Active liquid treatment by a combination of precipitation and membrane processes

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

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Nuclear energy and safety

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• Publié par: EUROPEAN-COMMISSION-DIRECTORATE-GENERAL-FOR-THE-INFORMATION-SOCIETY-AND-MEDIA-DI
• Nombre de lectures: 32
• Langue: English
• Poids de l'ouvrage: 4 Mo

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fommission of the European Communities
! Ml WÈfï--
Active liquid treatment
by a combination
of precipitation
and membrane processes
Report
EUR 10822 EN Commission of the European Communities
nuclear science
and technology
Active liquid treatment
by a combination
of precipitation
and membrane processes
R.G. Gutman, I.W. Cumming, G.H. Williams,
R.H. Knibbs, I.M. Reed, P. Biddle, CG. Davison,
J.W. Sharps, M. Smith, J.A. Jenkins,
J.A. Blackwell, T.E. Hilton, CE. Barclay,
Chemical Engineering Division
UKAEA Harwell
Didcot, Oxon 0X11 ORA
United Kingdom
Final report
August 1986
This work was performed partly in the frame of the indirect action programme (1980-84) of the
European Atomic Energy Community: 'Management and disposal of radioactive waste' under
contracts 179-81-31 WAS UK(H) and 285-82-31 WAS UK(H). This work was carried out with
financial support from the UKAEA, UK Department of the Environment, British Nuclear Fuels pic,
and Ministry of Defence. In the DoE context, the results will be used in the formulation of government
policy, but at this stage they do not necessarily represent government policy.
References to use of a particular manufacturer's product do not necessarily imply a preference for
that product.
Directorate-General
Science, Research and Development
1986 Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
Bâtiment Jean Monnet
LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting on
behalf of then 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, 1987
ISBN 92-825-6826-1 Catalogue number: CD-NA-10822-EN-C
© ECSC-EEC-EAEC, Brussels • Luxembourg, 1987
Printed in Belgium CONTENTS
Page No.
1. INTRODUCTION
2. SMALL SCALE EXPERIMENTS WITH SIMULATED WASTES 1
2.1 Treatment of Pond Waters 2
2.1.1 Removal of strontium by titanium hydroxide 2
2.1.2l of caesium by metal ferrocyanides 5
2.1.3 Combined removal process from strontium and caesium 6
2.1.4 Removal of strontium by calcium phosphate 7
2.2 Treatment of Alpha Effluents 7
2.2.1 Treatment of iron containing alpha effluents
2.2.2t of pure alpha effluents 8
2.2.3 Alpha irradiation of membranes 10
2.3 Treatment of Solvent Wash Liquors1
2.3.1 Simulation of effluent
2.3.2 Removal of zirconium2
2.3.3l of ruthenium4
2.4 Sludge Dewatering 15
2.4.1 Iron based sludges6
2.4.2 Diuranates8
2.4.3 Conclusions
3. EXPERIMENTS WITH ULTRAFILTRATION MODULES AND SIMULATED WASTES 1
3.1 Removal of Strontium from Pond Water with Titanium Hydroxide and Hollow
Fibre Modules9
3.2 Removal of Strontium from Pond Water with Titanium Hydroxide and
Carbosep Tubular module 27
3.3 Removal of Caesium from Pond Water with Metal Ferrocyanides and Hollow
Fibre Module
3.4 Removal of Alpha Activity with Ferric Hydroxide and Hollow Fibre Module 34
3.5 Sludge Dewatering 35
3.5.1 Magnetite sludges
3.5.2 Ferric hydroxide sludges6
3.5.3 Conclusions7
III — CONTENTS CONTINUED Page No.
4. SMALL SCALE EXPERIMENTS WITH REAL WASTES 37
4.1 Treatment of Harwell Low Level Wastes with Flat Sheet Membranes 3
4.2t ofl Low Level Wastes with Carbosep Tubular Membranes 40
4.3 Treatment of Harwell Medium Level Wastes with Flat Sheets 41
4.4t ofl Medium Level Wastes with Carbosep Tubular
Membranes 43
4.5 Treatment of Alpha Effluents from the UK Nuclear Site with Flat Sheet
Membranes6
4.6 Treatment of CEA Solvent Wash Liquors 48
4.6.1 Experimental
4.6.2 Results 51
4.6.3 Conclusions
5. CONSTRUCTION AND OPERATION ON SIMULATED AND REAL WASTES OF AUTOMATED
ULTRAFILTRATION UNIT4
5.1 Description of Unit
5.2 Operation for Strontium Removal from Simulated Pond Water 55
55.2.1 Run I
5.2.2 Run II 56
5.2.3 Run III 57
5.2.4 Run IV 58
5.2.5 Run V 58
5.2.6 Run VI 59
5.2.7 Conclusions 60
Operation with Harwell Low 1 el Waste 60
5.3.1 Run I 6
61 5.3.2 Run II
62 5.3.3 Run III
62 5.3.4 Run IV
63 5.3.5 Run V
63 5.3.6 Membrane cleaning
64 5.3.7 Conclusions
6. DEMONSTRATION ULTRAFILTRATION PILOT PLANT 65
6.1 Design and Construction of First Prototype
— IV — CONTENTS CONTINUED Page No
6.2 Design and Construction of Second Prototype 67
6.3 Process Control System for Seconde 68
6.4 Testing of Second Prototype 71
6.5 Installation of Pilot Plant at Effluent Treatment Site 74
6.6 Commissioning of Pilot Plant 75
6.7 Operation of Pilot Plant on Low Level Waste 76
6.7.1 Run I 78
6.7.2n II 78
6.7.3 Run III 79
6.7.4 Removal of activity in Run II 79
6.7.5l ofy in Run III 81
6.7.6 Comparison between ultrafiltration of ferric floe treatment
for LLW 82
6.7.7 Conclusion 83
7. CONCLUSIONS 83
REFERENCES5
ACKNOWLEDGEMENT6
TABLES 1-467
119
FIGURES 1-76
— V — 1. INTRODUCTION
The overall aim of this programme was to develop new processes, based
on the use of ultrafiltration, for the treatment of low and medium active
liquid wastes. In the last decade ultrafiltration has become an important
unit operation in many process industries, such as the food and dairy
industries where plants with membrane areas of several thousand m2 are now in
operation. The latest commercially available ultrafiltration membranes are
chemically and physically resistant, and able to filter out particles and
molecules down to sizes of only a few nanometres.
The potential application of ultrafiltration to the treatment of
radioactive wastes has however received little attention. In a recent CEC
(3)
review of Advanced Management Methods for Medium Active Liquid Wastes" ,
novel ways were described in which ultrafine activity absorbing precipitates
could be formed in effluent streams, in order to enhance the activity removal
efficiency during subsequent ultrafiltration. The novel processes
potentially offered enhanced decontamination factors and volume reduction
factors compared to existing effluent treatment processes. Such concepts
have now been examined practically, first in small scale feasibility
experiments with simulated and real wastes, then on a larger chemical
engineering scale using different types of ultrafiltration module. Finally,
in order to generate user confidence in the viability of ultrafiltration
processes for radwaste treatment, a demonstration pilot plant has been built
and operated on a real effluent.
2. SMALL SCALE EXPERIMENTS WITH SIMULATED WASTES
The purpose of these preliminary experiments was to determine whether
it was feasible to remove different nuclides from simulated radwastes by UF
based processes. The experiments were carried out on the smallest scale
practical, using flat discs of plastic membrane.
- 1 2.1 Treatment of pond waters
Spent fuel, that is clad in magnesium alloy cans, is stored in ponds
where the water is maintained at high pH in order to minimise corrosion.
Such pond waters have been found to become contaminated by fission products,
principally 137Cs and 90Sr, and are continually purged. The radioactive
contamination of the purge stream has in the past constituted one of the
major radioactive discharges from nuclear sites and has frequently been
removed by ion exchange processes. In the UK, for example, the SIXEP plant,
which uses inorganic ion exchange beds, has been installed recently to
decontaminate such purge streams prior to discharge from the Sellafield
reprocessing plant. Here, however, the possible treatment of these pond
waters by combined ultrafiltration and precipitation processes has been
investigated.
2.1.1 Removal of strontium by titanium hydroxide
Hydrous titanium oxide is an example of an inorganic ion exchange
(1)
material that has been found to have considerable potential for adsorbing
activity from liquid effluents. Its use in an ion exchange column involves a
costly process to produce the ion exchange granules, and also handling
problems during operation. An alternative approach is to precipitate the
material as TiiOH)^ in-situ at very low concentrations, and subsequently
remove the loaded precipitate from the stream by UF.
It was found that the addition of a solution of TiCl^ in dilute HCl to
the alkaline simulated pond water, whose composition is shown in Table 1,
gave a sub-micronic TiíOH)^ precipitate. The strontium removal efficiency of
this precipitate was studied using simulated pond water to which y-act:ive
Sr85 was added.
Initial experiments were carried out in flat sheet units like that
shown in Figure 1, which contained small flat discs of Ami con* UF membrane,
*Amicon Corporation, USA
-2-