Proof-of-principle measurements for an NDA-based core discharge monitor Page: 3 of 8
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PROOF-OF.PRINCIPLE MEASUREMENTS
FOR AN NDA-BASED CORE DISCHARGE MONITORL K. Halbige
Los Alamos National Laboratory
Group N-1. MS E540
Los Alamos, NM 87545 USA
ABSTRACT
The feasibility of using nondestructive assay instruments
as a core discharge monitor for CANDU reactors was investi-
gated at the Ontario Hydro Bruce Nuc:ear Generating Station
A, Unit 2, in Ontario, Canada. The measurements were made
to determine if radiation signatures from discharged radiated
fuel could be measured unambiguously and used to count the
number of fuel pushes from a reactor face. Detectors using the
(y,n) reaction thresholds of beryllium and deuterium collected
the data, but data from shielded and unshielded ion chambers
were collected as well. The detectors were placed on a fueling
trolley that carried the fueling machine between the reactors
and the central service area. A microprocessor-based electron-
ics system (the GRAND-I, which also resided on the trolley)
provided detector biases and preamplifier power and acquired
and transferred the data. It was connected by an RS-232 serial
link to a lap-top computer adjacent to the fueling control con-
sole in the main -reactor control room. The lap-top computer
collected and archived the data on a 3.5-in, floppy disk. The
results clearly showed such an approach to be adaptable as a
core discharge monitor.
INTRODUCTION
CANDU reactors are refueled semicontinuously in both di-
rections during operation so contro! the core reacuvity and to
use the reactor fuel efficiently. The refueling is carried out by
an automated fuei-handling system that move' fresh fuel from
a fresh-fuel port at a central storage area to the reactor face by a
"charge machine." Fresh fuel is "pushed" into one face of the
reactor from the charge machine, and irradiated fuel is simulta-
neously removed from the other face by a discharge machine.
The fuel is then transported back to the central storage area
where it is discharged into temporary storage through irradi-
ated fuel purs. A conceptual representation of this is shown
in Fig. 1.
At multi-reactor stations, the chiuge and discharge fueling
machines, which contain fresh or radiated fuel, are trans
ported on trolleys that move in the tunnels that connect the
reactors aad the central fuel storage area (CSA). A transverse
cross section of the tunnel and the reactor containment is
*Work was performed while on leave as a United States cost-
free expert to the Intemauonal Atomic Energy Agency.A. C. Monticone
International Atomic Energy Agency
Box 100, A-1400
Vienna, AUSTRIA
S-
\ CHARGE
)MACHINE
DISCHARGE FRESH FUEL
MACHINE
CENTRAL
STORAGE
AREA
IRRADIATED
FUEL PORT
Fig. . Conceptual diagram offueling cycle.
shown in Fig. 24a). A longitudinal cross section is shown in
Fig. 2(b).
A CANDU reactor might discharge Letween 55 and 65 fuel
bundles per week. At some multi-reactor stations, this number
is multiplied by the number of reactors. This large number of
irradiated fuel assemblies, coupled with the many possible
paths for diversion presented by the logistics of transporting
the fuel between the various reactors and storage areas, defines
the requirements of a safeguards approach. The classical
method for safeguarding Mould require seals and cameras at
strategic locations. These efforts could be supplemented by
short-notice random inspections (SNRI). Reviewing camera
images, verifying seals, and staging SNRI is very human re-
source intensive. Bence an alternative method of safeguarding
the fuel was sought.
An alternative described in this paper uses radiation detec
ors to monitor the movement of irradiated fuel between the rr
actor core and a central storage area. The thoughts on this
method were prompted by a feasibility study for a reactor
power monitor chat was done by Iot Engineering Ltd in
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Halbig, J. K. (Los Alamos National Lab., NM (USA)) & Monticone, A. C. (International Atomic Energy Agency, Vienna (Austria)). Proof-of-principle measurements for an NDA-based core discharge monitor, article, January 1, 1990; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1415684/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.