U2.02/96 Implem System Steam Gener Repla

Steam generators (SG) are components of the reactor coolant system (primary circuit) transferring the heat produced in reactor to the secondary circuit. As they serve for both reactor cooling and generating steam for main turbine-generator(s), they are crucial for safe and reliable plant operation. Due to natural ageing or material defects, the SG may require replacement within NPP lifetime. During 1990’s, SG replacement became a standard operation at nuclear power plants both in the USA and Western Europe. Substantial experience has been thus gained by Western countries in these activities, including development of special equipment and procedures, which resulted in increased work efficiency, shortened outage times and reduced radiation exposure.

Several replacements took place also at Ukrainian NPPs between 1987 and 1992, providing some experience and showing the need for improvement in specific activities like narrow gap welding, and using tools for cutting, aligning, fitting, welding and thermal stress relieving of the piping connected to the SGs. Therefore a project on implementation a system of SG replacement was proposed.

The general aim of the U2.02/96 project has been to help the Ukrainian nuclear industry to proceed with the SG replacement at a pilot plant with a minimum of further necessary development activity. The specific objective was to develop a project plan and strategy and develop key technologies for the SG replacement along with appropriate training of maintenance personnel from NPPs and engineering support organizations. The main focus was on:

Adaptation of narrow gap welding for use in SG replacement at Ukrainian NPPs

• Documentation for the certification of the narrow gap welding process

Use of tools and equipment for the cutting, aligning (optical survey), fitting, welding, thermal stress relief and decontamination of the piping connected to the SG to be replaced.

• Radiation protection during the SG replacement process.

Within the project, narrow-gap welding and pipe cutting/bevelling equipment was to be specified and procured.
For the pilot plant, the Zaporozhye 3 NPP was selected, as it was considered to be representative of the other Ukrainian NPPs. No actual SG replacement had to be performed within the project.

According to the ToR, the project work had to be implemented in the following 8 tasks:

• Task 1 – project management
• Task 2 - Identification and assessment of the technical constraints
• Task 3 - Generation of the strategy for SG replacement
• Task 4 - Definition and development of specific technologies including application of narrow gap welding techniques for SG replacement
• Task 5 - Creation of a management and quality system
• Task 6 - Production of an outline project plan, time and critical path schedules and risk analysis
• Task 7 - Organising and providing training courses
• Task 8 - Specification and procurement of selected equipment.

The contract was signed with a consortium “Framatone ANP S.A.S. – Framatome ANP GmbH (formerly Siemens) – ENSA” on 10 June 1999 for a 2-year period. As the local subcontractor, the Ukrainian company Pivdenteploenergomontazh was hired.

Despite some delays in the inception period, the initial phase of the project went well. The project was well planned and managed, the cooperation with the local partners was good and a clear strategy for SG replacement in Ukraine using new techniques was developed. The Ukrainian participants received adequate support in adapting western experience to local needs. The local subcontractor’s contribution was essential to good progress and completion of all activities within the original project schedule.

However, due to organizational and other changes within the Consortium (merge of Siemens AG and Framatome, name change), the work progress slowed down substantially, as the EC contract had to be revised and the interim payments to the Consultant were held up. The delays in interim payments finally resulted in suspension of some Contractor’s activities from January 2001. The new contractual arrangements were completed only on 20 February 2002 allowing the payments and project activities to restart. In the meantime, the Consultant contributed to Subcontractor’s activities, which played the key role in implementation of individual tasks, from his own budget.

The project was formally closed on 22 December 2004.

As results of the individual tasks, the Consultant has delivered and distributed the following documents from November 1999 to July 2001:

• For the Task 1 - Project description; Engineering Schedule; QM plan; List of Technical document; Handling of technical documents.
• For the Task 2 – Identification and Assessment of Technical Constraints
• For the Task 3 – SG replacement strategy and methods proposed for application in Ukraine
• For the Task 4 – SG replacement scenario; Implementation of primary piping welding technology; Guidelines for welding qualification and experience; Report on the implementation of western measuring technology;
• For the Task 5 – SG replacement project management recommendations; SG replacement on-site organization; SG replacement QA program;
• For the Task 6 – Overall work sequence plan; SG replacement performance schedule; SG replacement performance recommendations;
• For the Task 8 – Specification for the supply of an orbital NGTAW welding equipment; Operation and maintenance manual for primary pipe cutting and bevelling machine.
• Within the Task 7, three training courses were held on

Orbital narrow gap gas tungsten arc welding (5 specialists trained in France in March 2001),

Use of optical survey equipment (four specialists trained in France in April 2001)

Use of cutting and machining equipment (four specialists trained in Spain in May 2001).
As a tangible result of the project, two sets of narrow-gap welding equipment and one set of cutting & bevelling equipment were delivered to Ukraine in June 2001 with the customs clearance completed in September 2001. However, all the 15 spare SGs available in Ukraine had the primary pipe nozzles prepared for conventional welding only and no equipment to prepare the nozzles for the narrow-gap welding was available in Ukraine. Some other important equipment being out of scope of the contract, like optical survey equipment for pipeline alignment or equipment of primary nozzles decontamination was not available either. Therefore, the new SG replacement technologies could not be directly used without procurement of additional equipment.

Conclusions

The project objectives were met partially. Although most of the documents were produced, the requested training was arranged and equipment was delivered to Ukraine, the project was not fully implemented as originally planned and some agreed documents have not been delivered. Formally, the key technologies and training were delivered to Ukraine, but the achievements did not allow direct application of the technology for future SG replacement without follow-up actions, equipment procurement and additional funding.

The project results sustainability has been moreover compromised by organizational and personnel changes at the local Subcontractor, so some of the Subcontractor’s expertise obtained within the project may be lost.