Nuclear RPV Inspection in Record Time DEKRA Industrial Inspection Mechanized NDT

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World Record at Ringhals Nuclear Power Plant To perform an in-service inspection in a nuclear power station is no easy task. To perform a Reactor Pressure Vessel (RPV) inspection of a nuclear reactor pressure vessel is even more challenging. To perform a full RPV inspection, with three parallel operating manipulators in less than 5 days, is almost impossible.

The DEKRA Industrial Mechanized Inspection unit is no ordinary NDT supplier. Utilizing extensive know how of experienced NDT experts, mechanical engineers and probe designers together with the vast resources of DEKRA‘s global organization, the possibilities are endless. During the summer of 2020, DEKRA was assigned by the Swedish state company, Vattenfall, one of the largest energy producers in Northern Europe, to perform a Mechanized RPV Inspection of the Pressurized Water Reactor 4 at Ringhals Nuclear Power Plant.

The inspection of the RPV is carried out every 10 years to fulfill the regulations and to ensure continued safe operation of the plant. The scope in Ringhals consisted of:

> Connection welds, nozzle to shell welds, inner radius of the large inlet and outlet nozzles > Circumferential and Longitudinal Vessel Welds, inspected from the inside of Reactor Pressure Vessel > Bottom Mounted Instrumentation Nozzles (BMI) parent material, the tube weld and the fusion zone towards the J-groove weld > Visual examination of certain internal parts

Nuclear plant operators are always looking for inspection companies who can deliver a high quality in-service inspection in a safe and time efficient way, saving hours on the outage time line either to make room for other activities in the vessel or to get back on the grid and start producing power again.

RPV Inspection

Gungner, the submarine swimming in the bottom of the reactor entering 50 small bottom mounted nozzles, scanning the inside surface of the pipes as well as around the non-symmetric weld towards the bottom of the reactor

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The difference between the DEKRA ins-pection systems compared to other vendors is that instead of using cumbersome and heavy solutions, DEKRA has developed a unique inspection system using one fixed manipulator and two independently opera-ting free swimming robots. These robots are smaller, more efficient and with the ability to operate simultaneously. This not only saves time, but also makes other parts of the reactor pool available for parallel work, which also saves precious outage time for the plant owner.

In July 2020, DEKRA mobilized its in-house developed mechanized NDT mani-pulators Särimner, Gungner & Skidbladner using ENIQ qualified Ultrasonic & Eddy current techniques. The team of 25 well prepared engineers mainly from Sweden but also supported by experts from Lithua-nia entered the site. The project, starting 2 years earlier with preparations, was about to be finalized. Three teams were appoin-ted to perform the RPV inspection wor-king around the clock for almost 5 days. Teams consisted of mechanical engineers handling the robotics, data collectors ac-quiring the inspection data, data evalua-tors analyzing the signals and the project manager continuously reporting results to the customer. All teams and roles worked closely together, perfectly focused and co-ordinated. The robotics are designed and constructed to be able to work continuous-ly in highly radiated, contaminated under-water environments. One mistake or failure of equipment could cost hours of repair

time. DEKRA has many years of long ex-perience of this type of inspections and could perform the full inspection without any failures of the equipment.

4 days and 14 hours later, DEKRA could hand over documentation of the inspected reactor with an approved result to the sa-tisfied customer. Thanks to great commit-ment from everyone involved in the pro-ject, the inspection was performed in a record time of 4 days and 14 hours, beating DEKRA‘s previous record by 4 hours. This is unique and makes DEKRA probably the most efficient RPV inspection company in the world. Vattenfall, Ringhals, has a long tradition of collaborating with DEKRA and since 2010 DEKRA has performed all RPV inspections at the site in all 4 reactors. In addition, we supply Vattenfall with a large scope of services in the area of safety in all types of power generation plants.

“We appreciate DEKRA‘s service and wil-lingness to cooperate with the good quality of performance at Ringhals 4. The entire inspection in about 4.5 days was surpri-singly fast in such a difficult project,” says Håkan Stenius, project manager at Vattenfall.

The inspection, carried out with a global team of experts from DEKRA‘s internatio-nal hub of mNDT engineers, is a good example and a result of combined global knowledge, driven by DEKRA‘s new modern organization.

Very few companies in the world are able to carry out a Nuclear RPV inspection and no one has done it faster than DEKRA!

Särimner, the large nozzle manipulator. This is a remote operated swimming subma-rine which operates by docking and scan-ning 3 inlets and 3 outlet nozzles.

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Jonas Olsson, Data evaluator of BMI data

Per Sjöberg and Robin Jonnerhag, Data Collectors for Gungner and SärimnerSkidbladner – Manipulator for RPV Weld inspection

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Visiting adress Stockholm office: DEKRA Industrial AB Hemvärnsgatan 11B SE-171 26 Solna Sweden Phone: +46 10 455 10 00 dekra-industrial.se/en/contact dekra-industrial.se

Subject to change. HS12-11.20