Treatment, disposal, re-use of building demolition and site cleaning wastes from nuclear facilities

Directorate-General For Research And Innovation Directorate-General For The Information Society And Media European Commission

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Nuclear energy and safety

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• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-DIRECTORATE-GENERAL-FOR-THE-INFO
• Nombre de lectures: 41
• Langue: English
• Poids de l'ouvrage: 3 Mo

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tOR ISj ??
ISSN 1018-5593
iuropean Commi;
nuclear science
and technolooy
Treatment, disposal, re-use of
building demolition and site cleaning
wastes from nuclear facilities Publication of this report has been supported by the Dissemination of Scientific and Technical Knowledge
Unit, Directorate-General for Telecommunications, Information Market and Exploitation of Research,
European Commission, Luxembourg. European Commission
nuclear science
and technology
Treatment, disposal, re-use of
building demolition and site cleaning
wastes from nuclear facilities
H.J. Wingender, G.G. Simon, B. Sohnius (NUKEM)
J. Doran, A.W. Brant (WasteChem)
H. Cadiou, S. Goetghebeur (SGN)
NUKEM GmbH
IndustriestraBe 13
Postfach 1313
D-8755 Alzenau
Contract No FI-2W-CT90-0044
(Study period: February 1991-December 1992)
Final report
Work performed as part of the shared cost-programme (1990-94)
on 'Management and disposal of radioactive waste'
of the European Communities
Directorate-General H <l* m M
Science, Research and Development DA pi cijiv'.p DM- ,I
1994 lN c EUR 15188 EA
. . I Published by the
EUROPEAN COMMISSION
Directorate-General XIII
Telecommunications, Information Market and Exploitation of Research
L-2920 Luxembourg
LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of the
Commission is responsible for the use which might be made of the
following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1994
ISBN 92-826-8134-3
© ECSC-EC-EAEC, Brussels • Luxembourg, 1994
Printed in Italy SUMMARY
This report contains the results of an investigation of waste arising from building demo­
lition and site cleaning activities. The study does not consider wastes such as dismantled
and/or disassembled process equipment. These wastes are assumed to be removed from
the facilities prior to building demolition.
A comprehensive survey overview of building demolition was carried out by the three
partners (NUKEM - FRG, WasteChem - UK, SGN - F) for following nuclear facilities:
front end plants: enrichment and fuel fabrication (FRG, UK)
production plants: power reactors (FRG, UK)
back end plants : reprocessing and waste treatment (UK, F) and
fuel encapsulation (FRG)
The study was carried out according to the following tasks:
- collection and compilation of waste data and characterization
- investigation of sampling, monitoring, and analysis tools
- material classification and investigation of re-use and disposal possibilities
For standardization purposes, the information obtained from different facilities was re­
arranged in such a way that it reflects the waste arising from a 20 GWe fuel cycle
scenario (equivalent to 600 metric tons of heavy metal per annum).
Data collection was carried out in both the public and private sectors. Information on the
scope and volume of data in the private sector was, however, only partly available.
Presently, for the 20 GWe capacity scenario fuel cycle there is no existing nuclear plant
where decommissioning is in operation. The published data only concentrate on decom­
missioning of power reactors. Special efforts were necessary to estimate the waste
arising, from front end and back end plants.
The experience of operating enrichment plants has shown that no radioactive material
could remain on the surfaces or penetrate into the building structures. In the study, it was
assumed that a small amount of contamination can occur during the different steps of
operation. In that case, the waste arising and the radionuclide content are a rough
estimation. In the case of fuel fabrication and reprocessing plants, the buildings are
adjusted to the needs of a scenario fuel cycle. Methods were developed to ascertain radio­
active content in the structure of the buildings. A fuel encapsulation facility does not
exist. Therefore, special assumptions were needed to estimate the waste arising and also to calculate the radionuclide content in the structure of the buildings.
The total waste arising from the demolition of the building structures is listed in table 1
for the different plants in the fuel cycle. Approximately 90% of the wastes contain
reinforced concrete, 8% steel, 1.5% brickwork and 0.5% of other materials.
A unified scheme for demolition waste estimation is difficult, since the regulations and
the strategies practiced and/or envisaged are different from country to country and from
plant to plant. Therefore, the waste arising data listed in table 1 are strongly dependent
on the model used.
In the case of reactors, two different strategies are under consideration. In FRG the
practice to date in demolishing reactors considers all building structures in the restricted
access area. In UK only the parts of the building structures are considered where the
walls and floors could be contain radioactive material. The buildings external to the
biological shield are removed within 10-14 years of shut down. The demolition ant the
removal of the remaining structures occur after 100-135 years.
For other types of fuel cycle plants no experience exists. The demolition strategy of a
reactor cannot be transferred to other types of plants without additional assumptions. The
model used only considers the building structures which were assumed to contain radio­
activity.
In FRG and UK, the building structures which are considered to be contaminated are
fully demolished. Whereas in F, only the surface is removed from the walls. The average
layer thickness whichis assumed is approximately 34 cm. The waste arisings differ ap­
proximately by a factor 3 for the different methodologies used (s. table 1, back end
plants).
The main effect of these different methodologies - selection of plant area and wall
structure thickness - results in only changing the amount of waste classified as unre­
stricted use.
Two main types of building demolition strategies are considered: total demolition and step
by step demolition. The first case, as employed in France: the materials with and without
radioactive material are mixed. The average specific radioactivity is below the limits
given by the regulations. However, a release of this material for unrestricted use is not
possible. These waste materials must be disposed of in a near-surface landfill. The second
case, as employed in FRG and UK: to begin with first parts of walls and floors which
contain radioactivity are removed at first and then, the remaining building structures are
demolished.
The amount of contaminated soil is difficult to estimate. Experience only exists for older
plants in which such waste could be generated. In newer plants, such waste can be
excluded or the amount is insignificant compared to the volumes produced by other
sources. Therefore, this waste arising was not considered.
The secondary waste expected during the demolition phase is also small. The part with
iv -radioactive impact is less than 1 % of the total radioactive waste arising and was not
considered.
The determination of the expected radionuclide content, distributions, concentrations, and
dose levels necessitates several assumptions along with suitable models. Detailed expe­
rience only exists in the case of power reactor decommissioning. Here, the activation of
the material by neutron irradiation can be precisely determined. In order to calculate the
surface contamination, the operating data, the release rates of radioactive material, and
the possiblity for transfer of radioactive material were considered. The quantities expec­
ted are evaluated according to former decommissioning studies and/or experiences from
the plant operation.
The radioactive impact is conservatively calculated. A more precise estimation would be
possible with increasing experience on nuclear plant decommissioning, especially for the
front end and back end plants.
Assumptions for calculating the radioactive impact and surface contamination are made
with relatively high uncertainty. One uncertainty results from the assumption of the
residual contamination on the floors and walls after removal of the equipment from the
cell, and how to decontaminate the surfaces before the safe enclosure period, especially
for plants on which there is no decommissioning experience. The other uncertainty results
from the mass correlation contamination corresponding to surface contamination.
The wastes with beta and gamma radioactive constituents can be suitably monitored
(radionuclide content, distributions, concentrations, and dose levels) for release of these
materials into the environment. Particularly, in the case of non-destructive analysis
(NDA) techniques for large radioactive waste packages, the experiments and the routine
measurements demonstrate the applicability of a monitoring system. Detectors and measu­
ring systems are also suitable for localization of the contamination on building structures.
When a gamma emitter is utilized as a lead-nuclide the survey technique can be used for
measuring the surface contamination. With the application of the contamina