The 13th International Conference on Environmental ... - Events

Abstracts
4) 40126 – Detailed Standardized Decommissioning Parameters Calculation for Larger echnological Aggregates
and Relevant Buildings in Nuclear Power Plants using the OMEGA Code
Peter Bezak, Vladimir Daniska, DECONTA, a.s. (Slovakia); Ivan Rehak, DECOM, a.s. (Slovakia)
Computer code OMEGA, developed by DECOM a.s., is used for evaluation of nuclear facility decommissioning
activities. <strong>The</strong> Code implements in full extent the standardised cost structure PSL. Decommissioning activities of nuclear
facility are involved in compact calculation structure. Calculation models a real material and radioactivity flow and
reflects a radioactivity decay during decommissioning process. Calculation processes material items, which are linked to
decommissioning procedures (dismantling, demolition and decontamination procedures) in calculation structure.
Inventory database contains approx 90 standard material items of technological equipment (pipes, valves, tanks etc.),
approx 50 specific items (pieces, planked components etc.). <strong>The</strong> inventory database also contains 14 building categories
(masonry, concrete, steel construction etc.). A new task is costing the larger technological aggregates decommissioning
in nuclear power plants. <strong>The</strong> paper introduces development of larger technological aggregates inventory database. <strong>The</strong>se
aggregates include: 1. Reactor and its internals 2. Steam generator 3. Pressurizer 4. Refueling machine, etc.. Larger
technological aggregates decommissioning activities need to be implemented into decommissioning planning and costing
Code OMEGA. So decommissioning procedures representing these activities have to be developed for technological
aggregates, and dismantling unit factors need to be set up as well. A proper definition of dismantling techniques and
workgroups performing the techniques is also important, taking into account presence of activated and contaminated
materials to be dismantled. Where a dose rate is higher than a limit for manual dismantling, remote dismantling
techniques are applied. Paper introduces manual and remote techniques available for larger technological aggregates
dismantling. Dismantling procedures of larger technological aggregates are based on reversed sequence of their
commissioning. <strong>The</strong> paper also deals with specific dismantling procedures, when equipment is dismantled as a whole and
moved to a fragmentation facility. <strong>The</strong>re it will be fragmented to smaller parts, put into containers for disposal in
radioactive waste repository. Decommissioning of larger technological aggregates relates to buildings where aggregates
are housed in and the paper also deals with their demolition.
5) 40190 – Dismantling Method of Fuel Cycle Facilities Obtained by Dismantling of the JRTF
Fumihiko Kanayama, JAEA (Japan)
<strong>The</strong> Japan Atomic Energy Research Institute Reprocessing Test Facility (JRTF) was the first reprocessing facility
which was constructed by applying only Japanese technology to establish basic technology on wet reprocessing. JRTF
had been operated since 1968 to 1969 using spent fuels (uranium metal / aluminum clad, about 600kg as uranium metal
and 600MWD/T) from the Japan Research Reactor No.3 (JRR-3). Reprocessing testings on PUREX process were
implemented at 3 runs, so that, 200g of plutonium dioxide were extracted. After JRTF was shut down at 1970, it had been
used for research and development of reprocessing since 1971. <strong>The</strong> more mature research and development of nuclear are,
the more opportunity of dismantling of old nuclear facilities would be. JAEA has an experience of full scale of
dismantling through decommissioning of JPDR. On the other hand, we didn’t have that of fuel cycle facility. Moreover,
it is considered that dismantling methods of nuclear reactor and fuel cycle facility are different for following reason,
components contaminated TRU nuclide including Pu, contamination form being many kinds, and components installed
inside narrow cells. Dismantling methods are important factor to decide manpower and time for dismantling. So, it is
indispensable to optimize dismantling method in order to minimize manpower and time for dismantling. Considering the
background mentioned above, the decommissioning project of JRTF was started in 1990. <strong>The</strong> decommissioning project
of JRTF is carrying out phase by phase. Phase 1; Investigation for dismantling of the JRTF. Phase 2; R&D of
decommissioning technologies for dismantling of the JRTF. Phase 3; Actual dismantling of the JRTF. <strong>The</strong>re were several
components used for reprocessing and a system for liquid radwaste storage, and those were installed inside of each of
several thick concrete cells. <strong>The</strong> inner surfaces of each cell were contaminated by TRU nuclides including Pu. In phase 3,
components used in reprocessing and a system for liquid radwaste storage were dismantled. Moreover, concrete walls
(including ceiling) were opened to make entrances in this work. Effective practices for dismantling fuel cycle facilities
were obtained through these works. On this report, I introduce effective dismantle method obtained by actual dismantling
activities in JRTF.
6) 40191 – Computer Simulation of Cryogenic Jet Cutting for Dismantling Highly Activated Facilities
Sung-Kyun Kim, Kune-Woo Lee, KAERI (Korea Rep.)
Cryogenic cutting technology is one of the most suitable technologies for dismantling nuclear facilities due to the
fact that a secondary waste is not generated during the cutting process. In this paper the feasibility of cryogenic cutting
technology has been investigated by using a computer simulation. In the computer simulation, a hybrid method combined
with the SPH (smoothed particle hydrodynamics) method and with the FE (finite element) method was used. And also, a
penetration depth equation, for the design of the cryogenic cutting system, was used and the design variables and
operation conditions to cut a 10 mm thickness for steel were determined. Finally the main components of the cryogenic
cutting system were developed on the basis of the obtained design values.
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