AREVA’s Containment Venting Technologies and Experience Worldwide

Marina Welker Company: AREVA GmbH Address: Henri-Dunant-Str. 50, 91058 Erlangen, Germany Phone: +49 (0) 9131 900-95606 Email: [email protected]

Summary – The AREVA Filtered Containment Venting System (FCVS) is a product family that minimizes the environmental impact in case of a severe accident in a nuclear power plant (NPP). Our experience is based on a large-scale test and qualification program as well as on the design, licensing and installation of more than 80 projects worldwide. The product family provides flexibility regarding the adaptation to respective accident scenarios, applicable codes and standards, seismic design, supply chain, implementation and localization. AREVA has broad experience of managing fleet supplies, successful support of licensing and cooperating with original equipment manufacturers (OEMs) of pressurized and boiling water reactors (PWR and BWR).

1. INTRODUCTION In case of a postulated severe accident, the containment pressure might increase and threaten the containment integrity. The goal of the FCVS is to allow a controlled reduction of the containment pressure through venting cycles while in various filtration steps trapping the radioactive isotopes, thus drastically reducing off-site impact. The first AREVA FCVS (FCVS Standard) was developed almost 30 years ago by Siemens KWU, which later merged with AREVA. Over the years authorities but also nuclear power plants have increased the requirements on retention rates, especially regarding the organic iodine retention. As a consequence AREVA has continuously extended the FCVS product family in order to meet a broader variety of challenging performance requests.

2. AREVA’S FCVS AREVA offers the standard FCVS as a combined double-staged process. It uses the advantages of a high-speed venturi scrubber technology (wet stage) combined with an especially designed highly efficient deep-bed fibre filter (dry stage). All components are installed in a pressure vessel and operate under sliding pressure conditions. This results in a very compact system design.

 First stage=wet stage: the aerosols and the majority of gaseous iodine are accelerated in a venturi nozzle and are trapped in the “scrubber” liquid

 Second stage=dry stage: the remaining aerosols go through a section for droplet separation and filtering This unique combination of dry and wet stages enables to benefit from the technical advantages of both solutions. The AREVA standard FCVS can be extended with an optional third filtration stage which is targeted to meet higher requirements regarding organic iodine retention. It uses the advantage of the sliding pressure operation mode of the first and second stage to create passive superheating for the downstream third sorbent stage (I-CATCH process).

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 Third stage = I-CATCH: the organic iodine is efficiently trapped at the molecular sieve This third stage could also be installed as an upgrade to an already installed FCVS, e.g., in case of increasing requirements concerning organic iodine retention. The combination of the above named three stages allows a modular design to meet the constraints regarding possible locations / compartments in terms of the installation of the system. In addition the AREVA technology features the following unique advantages:

 significant reduction of the clogging risk in dry stage: with AREVA’s technology there is no risk of clogging since most of the radioactive aerosols are trapped at the wet stage  reliable retention and avoidance of activity re-suspension in the wet stage: the combination of scrubber with efficient downstream droplet separation provides a very beneficial dry gas condition for the downstream metal fibre fine aerosol filtration stage. This design avoids wet operation of the metal fiber filter sections and facilitates a reliable operation. The dry stage significantly reduces possible aerosol and iodine re-volatilization / re-suspension effects.  high thermal inertia of the wet stage: the trapped radioactive isotopes generate heat o In the wet stage >99% of the isotopes are trapped in the scrubber. The heat is safely absorbed by the scrubber liquid. The volume of the liquid is sufficient to allow for full passive cooling and temperature control by evaporation. The heat transferred from the FCVS to the room where it is installed is significantly reduced. This is important as in SBO scenarios HVAC is considered to be out of operation. o The remaining <1% of the isotopes are trapped in the second stage. Due to the low amount of such isotopes in the dry stage the risk of reaching self-ignition temperature at hot spots inside this stage as well as of aerosol melting is significantly reduced. 2.1 Tests and qualification After an intensive internal full-scale test and qualification program, AREVA performed and met all national and international qualification programs, including third party testing. Thus, AREVA demonstrated that all state-of-the-art international qualification standards are fulfilled. International experts recommend testing and qualification programs for containment venting devices under severe accident conditions. AREVA performed extensive tests as per these recommendations. These programs include tests with accident typical aerosols, Cs, I, hard-to-retain micro aerosols as well as tests concerning re-entrainment effects in the frame of the US ACE (Advanced Containment Experiments) Filter Test Program. A wide variety of aerosol types in different gas flow and gas content conditions have been tested in order to consider the different aerosol properties (e.g. solubility, hygroscopic, etc.) and the broad diameter range of the aerosols. Tests have also been performed for aerosols that belong to the range of the filter gap region. In addition, the retention of gaseous iodine (elemental and organic iodine) was tested. Used Aerosol Remark

 BaSO4 solid

 Uranine soluble; fine aerosol

 SnO2 solid; fine aerosol; high / low concentrations possible

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 CsI hygroscopic, soluble

 MnO solid

 DOP solid; fine aerosol AREVA verified the aerosol and iodine retention for the whole range of the relevant pressure operation. 2.2 Overview of AREVA’s FCVS Product Family Due to particular technical requirements of customers and safety authorities AREVA developed some specific technical FCVS features. All these developments are part of the AREVA FCVS Product Family. Table 1. AREVA’s FCVS Product Family

FCVS Plus FCVS Standard FCVS Basic I-catch

1. High speed 1. High speed 1. – venturi scrubber venturi scrubber 2. – 2. Metal fiber filter 2. Metal fiber filter 1. High speed venturi scrubber 3. Passive Filtration stages 3. Molecular sieve superheating (I-CATCH) 2. Demister and Molecular sieve stage (I- CATCH process) Decontamination

factors > 10.000 > 10.000 > 100 Fine aerosols (>99,99%) (>99,99%) (>99%) > 100.000 > 100.000 > 1.000 Large aerosols (>99,9999%) (>99,9999%) (>99,9%) > 1000 > 200 > 200 Elemental Iodine (>99,9%) (>99,5%) (>99,5%) > 10 - 10001 ~ 5 ~ 5 > 10-1000 Organic Iodine (>90-99.9%) (~80%) (~80%) (>90-99.9%)

Even the simplest FCVS leads to a reduction of radiological consequences by many orders of magnitude.

4. AREVA’S FCVS EXPERIENCE WORLDWIDE Since 1987, AREVA has designed, licensed and delivered more than 80 FCVS for different reactor types worldwide: PWR (including VVER), BWR and PHWR (CANDU). While the detailed system designs may differ with the reactor types, the unique AREVA design has shown to be

1 The organic iodine decontamination factor is subject to customization.

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sufficiently flexible for the respective required adaptation. Moreover, AREVA addresses customer- specific requirements by partnering, scope split flexibility (engineering, hardware delivery, turnkey) and localized manufacturing. AREVA has broad experience with the stringent application of different national codes and standards. Most of the delivered FCVS are installed in NPPs where AREVA is not the OEM.AREVA has successfully been working in close cooperation with plant OEMs, as different NPP types vary in design and, thus, require a customized approach to installing an FCVS. Table 2. AREVA’s FCVS projects

Reactor type Countries BWR, ABWR Japan, Germany Belgium, Brazil, China, Finnland, Germany, Japan, Netherlands, Spain, PWR, EPR Switzerland VVER Bulgaria PHWR Argentina, Canada, Romania, South Korea

The AREVA FCVS was able to fully satisfy the very stringent post-Fukushima design and licensing requirements in Japan for the restart of NPPs which made it the system of choice for OEMs of Japanese BWR plants. Regarding AREVA’s FCVS all main parameters and dependencies have been verified by large-scale tests. Moreover, AREVA’s JAVA facility as backup is available in AREVA’s laboratory in Karlstein/ Germany to perform additional tests in case new authority questions should arise. 4.1 Licensing experience with FCVS Based on AREVA’s experience with safety authorities around the world AREVA has gained a unique understanding of the important key points regarding licensing aspects. By now, AREVA has gained broad and long-term experience with FCVS licensing worldwide. Quick and qualified support of the customer and regular technical exchange are essential during the licensing process. AREVA’s worldwide presence allows to support customers in an optimal way and to participate in discussions with safety authorities. For almost 30 years, AREVA has frequently executed FCVS projects and successfully supported customers’ licensing issues. In parallel AREVA has been working together with different national and international committees and working groups. Thus, AREVA has gained a unique understanding of the subject of FCVS.

5. CONCLUSION AREVA’s FCVS product family meets a broad variety of regulatory requirements, technical specifications and different commercial boundary conditions in order to meet customers’ demands. For almost 30 years AREVA has been providing FCVS solutions respecting different requirements, supply conditions and partnership models.

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ACKNOWLEDGEMENTS Firstly, I would like to express my sincere gratitude to Norbert Losch for his support in preparing this paper as well as for his immense knowledge. Secondly I would like to thank the colleagues of AREVA’s FCVS team for their comments, questions and discussions. Also sincere thanks to Carolina Perez from AREVA Spain for her support during the preparations for this conference.

ABBREVIATIONS

ABWR Advanced Boiling Water Reactor ACE Advanced Containment Experiments BWR Boiling Water Reactor CANDU CANada Deuterium Uranium, Pressurized Heavy Water Reactor DOP Dioctyl phthalate EPR European Pressurized Water Reactor FCVS Filtered Containment Venting System HVAC Heating, Ventilation and Air Conditioning JAVA Jod- und Aerosol Versuchsanlage, Iodine and Aerosol Testing Facility OEM Original Equipment Manufacturers PWR Pressurized Water Reactor SBO Station Blackout TÜV Technischer Überwachungsverein, German Safety Monitoring Agency VVER Water-Water Power Reactor, Pressurized Water Reactor

REFERENCES. Hitachi-GE Nuclear Energy Adopts AREVA Technology for Filtered Containment Venting Systems to Improve Safety of Nuclear Power Plants in Japan, Press Release, Reuters, Tue Jun 4, 2013 AREVA Safety Alliance, Products, Services and Solutions, November 2012, AREVA 2012 The European PASSAM Project on severe accident source term mitigation, https://gforge.irsn.fr/gf/project/passam/ B.Eckhardt, N.Losch, Filtered Containment Venting System Designs. Development, Features, Qualification, Applications. NRC, July 2012, http://pbadupws.nrc.gov/docs/ML1220/ML12206A263.pdf OECD/NEA/CSNI Status Report on Filtered Containment Venting, NEA/CSNI/R(2014)7, 02- Jul-2014, https://www.oecd-nea.org/nsd/docs/2014/csni-r2014-7.pdf

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