Several projects related to the safety analysis of the Ignalina NPP or its safety systems have been performed. The joint Lithuanian - Sweden Barselina project - the first probabilistic assessment for RBMK type reactors - was conducted . A peer review of this Ignalina PSA project was conducted by Pacific Northwest National Laboratory. The hardware required to use US Nuclear Regulatory Commission computer code for conducting probabilistic risk assessment was purchased and delivered to the Ignalina Safety Analysis Group. A plant analyzer and computer workstation were delivered to the ISAG, with additional hardware to support the extension of the Ignalina plant analyzer to multiple simultaneous users. An evaluation of the RBMK-1500 accident confinement system  was performed by a joint team from Ignalina Safety Analysis Group and the Department of Nuclear Engineering, University of Maryland. The study of the RBMK-1500 ACS was performed using the state-of-the-art codes RELAP5 and CONTAIN, and is the first study that analyzes not only short-term, but also long-term (up to 24 hours) aspects of LOCA transients for primary system and the ACS.
An in-depth safety assessment of the Ignalina NPP was undertaken and as a result a Safety Analysis Report has been produced  and reviewed . The safety assessment of Ignalina NPP is the first attempt to perform Western-type safety analysis for any Soviet-design nuclear power plant. A plant-specific Safety Analysis Report is produced which will form the basis for decisions on future operation of Ignalina NPP. The SAR aims to:
The safety analysis will consider a safety assessment of both units at the Ignalina NPP. The main reference plant for the project is unit 1, but a survey is included which defines the differences between unit 1 and unit 2 and assesses their safety.
The assessment consist of two elements: Safety Analysis Report and an independent Review of Safety Report. The
report was Ignalina NPP responsibility, supported by RBMK design institute, RDIPE and Western engineering companies. The review was undertaken by Western and Eastern technical support organizations, including Lithuanian Energy Institute. A Panel of international nuclear safety experts, Ignalina Safety Panel, was established in accordance with the Grant Agreement. The objectives and role of ISP was to monitor and supervise the scope and production of the SAR and its review processes and to make independent recommendations to the Lithuanian Government, Ignalina NPP, VATESI and Donor Countries regarding a decision for continued plant operation and implementation strategies of the SAR and RSR recommendations once the assessment was finalized. The NSA provided 8.5 million ECU to fund the external assistance work.
The clear separation of the SAR production and its independent review, performed in parallel and providing interactive feedback has proven very effective in ensuring an objective in-depth assessment. The SAR and RSR teams have identified safety issues and make recommendations on necessary safety improvements in design, operation and safety culture required as sound basis for plant operation. All recommendations were accepted by the Ignalina NPP and included in new Safety Improvement Program . Implementation of all improvements will greatly improve the safety level of Ignalina. Main SAR results are presented in Sections 10 and 11 of this Source Book.
As to system analysis, the SAR defines more than 50 systems which constitute the main operational, safety grade and related support functions of the plant. The scope of analysis of these systems include Engineering Assessment of the capability of existing systems, assessment of the value of options for removing or reducing non-compliance’s and Single Failure Analysis. System analysis is performed primarily to demonstrate compliance with deterministic rules and standards in force in Lithuania and safety practice in the west. Assessment of the value of options forms an important input to the categorization and justification of non-compliance’s. Particular emphasis was laid on compliance with the single criterion. An investigation was carried out to determine whether all systems which are claimed as providing protection against faults are able to carry out their functions in the event of any single failure. The procedure to be followed in the work programs required that the vital safety system functions be shown to conform to IAEA Safety Practice . Non-compliance’s with requirements for robustness against single failure had to be justified. Additional safety aspects, such as the impact of maintenance, testability, reliability or external events (fire, flooding) on system functions were considered according to Western practice.
The depth of assessment of particular system depends on category of system. The category definitions are as follows:
Category A - These systems are front line safety of mitigation systems, or important process systems. A full Engineering Assessment and Single Failure Analysis was performed for category A system.
Category B - These systems are deemed to be less important than category A systems from a safety perspective, and there assessed in less depth. An Engineering Assessment was performed for each system and includes consideration of single failures.
Category C - These systems are considered less important as category A or B systems, but a separate Engineering Assessment was prepared nevertheless. The depth of the assessment is somewhat less than that for category B systems.
The Engineering Assessment typically comprises the following:
The Single Failure Analysis for a system is performed by identifying in the system, and assessing the impact of, its failure on the safety performance of the system. Recommendations are identified if single failure of a component can impact the ability of the system to meet its safety objective.
The reports of system analysis performed represents significant efforts and form a compilation of issues such as:
In order to present a coherent picture of the system analysis performed in the SAR, this Section presents the results integrated according to the following major functions:
It is necessary to emphasize that as a general consideration in this work, the international team has performed and reviewed analysis similar to that performed for the Ignalina NPP on NPPs that in theory were designed to very strict Western standards and criteria. In all cases, issues were identified that required corrective actions. This is not unanticipated. It occurs every time such analysis is performed. In fact, the international reviewers would have been most surprised to have a comprehensive investigation not identify anything that needed to be improved. This is why regulators request NPPs to perform new assessments and investigations - it leads to continuous safety improvement.