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

Abstracts
appropriate decommissioning costs of power reactors. In this paper, MCNP/ORIGEN2 code system which is being
developed as a source term evaluation tool was verified by comparing the estimated nuclide inventory from
MCNP/ORIGEN2 simulation with the measured nuclide inventory from chemical assay in an irradiated pressure tube
discharged from Wolsong Unit 1 in 1994. Equilibrium core model of Wolsoung unit 1 was used as a neutron source to
activate in-core and ex-core structural components. As a result, the estimated values from the analysis system agreed with
measured data within 20% difference. <strong>The</strong>refore, it can be concluded that MCNP/ORIGEN system could be a reliable
tool to estimate source terms of decommissioning wastes from CANDU reactor, although this system assumes constant
flux irradiation and snapshot equilibrium core model as a reference core.
3) 40294 – Evaluation of <strong>The</strong> Activated Radioactivity of Turbine Equipments in BWR
Masato Watanabe, Motonori Nakagami, Chubu Electric Power Co., Inc. (Japan)
<strong>The</strong> equipments in the main steam system under the plant operation were irradiated by the neutron emitted from
N-17 which is produced by (n,p) reaction of the coolant in Boiling Water Reactor (BWR) plants. However, only few
measures, regarding the radioactive concentration of N-17 in the main steam system of BWR, were indicated up to now.
In this study, the radioactive concentration of N-17 in the main steam system of the advanced boiling water reactor
(ABWR) plant, Hamaoka unit-5, is evaluated by the neutron flux measurements and calculations.
It was found that the concentration of N-17 at the reactor pressure vessel outlet nozzle of the main steam pipe is
approximately 3 Bq/cm3. It turns out that the concentration has small dependency on nuclear thermal power and that it is
relatively common among the BWR plants.
<strong>The</strong>n, the activated activities of turbine equipments and pipes in the main steam system are evaluated by using the
measured radioactive concentration of N-17. <strong>The</strong> activities of the equipments in the main steam system are relatively
very low level.
4) 40014 – Optimization of Quantitative Waste Volume Determination Technique for Hanford Waste Tank
Closure
Yi Su, David L. Monts, Ping-Rey Jang, Zhiling Long, Walter P. Okhuysen, Olin P. Norton, Lawrence L. Gresham,
Jeffrey S. Lindner, Mississippi State University (USA)
<strong>The</strong> Hanford Site is currently in the process of an extensive effort to empty and close its radioactive single-shell and
double-shell waste storage tanks. Before this can be accomplished, it is necessary to know how much residual material is
left in a given waste tank and the uncertainty with which that volume is known.
<strong>The</strong> Institute for Clean Energy Technology (ICET) at Mississippi State University is currently developing a
quantitative in-tank imaging system based on Fourier Transform Profilometry, FTP. FTP is a non-contact, 3-D shape
measurement technique. By projecting a fringe pattern onto a target surface and observing its deformation due to surface
irregularities from a different view angle, FTP is capable of determining the height (depth) distribution (and hence
volume distribution) of the target surface, thus reproducing the profile of the target accurately under a wide variety of
conditions. Hence FTP has the potential to be utilized for quantitative determination of residual wastes within Hanford
waste tanks. In this paper, efforts to characterize the accuracy and precision of quantitative volume determination using
FTP and the use of these results to optimize the FTP system for deployment within Hanford waste tanks are described.
5) 40120 – Implementation of Decommissioning Materials Conditional Clearance Process to the OMEGA
Calculation Code
Matej Zachar, Vladimir Necas, Slovak University of Technology (Slovakia);
Vladimir Daniska, DECONTA a.s. (Slovakia)
<strong>The</strong> activities performed during nuclear installation decommissioning process inevitably lead to the production of
large amount of radioactive material to be managed. Significant part of materials has such low radioactivity level that
allows them to be released to the environment without any restriction for further use. On the other hand, for materials
with radioactivity slightly above the defined unconditional clearance level, there is a possibility to release them
conditionally for a specific purpose in accordance with developed scenario assuring that radiation exposure limits for
population not to be exceeded. <strong>The</strong> procedure of managing such decommissioning materials, mentioned above, could
lead to recycling and reuse of more solid materials and to save the radioactive waste repository volume. In the paper an
implementation of the process of conditional release to the OMEGA Code is analyzed in details; the Code is used for
calculation of decommissioning parameters. <strong>The</strong> analytical approach in the material parameters assessment, firstly,
assumes a definition of radiological limit conditions, based on the evaluation of possible scenarios for conditionally
released materials, and their application to appropriate sorter type in existing material and radioactivity flow system.
Other calculation procedures with relevant technological or economical parameters, mathematically describing e.g. final
radiation monitoring or transport outside the locality, are applied to the OMEGA Code in the next step. Together with
limits, new procedures creating independent material stream allow evaluation of conditional material release process
during decommissioning. Model calculations evaluating various scenarios with different input parameters and
considering conditional release of materials to the environment are performed to verify the implemented methodology.
Output parameters and results of the model assessment are presented, discussed and concluded in the final part of the
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