“Great teamwork, as always,”
1. 10. 2019
says Zdeněk Kratochvíl, Manager of the Dukovany NPP Center at the NPP Services Division at ŠKODA JS a.s. in an interview for All for Power.
Automated Welding of Flap Valve at the Pipeline
How many employees of ŠKODA JS are permanently present at the Dukovany NPP center? I assume they are all members of the NPP Services Division?
At Dukovany NPP, approximately 125 employees from the NPP Services Division are permanently present; we are in charge of servicing the primary circuit equipment. This means we are responsible for the implementation of service activities as well as for the planning of repairs in the primary circuit machinery, and for the evaluation of those activities. As such, servicing starts in the planning of the repairs. This entails the preparation of work orders, preparation of work procedures, planning of inspections and tests, material requirements, spare parts and fixtures, requirements for equipment security, and, finally, creating safety requirements in radiation safety and occupational safety. An integral part of our work is the coordination of individual stages with ČEZ staff members and our subcontractors. Apart from the NPP Services Division, members of the Engineering Division are also present at the Dukovany NPP, which is a major benefit for NPP maintenance.
What is the team’s increased headcount during standard maintenance and maintenance during planned outages in any of the NPP units?
Our team often doubles in headcount for the implementation of maintenance during planned outages with employees from the Temelín NPP and Pilsen locations as well as with subcontractors who are integrated into individual teams.
How large was the team which was in charge of and implemented the project of the replacement of the non-return flap valve at Unit 3?
The preparation of the replacement of the non-return flap valve at the low-pressure system of emergency cooling of the reactor core took approximately one year, with the participation of many Škoda JS employees. Looking at the most important professions, we had designers, calculation specialists, welding engineers and technologists, the sales staff, inspectors, preparation technologists, plumbing fitters, pipe fitters, welders, welding operators as well as other equally important professions such as scaffolding builders, insulation workers, painters, and many more.
3D model of the flap valve and subsequent piping
In the article you say that Škoda JS could only deliver the project in superior quality and on time using its triangular model, which combines engineering, service and production for NPPs. Was that really an advantage for your work and how did you organize the process – did you establish an interdepartmental team?
In the field of NPP services, it is a major advantage if you can rely on your own people across all stages of the project, which was the case in the replacement of the flap valve. Coordination of individual activities of members from various divisions is no easy task. Therefore, we divided up responsibility for individual sections immediately after the first meeting; those responsibilities would be reviewed during regular inspection days.
All work was carried out very efficiently using our company’s triangular model and our knowledge of the VVER 440 NPP primary circuit also outside the Czech Republic. The expertise of our employees working on individual tasks also builds on experience from other NPPs, which is a major asset for the implementation of projects of this type.
The outage – and the replacement of the non-return flap valve – occurred at Christmas and the end of the year. Did you have enough people available? How did they and their families cope with the situation when most people desire to spend time together?
This certainly is an important issue, which is why we dedicated considerable effort during the preparation of the outage towards the development of a detailed timeline of the activities. In the process, we discussed with the operator of Dukovany NPP the manning of the shifts, especially over Christmas. Of course, the timeline also had to consider other colliding activities, for example, X-ray testing by NDT staff of another device in the proximity of our worksite in order to suspend our operations to prevent irradiation of the workers. Therefore, it was prior to the outage that we agreed with the operator to optimize the timeline of staff deployment on Christmas Eve and Christmas Day with the minimum headcount staying on duty in certain professions. However, finishing all activities on time was the most important aspect for everyone. It was because of the professionalism and dedication of all the staff that we managed to complete all the tasks on schedule. I would like to thank everyone participating in the implementation of the project for their hard work.
3D model of the MU IV welding head with special arc clamping solution
Did this project present Škoda JS with a repeatable experience or the possibility to expand the offer of services and supplies, or was it a unique albeit single endeavor?
As we provide maintenance in the primary circuit of NPPs, we often need to find solutions to repairs of devices with a high radiation load. The environment of NPPs operates under the ALARA principle for protection from ionizing radiation. This requires that the operation of individual sources of radiation must have the size of individual irradiation exposures, the number of exposed persons and the risk of their irradiation as low as reasonably acceptable while observing economic and societal concerns. Mastering the technology of automated orbital welding in our maintenance activities is a major contribution towards compliance with that requirement.
Automated welding is used in our company mostly in the Production Division in the Reactor Shop for cask welding and in servicing small-diameter piping. Therefore, we need to progress this skill further in the NPP Services Division. In the future, it would bring us the possibility to offer our expertise to other operators of VVER nuclear power plants.