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Basic leaching tests for pure long-lived ß emitters in radioactive waste

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ISSN 1018-5593
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European Commission
1er nude
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Basic leaching tests for pure long-lived ß
emitters in radioactive waste European Commission
nuclear science
and technology
Basic leaching tests for pure long-lived ß
emitters in radioactive waste
M. Noe, C. Riglet
CEA Cadarache
F-13108 St Paul-lez-Durance
A. Gonzales de la Huebra
CIEMAT
Avda. Complutense 22
E-28040 Madrid
AA. Pihlak, E. Lippmaa
Institute of Chemical Physics and Biophysics
10 Rävala Puiestee
Estonia Tallinn
Contract No FI2W-CT90-0032
Final report
Work performed as part of the European Atomic Energy Community's
shared-costprogramme (1990-94) on 'Management and storage of radioactive waste'
Task 3: Characterization and qualification of waste forms, packages and their environment
Directorate-General
Science, Research and Development
1996 EUR 17104 Eh A great deal of additional information on the European Union is available on the Internet.
It can be accessed through the Europa server (http://europa.eu.int)
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, 1997
ISBN 92-827-8983-7
© ECSC-EC-EAEC, Brussels · Luxembourg, 1997
Reproduction is authorized, except for commerciai purposes, provided the source is acknowledged
Printed in Luxembourg CONTENTS
I- BACKGROUND
Π- OBJECTIVES AND SCOPE 1
Π.1- Objectives
Π.2- Task distribution 2
ΠΙ- OVERALL WORK PLAN 3
TH. 1- Nature of the waste
HJ.2-e of the matrix 4
ΙΠ. 3- Leaching procedure and operating conditions
ΙΠ. 4- Procedure for mamtaining the leachants at fixed pH 6 and 8 β
ΠΙ.5- Manufacture of the specimens 6
ΙΠ. 6- Analytical treatments of the leachates η
m.7- Interpretation of the data
DL 8- Definition of the initial concentrations 9
IV- RESULTS AND DISCUSSIONS 10
IV. 1- Bitumen waste
IV. 1.1. Experimental data : report and analysis 1
IV. 1.2. Data interpretation1
IV.2- Thermo-setting resin coats
IV.2.1. Experimental data : report and analysis
IV.2.2. Data interpretation
IV.3- Cement waste3
rv.3.1. Contribution from CEA 1
- Experimental data
- Data interpretation
IV.3.2. Contribution from CIEMAT4
- Recall of work plan
- Reference leaching tests5
- Leaching tests with complexing agents 18
-g tests with real resins 20
- General conclusions for CIEMAT contribution 21
- References 22 V- RESULTS FROM THE "PECO EXTENSION" PROGRAMME 23
V. 1- Background 2
V.2- Work plan4
V.3- Results and discussion (summary) 26
V.4- Conclusions9
VI- GENERAL CONCLUSIONS 30
VI. 1- From embedded waste
VI. 2- From Sillamäe waste dump1
TABLES 33
FIGURES9
APPENDLX-1 85
Manufacturing Procedures and Nominal Compositions of
the Embedded Samples
APPENDLX-2 91
Results for Bitumen Embedded Waste Samples
APPENDLX-3 10
Results for Thermo-setüng Resin Embedded Waste Samples
APPENDIX-4 131
Results for Cement Embedded Waste Samples
APPENDLX-5 145
Report of Leaching Data Relative to 1ER Embedded in Cement (CIEMAT)
[Results from Tables 1-5 (omitted) have been transferred to Figs. 20-25 in the main text]
IV I - BACKGROUND
This work has been carried-out under the European Community Research and
Development Programme on the Management and Storage of Radioactive Waste, Task-3,
entitled : "Characterization and qualification of waste forms, packages and their
environment".
The contract under discussion was originally set for a period of four years, from
01/05.1991 to 30/04/1994, including two main contractors : CEA-Cadarache (referenced as
the Project co-ordinator), and CIEMAT-Madrid. Due to an unforeseen delay in the
preparation of the samples to be submitted to the leaching tests, a one year extension of the
contract was requested to the Commission (end of the work extended to 30/04/1995, with no
financial implication to the CEC).
In April 1994, a supplementary agreement was signed between the CEA and the
Institut of Chemical Physics and Biophysics of Tallinn, Estonia, as part of the Cooperation in
Science and Technology for Central and Eastern Countries (PECO). To help to the proper
implementation of this additional programme, the final deadline of the projet was extended to
the 31.10.1995.
At the last workshop organized in Cadarache, on 21-22 September 1995, all the work
under the scope of this project was terminated and the three parties submitted a first draft of
their contribution to the Final Report.
II- OBJECTIVES AND SCOPE
Π.1- Objectives
The technical solution under study to store long-lived radioactive waste consists in :
- embedding the materials in suitable confining matrices (glass, cement, bitumen),
- burying the coats in stable geological sites where the radioactivity will decrease naturally.
The evaluation of the confining capability of the matrices used -determined by
implementing leaching tests- makes it possible to assess the reliability of the process. Safety
studies indicate that the long-term risk mainly stems from long-lived radionuclides.
In addition, serious and irreversible risks of polluting the environment are raised in
Estonia, in the vicinity of the uranium ore processing facility of Sillamaë (next to the Russian
border), due to a wide storage of untreated g solid waste piled up for 50 years at the
edge of the Baltic sea, without any particular supervision.
In this context, the research contract is related to a basic leaching study of long-lived
pure β and α emitters in real and simulated wastes, in order to collect basic results about these radionuclides which are critical for the safety analysis of disposal storage sites and for the
protection of the environment. No reliable leaching data are available for these elements at
this time.
The original main objectives of this joint research programme were :
- collection of leaching data for β and α emitters so as to achieve the best evaluation of the
confining properties of various matrices (bitumen, cement, thermo-setting resin) containing
various types of waste (co-precipitation sludges, evaporator concentrates, ion-exchange
resins),
- definition and validation of suitable experimental leaching procedures taking into account
the variable nature of the waste and of the embedding materials,
- assessment of the leaching mechanisms, in order to modelize the long-term behaviour of the
waste packages or to anticipate the long-term risks for the environment.
In the context, of the additional research contract concluded with Estonia (PECO)
more specific objectives of this task were :
- collection of basic leaching data for those waste sludges which have been submitted neither
to any reprocessing treatment nor to any embedding process.
- evaluation of the pollution mechanisms of the environment and assessment of the long term
risk,
- validation of experimental leaching procedures, suitable for this kind of waste and which can
permit comparison between different tests.
II.2- Task distribution
O CEA-CIEMAT
- Working organization
- Setting-up of a working programme
- Harmonization of the leaching procedures.
e CEA
- Definition and manufacturing of the samples
- Implementation of the leaching experiments
- Collection of the data and interpretation.
θ CIEMAT
Selection of the types of the waste, the cement formula, and the elements to be
taken into account
Optimization of the analytical procedures
• Collection of the data and interpretation.
O CIEMAT
- Implementation of the leaching experiments with real resins
- Collection of the data and interpretation. θ Institute of Chemical Physics and Biophysics of Tallinn
- Drilling and sampling of the uranium extraction waste at the Sillamaë uranium
processing facility
- Radio - Physico - Chemical characterization
- Implementation of the leaching experiments
- Chemical analyses of the leachates
- Collection of the data and interpretation.
© CEA - CIEMAT - Institute of Chemical Physics and Biophysics of Tallinn
- Interpretation of the data
- Comparative study of the various experiments
- Final evaluation.
Ill- OVERALL WORK PLAN
An overview of the experimental matrix including the coating materials, the types of
waste and the leachants is reported in Table 1, as reproduced from the last Progress Report,
when all the leaching experiments had been completed. The overall duration of each leaching
test was typically 455 days. The philosophy which led to the selection of this task force is
indicated :
- in what concerns the relation of confining materials to leachants, in Figure 2.
- in what s the n of type of waste to confining matrices, in Figure 3.
A more detailled description of these different parameters is given in the following
paragraphs.
BX1- Nature of the waste
The types of waste to be embedded originate from either nuclear power plants (NPPs)
or reprocessing plants :
♦ From PWR power plants :
- used mixed anion-cation resins Duolite ARM9381 (CIEMAT) from a chemical and
volume control system (CVCS),
- evaporator - sodium borate - concentrtes (CEA).
♦ From BWR power plants :
- used mixed anion-cation resins EPIFLOC (CIEMAT) from a coolant cleanup system
(powdered form)?
♦ From reprocessing plants :
- chemical STE 3 La Hague (STE3 LH) type sludge. The ion exchangers were labelled with 63Ni and 90Sr. To test their methodology,
CIEMAT used at first synthetic ion exchange resins containing 63Ni and 90Sr. At the end of
the work real spent ion exhangers (1ER) from NPPs were tested.
The evaporator concentrate and STE3 LH sludges were labelled with Cs, Th, U, Tc
and I.
However due to the indectectability of Thorium in the leachates, the leaching tests
performed with cements were modified (evaporator concentrates) and Th was replaced by
Europium, Ruthenium and Cesium radioisotopes (137Cs, 106Ru, I52Eu).
III.2- Nature of the matrix
For the CEA programme, the waste samples were embedded in different types of
matrices (cement, bitumen and thermosetting resins) as indicated in Table 3. For CIEMAT,
the overall contribution was focused on 1ER embedded in cement.
III.3- Leaching procedure and operating conditions
The scheduled leaching tests are summurized in Table 2.
The variety of the tests aimed at studying for each kind of sample, the influence of :
- the nature of the water (demineralized or natural water)
- the temperature (25°C, 40°C, 50°C)
- the pH of the leachnat -pH = 4 and 8)
- complexing agents (EDTA, degradation products of REI)
- an original aim to study the leaching behaviour under irradiation has been
removed from this project.
All the leachants are characterized for their anionic, cationic and organic composition.
A complete characterization of the sludges, resins and coats is also performed, before the tests
start.
The cement or thermo-setting resin specimens are cylindrical samples, completely
immerged in the water. The bituminous specimens, more fragile, are kept their original mould
and only their top surfaces are covered with the leachant.
In that respect, the dimensions of the samples have been calculated so that :
- the volume of the specimen
- thee of the leachant
- the leached surface
is identical for all samples, whatever the nature of the wastes and the matrices. Figure 1
shows the practical leaching conditions which have been selected. The volume of leachant is
set at about 2 liters in order to have a constant thickness of water of 4-5 cm for all samples.