Using SPDS to bring Soviet-designed reactors closer to Western level safety8 January 1999
The introduction of Safety Parameter Display Systems (SPDS) into Russian designed reactors is a key part of Western efforts to improve safety levels in Eastern Europe. The two landmark events of Three Mile Island (TMI) and Chernobyl are the genesis of the Westinghouse SPDS programme.
Subsequent to TMI, the United States Nuclear Regulatory Commission (NRC) issued a report, NUREG-0696 that provided a clarification to the TMI action plans for improving the safety of nuclear power plants. This report defined the SPDS and the concepts of critical safety functions and malfunction detection. SPDS’s primary function, as stated in NUREG-0696, “is to aid the Operator in the rapid detection of abnormal operating condition”. Subsequent to NUREG-0696, Westinghouse developed a generic SPDS design, approved by the NRC, that is tailored through a conformance process to a plant’s specific attributes.
The Chernobyl accident led to joint Russian-Ukrainian and Western safety reviews of Russian-designed reactors which determined that plant instrumentation and control (I&C) for the RBMK-type reactors were insufficient relative to Western standards. Regarding VVERs, the reviews determined that the I&C systems, while for the most part of sufficient design, were at or near the end of their design lifetimes and that the systems have man-machine interface (MMI) deficiencies.
These and other findings were the impetus for nuclear safety programmes sponsored by the United States and other Western governments. One programme, sponsored by the US Department of Energy, funds the provision of SPDSs for RBMKs in Russia (plus Chernobyl) and VVER-1000s in Ukraine. Under this programme, Westinghouse received contracts to provide SPDS for up to 11 units each in RBMK and VVER-1000-type reactor installations.
Differences in Reactor types
The VVER-1000 reactors have similar fundamental characteristics to Westinghouse pressurised water reactors (PWRs). Like most nuclear units using light water technology, VVERs use water to both generate steam and to cool the reactor. Water also acts as a ‘moderator’, slowing neutrons which increases the chances of fission, contributing to safe operation because loss of water will result in a slowing of the nuclear reaction.
While similar, PWR and VVER-type reactor installations do have differences that result from the infrastructures that designed, implemented, and operated the reactors. This results in safety and reliability differences between the two reactor types. However, most important is the obsolescence of the existing I&C systems design lifetimes.
RBMK-type reactors use graphite, rather than water, as a moderator. Unlike PWRs and VVERs, the RBMK nuclear chain reaction and power output increases when cooling water is over heated and becomes steam. This design characteristic, correctable through fuel enrichment, was a principal cause of the Chernobyl accident.
Further, the safety reviews concluded that the RBMK’s accident-mitigation systems are limited and ineffective and the reactor control systems are not sufficiently flexible to ensure successful recovery.
Why the need for SPDS?
With an unfavourable design characteristic and insufficient I&C systems, the RBMK-type reactors are a prime candidate for immediate I&C modernisation. An SPDS is a logical step in this process.
Considering the relative complexity of the RBMK compared to PWR-type reactors, it has become obvious that the RBMK’s probability for significant events is unacceptable. Of considerable concern is the existing I&C time delay in presenting information to the operators (up to 20 minutes from data input to presentation). An SPDS, which can process data input from disparate plant systems quickly and provide a concise, informative and timely summary to plant operators, is an extremely valuable tool. It can alert operators to potential problems early enough to permit effective action using existing control systems, then warn of abnormal conditions arising during the recovery process. Such forewarnings, coupled with positive operator action, can prevent a severe incident from occurring.
VVER-type reactors, while significantly safer than RBMKs, also have MMI sufficiency issues with plant I&C. Besides the substandard MMIs compared to Western systems, the I&C systems have either passed their lifetimes or are fast approaching them. Consequently, augmenting a unit’s existing I&C with an SPDS improves both the operator’s information and, therefore, his ability to use the existing I&C systems. This could provide for safer overall operation until existing systems can be more thoroughly upgraded.
For both RBMK and VVER units, an SPDS provides not only an immediate operational benefit, but also a platform that can be extended to modernise upper-level plant systems because the SPDS system configuration is comprised of the same equipment that would be used in a Unit Information System replacement.
Thus, the rationale for installing SPDS is clear: provide plant operators with a quick and effective means of identifying problem areas and set in place a platform that is the first step to new, modernised I&C systems.
In the international market, Westinghouse’s experience shows that a partnership approach works extremely well. Combining engineering expertise and products with a strong local partner provides international customers with a technically strong product using locally-based expertise and support. With the breakup of the Soviet Union, Westinghouse and others realised that opportunities to provide modern I&C systems to nuclear plants in Russia and Ukraine will materialise and the ability to capitalise on this will require application of its partnership concept.
Local partnership is a practical precondition for participating in the Russian and Ukrainian domestic markets. Realising the significant potential market for nuclear I&C in Russian-designed reactors, Westinghouse began searching for viable local partners in the early 1990s. By the middle of the decade Westinghouse had culminated joint venture agreements in both countries.
In 1994, Westinghouse signed a consortium agreement with Khartron, a designer of control systems for the Soviet Union’s military missile and space programmes. This agreement founded the Westron joint venture with the principal charter to provide I&C systems to Ukraine’s nuclear power plants. A significant factor in forming this alliance was the designation of Khartron, by the Ukrainian Cabinet of Ministers, as the Chief designer and contractor for I&C modernisation in the Ukrainian nuclear power plants.
Partially funded under a defence conversion Nunn-Lugar grant, Westron quickly established itself by procuring orders from the South Ukraine and Zaporozhye Nuclear Power Plants for Computer Information Systems (CIS) upgrades. Using these orders, Westron was able to apply the technology transferred by Westinghouse and developed a staff of engineers and technicians that now numbers 85.
In 1996, following two years of negotiations and discussions, the Westek joint venture was established in Russia. NIKIET, the principal Russian partner, is the designer of RBMK reactors and the designated functional designer on the RBMK SPDS contract.
SPDS Project Implementation
The SPDS project implementation plan in Russia and Ukraine called for a mix of Westinghouse and local content in line with Westinghouse’s prior international experience and the requirements of the DOE-funded SPDS contracts. The Ukrainian case history is highly illustrative in this regard and subsequently served as the objective model for the Russian case.
Prior to receiving the VVER-1000 contracts, Westinghouse implemented this mixed-content approach on Westron’s initial CIS contracts. Ukrainian personnel capabilities, combined with a smooth technology transfer, enabled Westinghouse to accelerate its objectives for realisation of the desired project implementation model. Having achieved significant success on the initial projects, there was a high degree of confidence that the model could be successfully applied to the SPDS projects. The model can be summarised as follows:
• Westinghouse provides overall project management for the project and supervisory design direction; Westron, acting as Westinghouse’s agent, provides project management and coordination of Ukrainian activities.
• Hardware ‘kits’ and basic system and application software are provided by Westinghouse in line with its licensing agreement with Westron. Where practical, local suppliers are used to provide portions of the hardware ‘kits’ such as cabinet metal work.
• Westron assembles the hardware ‘kits’ into a system as prescribed by the system architecture jointly developed by Westinghouse and Westron. Westron then performs prescribed unit and system hardware tests.
• Westron develops the application software design based upon the system functional design and standard Westinghouse application software. It then codes and tests this software and integrates it into the assembled system along with the graphic displays.
• Westron integrates and tests the fully configured system, preparing it for the Factory Acceptance Test. Test procedures are developed by Westron (and other Ukrainian organisations as applicable) and are reviewed by Westinghouse.
• Westron ships the system to the plant, then provides technical direction to the local subcontractors that perform the erection and installation activities. Site testing and Site Acceptance testing are conducted under Westron’s technical direction using procedures developed by Westron and other Ukrainian organisations.
In summary, the bulk of system implementation activity is performed in Ukraine by Westron and other Ukrainian organisations. These include functional design, software and graphics design and implementation, test activities, installation design, erection, and commissioning, and licensing support. For the most part, the use of this implementation model has been an outstanding success in Ukraine.
Westek, due to the timing of the RBMK SPDS contract, was not able to fully implement this model on the initial systems. Specifically, hardware assembly and testing was performed by Westinghouse outside Russia. However, the new system contracts will have this work shifted to the Westek facilities in Moscow with the intent of fully implementing the model that has proved so successful in Ukraine.
VVER Project Status
The original VVER-1000 SPDS contract, awarded in 1997 by Burns & Roe Enterprises, the primary DOE contractor, was for the procurement of two pilot systems (Khmelnitsky Unit 1 and Zaporozhye Unit 5) and a development unit to be supplied to the Ukrainian functional design organisation (an organisation specified by the contract). Due to the functional designer’s inexperience, it was necessary to implement each project in two phases.
Phase 1 included installation of system equipment and a preliminary set of nuclear applications and graphic displays that was completed for both units in mid-1998.
Phase 2 involves completion of all interfaces to other unit I&C systems and the installation of the final set of nuclear applications and graphic displays. Both units are scheduled for completion in December 1998.
Using the existing CIS installation at South Ukraine Unit 1 as a base, an additional SPDS was contracted in 1998 for a phased delivery. Phase 1 was completed in mid-1998 with the installation of an initial set of SPDS hardware and preliminary SPDS applications and displays into an integrated platform with the CIS.
Completion of South Ukraine 1 SPDS, with installation of additional workstations, distributed processing units, and final software and displays is scheduled for April 1999.
Three additional contracts – South Ukraine 2, Rovno 3 and Zaporozhye 3 – were awarded to Westinghouse in 1998. These are now in the conformance process (adapting the generic design to the unit characteristics). These systems are scheduled for installation in late-1999.
RBMK Project Status
The original RBMK contract was awarded by Parsons Power, DOE’s prime contractor, in 1995 for a pilot system at Kursk 2 and a development system to be supplied to the Russian functional designer (NIKIET). The Kursk 2 system was installed in 1996 and entered full commercial operation in July 1997.
In 1997, Westinghouse received contracts for SPDS units at Leningrad 4 and Chernobyl 3, which will be completed in late-1998 and early-1999, respectively.
As a result of the successes on these projects, work has been initiated on the Leningrad 3, Smolensk 3, and Kursk 3 projects. Ultimately, NIKIET and Westek, as with Westron, will be capable of providing full support for maintenance, modifications and future expansion of these systems at all Russian installations, with minimum Westinghouse involvement.
Building from the Ukrainian and Russian experience, Westinghouse is following up on potential projects at Kozloduy Units 5 and 6 in Bulgaria.
In Russia, Westinghouse, in partnership with NIKIET, has been selected to perform the SKALA upgrades at Leningrad NPP (plant computers, CIS). At the same time, Westinghouse’s joint venture, Westron, has been designated as the supplier of CISs for Ukrainian NPPs.
Beyond current SPDS projects, and the immediate follow-on opportunities, there is a definite market need in the next 5-10 years. With existing I&C systems in the plants at or beyond their design lifetimes, the pressure to modernise and replace these systems will get stronger.
Westinghouse’s approach, with significant localisation, is targeted to make this modernisation as affordable as possible with modern technology. Experience on the SPDS projects has demonstrated that it is a highly effective approach.