ON SITE ASSISTANCE FOR ZAPOROSJE NNP

Zaporozhye NPP, located in Energodar, Zaporozhye Region, Ukraine comprises 6 power units and, with 6000 MW installed capacity, is the largest nuclear power generation facility in Europe.
Within the scope of the "TACIS Nuclear Safety Programme" ENBW Kernkraft Gmbh was contracted by the European Commission (EC) to provide support for improving the operational safety at Zaporozhye NPP. In the present service contract the German NPP GKN (Gemeinschaftskraftwerk Neckar) was the Consultant and provided On-site-assistance (OSA) to NPP Zaporozhe.

The objective of the present contract was to provide operational safety experience exchange to the NPP as well as the necessary services related to preparation of supply projects started under the TACIS 93 programme. The objectives of the operational safety experience exchange was to demonstrate EU best operational safety practices and their impact on plant operation safety to experts, managerial and operation staff of the NPP.
Three projects were initiated under this contract. The contract included the writing of Technical Specifications for engineering activities and technical equipment supply for the three projects as the technical basis for an invitation to tender. The projects were as follows:
U 1.03/93 A - Spare parts procurement for NPP Zaporozhe
In an existing paper “Necessary measures on safety improvements” safety related spare parts required for NPP Zaporozhe were listed. The project consisted of 2 parts:
Review of the existing spare part list and recommendations regarding which kind of spare parts of this list should be provided
Supply of spare parts (purchased under a separate supply contract – see U1.03/93A)
U 1.03/93 B - Measures to cope with hydrogen release in NPP Zaporozhe
The project consisted of the following phases:
1. Analysis-engineering judgement
Analysis of the design H2-release and quantity under consideration of the analytic and experimental experience - an engineering judgement (on the basis of the existing documents).
Analysis of the expected H2-concentrations inside the containment as a first approach by an integral assumption. According to the results of this assumption it could be necessary to use a computer-programme to make a detailed analysis with a multi-compartment-model. This multi-compartment-model shall be verified against the VVER - 1000 plant circumstances especially for the containment.

2. In-situ hydrogen measurements
For the surveillance of the H2-concentration following a design basis accident (e.g. Loss of Coolant Accident - LOCA) diffusion-telemetric-sensors are to be installed. The exact number and the arrangements of sensors depend on the above mentioned analysis.

3. Analysis of the H2-distribution inside the containment
In GKN unit 1 the H2-distribution is achieved by natural convection inside the containment. To support the natural convection it is necessary to increase the water-temperature in the containment sump. During design basis accidents the water-temperature will be held at 60 C. The increased water-temperature of the containment sump is sufficient enough to enable, even in local compartments, a mixture with a H2-concentration lower than that required for an inflammable mixture.
Forced measures for the aeration (ventilators and air ducts) are not needed for GKN unit I. The effectiveness of the counter-measures is depending on the results gained with multi-compartment computer-code.
According to the information which GKN received from the Zaporozhe NPP there is only a model of the compartments inside the containment available. This model is under consideration since 1992. It seems to be necessary to interrogate the actual status with the company “Atomenergoproekt” and the “Kurtschatow-Institut”, both are located in Moscow. The interrogation is not included in this project.

4. Analysis of H2-elimination with catalytic recombiners
The release of Hydrogen (H2) in the atmosphere of the reactor containment can lead to a formation of flammable mixtures of air and hydrogen which release energy when ignited. The H2-concentration can be reduced by catalytic recombination.

5. Development of a Technical Specification for the purchase of a Hydrogen Monitoring System
The hydrogen monitoring system was installed at ZNPP under the follow-on TACIS 94 programme (see U1.03/94B).
U 1.03/93 C - Fire protection-surface coated with fire resistant material on NPP Zaporozhe
The project consists of 2 phases:
1. Urgent needed fire protection measures by coating all structural steelworks in the building, coating also cables and cable penetrations.
2. General fire safety analysis building by building, room by room with following aspects :
Assessment of the existing structural and system-related fire protection equipment of the former USSR-standards against international standards.
Assessment of the gap between the above quoted standards with Western standards.
Review of the documents about the quality of the existing fire protection equipments.
Assessment of certification with the main emphasis of the test-procedures (what kind of qualification-test are performed).
Requalification of the existing fire protection equipment.
Fire load (kind and quantity of material which could burn with the presence of igniters).
Locations of operational and safety related components which shall be operable during and after fire.
Common assessment room by room; to identify devices which have to be operable but whose function not guaranteed.

Technical Specifications were prepared for the coating of structural steelwork of the turbine hall with intumescent material. The coating was performed under the follow-on TACIS 94 programme (see U1.03/94A).

The direct agreement contract implementation with ENBW Kernkraft Gmbh as consultant started on 20th September 1994 and ended on 20th September 1995.
The progress achieved on the projects included the development of the Technical Specifications for two supply projects "Hydrogen monitoring system" and "Coating of structural steelworks of the turbine halls with intumescent material". The "call for expression of interest" was published on 8th September 1995. Regarding the spare parts purchasing, 90% of the specified spare parts were delivered to the plant at end of the contract period.
Particular achievement in the area of operational safety experience exchange was related to "Control Rod Insertion Reliability", "Periodical Test of Safety Valves", "Implementation of a Quality-Assurance Management System" and "Guideline about Operation Assistance".