Post-disposal safety assessment of toxic and radioactive waste

Directorate-General For Research And Innovation European Commission

Description

Development and testing of the SACO methodology and code
Nuclear energy and safety

Informations

• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 12 Mo

Extrait

ISSN 1018-5593
European Commission
Post-disposal safety assessment of toxic
and radioactive waste: Development
and testing of the SACO methodology
and code
Report
EUR 16871 EN European Commission
nuclear science
and technology
Post-disposal safety assessment of toxic
and radioactive waste: Development
and testing of the SACO methodology
and code
R. H. Little,1 C. Torres,2 A. Agüero,2 D. Charles,1 K. J. Clark,1 P. R. Maul,1
I. Simón,2 G. M. Smith,1 P. A. Towler,1 B. M. Watkins,1 J. A. Woods1
1 QuantiSci (formerly Intera Information Technologies)
Chiltern House
45 Station Road
Henley-on-Thames
Oxfordshire RG9 1AT
United Kingdom
2 CIEM AT Instituto de Medio Ambiente
Avenida Complutense 22
E-28040 Madrid
Contract No FI2W-CT90-0042
Final report
Work performed as part of the European Atomic Energy Community's
shared cost-programme (1990-94) on
'Management and storage of radioactive waste'
Task 1 : Studies of Management Systems
Directorate-General
Science, Research and Development
1996 EUR 16871 EN 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, 1996
ISBN 92-827-6622-5
© ECSC-EC-EAEC, Brussels · Luxembourg, 1996
Printed in Luxembourg Executive Summary
The potential environmental impacts of land-based disposal of waste have
been recognised for several decades. However, to date, studies which have
attempted to quantify the impacts that might arise have been mainly con­
fined to the assessment of radioactive waste disposals. Little has been done
to quantify the impacts of non-radioactive (toxic) waste disposal, despite
its potential to create environmental and health hazards for hundreds if
not thousands of years. It was the aim of this study to help redress this
situation through the development and testing of a quantitative methodol­
ogy for the post-disposal safety assessment of land-based disposal facilities
for radioactive, mixed and toxic wastes.
The study has been undertaken by the Environmental Division of Intera
Information Technologies (now known as QuantiSci), United Kingdom,
and Instituto de Medio Ambiente (IMA) of the Centro de Investigaciones
Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain.
The research work programme was carried out in five phases.
• Phase 1 - a review was undertaken for radioactive, mixed and toxic
wastes of the different waste types, disposal practices, disposal cri­
teria, assessment methods and post-disposal impacts.
• Phase 2 - in the fight of the review, the SACO (Safety Assessment
Comparison) methodology and associated code were developed with
the aim of being applicable to a wide range of wastes and disposal
facilities.
• Phase 3 - the SACO methodology and code were then tested on a
representative set of realistic disposal sites (shallow and deep) and
waste types (toxic, radioactive and mixed).
Phase 4 - as a result of these tests, the SACO methodology and code •
were further refined and developed.
• Phase 5 - a further programme, using data from shallow and deep
disposal sites, was undertaken to test the revised methodology and
code.
The work undertaken under Phase 1 has been reported in European Com­
mission Report EUR 14627 EN. Phases 2 to 5 are described in this report,
with an overview of the work undertaken being given in Sections 1 to 5
and more detailed information being provided in Appendices A to J.
Ill The development and testing of the SACO methodology and code has
shown that quantitative assessment is becoming increasingly practicable
for a range of disposal options and waste types. It has demonstrated
that it is possible to apply a single quantitative assessment procedure to
a variety of contaminants (radioactive and toxic) in a variety of disposal
circumstances, thus contributing to coherent environment and resource
management. The assessment results can be used for comparison with
regulatory limits expressed in a variety formats, and to identify require­
ments for improved containment. The analysis of the disposal system also
allows for the identification of weaknesses in containment and weaknesses
in data, pointing to where improved understanding and further research
could lead to safer disposal.
The study has also shown the potential safety benefits of applying ap­
proaches developed within the nuclear industry to other industries. In­
deed, it has highlighted the need to consider longer timescales than usually
used when assessing toxic waste disposals.
Despite these advantages, there still remain some barriers to the appli­
cation of the quantitative assessment approach to toxic waste disposals.
One of the most significant is the quality of data, especially concerning
the waste source term and the behaviour of some contaminants in the en­
vironment. However, in the absence of certain site specific data, selected
generic data can be used to scope possible impacts. Furthermore, it is be­
coming increasingly necessary and practical to obtain site/waste specific
data. A further barrier is the perceived cost of such approaches. However,
costs can be minimised through the development of flexible approaches,
such as the SACO methodology, which can be used at differing levels of
detail.
In conclusion, it is considered that the application of the quantitative
approach allows for more informed, consistent and robust management
decisions to be made concerning a range of waste disposal issues. It is
now a question of when, rather than if, this approach will become generally
applied to support not only radioactive but also toxic waste management
decisions.
IV Contents
Summary of the SACO Study 1
1 Introduction
2 Development of the SACO Methodology 2
2.1 Possible Approaches
2.2 The SACO Methodology 4
3 Development of the SACO Code 7
4 Testing the SACO Methodology and Code 10
4.1 Initial Data Collection (Step 1) 12
4.2 Review of Criteria (Step 2)4
4.3 Data Review (Step 3)
4.4 Conceptual Models (Step 4)5
4.5 Screening of FEPs (Step 5) 16
4.6 Identification of Scenarios (Step 6)
4.7 Selection of Mathematical Code (Step 7)7
4.8 Additional Site Information Required by the Code (Step 8) 1
4.9 Verification and Validation of the Code (Step 9) 1
4.10 Calculation of End Points (Step 10) 18
4.11 Comparison with Criteria (Step 11) 20
5 Conclusions 2
6 References1 Appendix A The Work Programme 55
Appendix Β Identification and Collation of Generic Informa­
tion to Support the SACO Methodology 59
Β1 Introduction 5
B2 Waste Characteristics9
B3 Disposal Facility Characteristics 61
B4Geosphere Characteristics6
B5 Biospheres 7
B6 Regulatory Criteria3
Β 7 References 76
Appendix C Procedures for the Identification of Post-disposal
Impacts 132
CI Introduction
C2The SACO Approach3
C3 Other Approaches4
C4References 135
VI Appendix D Procedures for the Screening of Post-disposal
Impacts 139
Dllntroduction
D2Computer Implementation of Landfill Leachate Scoping
Calculations
D3Scoping Calculations for Liquid, Solid and Gas Releases 142
D4References 159
Appendix E Chemical Processes in Land-based Waste Dis­
posal Facilities 170
El Introduction
E2 Chemical Processes Acting in Waste Disposal Facilities 17
E3 Leachate Production2
E4 Gas Production 176
E5 References 183
Appendix F Biological Processes in Land-based Waste Dis­
posal Facilities 19
Fl Introduction6
F2 Biological Processes Acting in Waste Disposal Facilities 19
F3 Relevant Microbial Metabolic Processes 201
VII F4 Microbial Gas Generation 203
F5 Modelling Microbial Gas Generation6
F6 Microbial Effects on Leachate Generation and Migration 208
F7 References 209
Appendix G Development of the SACO Code 22
Gllntroduction 22
G2Development of SACO VI.09
G3Development of SACO V2.0 237
G4Enhancements to SACO V2.0 Input 243
G5Improved SACO Input Parameter Descriptions 249
G6Enhancements to SACO V2.0 Output 256
G7References 260
Appendix H Technical Overview of the SACO Code 293
Hllntroduction 293
H2Groundwater Flow Module4
H3Source Term (Aqueous Contaminant Release) Module 296
H4Gas Generation Module 30
VIM