Accurate fission cross-section of $sup 235$U from 0.002 to 0.15 eV and its reference value at 2200 m/s

Journal Article · Sat Sep 01 04:00:00 EDT 1973 · J. Nucl. Energy, v. 27, no. 9, pp. 645-676

OSTI ID:4415178

Deruytter, A J; Spaepen, J; Pelfer, P

A new precise measurement of the 2200 m/s fission cross section of /sup 235/U was performed with a slow chopper at the BR2 reactor (energy-range from 0.002 to 0.15 eV). Simultaneous recordings of pulse-height and time-of-flight spectra of successively compared /sup 235/UF/sub 4/-layers and standard'' elemental boron-layers were made. The detection of the /sup 10/B(n, alpha )/sup 7/Liand /sup 235/U(n, f) reaction fragments is made with excellent pulseheight resolution in low geomeiry with a surface-barrier detector. The absolute /sup 10/ B contents were determined from direct weighing in vacuum combined with careful chemical and isotopic analysis of witness foils. The relative /sup 10/B contents of the standard boron-foils were checked by their neutron induced reaction rates in the geometry of the fission experiment. The amount of uranlum on the fissile foils is determined by precise low geometry alpha -counting making use of the most recent and accurate alpha half-life values. The fission foils were also checked by alpha - and fission fragment counting in the geometry of the experiment. The fission cross section was calculated in the energy-range from 0.002 to 0.15 eV and the absolute value deduced at 2200 m/s was 587.6 plus or minus 2.6 barn. The value at 25 x 10/sup -3/ eV is 591.8 plus or minus 2.7 barn. These fission cross-section values were used to calculate the Westcott-g/ sub f/-factor for a 20.44 deg C Maxwellian distribution with the result: g/sub f/ = 0.9780 plus or minus 0.0010. (auth)

• Research Organization: Commission of the European Communities, Geel, Belg.
• NSA Number: NSA-29-001726
• OSTI ID: 4415178
• Journal Information: J. Nucl. Energy, v. 27, no. 9, pp. 645-676, Journal Name: J. Nucl. Energy, v. 27, no. 9, pp. 645-676; ISSN JNUCA
• Country of Publication: United Kingdom
• Language: English

Related Subjects

*NEUTRON REACTIONS-- THERMAL FISSION
*URANIUM 235-- NEUTRON REACTIONS
ALPHA DETECTION
ALPHA PARTICLES
BORON 10
BR-2 REACTOR
CROSS SECTIONS
EV RANGE
FISSION FOIL DETECTORS
FISSION FRAGMENT DETECTION
LITHIUM
N69151* --Physics (Nuclear
Experimental)--Nuclear Properties & Reactions
A >= 220--Nuclear Reactions & Scattering
NEUTRON CHOPPERS
NUCLEAR REACTIONS
TIME-OF-FLIGHT METHOD
URANIUM FLUORIDES