4 June 2022 | New Scientist | 7A MUCH-vaunted first wave
of mini nuclear power stations
may produce more radioactive
waste than traditional large-scale
reactors when generating the
same amount of power.
Small modular reactors
(SMRs) have been mooted by
their developers and proponents
as a cheaper and faster way to
build new nuclear power capacity,
with UK prime minister Boris
Johnson claiming they could be
generating electricity by 2030.
The US government has provided
financial support to the firm
NuScale Power to develop its
version of the technology.
But to date there has been little
independent assessment of how
the radioactive waste producedby SMRs would compare with
that from their large-scale peers.
Lindsay Krall at Stanford
University in California and her
colleagues used data NuScale
Power has shared publicly with
US authorities, and extrapolated
to model the waste from three
different SMR technologies. They
compared SMR technology with a
conventional 1.1 gigawatt nuclear
reactor, roughly a third of the
capacity of a nuclear plant being
built in south-west England.
They have found that SMRs could
increase the volume of short-lived
low and intermediate-level waste –
the two lowest of three categories –
by up to 35 times compared with a
large conventional reactor, when
looking at waste produced per unitof electricity generated. For the
long-lived equivalent waste, SMRs
would produce up to 30 times
more and for spent nuclear fuel,
up to five times more. The
variation in these figures reflects
expected variation in SMR designs
in development.“The information right now
being put out by reactor developers
can be seen as promotional,” says
Krall. “SMR performed worse on
nearly all of our metrics compared
to standard commercial reactors.”
The study suggests that SMRsMini nuclear reactors may create more radioactive waste for a given
amount of power than conventional reactors, reports Adam VaughanNuclear waste in spotlight
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Energyproduce higher volumes and
greater complexity of waste
because they are naturally
less efficient. Nuclear power
generation involves a nuclear
chain reaction, in which one
nuclear reaction in the reactor
core creates neutrons that then
go on to cause an average of one
or more subsequent nuclear
reactions. However, according
to Krall’s team, SMRs leak more
neutrons out of their core than
a larger reactor, so they cannot
maintain the self-sustaining
reaction for as long (PNAS,
DOI: 10.1073/pnas.2111833119).
Diane Hughes at NuScale Power
says the study relies on outdated
information and the waste per
unit of energy for its SMR
compares favourably with large
reactors. “We don’t agree with
the conclusion that the NuScale
design creates more used spent
fuel per unit of energy compared
to currently operating light water
reactors,” she says.
The UK government has
provided funding for Rolls-Royce
SMR to advance its own version of
the technology. This design wasn’t
considered in the new study, but
a company spokesperson said
Rolls-Royce SMR would be
submitting estimates on waste
volumes as part of its years-long
journey through the UK nuclear
regulatory approval process,
which started in April. The Rolls-
Royce SMR design “includes
some technical innovations
that reduce waste arisings”,
said the spokesperson.
Very few countries have made
progress on plans for long-term
facilities to store their nuclear
waste underground, with Finland
and Sweden two of the exceptions.
“We need to get more serious
about practically managing
[SMRs] nuclear waste,” says Krall. ❚Concept image
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“SMR performed worse
on nearly all of our metrics
compared to standard
commercial reactors”