Absolute measurement of the cross section for 23 keV neutron activation of thorium
Measurement has been made of the thorium radiative capture cross section using Sb-Be photoneutrons and an absolute activation method. The average of two determinations gave a value of 604 mb at 23 keV neutron energy with a 4% estimated error from all sources (+-1 sigma). In each experiment, a cylindrical shell target of natural thorium metal was irradiated for approximately two weeks by a centrally-positioned Sb-Be source. The accumulated 27-day half-life /sup 233/Pa, activated by neutron capture in thorium, was recovered by solvent extraction with diisobutylcarbinol after first dissolving the target in hydrochloric acid. Ninety percent recovery of protactinium was obtained, as measured by isotopic tracing with /sup 232/Pa. The 1.3-day half-life /sup 232/Pa had to be produced immediately before each use. A thin thorium foil was irradiated with 11 MeV protons using a tandem van de Graaff accelerator. The /sup 232/Pa was then recovered by chemical separation. /sup 233/Pa activity was measured by counting the 312-keV decay gamma with a Ge(Li) detector. Detector efficiency was determined by indirect calibration against a /sup 237/Np deposit assayed by alpha counting at the National Bureau of Standards. The Sb-Be source strength was measured by the manganese bath method, using a /sup 252/Cf source for calibration, traceable to the NBS II neutron standard. Flux per unit source strength was determined by Monte Carlo modelling of the source/target irradiation geometry.
- Research Organization:
- Michigan Univ., Ann Arbor (USA)
- OSTI ID:
- 5227764
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
A=220 & above
Experimental-- Nuclear Reactions & Scattering-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTIVITY LEVELS
BARYON REACTIONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CAPTURE
CROSS SECTIONS
DATA
DAYS LIVING RADIOISOTOPES
ENERGY RANGE
EXPERIMENTAL DATA
HADRON REACTIONS
HEAVY NUCLEI
INFORMATION
ISOTOPES
KEV RANGE
KEV RANGE 10-100
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
NUMERICAL DATA
ODD-ODD NUCLEI
PROTACTINIUM 232
PROTACTINIUM ISOTOPES
RADIOACTIVATION
RADIOISOTOPES
TARGETS
THORIUM 232 TARGET