Page 252 - Beyond Decommissioning

Experience and lessons learned 233

Fig. 6.30 Garching FRM reactor (the Atomic Egg).
Photo by M. Laraia.

the scope of the operating license the fuel elements were removed and shipped to the
USA. The decommissioning license of May 30, 1983 comprised the decommissioning
of the plant, the dismantling of plant components, and the achieving of safe enclosure
of the shielding block with the former reactor pool. With a separate license notice of
May 24, 1984 the facility was allowed to remain under safe enclosure. The reactor hall
was released from nuclear regulatory control, but the shielding block is still under
nuclear regulatory control (Fig. 6.31).

6.5.10 Musashi Reactor, Japan (Musahi et al., 2008)

This 100-KW, Triga Mark II reactor started operation in 1963. Reactor operation was
shut down on December 21, 1989 due to small leakage of water from the reactor tank.
After shutdown, investigations about the incident causes, making plan of repair and
discussions on restart or decommissioning lasted many years. Finally, the decision of
decommissioning the reactor was made in May 2003.
A redevelopment plan is described in Musahi et al. (2008), consisting of the use of
the Musashi reactor simulator.
The operation console and the control rod drive are decommissioned. Simulated
fuel elements and grid plate compose the simulated reactor core. The type and core
location of the fuel elements are identified through electric circuits. Core character-
istics are reproduced on a personal computer using the actual operation data of the
reactor and neutron transport calculations are effected with Monte Carlo codes. Oper-
ation of control rod, core characteristics, core configuration, and instrumentation data
are mutually linked and controlled by an interface. The software that calculate core
thermal power and reactor period was prepared based on a time-dependent diffusion