Session 5.7. Chemistry Related Technology

The session comprised six papers on chemistry related technologies for liquid metals, water and gas.

A. Legkikh (Russian Federation) introduced the methods for controlling the oxygen concentration in heavy liquid metal (lead and lead–bismuth) in nuclear reactors and test facilities. He presented several technologies and noted the following conclusions:

 The inert gas–oxygen gas mixture method is efficient and convenient in small test facilities (up to 10 L) with static liquid metal;

 The hydrogen–water (steam)–inert gas mixture method can be effectively used for coolant oxidation in research facilities having isothermal operating conditions and experimental installations without forced circulation of coolant; and

 The solid phase method has been indicated as the most advanced method to control the oxygen concentration in non-isothermal loops with forced convection.

C. Fazio (EC) gave an overview on corrosion of the materials in the fast reactor environment, focussing on the LFR and SFR. Ms Fazio highlighted the importance of chemistry control and, in particular, the oxygen control to assess the corrosion of structural materials when exposed to the liquid metals. There were the following conclusions:

 Materials corrosion needs attention since it can cause potential loss of load bearing capability and loss of mechanical strength of the components;

 Corrosion in liquid sodium seems to be less severe with respect to Heavy Liquid Metal (HLM);

 Corrosion mitigation options that have been investigated are strictly related to the chemistry of the liquid metal; and there are known technologies with regards to sodium, although further improvement should not be excluded as they are still under investigation with regards to HLM. However, knowledge of the ‘chemistry’ of the liquid metals is essential for corrosion control;

 A step forward is needed for both sodium and HLM for evolving from experimental and empirical assessment to physical models.

A. Aerts (Belgium) presented the conditioning and chemistry programme for MYRRHA.

MYRRHA is an LBE cooled 100 MW(th) accelerator driven system under development at SCK•CEN. The MYRRHA chemistry control programme has essentially three components:

oxygen control and monitoring, coolant impurity management and radionuclide release and capture. The author summarized the achievement of the chemistry control programme as follows:

 Accurate and precise oxygen sensors for LBE cooled systems were developed and tested;

 Oxygen control with a solid phase method was accomplished on both laboratory and pilot scales. Moreover, electrochemical oxygen pumps were also developed and tested;

 By experiment and theory, a scientific basis has been established to assess the behaviour of impurities (corrosion products, etc.) in LBE, which guides the

 A global thermochemical model has been developed that describes the complex radionuclide chemistry in the LBE and progress has been made in understanding radionuclide/polonium chemistry and predicting release from the LBE.

The contribution of R. Askhadullin (Russian Federation) on strategies for maintaining appropriate technology of heavy liquid coolants in advanced nuclear power plants was presented by A. Legkikh who discussed the following items:

 The design and building of coolant technology methods and tools, and their direct implementation are needed for coolant preparation, power plant start-up, lifetime operation and decommissioning;

 The coolant technology methods and tools, which are under development for the power plant, include the following components: (i) hydrogen purification of the coolant and circuit from slag forming impurities, (ii) dissolved oxygen control in the coolant to ensure corrosion protection of steels, (iii) coolant and cover gas filtration unit, (iv) coolant purification from impurities, and (v) a system of coolant control in both reactor and non-reactor conditions;

 A key point that ensures the reliable operation of future HLM reactor systems is the training of specialists in HLM coolant technology.

V. Yurmanov (Russian Federation) (representing K. Shutko) presented the development of steam–water cycle chemistry for the steam generator of the MBIR. V. Yurmanov indicated in the presentation that neutral water chemistry had been proposed for the SG of the MBIR for the following reasons:

 Simple chemistry control and monitoring and reduced capital cost due to the absence of any chemical reagent dosing into feedwater;

 The absence of hydrazine and ammonia dosing eliminates both toxicological hazards for personnel and the required exchange capacity of ion exchangers; and

 Elimination of deposits from SG surfaces during operational transients.

The contribution concluded with a suggestion to the IAEA to develop a water chemistry control programme for LMC fast reactors similar to the SSG-13 (2011\2014) issued for LWRs and to improve the current edition of LMC guidelines (NP-T-1/6 (2012)).

L. Bĕlovský (Czech Republic) contributed to the session with a presentation on helium recovery from the guard vessel atmosphere of the ALLEGRO reactor. The ALLEGRO reactor is a helium cooled fast reactor under development within Europe to demonstrate the viability of the GFR technology. ALLEGRO has a specific design feature which is the close containment–guard vessel. A potential deployment of GFRs would require large quantities of helium, therefore, a key requirement of the GFR is to address the helium economy (recovery of expected helium leakage into the guard vessel). The question addressed in this contribution is related to the technical and economic viability of the recovery of leaked helium from a N2+He mixture. The studies performed had shown that the membrane technology seems to be suitable to answer this question. However, membrane separation can be further optimized. The next step would be to perform a small-scale experiment to demonstrate the scalability of the complex helium recovery system.

TABLE 7. PRESENTATIONS FROM SESSION 5.7. – CHEMISTRY RELATED TECHNOLOGY Chair: A. Legkikh and C. Fazio

Id Presenter Country Title

CN245-392 PPT-392

A. Legkikh Russian Federation

Methods of controlling concentration of oxygen dissolved in heavy liquid metal coolants (lead and lead-bismuth) of nuclear reactors and test facilities

CN245-562 PPT-562

C. Fazio (Invited)

EC Materials corrosion in Fast Reactor environment

CN245-211 PPT-211

A. Aerts Belgium The Conditioning and Chemistry Programme for MYRRHA

CN245-393 PPT-393

R. Askhadullin Russian Federation

Strategies of maintaining appropriate technology of heavy liquid metal coolants in advanced nuclear power plants CN245-543

PPT-543

V. Yurmanov Russian Federation

Development of steam-water cycle chemistry for steam generator of research reactor MBIR

CN245-390 PPT-390

L. Bělovský Czech Republic

Helium Recovery from Guard Vessel Atmosphere of the ALLEGRO Reactor

5.5.8. Session 5.8. Structural Materials