Flow of knowledge13 December 2016
Water chemistry in nuclear plants is a key area of recent focus in research and discussions internationally reports Patrick Reynolds.
The last year has seen two notable steps forward for knowledge sharing in water chemistry developments
in the international nuclear industry – key guideline updates issued by the US Electric Power Research Institute (EPRI); and the latest packed gathering of the international Nuclear Plant Chemistry (NPC) conference held in the resurgent UK market, and also finally marking its return to the nation where it started and had been formerly known as the ‘Bournemouth Conferences’.
EPRI produced two ‘roadmaps’ in early 2016 to show and tell what it says “success looks like” in water chemistry in nuclear facilities, including reference to key tasks and roles to be performed by stakeholders. The roadmaps are: ‘Water Chemistry Guidelines for Advanced Light Water Reactors’; and, ‘Chemistry Technologies for the Mitigation of Corrosion Product Fouling’.
With the nuclear sector rising again in the UK with a number of new build projects, such as Hinkley Point C and Wylfa Newydd, the NPC event returned to the UK for its 20th International Conference on Water Chemistry in Nuclear Reactor Systems (NPC 2016). The packed week-long NPC 2016 programme in early October covered chemistry of plants, including technological improvements, operating experience with both boiling water reactors (BWR) and pressurised water reactors (PWR), and also R&D and alternative reactor designs.
EPRI push on water chemistry
EPRI’s Water Chemistry Program is a body of activity that undertakes R&D, evaluates operating experience and develops guidance to help meet the challenges of material corrosion rates, fuel performance and plant radiation fields – and so overall optimisation of plant performance.
As EPRI observes, water chemistry control “is critical to the economic operation of commercial power reactors” as well as to the long-term ageing management of plant components. Its R&D programme for water chemistry in 2017 is to include:
- Continuing to use its Chemistry Monitory and Assessment (CMA) project to collect and evaluate global BWR and PWR water chemistry data; the additional information will further help in the aim of benchmarking specific water chemistry regimes, optimising operations at plants, and supporting further R&D work; as part of the work, EPRI is also developing web access tools to help gather operational chemistry and BWR data.
- For PWR secondary chemistry, to complete the review and assessment of available industry experience with filming amines towards identifying suitable candidates for application in plants; also on amines
- in PWR secondary systems, R&D effort is underway to identify and resolve how best to use advanced amines in minimising their potential impact on turbine materials.
- Also on PWR secondary systems, to begin work on the impact of dispersant application on side deposits.
- For BWR chemistry, to keep developing software tools for standard calculation of criteria such as conductivity, KOH for pH control, and also an ion exchange module.
- Complete a fundamental study on the effect of surface micro-chemical environments on activity transport and deposition.
- In terms of online analyses, to demonstrate a system for study of deleterious anion species and to evaluate technologies to examine corrosion products, respectively.
- To help safety of workers in terms of exposure and contamination events, the research work is to complete assessment of technologies able to produce a hydrophobic surface at plant-worker interface.
- To help address the challenges in water chemistry, EPRI has also produced two ‘roadmaps’ to show and tell what it says “success looks like”, including reference to key tasks and roles to be performed by stakeholders through incorporation into plant procedures. The latest versions of the two roadmap guidelines were issued in 2016.
Roadmap: Water Chemistry Guidelines for Advanced Light Water Reactors
As EPRI noted in its roadmap out in August 2016, no guidelines yet exist for water chemistry control and diagnosis for operating advanced light water reactors, and also water chemistry control guidance does not address hot functional testing and initial plant start- up activities.
For recent plant designs, it says, the details have come from general assumptions on typical water chemistry environments, largely based on current industry practices – which do include previous applicable versions of EPRI guidelines, it adds.
Where and how differences exist, whether due to further improvement in industry practices or “fundamental differences in plant design”, EPRI says the gaps needed to be closed for PWR design prior to mid-2015 to support the planned 2017 start-up of the AP1000TM in the US, with the BWR designs to follow.
EPRI’s work on this front is to produce industry-consensus water chemistry control guidance for advanced plant designs that is consistent with guidance available for the current fleet. It adds that, specifically, and in addition to the AP1000TM, the work addresses the US-EPRTM, APR1400, US- APWR, ESBWR and ABWR designs.
The most recent update of the roadmap, under development since 2011, brings up to date the current schedule for start-up of advanced plant designs and project tasks. Start-ups scheduled over 2017-20 include: first UAE APR1400; French and Finnish EPRs, respectively; and, first US AP1000. The programme chart shows 2016 as start-up for the first Korean APR1400 and Chinese AP1000, respectively.
Based on the information, EPRI worked with utilities to implement plant-specific Strategic Water Chemistry Plans. It notes that utilities will need to train existing and new chemistry managers and technicians on these plans, and adds that supply chain vendors will have to use the guidelines to support new plant development.
In other work on guidelines, EPRI in early 2017 expects to publish on PWR secondary chemistry, and it is also looking to publish revised guidance for condensate polishing system operation to optimise performance with current media and equipment.
Water chemistry was also part of research collaboration EPRI had recently with Horizon Nuclear Power in the run-up to the UK-based new build developer becoming a fully joined up research partner in the US organisation’s nuclear programme (see EPRI: joined by Horizon).
UK hosts NPC once more
For the first time this century, and after last hosting the industry’s key ‘Bournemouth Conference’ in 2000, the major water chemistry gathering returned to UK shores – this time to the City of Brighton.
After many years of the UK having hosted the large gathering, just after 2000 as the fortunes of the nuclear sector waned in the country the torch was passed to others to carry (see Bournemouth Conferences).
But with the nuclear sector resurgent in the UK, the nation was able to invite, and host, the NPC event for its 20th International Conference on Water Chemistry in Nuclear Reactor Systems (NPC 2016). Over five days, the main programme covered technology, operation and R&D, and much focus was given to BWR and PWR systems and experience. The conference organiser was the Nuclear Institute.
Keynote presentations included EPRI discussing chemistry control to meet the demands of operating modern plants, while the host nation provided a briefing by the Office for Nuclear Regulation (ONR) on regulating chemistry for nuclear plants in the UK. An activity update on water chemistry from Japan was provided by the Japan Radioisotope Association (JRA).
Over the majority of the week, the multiple sessions of the main event were given over to both PWR and BWR, respectively – focusing on primary and then progressing to secondary water chemistry.
On primary PWR chemistry, delegates heard about: EDF’s Flamanville 3-EPR commissioning, and also its silica management in the French fleet; and, EPRI on evaluating potassium hydroxide for reactor coolant pHt control in Western PWRs, and also the impact of dissolved hydrogen on fuel crud and boron accumulation.
Areva discussed the chemistry concept for dose rate minimisation treatment of new and decontaminated plants and PHWRs; Studsvik Nuclear AB presented on variables influencing Co-60 uptake using simulated PWR chemistry; Rolls Royce talked about modelling and experiments on localised crud deposition; and ANT International told delegates about theoretical and practical aspects of primary and secondary chemistry in PWR/VVER (Voda Voda Energo Reactor).
In sessions covering PWR secondary chemistry, NPC delegates heard presentations from: EPRI on dispersant operating experience; Dominion Engineering on experience with deposit management; CEA on steam generator tube fouling that impacts how polyacrylic acid can deal with iron oxides deposition; EDF also on tube fouling, focusing on laboratory tests to examine chemical cleaning impacts on oxides deposition and impurities behaviour; EDF and Vattenfall on Mossbauer analysis on some plants; Laborelec on an alternative to hydrazine as an oxygen scavenger; and, IRSN looking at safety-related chemistry stakes.
On primary BWR chemistry, delegates heard about: UK’s National Nuclear Laboratory (NNL) on material and activity transport modelling; and, discussions on mitigation work for inter-granular stress corrosion cracking (IGSCC) by EPRI, National Tsing Hua University, and jointly by Toshiba and Tokyo Electric Power Co, respectively.
Studsvik presented on Nordic experience on water chemistry options for internal pump BWRs; Hitachi-GE Nuclear Energy discussed development of a suppression method for deposition of radioactive cobalt by a platinum treatment after chemical decontamination; Iberdrola talked on experience of decontamination and post- decontamination passivation treatment of the RRS loops and RWCU system at Cofrentes plant; and the University of Manchester presented on cobalt incorporation into austenitic stainless steel surface oxide.
The programme also packed in sessions on auxiliary systems, lifetime management and plant ageing, and water chemistry in context of other topics such as fuel and radiation fields. There was also discussion on other reactor and accident management.
NPC 2016 took place at the same time as the 11th Specialist Workshop on Radiation Chemistry and Electrochemistry in the Nuclear Fuel Cycle, which rounded off the week-long intensive briefing.
As an established feature of the international conference circuit – taking place every two years in Europe, Asia or North America – the next NPC event is to be held in the US.