ThorEA - Towards an Alternative Nuclear Future.pdf

4.7.5 From megatons to megawatts:
Weapons decommissioning
Since its development for commercial purposes, civil nuclear
power has raised concern about its diversion for military
purposes and the threat of nuclear weapon proliferation.
However, since the end of the Cold War attention has shifted
towards the use of military uranium as a source of fuel for
commercial nuclear reactors. Since 1987 the United States
and countries of the former USSR have signed a series of
disarmament treaties to reduce the nuclear arsenals by
about 80%.
Fissile nuclear materials can be converted into nuclear
fuel, since the main material is highly enriched uranium
(HEU), containing about 90% U-235. HEU can be blended
with natural uranium (0.7% U-235) to produce commercial
reactor-grade nuclear fuel. The global stockpile of HEU
amounts to 2,000 tonnes, equivalent to twelve times annual
world mine production. World stockpiles of weapons-grade
plutonium are reported to be some 260 tonnes, which if
used in mixed oxide fuel in conventional reactors would be
equivalent to over a year’s world uranium production. As
previously mentioned, military plutonium can be blended
with uranium oxide to form MOX fuel.
After low-enriched uranium (LEU) or MOX is burned in
power reactors, the spent fuel is not suitable for weapons
manufacture. Since the late 1980s and by 2009 a total of 367
tonnes of HEU had produced some 10,621 tonnes of lowenriched
fuel, equivalent to 14,686 nuclear warheads.
Using Thorium-based fuels to eliminate weapons-grade nuclear
material presents significant advantages over the use of MOX:
such system is significantly more proliferation resistant, the
fuel can be easily made with existing technology and a lot
more plutonium can be put into a single fuel assembly than
with MOX, so that three times as much can be disposed of as
when using MOX, at a much faster rate. Finally, the spent fuel
amounts to half the volume of MOX and is even less likely to
allow recovery of weapons-useable material than spent MOX
fuel, since less fissile plutonium remains in it. Since the 1990s,
Russia has had a programme to eliminate its nuclear stockpile
through Thorium-based fuels.
Since 1996, the UK has been systematically reducing its
nuclear weapon stockpile, from 300 warheads (about 45
tonnes of weapons-grade material; of those, 70% HEU and
330% Pu) to “less than 200” by 2001. Current plans aim at a
further 20% reduction to 160 warheads. This implies a total
of approximately 20 tonnes of weapons-grade material to
eliminate, not including the upgrade to UK’s nuclear arsenal.
This nuclear material could be incorporated in ADSR fuel,
and thereby effectively eliminated UK’s. Given the very low
fraction of plutonium and higher actinides produced in the
thorium fuel, and the ADSRs fuel flexibility, weapons-grade
material could serve as a seed for the breeding process, with
concentrations being reduced to marginal and non-weapons
grade amounts.
Additionally, the UK would be developing a system to
effectively eliminate military nuclear stockpile for other
countries such as the US and former Soviet states. ADSR
technology could help to eliminate such material producing
electricity as a by-product.
4.7.6 Opportunities for hydrogen production
High temperature reactor (HTR) systems operating at above
750C are possible process heat sources for thermo-chemical
hydrogen production using the sulphur iodine cycle. HTR
systems pose particular materials challenges as neither
austenitic or ferritic martenistic are suitable at such high
temperatures (e.g. problems of cyclic softening). Oxide
Dispersion Strengthened (ODS) steels may be suitable for
high temperature nuclear applications, but much further
work is required and it is noteworthy that no European facility
exists for the bulk production of ODS steels. Much useful work
will be done by those working on critical HTR research.
Alternatively hydrogen can be produced by electrolysis. High
temperature steam electrolysis is especially attractive. Such
capabilities could complement the intrinsic flexibility of a
Thorium ADSR power station. Such flexibility and the ability
to load follow with grid supplied power is likely to be of
great importance in future decarbonised electricity systems
comprising renewables and nuclear power.
A report prepared by: the thorium energy amplifier association 39