EMERSONOvation®-based Computerenhanced Rod Position Indication System

Nuclear Automation 

Background

Westinghouse’s Ovation®-based computerenhanced rod position indication (CERPI) system 

provides enhanced reliability, and reduced 

operation and maintenance (O&M) costs. It 

consistently provides an accurate indication of rod 

position with the lowest installation cost possible.

This product design integrates more than 200 

reactor years of documented lessons learned from 

analog rod position system (ARPI), state-of-the-art 

detector interface cards and Ovation controller 

technology.

Functions include:

• Control rod position indication

• Control rod bottom alarm

• Detector temperature compensation

• Detector linearity compensation

• Operator alarm capability

• One-pass calibration

This is the most cost-effective alternative to the 

complete replacement of the existing ARPI system.

Ovation®-based Computerenhanced Rod Position 

Indication System

Description

This system replaces the electronics portion of the 

ARPI system within Westinghouse plants. The system 

consists of a detector interface board for each rod, 

redundant Ovation controllers and a new computerized 

human-machine interface (HMI). This resolves the 

issues of difficult and timely calibration and inaccurate 

position indication for rods across the power range.

A rod drop test system is included as part of this 

upgrade. Plant technical specifications require rod 

drop time testing following a refueling outage so that 

the rods insert properly and within the time-response 

requirements of the plant’s safety analysis. This system 

reduces critical path time by automatically analyzing 

the data from each rod during a reactor trip and 

displaying the results.

Features

• Low-cost installation

Utilizes the existing linear voltage transducer (LVTs), 

eliminating as-low-as-reasonably-achievable concerns 

and cost.

• One-pass calibration

The Ovation-based computer-enhanced rod position 

indication system provides simplified, computercontrolled, non-interactive, zero and span (gain) 

adjustments.

• Computer algorithm compensation

Detector ambient temperature and the non-linearity of 

the LVT sensors have been compensated for utilizing 

custom algorithms based on operating experience.

• Low detector crosstalk

Two different frequencies are used to drive rod LVTs, 

minimizing the negative effect of detector crosstalk.

• Maintenance and Test Panel

Maintenance programs provide calibration history as 

well as single, click-of-the-mouse, computer-controlled 

calibration for zero and span settings.

• Operator Modules

Operator modules are provided to enhance the operator’s 

capabilities. The rod information is directed to control 

board-mounted flat panel displays and existing plant 

computers.

• Control rod alarms

With the greatly improved accuracy of the system’s rod 

position indication, dependable alarming for control 

failures and rod bottom has been made available.

• Redundant Ovation controllers

Proven digital technology with guaranteed longterm support.

• Proven performance

This design was established by working closely with utility 

staff and using ARPI lessons learned for more than 200 

reactor years of operation. It has been well tested and has 

replaced several ARPI systems. The results show that this 

upgrade resolves the problem at a low-installation and 

lifetime cost.

Benefits

• Elimination of deratings and callouts as a result of 

limiting condition of operation entry from ARPIincreased profit

• Minimization of rod position indication calibration 

in start up, resulting in reduced critical path time

• Accurate indication of rod position, resulting 

in increased operator confidence

• Elimination of ARPI work-arounds, serving 

to increase operator efficiency

• High reliability resulting in lower O&M cost

• Existing installations provide low-risk solution

• Direct replacement for ARPI and low-cost installation

• For rod drop testing, the ability to automatically 

perform trending analysis that compares rod drops over 

time