not all nuclear waste is the same. One type is essentially the leftover bits of the split atoms — the “daughter atoms” — which remain radioactive for centuries. That’s not ideal, but it is certainly manageable. The material can be stored above ground for a few hundred years, after which it would be harmless.

A second category of waste, however, involves those atoms that absorb the bombarding neutrons but don’t split. These atoms became new materials, including several kinds of plutonium (very, very toxic) and other, even less familiar elements — all called “transuranics.”

Some of these new elements remain radioactive for hundreds of thousands of years, presenting a much more complicated disposal problem.

But what if these “transuranics” could themselves be split? Yet more energy would be derived — but perhaps more importantly, the resulting waste, while still radioactive, would be far less long-lived.

With the exception of a small portion of the plutonium, fission reactors are typically unable to split these new elements. The fusion process, however, can.

According to Swadesh Mahajan, a senior research scientist at theInstitute for Fusion Studies at the University of Texas, that’s the idea behind what would amount to a combined-cycle,fission-fusion hybrid reactor. Dr. Mahajan and his colleagues said they’d published their hypothesis for such a system in the journal Fusion Engineering and Design.

At the heart of the concept — which exists only on paper — is what the scientists call a “compactfusion neutron device.”

“Compact” is the operative word.

So far, designs for fusion reactors have tended to be prohibitively large. The International Thermonuclear Experimental Reactor being planned in Cadarache, France, for example, is more than 32 feet long on a side. But the Texas designers say their compact design is just 5 feet long.

“The whole device could fit in a small-sized room,” said Dr. Mahajan. 
The study was co-authored by Dr. Mahajan, along with Mike Kotschenreuther, Prashant Valanju and Erich Schneider.

The researchers say this would allow a “blanket” of waste material around the core of a fissionreactor to be broken down by the neutrons arising from fusion.

However realistic it might be, it’s not likely to get off the ground quickly.

“A prototype is going to take a billion dollars to make,” Dr. Mahajan said, “and it’s at least 10 or 15 years down the road.”

Alternative Energy, Energy Business, Energy Economics, Nuclear Energy,The Environment, fission,fusion, Nuclear Energy, nuclear waste

Since that zumbo highly complicated fusion design did not yet succeed in producing the endless and cheap energy that was promised, looks like some of the scientists working on that design are planning to salvage that design for what it has to offer : destroy the only other viable fuel source that we have today - transuranics which can be burned in a fission reactor (fast reactors).

This plan of destroying “nuclear waste” (none of this is waste.. it is valuable fuel) is not only costly but highly unneeded.

We already have enormous research experience and even commercial designs to solve the nuclear “waste” problem. This is called the Integral Fast Reactor, and the commercial version is GE’s PRISM reactor design. Interested readers can refer to the brilliant book of Tom Blees “Prescription for the Planer”.

— vakibs December 13, 2008

#6 vakibs:

Your comment, “…that zumbo highly complicated fusiondesign did not yet succeed in producing the endless and cheap energy that was promised…” misrepresents fusionenergy research efforts. By your comment it sounds as though there has already been an experiment built to attempt to make fusionenergy. Nothing could be further from the truth. Even though, the basic design for an experiment big enough to yield large net gains in energy has been known about since the late 70’s and early 80’s, no such experiment has ever been built. In fact, despite scientific breakthroughs that occurred over the past decades, funding for magnetic fusion research in the US has been oppressively small. The scientific feasibility of magneticfusion was proven in the late 1970’s and early 1980’s. In 1980, following an extremely favorable recommendation from a presidential inquiry into the scientific merits of all alternative energy sources (including solar and wind) ordered by then president Jimmy Carter, Congress passed a $20 billion R&D spending package entitled, “The MagneticFusion Energy Engineering Act of 1980.” The intention of this Act was to develop magnetic fusion into a commercial energy source by the year 2000. Without any scientific justification the incumbent president Ronald Reagan diverted nearly all of the funds allocated to fusion energy into the Star Wars Missile defense boondoggle. Even the 2007 Nobel Peace Prize recipients of the Intergovernmental Panel on Climate Change describe magnetic fusion in their report as, “…scientifically feasible.” Because, and only because, of political inaction, do we not have this power today.

— Josh KingJanuary 14, 2009