Results from the testing of high temperature neutron detectors in a liquid metal fast breeder reactor at temperatures up to 1000$sup 0$F (538$sup 0$C) Page: 2 of 10
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RESULTS FROM THE TESTING OF HIGH TEMPERATURE NEUTRON DETECTORS IN A
LIQUID METAL FAST BREEDER REACTOR AT TEMPERATURES UP TO 10000F (538C)
Gerald E. Yingling and Glenn F. Popper
Components Technology Division
Argonne National Laboratory
Argonne, IllinoisABSTRACT
This paper presents a summary of results from the
performance testing of two high temperature neutron
fission counter-cable assemblies and a high temper-
*ture gamma compensated ionization chamber-cable
assembly in a typical Liquid Metal Fast Breeder
Reactor (LMFBR) nuclear environment at temperatures
up to 1000*F (538*C). A brief description of the
test program, instruments and facilities is also
included.
ITRODUCTION
The Liquid Metal Fast Breeder Reactor (LMFBR) pro-
gram has set stringent requirements on the neutron
monitoring systems that are necessary to measure
the core neutron flux for subcriticality, control
and safety purposes. In the LMFBR, large residual
gama fluxes, that are produced by sodium, struc-
tual and core material activation, in the order of
106 R/hr are foreseeable in the vicinity of the
neutron sensors. Neutron monitoring systems must
therefore be capable of discriminating against
these large unwanted gamma signals. The design of
the reactor internals usually makes it difficult to
obtain a sufficient neutron flux outside the vessel
to allow subcritical source range or startup detec-
tors to produce the required minimum count rate.
Low level flLx monitoring (LLFM) sensors must
therefore be placed in the high temperature envi-
ronment of the reactor vessel and operate in the
temperature range from 300 F (149 C) to 1100*F
(593C). Placing low temperature sensors in cooled
thimbles, such as is done in the Experimental
Breeder Reactor-Il (EBR-I1), becomes economically
unrealistic for large plants. In vessel placement
of neutron sensors require that radiation damage
from large total integrated neutron doses have a
negligible effect on the performance of the sensors
to assure an extended life and therefore minimize
their costly replacement. Retracting the sensors
from a high level neutron flux to a low level neu-
tron flux environment can extend the sensor life
but poses handling and safety problems. Wide range
neutron monitoring systems utilizing single, fixed
position, high temperature sensors are a desir-
able concept. Clearly, the need exists for high
temperature neutron sensors that will operate in
the LMFBR in-vessel environment and specifically
*Work performed for the U.S. Energy Research and
Development Administration.for fixed position, high temperature sensors that
will operate in the counting, mean square voltage
(MSV) and ionization current modes. Proven reli-
able high temperature neutron sensors for the LMFBR
environment are not yet available.
Several detector manufacturers are involved in de-
veloping and supplying commercial high temperature
neutron detectors. Domestic manufacturers include
Reuter-Stokes Inc., Westinghouse Electric Corpora-
tion and General Electric Co. Foreign manufac-
turers include the British Twentieth Century Elec-
tronics Limited and The Plessey Company Limited;
and the French Radiotechnique - Compelec.
The Argonne National Laboratory (ANL) Components
Technology Division has been engaged in a Neutron
Detector Technology development program that eval-
uates and qualifies prototype or commercial neu-
tron sensors that may meet present and future re-
quirements for LMFBR applications.
This paper presents the significant results ob-
tained from the testing of a Reuter-Stokes Model
RSN-286 and a Westinghouse Model WX-31384 fission
counter-chambers; and a Westinghouse Model WX-30950
gamma compensated ionization chamber in the EBR-II
Nuclear Instrument Test Facilities (NITF). A brief
description of the test program, instruments and
facilities is also included.
TEST PROGRAM
A typical neutron detector evaluation program con-
sists of preliminary testing, reactor life proof-
testing and post-irradiation failure analysis. The
latter may not be required if the reactor testing
did not produce a failure mode.
During the preliminary testing phase of the pro-
gram, the electrical and nuclear specifications of
the detector are checked and compared to the pub-
lished values of the manufacturer. This phase of
the program also establishes the pre-irradiation
base data for future comparisons. In addition to
the room temperature testing, the detector-cable
assembly is also tested in a furnace facility at
temperatures up to the maximum rated detector tem-
perature. This testing includes a 30 day life test
at the maximum test temperature that will be used in
the reactor proof-testinq phase of the program.
The furnace facility can heat .15 feet of the de-
tector-cable assembly in about the same geometry asForm B3-20
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Yingling, Gerald E. & Popper, Glenn F. Results from the testing of high temperature neutron detectors in a liquid metal fast breeder reactor at temperatures up to 1000$sup 0$F (538$sup 0$C), article, January 1, 1975; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc863607/m1/2/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.