A good beginning! The first30-year nuclear outage concluded successfully!

Recently, Unit 2 of Daya Bay NPP connected to the grid successfully after outage, marking the successful conclusion of the first 30-year nuclear outage in CGN. This is also the first 30-year outage of a domestic large nuclear power unit.

More than ten major modification projects were successfully implemented in this outage, including modification of the self-developed and self-implemented DCS system, turbine LP cylinder modification related to capacity expansion of conventional island, generator stator modification, etc.

Outage Command Center: Well-coordinated “all activities as in a chess game”

More than ten major modifications and maintenance activities were required for this outage. Together with the influence of routine maintenance jobs, there were cases that many projects were ongoing and managed at the same time slot. How to refine the allocation of resources with multiple cross operations? By thinking proactively and working innovatively, the team of Outage Command Center led the development of 2D electronic sand table, which was used for many full-process “wargaming exercises” over the implementation process of the overall outage so that all projects were conducted in an orderly manner.

Meanwhile, Outage Command Center constructed a multi-project management atmosphere with top-to-down and left-to-right interactions and promoted outage activities as “in a chess game”, regarding field issues.

With a scientifically sound “blueprint” for outage plan, it is also necessary to well control minor changes to the degree of “one brick and one tile”. The team of Outage Command Center engaged in the field activities to timely and accurately keep up with the progress of the “last mile”, held daily briefings, and adjusted resource allocation plan based on the actual dynamics in the field, achieving the refined planning management and the scientific change management, and delivering the elaborately-plotted blueprint into reality to help the successful completion of the 30-year outage. 

DCS modification: Digitalization modification of analog control system of the world’s first operational M310 reactor

“All DCS displays are normal, DCS system is operating stably, and system commissioning is fully completed!” At the beginning of the new year, Daya Bay DCS modification project, applying the non-safety class DCS platform (digital I&C system platform) SH_N with independent intellectual property rights owned by CGN, completed all the field commissioning activities. This marks that the digitalization modification of analog control system of the world’s first operational M310 reactor has met all the operation criterion and will safeguard the safe, stable operation of the unit.

Daya Bay DCS modification project involved products with long-lead time in design and R&D. Through a 100-day campaign to tackle issues in field commissioning activities, teams such as engineering design, product R&D, testing, and production collaborated fully, ensuring the smooth implementation of modification activities and the steady progressing of outage milestones.

Once all the post-DCS modification requalification tests were completed, a simple click at the engineering station would complete the complex operations of cable removal &connection as well as signal source connection that had to be completed in a cabinet or in the field previously.

LP cylinder modification: Start again with “core replacement”

This outage was faced with the first 1,000MW-level turbine LP cylinder modification in the domestic nuclear power sector. Key components such as inner casings, rotors, retaining rings, bearings as well as hundreds of other components were modified and replaced, and the assembly and fitting of those components were complicated.  

Before the rotor was put into the cylinder, tens of thousands of measurements and analyses had to be performed by the project team. Analysis, study and demonstration were conducted to inner casings and bearings through wire drawing, laser measurements and other approaches, which verified the conditions one-by-one prior to rotor installation so that the rotor installation into the cylinder went smoothly and the equipment safety was safeguarded.

During project implementation, heavy lifting operations were performed over a hundred times. How to ensure the absolute safety in hundreds of lifting operations? “Maintain a mindset of walking on thin ice, take ‘each time’ as the ‘first time’, and orient to details in every job from the perspective of overall project control”. This was the winning key that the project team ensured the safety in hundreds of heaving lifting operations.

The LP cylinder modification team resided in the field during outage, worked day and night, tackled a series of critical and key modification technologies, and completed the “core removal” of turbine LP cylinder, allowing Unit 2 of Daya Bay NPP turbine generator that has been operating for 30 years to thrive again.

The successful conclusion of the 30-year outage of Unit 2 of Daya Bay NPP provides effective assistance to the high-quality development of CGN and will continuously provide safe and reliable clean energy supply to the socio-economic development of the Guangdong-Hong Kong-Macao Greater Bay Area.