There are several reasons why an updated version of this publication has been prepared. The most important one is that the safety improvement process at the Ignalina Nuclear Power Plant is both active and ongoing. The first significant Safety Improvement Program was defined in 1993 and has implemented. It led to the signing of a Grant Agreement in 1994 between the Lithuanian Government, the Ignalina NPP and the European Bank for Reconstruction and Development on behalf of the Nuclear Safety Account. A Safety Improvement Program sponsored by NSA are not only safety upgrading projects at Ignalina NPP. In addition several bilateral safety enhancement projects with USA, Sweden, Finland and other Western countries completed or underway. These projects have led to implementation of hardware and modification of operating procedures.
The second reason for updating the Source Book is that several extensive projects were initiated and completed which analyzed safety issues of the Ignalina NPP and considerably expanded the available information in this area. An In-Depth Safety Assessment of the Ignalina NPP sponsored by EBRD has been completed and a Western-type plant-specific Safety Analysis Report was produced in 1996. The results of the fourth phase of the Barselina project - a probabilistic study of the Ignalina NPP - is also available. A thermal- hydraulic evaluation of the RBMK-1500 Accident Confinement System has been performed in 1995-96. This study was performed using state-of-the-art codes RELAP5 and CONTAIN and includes analyses not only short-term, but also the long-term (up to 24 hours) aspects of LOCA transients for primary system and the ACS.
On the base of the recommendation of the In-Depth Safety Assessment project a new Safety Improvement Program of Ignalina NPP (SIP-2) has been prepared and was approved by the Lithuanian authorities in April, 1997. The SIP-2 program includes a safety upgrades which should be implemented at the plant by 2000.
Finally, this version of the "Ignalina RBMK-1500. A Source Book" is not only updated but also considerably extended. In addition to the systems described in the first version, it includes a description of such systems as the Reactor Cavity Overpressure Protection System, Fuel Cladding Integrity Monitoring System, Emergency Power Protection System, Electric Power System, Steam and Power Conversion System, Service Water System, Intermediate Circuits System as well as other auxiliary systems. Results of the In-Depth Safety Assessment of the Ignalina NPP, especially results of system analysis and accident analyses, as well as Barselina project are discussed in Sections 10 and 11. Safety management and plant operation are described in Section 12. Section 13 discusses safety improvements performed at the Ignalina plant after the Chernobyl accident and during implementation of the first Safety Improvement Program as well as the new Safety Improvement Program.