POWER July 2011 - 12

that actual damage to the reactor pressure
vessel is limited, based on temperatures
around it. The utility is expected to
release similar findings about fuel meltdown
at Units 2 and 3. Meanwhile, computer
simulations of the damaged units
suggest that Unit 1 has one hole, Unit
2 may have two breaches, and Unit 3's
cooling systems may have been breached,
TEPCO said.
Japan's response to the dire crisis was
exemplary under the circumstances, but the
country's regulation of its nuclear power sector
and safety preparedness was faulty, the
International Atomic Energy Agency (IAEA)
said in a preliminary report released in June
(Figure 4). Specifically, the IAEA said that
officials had underestimated the threat from
tsunamis to coastal nuclear plants. " Nuclear
regulatory systems should address extreme
external events adequately, including their
periodic review, and should ensure that regulatory
independence and clarity of roles are
preserved in all circumstances in line with
IAEA safety standards, " it says.
Japan has responded to the report by admitting
that poor oversight contributed to
the disaster and that it would overhaul regulation
of the country's nuclear power sector.
Japan's Nuclear and Industrial Safety Agency
(NISA) has so far already announced new
safety measures. Only 19 of the country's 54
reactors are in operation, and local governments
have reportedly been waiting for the
new standards before approving restart of
the remaining reactors.
Prime Minister Naoto Kan and NISA officials
have come under fire for failing to
completely disclose key information about
the crisis and ensuing radiation. In early
June, for example, NISA officials revealed
that the Fukushima accident had generated
770,000 terabecquerels of radiation-
more than twice the radiation previously
estimated. That figure is reportedly seven
times the radiation emitted by the accident
at Three Mile Island but just 15%
that from Chernobyl.
Crews continue scrambling to control
the situation at the Daiichi plant, which
suffered critical power loss after a magnitude
9.0 earthquake and 14-meter (46foot)
wave-more than twice the height
of the protective wall at Fukushima-and
saw subsequent explosions at Units 1, 2,
3, and 4. TEPCO has begun preparatory
work for installing a cover over the Unit 1
reactor building as an emergency measure
to prevent the dispersion of radioactive
substances until mid- to long-term measures,
including radiation shielding, are
implemented. Nitrogen gas is still being
injected into the Unit 1 containment ves12
sel
to reduce the possibility of hydrogen
combustion inside the vessel.
As of early June, closed-loop cooling
had not yet been established, and freshwater
was being continually injected both
via the feedwater system lines and the fire
extinguisher lines into the reactor pressure
vessels at Units 1, 2, and 3. TEPCO in May
also began installing a supporting structure
for the floor of the damaged spent fuel pool
of Unit 4 (Figure 5). TEPCO believes that
the damage to the Unit 4 building could
have been caused by " hydrogen generated
at Unit 3 that flowed into Unit 4. "
Meanwhile, TEPCO continues to deal with
massive volumes of stagnant water in the
basement of the turbine buildings of Units 1
and 3 that has high levels of radioactivity. It
is trying to transfer the water into condensers,
a radioactive waste treatment facility,
the high-temperature incinerator building,
and temporary storage tanks.
Holtec, Westinghouse Roll
Out Small Modular Reactor
Designs
As the Daiichi nuclear crisis has governments
around the world reconsidering their
nuclear-heavy energy plans and scrutinizing
the safety of existing reactors and
third-generation designs, several developers
are touting the merits of small modular
reactors (SMRs). A growing number of
SMR developers are considering applying
for design certification from the U.S. Nuclear
Regulatory Commission (NRC). Among
them are NuScale Power, with its 45-MW
modular units, and Babcock & Wilcox, proposing
a 125-MW mPower design. (For more
on these plans, see " Nuclear Power in the
Shadow of Fukushima, " p. 66) Joining that
list are two new designs announced earlier
this year: Holtec International's 140-MW
modular reactor and Westinghouse's 200MW
integrated pressure water reactor.
Holtec in February said that the proof-ofprinciple
studies of its HI-SMUR 140 were
completed. The reactor's core is located
completely underground, operated by gravity-induced
flow instead of a reactor coolant
pump. Developers say it does not rely
on offsite power for shutdown, and it can
be installed as a single unit or a cluster at a
site. " The waste heat from HI-SMUR's power
generation can be rejected through a water
cooled or air cooled condenser or a combination
thereof, " Holtec said in a statement.
" Eliminating the reactor coolant pump and
the need for emergency or off-site power
to cool the reactor core in the event of a
forced shutdown, are among the distinguishing
design features of HI-SMUR that define
www.powermag.com
POWER | July 2011
its mission of utmost safety and security. "
Among other features are its small footprint,
a 24-month construction cycle, a miniscule
site boundary dose, large inventory of coolant
in the reactor vessel, and its modularity.
Holtec plans to fund development of the
reactor itself-bypassing the fate of the
Oregon State University-developed NuScale
SMUR. NuScale Power earlier this year
stopped work on contracts and has since laid
off most of its 100-person workforce after its
primary investor firm, the Michael Kenwood
Group, was hit with a lawsuit by the Securities
and Exchange Commission on allegations
that it was improperly diverting investors'
money. Employing a handful of executives,
NuScale says it will continue to work toward
submitting an application for design certification
next year. Holtec, which is in the
process of submitting documentation for intellectual
property protection under U.S. and
international law, also plans to seek license
application by the close of 2012.
Earlier in May, the Shaw Group announced
it would provide phase one engi6.
A small package. Westinghouse's unnamed
200-MW integrated pressure water reactor
features core and reactor vessel internals
that are derived from its AP1000, a third-generation
design. Horizontally mounted axial-flow
canned motor pumps provide the driving head
for the reactor coolant system. The design also
features a compact steam generator and pressurizer
integrated into the reactor vessel head,
which eliminates the need for a separate component.
Courtesy: Westinghouse
http://www.powermag.com
POWER July 2011

Table of Contents for the Digital Edition of POWER July 2011
