  For a high energy electron facility, the estimates of induced radioactivity
in materials are of major importance to keep exposure to personnel and to the
environment as low as reasonably achievable. In addition, an accurate
prediction of induced radioactivity is also essential for the design, operation
and decommissioning of a high energy electron linear accelerator. The research
of induced radioactivity focuses on the photonuclear reaction, whose giant
resonance response in the copper is ranging from 10 MeV to 28 MeV. The 200 MeV
electron linac of NSRL is one of the earliest high-energy electron linear
accelerators in P. R. China. The electrons are accelerated to 200 MeV by five
acceleration tubes and collimated by the scrapers made of copper. At present,
it is the first retired high-energy electron linear accelerator in domestic.
Its decommissioning provides an efficient way for the induced radioactivity
research of such accelerators, and is a matter of great significance to the
accumulation of the induced radioactivity experience. When the copper target is
impacted by an 158 MeV electron beam, the number of photons generated whose
energy are in the range of giant resonance response is the largest. Thus, this
paper focuses on the induced radioactivity for a copper target impacted by the
158 MeV electron beam. The slicing method is applied in the research. The
specific activity of each slice was measured at cooling times of ten months and
the results were compared with the prediction from the Monte-Carlo program
FLUKA. The simulation results are in good agreement with the measurement
results. The method by Monte Carlo simulation in this paper gives a reasonable
prediction of the induced radioactivity problem for the high-energy electron
linear accelerators, laying a foundation for the accumulation of the induced
radioactivity experience.
