Method and apparatus for measuring reactivity of fissile material

Patent · Tue Jan 01 00:00:00 EST 1985

OSTI ID:865310

Lee, David M ^[1]; Lindquist, Lloyd O ^[2]

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1. Los Alamos, NM
2. Santa Fe, NM

Given are a method and apparatus for measuring nondestructively and non-invasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. No external neutron-emitting interrogation source or fissile material is used and no scanning is required, although if a profile is desired scanning can be used. As in active assays, here both reactivity and content of fissionable material can be measured. The assay is accomplished by altering the return flux of neutrons into the fuel assembly. The return flux is altered by changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons. Two measurements of either emitted neutron or emitted gamma-ray count rates are made and are then correlated to either reactivity, burnup, or fissionable content of the material being assayed, thus providing a measurement of either reactivity, burnup, or fissionable content of the material being assayed. Spent fuel which has been freshly discharged from a reactor can be assayed using this method and apparatus. Precisions of 1000 MWd/tU appear to be feasible.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• DOE Contract Number: W-7405-ENG-36
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 4493810
• OSTI ID: 865310
• Country of Publication: United States
• Language: English

Related Subjects

method
apparatus
measuring
reactivity
fissile
material
nondestructively
non-invasively
internal
probing
burnup
content
emits
neutrons
fissionable
components
external
neutron-emitting
interrogation
source
scanning
required
profile
desired
active
assays
measured
assay
accomplished
altering
return
flux
fuel
assembly
altered
changing
reflecting
existing
passive
neutron
emissions
assayed
interrogating
measurements
emitted
gamma-ray
count
rates
correlated
providing
measurement
spent
freshly
discharged
reactor
precisions
1000
mwd
appear
feasible
spent fuel
fuel assembly
fissile material
fissionable material
count rate
count rates
reflecting material
passive neutron
neutron emissions
neutron emission
emitted neutron
fissile content
/376/976/