SUPPORT ZAPAROJE6, ROVNO4 & KHMELNITSKY2

The Modernisation Programme for Rovno 4 and Khmelnisky 2 NPPs of VVER 1000 type was developed on behalf of the GOSKOMATOM of UKRAINE by KIEP of Ukraine as General Designer and MOHT, an association of Russian designers, with the participation of Rovno and Khmelnitsky nuclear power plants and under the leadership of the Project Management Group, supported by the Consortium EDF/Tractebel/lVO P.E. The development of the Modernisation Programme took from June 1994 to November 1996. In November 1996, the Programme was concerted with the State Nuclear Regulatory Authority of Ukraine (SNRAU) and RISKAUDIT, a consortium of Western Nuclear regulatory Authorities supporting SNRCU, and agreement was reached that the units when modernised will meet the good international design safety standards.2)

The main objectives of the current project was to provide an independent design review of the proposed modernization programme. The Design Review was made as a specific review against proven international guides and practices in order to evaluate the basic design of the Modernization programme in particular its completeness and consistency.

During the Design Review, performed in KIEP offices from 16 to 30 of April 1997, sixty four Basic Design documents (among a total of 182) were duly analysed. Among them, four are selected as the most important ones and described in the following.
Fire Hazard
The fire hazard review covered fire prevention, fire detection and extinguishing, means to limit the spread of fire as well as the consistency with the fire hazard analysis.
The measures developed under the fire hazard risk review covered ways to reduce the major potential effects of fire related to safety, availability and personal safeguard. They advise a vulnerability study to determine protective passive, active and detection measures. Given the scope of the vulnerability study, it is advisable to clearly specify the selected method which should be based on a deterministic method before further implementation of the studies. This method is the most efficient of those currently available.
In addition, it was recommended, before deciding to implement the new detection systems, that potential interference with the planned radio communication system be carefully analyzed.Emergency power systems
The emergency power systems review covered the alternating current power system, the direct current power system, and checking the non-interruptible alternating current system of the emergency power supply as well as the stand-by electrical power systems, electrical penetrations, cables and capacity to react to station black- out.
The measures proposed for the field of electricity can be broken down into four sub-categories:

Replacement of existing equipment by more reliable and more efficient equipment (5 measures).

Significant modification of the system including use of additional equipment (such as additional diesel generator sets).

Studies which may prompt modifications in plant operating practice, automatic controls, or even the use of additional equipment (4 measures).

Monitoring systems (6 measures).

Accident analysis
The review dealt with the six measures determining accident analysis and with those analyses or modifications involving a potential impact on accidents. Analysis of reactivity transient prevention and measures involving accident operation were identified as having the highest impact. The scope of accidents analysed is considered satisfactory. However several methodological issues will have to be specified, notably the categorisation of design basis accidents (according to the IAEA - Extra Budgetary Programme Report on WWER accident analysis).
Regarding the associated measures, the most important identified additional needs were:

analysis of the risk induced by the automated control of steam generator header failure accident;

confirmation that pressuriser safety valves are capable of ensuring the feed-and bleed discharge flow.
Protection against over pressurisation
Protection against over-pressurisation of safety related components was reviewed especially considering the safety related issues ranked at the highest level by IAEA. The documents relating to the review cover primary circuit overpressure protection at nominal and low coolant temperature, steam generator safety valves and the equipment to allow use of the pressuriser safety valves for feed and bleed operation.
In order to allow a timely and adequate implementation of the corresponding measures, further consideration should be given to the following main interfaces:

interface with other accident mitigation measures, mainly in case of primary to secondary leakage and beyond design basis accidents;

interface with equipment qualification measures;

interface with in-service inspection and testing;

interface with accident analysis and equipment design calculations.

Comments

(quality of the results, lesson learnt, recommendations for follow-up)
The comments produced by the experts covered five important areas related to plant improvements. The comments were given on the completeness of the Basic Design and possible impact on interface areas. The Consortium recommendations were supposed to be dealt with in the future engineering works.
Among these, measures relating to:

Primary to secondary leakage management;

Feed and bleed capability;

Methodology of the fire vulnerability study; needed to be solved as soon as possible in order to complete the basic design.
The other recommendations identified by the experts were to be taken into account in due course according to the project schedule.

Further Information

Further information on the project results could be sought from the beneficiary organization.
The Project Final report is available at the JRC-IE archive.