Here is Nucleonics Week's take on the EPRI study story.....
Jaro
NUCLEONICS WEEK - June 20, 2002
CONTAINMENT BREACH FROM JET CRASH
HIGHLY UNLIKELY, SAYS EPRI STUDY
A large commercial jetliner deliberately flown into a nuclear
plant would not be able to penetrate the containment,
according to preliminary findings of an Electric Power Research
Institute (EPRI) study.
The study has not been made public, but the findings were
disclosed June 17 by Stephen Floyd, senior director of regulatory
reform at the Nuclear Energy Institute (NEI).
He told reporters at a National Press Foundation seminar
that a final version of the study, which focused on the impacts
of an aircraft crash into a reactor, would be completed later
this month and then it would be peer-reviewed. It could undergo
a broader review after that by other interested parties,
such as Union of Concerned Scientists and Nuclear Control
Institute (NCI), Floyd said. A public version is expected to be
released, though he did not know when.
Floyd said the concern that the jet's engine would cause
the most damage was not borne out by the study. Instead it
found the "mass of the airplane" was more problematic than
the engine, which would "telescope" or become "pancaked"
upon impact, he said.
Damage caused by a fire erupting from aircraft fuel released
in the crash also would not breach the containment, he
said the study found. He said the fuel would burn itself out in
around 10 to 20 minutes.
But NCI President Edwin Lyman said at the seminar that
he believed it would be possible for a jet to penetrate a containment
building. He said calculations using a modified
National Defense Research Committee formula, which he
labeled as conservative, showed a Boeing-767 jet engine
flying at "maximum cruising speed" could penetrate several
feet of reinforced concrete.
Moreover, Lyman said it was not necessary to penetrate
the reactor building to disrupt the plant. For example, a hit to
the auxiliary buildings would cause considerable problems, he said.
The airplane crash study was prompted by concerns over
the Sept. 11 terrorist attacks and what would happen if terrorists
crashed a commercial plane into a nuclear power plant.
NRC is conducting its own engineering analyses of a
jetliner crash and will look at the effects of the impact and the
resulting fire on the containment building and other support
facilities. Floyd said the agency has not been sharing information
with the industry on those results, and he did not know
when the study would be completed.
The NRC contracted with the Argonne National Laboratory
in the early 1980s to conduct an aircraft hazards analysis.
That report, published in 1982, looked at accidental crashes,
not deliberate acts. The report said that plants under construction
at the time did not have containments designed to "take
the impact" of a large commercial aircraft.
The Argonne report said the criticality control systems in
a PWR-control rods/drives and safety injection systems-
were well protected against a direct impact of a crash but
found some support subsystems, such as water intakes, were
not. "Furthermore," the report said, "offsite power is quite
vulnerable to direct impact in case of an aircraft crash."
For BWRs, the report said the "entire" reactor shutdown
system was protected inside the containment but there were
risks in "nonhardened" areas of the plant, particularly the
switchyard and turbine hall. "It should be kept foremost in
mind that the combined effects of impact and fire due to an
aircraft crash open the possibility for numerous multiple failures."
The report urged further study in this area.
Small Planes Not A Threat
Commercial planes have not been the only concern since
Sept. 11. A new report commissioned by the Aircraft Owners
& Pilots Association concludes small aircraft, referred to as
general aviation, are not a serious threat to nuclear power
plants. Its report, dated May 16 but released June 6, found
that a small plane could not penetrate the concrete containment
and that an attack on the auxiliary buildings also would
not cause a safety failure.
"Given that aircraft size and speed are two crucial elements
in the damage equation, a light, general aircraft weighing
less than 6,000 pounds traveling at under 300 miles per
hour simply lacks the energy to cause significant damage,"
concluded the report's author, consultant Robert M. Jefferson of New Mexico.
A small plane crash also would not be able to ignite zirconium
cladding on spent fuel, the report said.
Jefferson said "solid" zirconium does not melt until reaching about 3,330
degrees F, although "shavings or dust will burn."
That means a terrorist would have to chop the fuel cladding into small
pieces before it would ignite-and would need large quantities
of it to get the desired reaction. He said aviation gasoline
burns at about 2,000 degrees F and would need hours to reach
the temperatures required to burn the zirconium shavings, an
impossibility since the largest light aircraft carries less than
300 gallons of fuel. The fire would last "only milliseconds," Jefferson said.
Jefferson also dismissed the possibility for a small aircraft
to strap on explosives to breach a containment building and
cause a core meltdown. He said small aircraft would not be
able to carry thousands of pounds of explosives and that the
explosives would have to be carried in the passenger cabin or
cargo compartments, away from the nose of the plane and
point of impact, reducing the possibility of any damage to the containment.
Floyd repeated what the industry has frequently said since
last fall: The government and public should not focus only on
nuclear plants. He said other types of facilities and "soft
buildings," such as hospitals, schools, and shopping centers,
would pose more risks in terms of damage and deaths. A
Senate committee is, in fact, scheduled to vote next week on a
bill introduced by Sen. Jon Corzine (D-N.J.) that would require
increased security at chemical plants.
Floyd said the nuclear industry is doing its part to cut risks
of a terrorist attack. It has stopped granting temporary
unescorted access to nuclear power plant workers. He said
personnel must now wait for criminal background checks to
be completed before being allowed into protected areas without an escort.
NCI's Lyman criticized the industry's response time to
NRC's Feb. 25 security orders, saying 73% of the plants had
requested extensions up to 5.5 months to provide schedules.
He said compliance with a requirement for truck bomb analyses
in particular was a problem because the plants didn't have
the "technical means" for making the evaluations.
But Floyd defended the time it was taking for reactor
operators to develop a schedule for implementing the security
orders. He said there was initially a disagreement between the
NRC staff and industry on the codes that could be used. The
interim compensatory measures assumed a larger bomb than
the one specified in the design basis threat (DBT) that companies
have been using to structure their defensive plans.
Floyd said the codes that NRC wanted the industry to use were classified
by the Department of Defense, and the industry did not have access to them.
Floyd said the industry is concerned about what the final
DBT requirements will be, since making changes is "never
easy or inexpensive." But Floyd was skeptical that the commission
would act soon on DBT revisions. "I think they are
going to take a stab at it," he said. "But I think they feel they
could be overridden by the Office of Homeland Security."
-Jenny Weil, Washington