Proof-of-principle measurements for an NDA-based core discharge monitor Page: 6 of 8
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7
g
U
wBe(y, n) DETECTOR RESPONSE
24 - I -T-- T-T- --T-
22
20
1e -
16 -
14
12
10
a
6
4
2 -
0 2 L LL L L 2
0 2 4 6 a 10 12 14 16 ta 20 22 24 26
ELAPSED TIME (thousand seconds)Fig. 4. A complete fuel campaign as detected by the Be(yn).
continuum. Nine minutes after the first push a second one oc-
curs with a peak of approximately 68()0 counts/s. These two
pushes were from channe C-09, which was approximately 15
m from the detectors. At this reactor, the bundles are pushed
in pairs. The second peak is larger because those bundles
were closer to the center of the reactor and hence they were
exposed to a higher neutron flux.
The structure of the data after the second push and up to
8000 s is indicative of the motions of the discharge machine
as it rotates to put the shield and end plugs back into the fuel
channel. The x-y stage then transports the fueling machine
magazine to the next channel to be fueled. The decay of the
radiation from the stationary discharge machine can be ob-
served during the time it is stationary. The high and low ex-
cursions before the third push are due to the rotations of the
fueling machine magazine to remove end and shield plugs and
position an empty chamber to receive the fuel from the next
push. The next twc pushes occurred just after 8000 s. These
pushes were fr.m channel V-11, which is significantly closer
to the detectors: approximately I I m from the detectors. The
rotations of the magazine and translations of the discharge
machine and the decay of the radiations from the fuel inside the
machine are again clearly visible on the response curve as the
discharge machine is moved to position X-19 for four pushes.
On these pushes, little humps aae visible on the leading edges
of the response peaks (Fig 5). These bumps are indicative of
the fueling procedure by which the assemblies are pulled
slightly and then pushed back to assure that they have been
secured. Here the unequal core flux effect on the activities of
the bundles is clearly visible in the relative heights of the
peaks. When the fueling machine is full, the continuum is
significandy higher. The fueling activities tn the vault lasted
about 4 h.
At about 19 000 s, a large signal excursion was noted.
With the help of the fuel-handling personnel, the mystery of
this monolith was explained as follows. The first large excur-
%ion is due to the x-y stage banging the discharge nachineg
0
w
0
w
N24
22
20
1a
16
14
12
10
6
4
2
0Be(y, n) DETECTOR RESPONSE
- ----- -- - --- ----- - - T - - ---- .-12
13
14 1s 16 17
ELAPSE') TIME (thousand seconds)J
19Fig. S. Leading-edge bumps on response peak.
down to the elevator on the fueling trolley. The delay at about
the mid-height point results from the discharge machine being
transferred from the x-y stage to the elevator. The elevator
then brought the discharge machine down to the trolley bed
where the machine was repositioned. Once the machine was
in position on the trolley, the trolley traveled (carrying both the
discharge machine and the detectors) to the CSA. The decay
of the radiation during the travel is clearly visible. The fueling
machine 'vas between I and 3 m from the detectors during the
trip. The process of moving the fueling machine from the
trolley to the x-y stage at the CSA and then to the spent-fuel
por is reversed from the process in the vault. Note that the
x-y stage sat for a while before carrying the discharge machi il!
to the port. This produces the decay visible on the falling ed ,e
of the monolith. A further decay can be seen before the fuel
was pushed into the spent-fuel port. The signature of the
transfer of the irradiated fuel into the storage areas is shown
better in Fig. 6.I
I
I0(y, n) DETECTOR RESPONSE
12 t---r ----T T----r --r -- - -1 r 1
10
12
e
II
44
E
2
2
741 250 25.2 254 256 25 210 262 264 265 265 2F0 21?2
ELAPSED TIM1E (thousand seconds)Fig. A. Signature rf irradiated furl transfer to the ventral %tor
age area.1
1
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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/m1/6/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.