Elsevier

Nuclear Engineering and Design

Volume 265, December 2013, Pages 424-430
Nuclear Engineering and Design

Cost evaluation of I&C upgrade approach in nuclear power plants

https://doi.org/10.1016/j.nucengdes.2013.09.022Get rights and content

Highlights

  • Cost evaluation process for I&C system upgrade is built.

  • 4 cost factors affecting I&C system upgrade are described.

  • Additional cost incurred by a phased upgrade is calculated.

  • Cost for system upgrade between upgrade implementations is compared.

Abstract

Utilities have recently been debating the respective pros and cons of implementation of a multi-phase upgrade during several normal outages versus a single major upgrade implementation during a prolonged outage. We have studied these approaches and have been developing the basic design of nuclear power plants (NPPs) instrumentation and control (I&C) upgrade since early 2008. As part of this study, analyses of the NPPs I&C systems were conducted and the need for upgrading the systems was raised. One of the primary concerns regarding the system upgrade is a cost-benefit implementation, which will influence the upgrade approach. From this viewpoint, the I&C upgrade must consider economic factors such as I&C vendor cost, architecture engineering cost, installation cost, utility cost, and other transition costs such as training and procedure development. This paper presents a comparison study of economical aspects including cost evaluation between the aforementioned upgrade implementations and suggests a solution for I&C upgrade approach.

Introduction

Nuclear power plants (NPPs) will be rapidly faced with an equipment obsolescence problem in the near future because of the shorter equipment or system life cycle. The current replacement policy for the systems focuses on spare parts. This policy will not continue due to the obsolescence problem. Therefore, it is inevitable that the systems will be retrofitted or upgraded with new equipment. In an effort to address this problem, we have studied the upgrade of I&C systems for NPPs, whose I&C systems are expected to face significant problems due to obsolescence of I&C equipment in the near future. For this, we have studied the approaches and have been establishing the basic design for NPPs upgrade since early 2008. The I&C systems of NPPs were analyzed in a previous study (NETEC, 2007), in which it was determined that extensive hardwiring was used to transfer signals between the cabinets even though many of the systems were implemented with digitalized signals. The analysis results of the I&C systems were used for further study of upgrading the I&C systems. Our goal for the upgrade is that digital platform-based technology should be employed to integrate the I&C systems and cabinets. The digital technology is advanced and may utilize a distributed control system (DCS) and programmable logic control (PLC). In our study, one of the primary concerns over the system upgrade is a cost-benefit implementation, which will influence the upgrade approach. EPRI reported the ability to complete a plant-wide I&C upgrade within a normal planned outage of 30 days or less, revolutionizing the nuclear power industry's approach to I&C upgrade and allowing the industry to more quickly reap the extensive benefits of upgrade (EPRI, 2004). The cost evaluation derives from an analysis of the plant-wide I&C architecture design (NETEC, 2008a, NETEC, 2008b). From this viewpoint, the I&C upgrade must consider economical factors such as software, hardware costs, design engineering cost, installation cost, utility cost, and so on in the implementation. In this paper, we propose a method to evaluate cost from the plant-wide I&C architecture design and present a comparison study between approaches from the evaluation with a focus on economical aspects, and suggest the I&C upgrade approach that should be followed.

This paper is organized as follows. Upgrade implementation is described in Section 2, plant-wide I&C architecture design is described in Section 3, 3-phase upgrade of I&C systems is described in Section 4, design changes in phased implementation is described in Section 5, cost evaluation is described in Section 6, discussion and conclusion are described in Sections 7 Discussion, 8 Conclusion.

Section snippets

Upgrade implementation

Many utilities are debating the merits of a phased upgrade implementation versus a single major upgrade implementation. There are of course advantages and disadvantages with both approaches. The main advantages with a single major upgrade during a prolonged outage are that temporary hybrid solutions are avoided in the control room and for the control equipment. Also, consistency in system versions, both hardware and software, is reached easily. The main advantages with phased upgrade

Plan-wide I&C architecture design

The safety I&C systems can be designed with nuclear qualified PLCs and the non-safety I&C systems can be integrated with advantageous features of the DCS. We established the goal that the safety I&C systems of the NPPs be upgraded with a PLC-based platform and non-safety systems with a DCS-based platform. Cables connected to transmitters installed inside the containment are not changed, because they can operate for more than 60 years and a 3-phase upgrade strategy is reasonably acceptable.

3-Phase upgrade of I&C systems

The overall upgrade of I&C systems cannot be completed in a single phase due to concerns of safety and operability. For enhancing the safety, the non-safety systems are upgraded first. After ensuring the stabilization of the upgraded systems, the safety systems are upgraded. Another concern is that the MCR upgrade will impact the I&C upgrade. Thus, the impact of the upgraded I&C systems on the existing systems should be considered in terms of their operability in the MCR. For the several phases

Design changes in phased implementation

Design changes by systems in each implementation under the 3-phase upgrade are derived from signal interfaces between two systems or cabinets changed. For the signal interfaces, we take an example for the input and output signal interface of NPIS (non-safety process instrumentation system) changed under our 3-phase upgrade, outlined in Table 1, Table 2 respectively. The design changes by systems are calculated from the number of signal interfaces changed by installation and removal of I/O

Cost evaluation

A phased upgrade design changes process incurs additional costs when all phases are compared with a single major upgrade project. Cost added by the change of I&C architecture in a phased upgrade is crucial in cost evaluation. We reviewed four cost factors for the cost evaluation. The four cost factors are: I&C vendor cost, architect engineer cost, installation cost, and utility cost. The cost evaluation begins with the standpoint of signal interfaces changed between two systems or cabinets

Discussion

Signals in tables are counted manually from I&C signal interface drawings and the numbers in tables are calculated from the values based on the system specification in KSNP. The cost evaluated should not be interpreted as being representative of any particular supplier or utility. In the same context, concern has been expressed about the absolute accuracy of the estimates for any particular upgrade. Each utility should evaluate the reasonability of the estimates given their particular situation

Conclusion

We presented a comparison study of economical aspects including cost evaluation between the aforementioned upgrade implementations and suggested a solution for I&C upgrade approach. For an I&C upgrade economic factors such as I&C vendor cost, design engineering cost, installation cost, and utility cost in the implementation should be considered. We proposed a method to evaluate the cost from the plant-wide I&C architecture design and presented a comparison study on economic aspects. Between two

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