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  • Co-funded by the

    MIND

    (GRANT AGREEMENT: 661880)

    DELIVERABLE 4.6

    Implementers’ Review Board Evaluation Report

    Authors: Achim Albrecht (Andra), Johan Andersson (SKB, editor), Matthew Bailey (RWM), Mehran Behazin (NWMO), Benny de Blochouse (Ondraf/Niras), Rosemary Hibberd (RWM), Klas Källström (SKB), Tiina Lamminmäki (Posiva), Olivier Leupin (Nagra), Patrik Sellin (SKB). Date of issue of this report: 21.05.2019 Report number of pages: 52 Start date of project: 01/06/2015 Duration: 48 Months

    This project has received funding from the Euratom research and training programme 2014-2018 under Grant Agreement no. 661880

    Dissemination Level

    PU Public PU

    PP Restricted to other programme participants (including the Commission) Services)

    RE Restricted to a group specified by the partners of the MIND project

    CO Confidential, only for partners of the MIND project

  • Publishable Summary

    Microbiology In Nuclear waste Disposal (MIND) is an interdisciplinary project consisting of two

    experimental work packages and a third one that handles integration of society and policy-oriented

    studies. As a part of the project an Implementers Review Board (IRB) was organized consisting of

    representatives of the Nuclear Waste Management organisations in the countries contributing to

    MIND. In this evaluation report the IRB discusses microbial issues of potential importance to post

    closure safety, assess the contribution by MIND in resolving these issues and indicates potential needs

    for further research. These issues are:

     The swelling of bentonite and its role in preventing sulphate reduction, sulphide migration and “microbial induced” corrosion

     Microbially mediated gas generation including gas consumption and gaseous C-14 containing species

     Microbially induced organic waste matrix degradation - main factors of influence and major principles

     Microbially enhanced processes potentially affecting radionuclide transport / migration

     Environmental parameters that limit microbial impacts in different repository environments.

    The MIND project has without doubt significantly enhanced our knowledge basis on microbial

    controlled processes. These processes where electron transfers occurs are by far the most relevant as

    microbial metabolism is based on the energy derived from these bio-(geo-)chemical redox reactions.

    Key reactions such as organic matter or hydrogen gas oxidation or oxyanion (nitrate, sulphate and

    carbonate) reduction do not occur without microbial catalysis. Furthermore MIND has helped to

    reduce uncertainties in regard to the limits of life within the engineered barrier system of waste

    disposal facilities and some host rock types (i.e. clay rocks). The limit in regard to pH (concrete

    barrier) and density of bentonite barriers or keys are now well established. The limit of life for

    compacted clay host rocks is also better constrained. The limit of life approach allows in the specific

    cases to distinguish a geochemical evolution without microbial catalysis from situations where the role

    of microbes, i.e. associated reaction catalysis, should be explicitly considered (i.e. biogeochemical

    evolution).

    The project also contributed to our understanding and quantification of chemistry related transition

    periods, such as desaturation, of which the length is a function of hydraulics and of gas generation, the

    latter in part controlled by microbial activity either by gas oxidation (H2) or formation (N2, CO2, CH4)

    depending of course on the waste type and the inventory and the local conditions (host rock).

    In some cases discrepancies persist between studies explicitly considering microbial activity and those

    looking mostly at global processes. The role of reduction of Fe(III) in smectite or of sulphate reduction

    on corrosion are two examples studied within the MIND project. It is clear that in microcosms in the

    presence of organic matter bioreduction of Fe(III) and sulphate can be observed but the related impact

    on bentonite swelling or corrosion has not been observed in underground rock laboratories. This

    indicates the need to couple the surface and URL experiments and to get as close as possible to

    repository conditions even in surface laboratory tests.

  • Contents

    1 Introduction .................................................................................................................................. 1

    2 Accomplishments of MIND in relation to Microbial issues, processes and conditions of relevance to Post Closure Safety of Nuclear Waste repositories ............... 2

    2.1 Introduction .......................................................................................................................... 2

    2.2 The swelling of bentonite and its role in preventing sulphate reduction, sulphide migration and “microbial induced” corrosion ...................................................... 2

    2.2.1 Introduction of issue.................................................................................................. 2

    2.2.2 Why of relevance and when ..................................................................................... 4

    2.2.3 Achievements within MIND ...................................................................................... 4

    2.2.4 What remains to be resolved of common interest to WMO:s ......................... 6

    2.3 Microbially mediated gas generation including gas consumption and gaseous C-14 containing species ............................................................................................................... 6

    2.3.1 Introduction .................................................................................................................. 6

    2.3.2 14C Origin, relevance and uncertainties ................................................................ 7

    2.3.3 Gas generation, pressure build up and consumption ...................................... 7

    2.3.4 Achievements within MIND .................................................................................... 13

    2.3.5 What remains to be resolved of common interest to WMO:s ....................... 15

    2.4 Microbially induced organic waste matrix degradation - main factors of influence and major principles ................................................................................................. 15

    2.4.1 Introduction of issue................................................................................................ 15

    2.4.2 Why of relevance and when ................................................................................... 19

    2.4.3 Achievements within MIND .................................................................................... 19

    2.4.4 What remains to be resolved of common interest to WMOs ........................ 22

    2.5 Microbially enhanced processes potentially affecting radionuclide transport / migration ......................................................................................................................................... 22

    2.5.1 Radionuclides in the waste and those making the dose ............................... 22

    2.5.2 Microbiology and mobility of radionuclides ...................................................... 23

    2.5.3 Case study 1: C-14 ................................................................................................... 25

    2.5.4 Case study 2: Se-79 ................................................................................................. 26

    2.5.5 Case study 3: Tc-99, uranium, other actinides and analogues .................... 27

    2.5.6 Why of relevance and when ................................................................................... 27

    2.5.7 Achievements within MIND (incl. cooperation) ................................................ 28

    2.5.8 What remains to be resolved of common interest to WMO’s ....................... 29

    2.6 Environmental parameters that limit microbial impacts in different repository environments ................................................................................................................................. 30

  • 2.6.1 Introduction of issue................................................................................................ 30

    2.6.2 Characterization of life in host rock of near and far-field .............................. 31

    2.6.3 Characterization of life in the near-field ............................................................. 32

    2.6.4 Characterization of life in repository interfaces ............................................... 35

    2.6.5 Achievements within MIND .................................................................................... 35

    2.6.6 What remains to be resolved of common interest to WMO:s ....................... 37

    3 Other contributions by MIND ................................................................................................. 38

    4 Issues that remain to be resolved ........................................................................................ 39

    5 Conclusions .................................................................................................