Program - Brookhaven National Laboratory

in the evaluated nuclear data files such as ENDF or JEDNL. Therefore, the modified neutron/gamma
cross section constant based on JENDL-2 were developed in the previous study in Joyo and the gamma
heat rate increase approximately 40% by considering the delayed gamma intensity as evaluated by Yoshida
[1]. In this study, the new neutron/gamma cross section constants based on JENDL-3.2 and JENDL-4.0
are being developed. To evaluate all gamma ray effect, delayed gamma yield were added to JENDL-
3.2 and JENDL-4.0. Based on these modified JENDL-3.2 and JENDL-4.0, the MCNP-type library for
Mote Carlo transport calculations, JSSTDL and MATXSLIB-type library (100 neutron groups and 40
gamma groups) for conventional discrete ordinate multi-group transport code were generated. In this
modification, the prompt gamma ray yield data which was given only for U-235, U-238 and Pu-239 in
JENDL-3.2 were prepared for all actinides. Through the neutron and gamma ray coupling calculations for
Joyo core based on the transport theory as a fixed source problem, it was made clear that the gamma flux
and heat rate increase approximately 40% by considering the delayed gamma intensity in both JENDL-
3.2 and JENDL-4.0. The effect of lack of the prompt gamma ray yield data except for U-235, U-238
and Pu-239 in JENDL-3.2 is approximately 10%. The calculated gamma heat rates were verified against
measured data by the on-line irradiation rigs, which name is instrumented assembly (INTA), loaded in the
Joyo core fuel region. In the INTA, online thermocouples were equipped surface and inside of insulated
irradiation capsules. First, temperature of an irradiation specimen in each capsule was evaluated using the
finite element method code FINAS with a capsule model in RZ geometry, taking into account the sodium
temperature measured by the thermocouple at surface of the capsule as a boundary condition. By using a
heat transfer calculation, temperature distribution in a capsule was converted to gamma heat rate. It was
confirmed that the calculated gamma heat rates agreed with the measurements within 5%.
[1] Yoshida, T. et al., “Calculation of the Delayed Fission Gamma-Ray Spectra from U-235, -238, Pu-239,
-240, and Pu-241; Tabular Data,” JAERI-M-89-037 (1989).
DE 5 5:00 PM
New Prompt Fission γ-ray Data in Response to the OECD/NEA High Priority Request
S. Oberstedt, R. Billnert, T. Bry´s, G. Geerts, F.-J. Hambsch, M. Vidali
European Commission, Joint Research Centre IRMM, 2440 Geel, Belgium
A. Oberstedt
CEA/DAM Ile-de-France, Bruyères-le-Chatel, 91297 Arpajon Cedex, France
T. Belgya, Z. Kish, L. Szentmiklosi
Institute of Isotopes, Hungarian Academy of Science, 1121 Budapest, Hungary
With the potential of advanced nuclear reactors, a better understanding of the fission process is required.
Since four out of six of the impending Generation-IV reactors are fast ones, the excessive heat deposition
requires an innovative core design. Approximately 10% of the deposited heat is due to γ-ray energy, from
which about 40% is due to prompt fission γ-rays. According to Rimpault et al. [1], the uncertainty with
respect to the γ heating should not exceed 7.5% to adequately model these cores. Using the present
evaluated data leads to an underestimation of the γ-heating by up to 28% for the main reactor isotopes,
235 U and 239 Pu. Since the underlying experimental data dates back to the early 1970s, the OECD/NEA
has included an urgent request for new experimental data in its High Priority Data Request List [2]. The
Nuclear Physics Unit of the European Commission Joint Research Centre together with co-workers has
taken up the challenge to respond to the OECD request and started a measurement programme on prompt
fission γ-rays. During recent years we have started this programme by carrying out thorough studies of
new and highly efficient γ-ray detectors based on cerium-doped lanthanum-halide and cerium-bromide
crystals, aiming at very fast timing in conjunction with a good energy resolution [3,4]. In the final setup
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