Since its creation in 1974,
the U.S. Nuclear Regulatory Commission (NRC) has been a principal sponsor
of research to advance nuclear technologies. Because ORNL has been a leading
participant in the performance of NRC research, we have been better able
to maintain our role as a nuclear laboratory, especially over the past
15 years. "We are still doing important nuclear safety work for the NRC,"
says Claud Pugh, head of NRC programs at ORNL.
For example, in 1998 ORNL investigated whether electric utility industry
restructuring would increase the risk of loss of off-site power (LOOP)
to nuclear power plants. Risk analyses have shown that LOOP events lead
to increased risk of reactor fuel core damage in the event of an accident.
An ORNL teamóB. J. Kirby of the Engineering Division and A. Bruce Poole
and John D. Kueck, both of the Engineering Technology Divisionófound
significant differences in the way restructuring is being carried out
during their visits to 17 nuclear plants in 10 regions.
Historically, the electric power industry in the United States has
been dominated by utilities that control the generation, transmission,
and distribution of electricity in their service areas. With restructuring,
power suppliers will compete for customers located anywhere on the national
transmission grid, and regional grid control will be the responsibility
of independent system operators (ISOs).
"It is uncertain how the ISOs will maintain reliability of the grid,
and specifically, the reliability of the circuits that provide power
to nuclear power plants," Kueck says. "The nuclear industry and NRC
need to better understand the synergism among power plants within a
given region." They also must understand how distribution of responsibilities
and increased competition for the most economical power (often obtained
from outside an ISO's geographic area) can affect the potential for
LOOP events. To get better answers, probabilistic risk assessments may
In the Heavy-Section Steel Irradiation Program, Randy Nanstad, Shafik
Iskander, Don McCabe, and Mikhail Sokolov, all of ORNL's Metals and
Ceramics Division, have been developing data to account conservatively
for irradiation embrittlement of reactor pressure vessel steels. Neutrons
from reactor fuel cores cause the ferritic steels in reactor pressure
vessels to become a little brittle, but they normally don't develop
cracks from the high temperatures and water pressures typical of reactor
operation. To determine how resistant these embrittled vessel steels
are to fracture, the researchers, including ETD's John Merkle, have
developed a new experimental fracture mechanics method that requires
fewer experiments than were needed before for each steel examined.
"The method helps the reactor operator and the NRC determine whether
the embrittled steel is sufficiently resistant to fracture to ensure
that the continued operation of the vessel is safe," Nanstad says.
This "master curve" concept has been accepted as an American Society
for Testing and Materials standard. Other countries are considering
using the concept in their commercial nuclear power programs. This accomplishment
is one of many reasons why ORNL has long been the NRC's lead laboratory
for nuclear pressure vessel technology.