From: Lawrence Johnston (johnston@uidaho.edu)
Date: Mon Jun 02 2003 - 12:03:04 EDT
George - Thanks for the suggestion of where to get the Tritium
for the D-T reaction fusion power. I did not remember this
method.
To make this practical, though, it seems to me that all the
neutrons from the D-T reaction must be rounded up to make the
recovery reaction
Li^6 + N => T + He^4.
It would be very surprising if the efficiency of that process
could be made more than 10%, since the neutrons would have to
survive penetration of the containment vessel, and then enter a
recovery blanket, and then face the finite cross-section for the
recovery reaction. Thus some other source of neutrons, or of
Tritium, is needed. Or perhaps they can reach the temperatures
where the D-D reaaction could work.
I remember that early-on, both fission and fusion seemed to offer
cheap power, but fission soon became a practical reality, while
fusion power, fifty years later, keeps receding into the
indefinite future. Seems to me that an entirely new idea for a
source of energy is in order. What bright kid will figure it
out? Will that kid be a nuclear physicist? A particle physicist?
chemist? An engineer? a poet?
Best, Larry Johnston
---------------------------
George Murphy wrote:
> Larry -
> I appreciate the historical insights from you and Moorad. Concerning the
> original question about the source of tritium for the D-T reaction, I quote from the now
> ancient (1960) _Project Sherwood_ by Amasa Bishop:
>
> "In addition, since tritium does not occur naturally in nature (sic!), the
> neutrons (from the D-T reaction) must be used to regenerate the tritium from lithium, by
> means of the reaction
>
> n + Li6 -> T + He4 + 4.8 MeV.
>
> In this way the tritium may be completely recovered. Thus, it acts as a sort of
> catalyst for the reaction, the fuel actually consumed being deuterium and lithium."
>
> My own experience with plasma physics has been wholly theoretical, an offshoot
> of my Ph.D. work on MHD in general relativity. & my only encounter with the hazards of
> tritium was when somebody in the spectroscopy lab at Hopkins broke a tube of it, causing
> a shut-down of the building.
>
> Shalom,
> George
>
>
> Lawrence Johnston wrote:
> >
> > Moorad - thank you for the information on your Advisor, Emil
> > Konopinski, and his calculations of the D-T reaction. Emil was a
> > good friend of MY thesis advisor, Luis Alvarez. I think I met
> > Emil at a party at Alvarez' house, in 1944. His calculations
> > were good, but I guess Oppenheimer did not sufficiently trust
> > their calculations of the Fat Man bomb's energy release.
> >
> > Just as Alvarez and I (and Wolfgang Panofsky) were about to take
> > off in our instrumented B-29 to make measurements of the Trinity
> > test, July 16, 1945, Oppenheimer called Alvarez and ordered him
> > to stay at least 25 horizontal miles from the Alamogordo Trinity
> > test site, since he felt unsure of the bomb's energy output. We
> > were planning to use the Trinity explosion as a dress-rehearsal
> > for our soon-to-come measurements of the energy output of the
> > bombs that were later dropped on Hiroshima and Nagasaki. Our
> > measurements were not needed for the Trinity test itself, since
> > there was a large amount of instrumentation on the ground. Most
> > of those detectors were blown up in the explosion, but not before
> > their output was recorded remotely behind the personnel bunkers.
> >
> > We took off anyway from Kirtland Airforce base, and went through
> > our routine drop of parachute gages at 30,000 feet altitude,
> > while we listened by radio to the countdown from the ground
> > bunker for the explosion on top of the steel tower. When the
> > bomb went off as hoped for, all of us were thankful that our
> > particular components of the Implosion system worked. If it had
> > fizzled, we would forever since have wondered if the fizzle was
> > our fault. And of course I was thanking The Lord. Alvarez was an
> > atheist so I don't know whom he was thanking.
> >
> > Thanks, Moorad. Larry Johnston
> >
> > =======================================================
> > Lawrence H. Johnston home: 917 E. 8th st.
> > professor of physics, emeritus Moscow, Id 83843
> > University of Idaho (208) 882-2765
> > Fellow of the American Physical Society
> > http://www.uidaho.edu/~johnston/homepage.html =========
> >
> > Moorad Alexanian wrote:
> >
> > > It was Emil J. Konopinski, my PhD thesis advisor, who suggested when
> > > at Los Alamos the use of D-T (deuterium-tritium) rather than D-D
> > > reaction for the atomic bomb owing to the larger cross section of the
> > > D-T reaction. He was also the one who calculated that the explosion of
> > > an atomic bomb in the atmosphere would not ignite the atmosphere; such
> > > were the fears and the unknowns of the early nuclear efforts.
> > >
> > >
> > >
> > > Moorad
> > >>
> > > Tritium http://www.triumf.ca/safety/rpt/rpt_8/node8.html
> >
> > > _____ > Tritium is an isotope of hydrogen which has one proton and
> > > two neutrons . It emits beta particles only and has a half-life of
> > > 12.3 years. The maximum beta energy is 18 keV, and the mean beta
> > > energy is 6 keV. A beta particle with energy of less than 70 keV will
> > > not penetrate the dead outer layer of the skin. Therefore, tritium is
> > > not an external radiation hazard , but when taken into the body it
> > > becomes an internal hazard .
> > >
> > > Tritium is produced in accelerator cooling water systems which are
> > > subjected to large proton or neutron fluxes such as those of the meson
> > > production targets of the TRIUMF 500 MeV facility. The tritium is
> > > produced by spallation reactions with oxygen, nitrogen and carbon
> > > nuclei present in the water systems and to a much lesser degree by
> > > radiative capture of neutrons by the deuterium nuclei in water. The
> > > tritium atom then combines with a hydrogen and oxygen atom to form
> > > the molecule HTO, often called tritiated water.
> > >
> > > Tritium does not contribute any significant part of the dose at
> > > TRIUMF, and most uptakes would be acute rather than chronic.
> > >
> > > Uptakes of tritium usually result from inhalation and skin absorption,
> > > but ingestion is also possible. The blood distributes tritiated water
> > > equally among all the body fluids, just as it does with normal water.
> > > All the soft tissues in the body will be irradiated by the decaying
> > > tritium and they constitute 90% of the body weight. As a result any
> > > tritium in the body will lead to a whole body equivalent dose .
This archive was generated by hypermail 2.1.4 : Mon Jun 02 2003 - 12:02:19 EDT