1)Background
The South Ukraine Nuclear Power Plant site has three VVER-1000 units in operation. A fourth unit was moth-balled in the early 80's half wav through civil construction. No equipment had been installed and the turbine hall building is presently being completed to host a mechanical work shop.
The site is located 350 km south of KIEV on the banks of the South Bug river. The construction of the first unit began in April 1976 and the unit synchronized to the grid in December 1982. The second and the third unit were commissioned in January 1982 and September 1989 respectively.
Under the TACIS programme a number of projects have been implemented by Western companies to assist the implementation of plant safety upgrading. Executive summary of the current project is attached at the end of this record.
2)Objectives
The main objectives of the Extension of Phase 1 of U.1.02/92 was to continue to provide assistance to the plant management in the design, assessment and implementation of a number of plant safety improvement projects.
In particular the following activities were to be implemented:
• General site assistance through the continuous presence of western experts on site coordinating information exchange between South Ukraine and Spanish and Belgium NPPs and experts exchange visits.
• Overall management of four projects included in the TACIS-92, preparation of Terms of Reference and Technical Specifications associated to TACIS 93/94 programme and preparation of proposal for the projects to be covered by TACIS 95.
• Preparation of studies related to the modernization of the I&C and issue of Technical Specifications associated with future tenders.
• Preparation of studies and technical specifications for the following project equipment:
o 1) Reactor Vessel Inservice Inspections;
o 2) Steam Generator feedwater control modifications;
o 3) Automatic control of primary circuit weld.
• Support to the CEU procurement agent for the first priority spare parts supply.
• Participation with the plant staff in the reception of the spare parts.
3)Project Results–Achievements (as requested by the TORs)
For each of the above mentioned safety implementation projects the Contracted supported the plant management and contributed to the development of detailed terms of reference which were needed to procure equipment and actually implement the proposed safety upgrades. The summary of the work performed for each of the issues is given bellow as stated in the project final report:
Reactor Pressure Vessel Inservice Inspections
A comparative study has been performed between the standards used in the ex Soviet Union and other internationally recognized codes such as the Section XI of the ASME Code, in order to establish the applicable standards for the In-Service Inspection Program Proposal.
However, to apply the requirements of the Section XI of the ASME Code for defining the In-Service Inspection Program for a component or piping, is necessary that its design is according with the requirements of the ASME Code Section III. Before carrying out such analysis, a comparison was performed between the Mechanical Design Requirements of the latter and those in force in the Soviet Union when the Plant was designed.
Once the comparative study was performed it could be seen that the requirements of both regulations are similar, however the specific limits in each case do not permit to conclude that the fulfilment of one regulation, means also that the requirements of the other are also met. Therefore, it was unavoidable to perform the stress analysis according to the Section III of the ASME Code in order to define the In-Service Inspection Program Proposal according to the Section XI of that Code.
The stress analysis performed is included in the document RPVISI-94-01 "Reactor vessel stress analysis".
Having taken into account the design and the results obtained from the stress analysis performed, it was concluded that the inspection requirements defined by the ASME Code Section XI, in relation to scope, examination techniques, frequencies and acceptance criteria, are basically acceptable for the surveillance of the structural integrity of the reactor vessel.
In order to establish the scope and frequency of the inspections, the In-Service Inspection Program, which is included in the document RPVISI- 94-02 "Reactor pressure vessel ISI program proposal”, has been issued.
An Indication Assessment Manual applicable to indications exceeding acceptable limits established in previous analysis and included in the document RPVISI-95-03 "Reactor pressure vessel Indication Assessment Manual", has been drawn up.
The scope and the budget of this project was modified according SUK-NPP requirements, due to that SIEMENS will give to the plant, a vessel in-service inspection system for free. In fact the activities related to this project were initiated, under the present contract, on April 1994.
Later on, SUK-NPP asked UNESA to do the activities mentioned initially in this project TOR but non included in SIEMENS supply and after knowing the scope description from SIEMENS, the Phase1 Extension activities of this project were initiated. During the stays at the plant of the western experts, enough data were collected and technical discussions took place to elaborate the above mentioned documents, that have been translated and presented to the SUK NPP specialists based on the following technical items:
• Finite element modelization of the beltline and bottom of the reactor pressure vessel;
• Distribution of temperature and stresses along the vessel wall thickness in the zones Irradiation surveillance program results;
• Analysis of the operational transients;
• Modelisation of the vessel flange and cover flange junction;
• Fracture mechanical analysis.
One activity not included in SIEMENS supply was the inspection system for ECCS injection nozzles. Regarding this matter two technical specifications have been drawn up both included in the following documents:
• RPVISI-04 "Ultrasonic testing system in immersion tank. Technical specification South Ukraine NPP", to prepare the inspection procedures in laboratory.
• RPVISI-9S-0S "Ultrasonic inspection system for SIS nozzle to vessel shell welds. Technical specification South Ukraine NPP".
Stem Generator Water level and Feedwater Flow Control
Considering the initial budget constrains, an agreement was reached to:
• install the new control system in both Units 1 and 2;
• replace the feedwater control valves and their bypass valves on both units;
• delay some projects originally planned in the TACIS 93/94 program to TACIS 95 and use the corresponding funds for this project.
A detailed design for the improvement of the system was made and the three following associated Technical Specifications for the equipment supply were issued, reviewed and approved by the plant and GOSKOMATOM:
• Technical specification for the control system of the steam generator and feedwater control.
• Technical specification for transmitters, Pt100, calibration valves for ΔP measurements, condensate pots and thermowells for the feedwater and SG level control system.
• Technical specification for the feedwater control valves.
Contacts with the CEU procurement agent (FICHTNER) for the equipment related to this project, Tender No PAINSP/SUK 001/93-94was initiated, the evaluation criteria and evaluators selection done. Also frequent contacts were maintained with the bidders to clarify their questions about the specifications requirements.
The open tendering process was initiated early March 95.
For this project the plant contracted the local engineering organisation (L'vovORGRES) to coordinate all the activities to be performed by the counterpart. Kick-off meetings was organized with L'vovorgres.
The activities of this project were supposed to continue under the scope of TACIS 93/94 with the final objective to have the respective system in operation in 1996. The Particular terms of Reference (TOR) for these activities was also issued, reviewed according with the EC-DGI comments and the final version was included in this project report.
Automatic control of primary circuit piping welds
In order to establish the applicable standards for the In-Service Inspection Program Proposal, it has been performed a comparative study between the applicable standards of ex Soviet Union and other internationally recognized codes and rules, such as the Section XI of the ASME Code, The requirements of both regulations for piping inspection were found similar.

The stress analysis performed as well as the allowable flaw sizes calculated, were included in the document PCPW-94-01 "Primary circuit piping stress analysis". It was concluded that the inspection requirements defined by the ASME Code Section XI, in relation to scope, examination techniques, frequencies and acceptance criteria, are basically acceptable for the surveillance of the structural integrity of the reactor coolant loop piping.
The In-Service Inspection Program for the reactor coolant piping system, was included in the document PCPW-94-02 "Primary circuit piping ISI Program Proposal". This document also includes a Data Base for handling a complete list of areas with all information and drawings.
In accordance with the document "Particular terms of reference for project “South Ukraine NPP -Automatic Control of Welds of Primary Circuit Piping", a feasibility study should also be carried out regarding to the application of the inspection program, such that if physical or radiological access conditions or other various issues were to prevent development, alternative solutions might be found.
In order to check the physical conditions of the Primary Loops, a visit was performed to SUK-NPP. The results of this visit were included in the document PCPW- 94-03 "Feasibility study of primary circuit piping welds inspection program", concluding that no obstacles have been detected that might prevent mechanized ultrasonic inspection of the referenced areas.
The functional, operational and supply requirements of the automatic ultrasonic inspection system to be used for the welds of the Primary Loops in WWER 1000 Nuclear Power Plants, were established in the document PCPW-94-04 "Ultrasonic inspection system for primary loops technical specification South Ukraine NPP".
Finally, the report PCPW-94-05 "Technical specification for the manufacturing of calibration blocks and validation of the primary circuit loops of the South Ukraine Nuclear Power Plant" was performed. This document described the necessary information to fabricate the calibration block to be used in ultrasonic inspection of the circunferential welds of the South Ukraine NPP.
During the stays at the plant of the Western experts, enough data were collected and technical discussions took place to elaborate the above mentioned documents that have been translated and presented to the SUK NPP specialists based on the following technical items:
• Piping support system calculations, finit element mesh;
• Modelisation of the primary loop piping;
• Inspection areas maps;
• Dead-weight and thermal expansion stresses calculations.
4)Comments (quality of the results, lesson learnt, recommendations for follow-up)
The prepared Terms of Reference and Technical Specifications facilitated the implementation of the selected plant modernization projects at South Ukraine NPP.
It was further noted that the selected projects were all of generic interest and therefore can be very useful for other Ukrainian and Russian plants.
Further information
Further information on the project results could be sought from the beneficiary organizations.
The Project Final report is available at the JRC-IE archive.
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