Published: Jan 1989
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In reactor metrology, the neutron spectrum of the spontaneous fission of Cf-252 has been used as a standard for many years. Nevertheless, the shape of this spectrum has not yet been unambiguously established. Only recently, the situation changed completely. Based on experimental data, a systematic evaluation of the spectrum was made. The result defines the spectrum with a precision never before attained and comprises a complete uncertainty covariance matrix.
First, a short review of the past status of the definition of this spectrum and the associated problems is given. The reason that recent measurements of the Cf-252 neutron spectrum produced more reliable results is discussed. The experimental data base and the steps of the evaluation procedure are discussed. The result obtained is compared with attempts to describe the Cf-252 neutron spectrum on a theoretical basis. The result of the evaluation is presented, and the progress in defining these data as an internationally accepted standard is reviewed. Finally, the impact of the improved knowledge of the Cf-252 neutron spectrum on past and future reactor dosimetry data is discussed.
californium-252, spontaneous fission, neutron spectrum, least-squares evaluation, standard
Physikalisch-Technische Bundesanstalt, Braunschweig,