Measurement of cumulative photofission yields of 235U and 238U with a 16 MeV Bremsstrahlung photon beam

Abstract

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New measurements of cumulative photofission yields of 239Pu, 235U and 238U with a 17.5 MeV Bremsstrahlung photon beam and progress toward actinide differentiation

“…In the frame of a long-term research program conducted by the Nuclear Measurement Laboratory of CEA IRESNE Institute in France, this work follows the study recently reported in [19], which provided cumulative photofission yields of 235 U and 238 U with a 15.8 MeV Bremsstrahlung beam produced by a linear electron accelerator (LINAC) in CINPHONIE casemate of CHICADE nuclear facility [20]. We present here new cumulative photofission yields for 239 Pu, and again for 235 U and 238 U, which are measured with the same setup but with an endpoint electron energy of 17.5 MeV.…”

Localization of nuclear materials in large concrete radioactive waste packages using photofission delayed gamma rays

“…Another important task for the characterization of nuclear materials by active photon interrogation is the accurate measurement of the cumulative yields of photofission products, as reported in [10] for 235 U and 238 U. Additional experiments have been recently performed to measure the cumulative photofission yields of 239 Pu, which will be published soon, as such data are extremely rare so far in the literature.…”

“…A series of photofission products liable to allow 235 U vs. 238 U discrimination in the global photofission signal have been identified in [10] . This work will be continued for uranium vs. plutonium differentiation using our measured uranium and plutonium photofission yields.…”

“…A 20 cm thick lead collimator with a rectangular aperture allows to focus the beam on a slice of the radioactive waste package. The collimator is surrounded by 20 cm thick polyethylene blocks and a cadmium layer of 2 mm is added at the front face in order to limit the photoneutron flux produced in the tungsten target and in the lead collimator by (γ,n) reactions of the bremsstrahlung high energy photons [10] . The LINAC and the collimator surrounded by the neutron shielding are shown in Fig.…”

“…Ref. [10] reports delayed gamma-ray spectra obtained with a similar setup on the bare uranium samples (without the concrete matrix), and presents usable peaks of some photofission products in view to localize actinides. Given acquisition times shown in Table II, especially 45 min in the first position, 138 Cs is a particularly suitable photofission product because of its half-life 𝑇 1/2 = 2004.6 𝑠.…”