| As utilities
seek to build new nuclear power plants around the world, questions remain
about whether the newer reactors are sufficiently foolproof to be adopted
on a large scale, says Susan Q. Stranahan
In 2007, the first application to build a new
reactor in the United States in more than three decades was filed with
the Nuclear Regulatory Commission (NRC).
By the end of that year, four more applications had landed at the agency.
In 2008, 12 additional applications arrived, with one more filed in 2009.
Nuclear backers proclaimed a "renaissance" underway.
The NRC, which over the years had lost personnel
because of a shortage of work, geared up, hiring 1.000 new staffers to
handle the licensing requests. Things got so crowded at the Office
of New Reactors that in May the agency broke ground for a third office
building in suburban Washington.
A new generation of nuclear power is indeed
taking shape, driven, in large part, by a growing sense among environmentalists
and policymakers that any strategy to wean the U.S. off planet-warming
fossil fuels must include construction of more nuclear power plants. But
how safe will this new generation of nuclear power plants be in comparison
to the existing fleet of 104 plants that currently generate 20% of the
Perhaps the most critical difference is that
the new designs are simpler and rely less on human or mechanical intervention
in the case of accidents. Settling on a standard design was one recommendation
made after the 1979 accident at Three
Mile Island. Some designs, for example, use gravity to provide
emergency cooling water rather than pumps, which can fail. Some reactors
now have redundant safety features, like extra pumps. In addition, the
NRC has increased regulatory scrutiny of the new designs, ordering, for
example, additional safety features or engineering changes to improve delivery
of emergency cooling water.
Russ Bell, director of new plant licensing
at the industry's Nuclear Energy Institute
in Washington, maintains that the new plants will be extraordinarily safe.
Government risk assessments for the new reactor
designs say that an accident that could damage the reactors' cores would
likely occur once every 10 million years — an order or two of magnitude
lower than the U.S's existing nuclear power plants. And even were a core-damaging
accident to occur, Bell says that does not mean radiation would escape,
since the reactors have containment buildings and systems designed to prevent
releases of radioactivity.
Since the terrorist attacks of Sept. 11, 2001,
all containment structures on new nuclear plant designs in the U.S. have
been re-engineered to withstand the direct impact of a jetliner. This does
not mean, however, that new containment designs are foolproof. The containment
structure on a popular Westinghouse design, which seven utilities are now
considering building, has been upgraded, but the NRC determined it probably
won't withstand a severe earthquake.
It's also worth noting that the NRC does not
require the new plants to be any safer than existing ones. Rather, it only
requires the plants to "provide the same degree of protection" as
the current generation of reactors.
The new reactors remain a work in progress.
Even without knowing exactly what the finished reactors will look like
— or cost — some utilities have already made their choices, spurred on
by promises of federal subsidies and political pressure to cut carbon emissions.
In a speech to industry leaders in May, Nuclear Energy Institute CEO Marvin
Fertel said that the construction of nuclear reactors to provide additional
power and to replace older plants — U.S. reactors are limited to 60 years
of operation — means that 187 new nuclear power plants must be built by
Many outside the industry believe that figure
is unrealistically high.
Elsewhere around the globe, nuclear power
expansion is underway. Today, 436 reactors are operating in 31 countries,
generating about 15% of the world's electricity. Fifty reactors are
under construction, primarily in China, South Korea, and Russia, with the
fastest growth in Asia. India, France, and Finland
also are building new plants.
Although the new U.S. reactors will have some
"design enhancements" — digital controls versus analog dials, for
example — "at bottom they are based on familiar and proven technology,"
says Bell. The two underlying technologies – pressurized water reactors
and boiling water — have been around since the start of the nuclear power
era. (In a pressurized water reactor, superheated water is pumped under
high pressure to the reactor core; the heated water then transfers its
thermal energy to a secondary steam system that turns a turbine to generate
electricity. In a boiling water reactor, the water is injected directly
into the core, creating a water-steam mixture that turns the turbine. Most
reactors in the U.S. are pressurized water reactors.)
Those technical similarities are a good thing,
according to nuclear safety watchdogs. "The further away you are from
systems in common use and from actual construction experience, the bigger
the uncertainties are going to be," says Edwin Lyman, senior scientist
with the Union of Concerned Scientists
(site France), which has been evaluating
reactor safety for four decades.
Under ideal circumstances, there would be
just one or two designs under consideration, not five. Settling on a "standardized"
design was among the recommendations made by nuclear advocates and critics
alike in the aftermath of 1979's accident at Three Mile Island in Pennsylvania.
Having just one or two "off-the-shelf" designs would simplify licensing,
construction and operation, and hold down costs. This country's existing
reactors are custom-made; no two are alike, which means they are extremely
complex to build, run, and regulate.
But companies hoping to dominate the U.S.
market have filed applications to build a variety of designs, and the NRC
has committed to reviewing the massive documentation for each.
For many at
the NRC, this is new work: Half the agency's workforce has been on the
job for less than five years. And the information provided by the manufacturers
is sometimes lacking. Last year, NRC chairman Gregory B. Jaczko complained
that "we have incomplete designs and less than high-quality applications
submitted for review."
It will be at least 2012 before the first
new design wins final approval from the NRC. The four other designs are
lined up behind that on the NRC's calendar, pushing licensing into the
middle of the decade. Indeed, the approval process already is behind schedule
because of safety issues with some reactor designs, such as the integrity
of the containment dome around the AP 1000 design from Westinghouse.
Most experts don't expect a new reactor to
be operating in this country before late 2016 or early 2017.
The pace of design reviews and licensing contrasts
sharply with the political push to build new nuclear plants, which are
regarded by many on Capitol Hill and in the White House as key to combating
climate change. That has created the curious situation in which utilities
have announced plans to build reactors from specific vendors before they
know everything about what they're buying. Part of the reason utilities
are committing to new construction now is to snag attractive financial
inducements from Washington that are being offered on a first-come, first-served
In recent months, the Obama administration
and nuclear backers in Congress have beefed up incentives first offered
in the 2005 Energy Policy Act. In February, the White House announced $18.5
billion in tax credits, as well as loan guarantees for new reactors. The
Kerry-Lieberman climate bill would raise the guarantees to $54 billion,
and some in Congress favor no limits. (The loan guarantees are regarded
as critical to help utilities cut their borrowing costs for the first new
reactors, each of which is expected to cost $10 billion to $12 billion.)
What are the designs under review and what new features do they include?
One important distinction is whether the reactors
rely on "active" emergency cooling systems (which depend on mechanical
equipment and uninterrupted electrical power supplies) or "passive" systems
(which rely on gravity or other natural features). Current reactors utilize
active systems. Adoption of passive systems was ranked high on the list
of recommended safety changes in the aftermath of Three Mile Island, although
passive systems could pose risks, such as being unable to supply enough
water where it's needed, when it's needed.
There is very little actual experience in
either the construction or operation of the new reactor designs to guide
utilities in making their choices. "There doesn't seem to be much difference
in the price ranges of the various designs," says Lyman. "But a
lot of the cost will have to do with the learning curve of building new
reactors again." (There have been no new reactor construction starts
Will this new generation of reactors be safer than
the current nuclear plants? Ask that of the industry's Russ Bell and he
chooses his words carefully, because to imply that the new reactors are
"safer" than the old ones infers that the existing plants are less safe.
"We think all our plants are safe,"
The industry has performed complex mathematical
analyses called probabilistic risk assessments to measure the likelihood
of a serious accident, says Bell. "When you run the numbers on the newer
designs, as you'd expect, the chance of a damaged core or release of radiation
accident is much, much lower than the current fleet," he says. "But
the numbers are very low for all the plants."
The analysis is limited, however. Computed
risks for new reactors are lower than for current designs "when only
internal events are considered," according to a 2009 report that the
Nuclear Energy Institute wrote for the NRC. (That includes fires or pipe
breaks, for example.) But when risks of damage caused by external events
— earthquakes, for example — are factored in, the new reactors are no safer
than older reactors. In addition, because utilities have no operating experience
with the new reactors, the probable risk assessments are purely theoretical
and not as reliable as years of actual operating data from existing plants.
While the NRC continues its evaluation of
the five reactors, Lyman argues that none is as safe as it could be. The
new designs are engineered only to withstand a predictable sequence of
events, something engineers theorize may happen. In nuclear parlance that
is called a "design basis accident." The new reactors, like their
older counterparts, are not designed to survive an unexpected sequence
of events. That is the critical flaw, says Lyman: "Three Mile Island
was a beyond-design-basis accident."