Cerenkov Light Production in a Water Moderated Nuclear Reactor
Cerenkov Light Production in a Water Moderated Nuclear Reactor
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Date
1963
Authors
Madey, Robert William
Advisor
Duffey, Dick
Citation
DRUM DOI
Abstract
An experimental investigation of the production
of Cerenkov radiation in a water moderated nuclear
reactor is conducted using a photomultiplier as a
light sensor. The variations in light intensity
are studied during various phases of reactor operation,
namely: startup, steady state and shutdown.
The relevant theory is presented as an aid in interpreting
and extrapolating the experimental results.
It is found that for transients such as startup,
the light signal is directly related to reactor power
for periods (e - folding time) faster than about 20
seconds. Additional transient data acquired from
measurements performed on a TRIGA pulsed-type reactor
illustrate the excellent agreement between the Cerenkov
detector and a conventional ionization chamber for
measuring pulse characteristics such as peak power,
pulse half-width, and prompt period. The proportionality
between reactor power and Cerenkov signal is no
longer valid for whole core measurements made at steady
state power level because of the gradual increase of the
Cerenkov signal as a result mainly of fission product contributions. Selective scanning of the Cerenkov
spectrum through the use of interference filters over the wavelength range 3500 Å to 5530 Å results
in a lower buildup fraction. Indications are that
measurements further into the short wavelength
region may yield a light sensor, and hence a good
power detector, independent of any fission product
buildup. The decrease in the Cerenkov light intensity
after shutdown is measured for reactor operating times from
20 minutes to 4 hours. Comparison of the empirical
data with theoretical considerations results in good
agreement for shutdown times ranging from 500 seconds
to 10,000 seconds.
Spectral measurements made through 17 feet of water
with a Hilger quartz spectrograph show a spectral distribution ranging from 2500 Å to 6000 Å. A calculated spectral
distribution is compared with the measured spectrum after
correcting for water attenuation.