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NuclearPlantJournal.com Nuclear Plant Journal, September-October 2015
materials and calibrated in a sophisticated
manner so that they can measure
hydrogen in a wide variety of challenging
environmental conditions.
The comprehensive development
and multi-phase testing was performed
over a three year test period.
The initial testing consisted of
verifying the performance of the
hydrogen sensor to measure hydrogen
concentration for basic temperature
dependency, stability at temperature,
and performance under varying oxygen
levels. The test conditions included the
very extreme temperatures of 600°C,
650°C, and 700°C, which are far in excess
of predicted SA temperature conditions.
The next set of tests were to verify
performance in an integrated temperature
control test which ramped the temperature
at a constant rate, additional stability tests
at high temperatures, a high radiation
environment test at two high radiation
dose rates, performance under pressure,
stability at high pressure conditions,
water vapor testing, additional testing
at high and low oxygen conditions, and
response time testing. Radiation exposure
tests were performed to a Total Integrated
Dose of 500 MRads, which is over 2.5
times previous radiation exposures for
Class1E equipment. Pressure testing
was performed from room conditions
up to 150 Psig, which is almost 300%
of containment design pressure. Low
oxygen testing was performed since
many containments are inerted to provide
additional combustible gas control.
The purpose of testing at these extreme
conditions was to ensure that the sensors
would be operable and accurate in every
SA condition.
In the final year of testing, tests were
performed to measure hydrogen sensor
performance when coexisting substances
were present, stability with coexisting
substances, varying high dose rates,
combined environment performance,
harsh environment testing, compensation
verification, and seismic testing.
The coexisting substances, gases
were Iodine (I2), Cesium Iodide (CsI),
Methyl iodide (CH3I) and Carbon
Monoxide (CO). Coexisting substances
have little effect, except for CO. The
Hydrogen sensor also reacts to CO, which
is another combustible gas and generated
from Molten core Concrete Interaction
(MCCI). This is a very significant
development because the ability to detect
carbon monoxide contributes to the
ability to monitor SA progress and efforts
to mitigate SA conditions.
The development and testing on
the GLSEQ hydrogen monitor have
demonstrated a new instrumentation
capability for severe accident monitoring
and the ability to detect fuel damage and
reactor breach. The GLSEQ hydrogen
monitor provides an advanced level of
safety since they are independent of
existing instrumentation, specifically
designed for severe accidents, and provide
condition monitoring information during
normal conditions. GLSEQ hydrogen
sensors are then integrated into Post-
accident monitoring GLSEQ Hydrogen
Risk Management System (HRMS).
The GLSEQ HRMS replaces
antiquated combustible gas systems that
breached containment, relied on bulk
sampling, and were difficult to maintain.
GLSEQ HRMS requires no maintenance
and contains the following features:
Designed for SA
Converts hydrogen gas directly
to an electrical signal
Continuously monitors the
containment gas
Does not utilize a gas sampling
system
Measure and Locate SA conditions
Measures Hydrogen, Oxygen,
Carbon monoxide, temperature,
pressure, and relative humidity
Evaluates Risk of Explosion
GLSEQ Sensor Processing Unit
(SPU) analyzes explosive risk
Displays Shapiro-Moffette Ex-
plosive risk information
Data continuously recorded and
stored in an event recorder
Mitigation information
Pre-engineered
mitigation
solutions are displayed for the
Severe Accident...
GLSEQ Hydrogen Monitor.
