Nuclear Plant Journal, July-August 2014 NuclearPlantJournal.com
25
prising several canister designs. Recent
studies have indicated that canisters may
be susceptible to chloride-induced stress
corrosion cracking (CISCC), particularly
those located in marine environments.
Other degradation mechanisms such as
general corrosion are also possible though
considered less likely.
Nondestructive inspectionof thesedry
storage canisters for the presence of stress
corrosion cracking and other potential
degradation would advance understanding
of these phenomena. The limited access
around the canisters, however, presents a
challenging inspection environment due
to high surface temperatures and radiation
fields.
EPRI has developed a four-step
approach to address this challenge. First,
EPRI is leading collaborations among
multiple universities, vendors, utilities,
and national laboratories to coordinate
research and planning. Second, EPRI is
creating representative mockups of the
canister designs of interest with embedded
flaws to test nondestructive evaluation
(NDE) techniques. Third, EPRI is
identifying promising NDE technologies
that can inspect dry storage canisters for
the degradation mechanisms of concern.
Finally, EPRI is investigating robotic
delivery systems that could support in-
situ inspections of the dry storage canister
systems of interest. The end goal is to
deploy NDE technologies to inspect a
canister by the end of 2017.
EPRI has already teamed with
vendors and utilities to perform surface
inspections of canisters at three sites
and is using lessons learned from this
experience to inform ongoing efforts.
The EPRI Report, Calvert Cliffs Stainless
Steel Dry Storage Canister Inspection
(1025209), describes a number of
inspections performed on a dry storage
system. Additional information is
contained in EPRI Report 1022916 and
on the NRC’s ADAMS website.
Contact: Jeremy Renshaw, telephone:
(704) 595-2501, email:
Nano-Sensor
Solid-state nano-sensing technology
offers near-term potential for achieving
a 20% reduction in existing equipment
requirements for remote detection and
monitoring of hydrogen in nuclear plant
containment structures. EPRI is also
investigating a self-powered hydrogen
sensor that could withstand severe loss-
of-coolant accident (LOCA) conditions
inside containment.
Early detection of significant hydro-
gen generation during an accident sce-
nario would provide invaluable guidance
to plant operators regarding the optimal
course of action for minimizing the re-
lease of radioactivity to the environment.
Current hydrogen monitors require sig-
nificant auxiliary infrastructure because
the analyzer elements are outside contain-
ment. EPRI began exploring novel hydro-
gen sensing technologies and energy har-
vesting concepts in 2012, with the stretch
goal of developing a low power, accurate
hydrogen sensor suitable for continuous,
self-powered operation in containment.
Through scouting efforts, two tech-
nologies were selected as the most prom-
ising for powering in-containment sen-
sors: radiation (beta-voltaic) and thermal
(thermoelectric) energy harvesting (EPRI
Report 3002002107). In follow-on work,
EPRI is pursuing near-term nuclear plant
application of a nanostructure-based sen-
sor fabricated from ceramic semiconduc-
tors and designed specifically for severe
environments. Researchers have demon-
strated accurate hydrogen sensing in con-
ditions simulating normal operations and
LOCA conditions in laboratory testing
of a purpose-built prototype. This sensor
initially is being designed for direct re-
placement of existing sensors in installed
hydrogen monitoring systems. However,
its lower power requirements and abil-
ity to withstand extreme environments
indicate promise for future development
as a self-powered sensor (EPRI Report
3002002881).
By eliminating the need for multiple
flow meters, pressure regulators, and
associated components, the solid-state
nano-sensor could reduce equipment
requirements by about 20%, and also
reduce maintenance and calibration labor.
Contact: Jeff Greene, telephone:
(704) 595-2666, email:
jgreene@epri.
com
.
Source: Electric Power Research
Institute’s (EPRI) Nuclear Executive
Update, May 2014.
