The CPS is an integrated system which provides for normal reactor control and power regulation, as well as automatic safety-related reactor shut-down when certain reactor operational limits are exceeded. So, the Control and Protection System serves for dual purpose of reactor power control during normal operation and reactor shutdown under accident conditions. Such a dual purpose system would not be allowably by Western safety authorities. The SAR study of the CPS confirmed the findings from the previous RBMK safety studies that there was inadequate separation of the control and protective functions within the CPS. Specific problems identified includes:
The Safety Analysis Report does not make a safety case which justifies the acceptability of the current design of CPS. The design features of the system are only provided in a very limited detail in the system description. This description focuses heavily on the power distribution control and local area regulating systems. Very little description is provided regarding the emergency reactor shut-down provision which effect safety and reliability. The Engineering Assessment was prepared to substantiate the case that the CPS is in compliance with key regulatory requirements. The Engineering Assessment actually produced is based on a very large number of proprietary internal RDIPE technical reports which have not been released for independent assessment. In a number of areas the Engineering Assessment states that regulatory requirements is met. The documentation does not in all cases state how the requirement met. The documentation does not provide an identification of what parts of the regulation there is compliance, specific design features which are not in compliance with regulations, and the technical justification for allowing continued operation despite the non-complianceís. The Single Failure Analysis is supposed to confirm that no single failures are present that can defeat the functioning of the system. Thus the key documents prepared to demonstrate the safety case fail to identify basic design and operational characteristics, fail to demonstrate how regulatory criteria are complied with, and fail to show that there are not major single failures present in design.
The position taken by SAR was: because the CPS not designed to Western standards, the lack of separation between control and protective function is pervasive, it was proposed that instead of trying to separate the two functions within the existing CPS, a second diverse shutdown system be designed and implemented. This diverse system would provide fast shutdown for all accident sequences and covers all accidents within design basis set for Ignalina NPP. However, such a system requires approximately four years to engineer, install and commission. Ignalina NPP agreed with this proposal. EBRD has already funded through the Safety Improvement Program of Ignalina NPP  a feasibility study for a second shutdown system. Several options were investigated in this study and a second shutdown system with ball-type absorbers was proposed. Ignalina plant staff engineers have visited the United Kingdom and convinced that operating model of the shutdown system with ball-type absorbers does not exist, in spite of statements that such system are used at British plants. Development of a new shutdown system which has no predecessors would require inadmissible long period of time which is commensurable with plant operation lifetime. This drastically change the opinion of Ignalina staff about the shutdown system with ball-type absorbers and thus such an option was not accepted by the Ignalina NPP on October 9-13, 1995 in the Vienna meeting where design options for second shutdown systems for RBMK reactors  were discussed. Therefore, the plant asked an European Commission to initiate an additional project and provide financial support to perform a feasibility study of a second shutdown system for Ignalina NPP, taking into account experiences on the development of independent shutdown systems for RBMK reactors.
The RSR evaluated the limited design information contained in the CPS system description, and the SAR Engineering Assessment and Single Failure Analysis. In order to understand the basic design details the RSR conducted two walkdowns of the installed system and met with Ignalina plan personnel involved in operation and maintenance of the CPS. These walkdowns were done without the benefits of any detailed wiring diagrams of the CPS. The Ignalina staff were responsive and they attempted to provide all requested plant documents. The walkdowns, limited as they were due to lack of the wiring diagrams and schematic, confirmed the basic design concerns of the SAR team. The walkdowns and subsequent discussions with plant staff also identified some CPS safety issues not identified by the SAR work. The RSR reject the safety case presented in the SAR submittal on CPS based on the failure to provide the basic design information and supporting information contained in the referenced topical reports which justify compliance with regulatory criteria. The RSR recommended that Ignalina NPP :
The Ignalina Safety Panel holds the view that the most important safety issues in design and operation must be resolved without delay. Among the SARís recommendations are the installation of second independent shutdown systems at both units, but this would take about 4 years. The Ignalina Safety Panel did not recommend the installation of such system at unit 1 because it is expected to be shut down between 1999 and 2002. In particular, the ISP recommends that before either unit restarts from its 1997 maintenance outage the following items related to CPS should be resolved:
A number of issues concerning CPS, that were raised by SAR and RSR teams have been resolved by the Ignalina NPP and, in the opinion of VATESI, the planning of compensatory measures for lack of scram diversity has reached an acceptable stage to permit restart. Ignalina NPP plans to introduce an independent high pressure scram parameter aimed at removing residual concerns about ATWS scenarios during the next outage. The other follow-up actions to resolved critical CPS issues are further discussed in detail together with related EPPS critical issues in the next Section.