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I reiterate my point that the HTGR is about ten years behind
the ALWR because of the need for an approximately ten-year
Tong HTGR demonstration project to precede NRC design certification. Such a demonstration project is not required
for the ALWR.
COMMITTEE ON ENERGY AND NATURAL RESOURCES
Following up on the discussion at the hearing on the
Also, I have been told that, with the HTGR, there would be a potential for release of radiation in the event that the graphite moderator caught on fire. Could you please elaborate on this risk? What would potentially cause the graphite to catch on fire? Under those circumstances, wouldn't it be appropriate to have a containment structure over the reactor to prevent any release of radiation to the accessible environment?
Your concerns about meltdown, graphite fires, and a
containment structure have been considered for many years by
the gas-cooled reactor community including the Nuclear Regulatory Commission (NRC) and overseas high temperature
gas-cooled reactor (HTGR) developers. First, it should be
said that meltdown is not an appropriate description for the
HTGR concept, as HTGR fuel is fully ceramic and its failure,
which is at temperatures in excess of 1600 degrees C is
characterized by fission product diffusion through barriers
that maintain their geometry. The rearrangement of
fissionable material in the core or disruption of the core
itself does not occur. Of course, HTGR fuel failure
potentials and consequences are major concerns.
being addressed in the modular high temperature gas reactor
of high temperature fuel, and the control of pathways for
fission product transport to the environs.
The graphite fire potential was evaluated by the NRC (with assistance from Brookhaven National Laboratory) during the Fort St. Vrain licensing process, following the Chernobyl accident and in the course of its preapplication review for
the MHTGR. The NRC states that it believes that air
availability pathways, including flow channels in the core, would not support a sustained or damaging graphite fire even if a containment structure was not provided. The NRC states that confirmatory experiments might be desirable but has not yet stated this as a requirement. The Department is renewing
interactions with the NRC and the subject of graphite fires
will be included in these forthcoming discussions.
QUESTIONS FROM SENATOR WALLOP
Would you agree that the long-term promise of nuclear energy is essentially unlimited through the development of advanced liquid metal reactor technologies?
It was recognized early in the development of nuclear power that if nuclear fission energy is to make a large contribution to the world's energy supply for the long term, that is, beyond a number of decades, a reactor type is needed which can utilize essentially all the fissionable material available in nature from uranium ore, as opposed to the current light water, heavy water, and graphite moderated
reactor systems which utilize only about one percent of the
energy available in uranium. The advanced nuclear reactor
development work carried out worldwide over the past several
decades suggest that the liquid metal (sodium) cooled reactor