NUREG/CR-6888

ORNL/TM-2005/75

Emerging Technologies in

Instrumentation and

Controls: An Update

Oak Ridge National Laboratory

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research

Washington, DC 20555-0001
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NUREG/CR-6888

ORNL/TM-2005/75

Emerging Technologies in

Instrumentation and

Controls: An Update

Manuscript Completed: November 2005

Date Published: January 2006

Prepared by

K. Korsaha, R.. Wetheringtona, R. Wood'

L.F. Millerb, K. Zhaob A. Paulb

aOak Ridge National Laboratory

Managed by UJT-Battelle, LLC

Oak Ridge, TN 37831

b University of Tennessee

315 Pasqua Engineering Building

Knoxville, TN 37996-2300

C. E. Antonescu, NRC Project Manager

Prepared for

Division of Engineering Technology

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC Job Code Y6962
NUREG/CR-6888, has been reproduced

from the best available copy.
ABSTRACT

This report is a summary of advances in eight instrumentation and control (I&C) technology focus areas

that have applications in nuclear power plant digital upgrades as well as in new plants. It is the second in

a series of planned update reports (the first one was NUREG/CR-6812) in an NRC-sponsored Emerging

Technologies study. This study is designed to provide "heads-up" information that will make the NR.C

better prepared to make regulatory decisions in these areas.

This study update focuses on advances in sensors (e.g., temperature, neutron and thermal power sensors)

and their potential regulatory impact. Highlights of the findings and conclusions in this report are as

follows:

1 The silicon carbide neutron detector has advanced past the developmental stage. However, important

information such as long-term performance (degradation information), drift, etc., could not be

adequately assessed. While the detector has a wide dynamic range (with potential for replacing

present-day startup, intermediate, and power range monitors), it is important that a combined neutron

monitor based on this technology not only exhibit the full dynamic range from startup to 100%

power, but also be shown to maintain performance over the long term when at 100% power. Progress

in the development of these detectors should continue to be monitored, because of the potential for

improved operating and safety margins that such detectors will provide, should they also meet the

criteria mentioned above.

2. The Johnson noise thermometer could be commercially available for nuclear power plant applications

within 5 years. A temperature sensor based on Johnson noise is immune to the drift that plagues

thermocouples and resistance thermometers. The lack of drift has advantages that could have

regulatory implications such as extending calibration intervals. The technology should continue :o be

monitored.

3. Sensors that are less developed and therefore will require a longer time to reach commercialization

are scintillation-based sensors for in-core temperature and flux measurements and vacuum

nanotriodes. In the case of scintillation-based sensors, the primary deficiencies in the technology

preventing its use for in-core measurements have been the lack of an effective technique for

measuring light within reactor core environments and the rapid darkening of fiber-optic light pipes in

high radiation fields. Additionally, scintillation materials darken too rapidly to be useful in bulk form

near a nuclear reactor core. For the purposes of this update, no significant progress in overcoming

these problems were identified. In the case of vacuum nanotriodes, the technology is also still in

early research. However, because of the advantages that advances in both technologies could provide

for nuclear power plant I&C, both scintillation-based sensors and vacuum nanotriodes should

continue to be monitored.

4. Variability in the radiation response of COTS devices is a significant radiation hardness assurance

(RHA) issue. Approaches such as radiation-hard technologies and improved manufacturing processes

mav overcome this impediment. For example, advances in radiation-hardened electronics are giving

rise to technologies such as phase transition-based random access memories (P-RAMs), which may

make application of I&C in harsh environments such as containment possible. These technologies

should be monitored.

5. A set of best practices in digital communication in nuclear power plant safety I&C systems should be

developed to support the review of digital I&C system upgrades in current generation plants, as well

as in Generation III and Generation IV plants.

iii

FOREWORD

This NURElG-series report documents an investigation of emerging instrumentation and control (l&C)

technologies and their applications in nuclear power plants. In conducting this investigation under contract

to the U.S. Nuclear Regulatory Commission (NRC), Oak Ridge National Laboratory closely followed

the research approach used in an earlier study documented in NUREG/CR-68 12, "Emerging Technologies

in Instrumentation and Controls," dated March 2003. Thus, this study and its predecessor comprise

the first two entries in a series of periodic reports introduced in the NRC's "Research Plan for Digital

Instrumentation and Control." This series of reports will be used to understand how cutting edge technologies

and advancements in current technologies might affect the digital I&C program in the coming year-s.

Toward that end, these reports are intended to (1) document emerging technologies in the nuclear I&C field

(2) describe the status of specific technologies that have potential applicability for safety-related systems

in nuclear power plants, and (3) identify related research needs.

As the baseline for the series of reports, NUREG/CR-6812 provided a broad-brush overview of I&C.

technologies. As the second entry in the series, this report updates the information in NUREG/CR-58 12

and describes the current state of development in the technology focus areas identified in that report:.

In so doing, this report also presents a detailed investigation of advanced sensors, which this investigatioi

identified as an emerging technology that can affect safety and operating margins.

Caryirector #

Car.. Paperie Di

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

v

TABLE OF CONTENTS

ABSTRACT ................................................ iii

FOREWORD ............................................... v

LIST OF FIGURES ............................................... ix

EXECUTIVE SUMMARY ................................................. xi

ABBREVIATIONS AND ACRONYMS ............................................... xv

1. INTRODUCTION ................................................ I

1.1 Scope of Study ............................................... 1

1.2 Research Approach ................................................ 1

1.3 Structure of Report ................................................ 1

2. SUMMARY UPDATE OF INSTRUMENTATION AND CONTROLS (I&C) TECHNOLOGIES.. 3

2.1 Sensors and Measurement Systems .3

2.1.1 Silicon Carbide Flux Monitor .. 4

2.1.2 Solid-State Neutron Flux Monitor .. 4

2.1.3 Fuel Mimic Power Monitor (or Constant Temperature Detector) . . 4

2.1.4 Scintillation-Based Measurements for Temperature and Flux . . 7

2.1.5 Johnson Noise Thermometry .. 7

2.1.6 Magnetic Flowmeter for Measurement of Primary Coolant Flow . . 7

2.1.7 Fabry-Perot Fiber-Optic Temperature Sensor .. 8

2.1.8 Optical Pressure Sensors .. 8

2.1.9 Gamma Ray Tomographic Spectrometry .. 8

2.1.10 Hydrogen Sensor ................. 9

2.1.11 Smart Sensors ................. 9

2.2 Communication Media and Networking .10

2.2.1 Sensor Buses .. 10

2.2.2 OLE for Process Control ...................................... 13

2.3 Microprocessors and Other Integrated Circuits ...................................... 14

2.3.1 Radiation-Hardened Integrated Circuits .14

2.3.2 System on a Chip .. 15

2.3.3 Optical Processors .15

2.3.4 Vertically Stacked Integrated Circuits .. 16

2.3.5 Nanotriodes .17

2.3.6 Microelectromechanical Systems (MEMS) .............................. 17

2.:3.7 Molecular-Scale Electronics .18

2.4 Computational Platforms .19

2.4.1 Application-Specific Integrated Circuits (ASICs) and Application-Specific Software . 19

2.4.2 Real-Time Operating Systems .20

2.5 Surveillance, Diagnostics, and Prognostics .22

2.5.1 Model-Based Techniques .22

2.5.2 Fault Detection for Field Devices .23

2.5.3 Forewarning of Failure in Critical Equipment .23

2.5.4 Control Loop Performance Monitoring .23

2.5.5 Vision-Based Diagnostics .24

2.5.6 Laser-Based Alignment Monitoring .24

2.6 Control and Decision .25

2.6. I Data Acquisition and Control in Industrial Plants .25

2.6.2 Supervisory Control System .28

2.6.3 Intelligent Agent-Based Control .28

2.6.4 Non-Mathematical Flow Methods .29

vii
2.7 Human-System Interface ...................... 29

2.7.1 Control and Monitoring Systems .29

2.7.2 Software Agent-Based Operational Support Systems .30

2.7.3 Virtual Collaborators .30

2.7.4 Biometrics.32

2.7.5 Automated Visual Surveillance for Facility Monitoring .32

2.7.6 Virtual Reality ......... 33

2.8 High-Integrity Software ....................................................... 33

2.8.1 Software Development Technologies, Methodologies, and Tools .33

2.8.2 Object-Oriented Language: Real-Time Java ............................................... 36

3. DETAILED INVESTIGATION OF ADVANCED SENSORS ............................................... 37

3.1 Silicon Carbide Flux Monitor ............................................... 37

3.1.1 Basic Principles of the Technology . . .37

3.1.2 Maturity of the Technology .......................... 38

3.1.3 Potential Regulatory Impact . . . 39

3.2 Solid-State Neutron Flux Monitor ............................. 39

3.2.1 Basic Principles of the Technology . . .39

3.2.2 Maturity of the Technology .......................... 39

3.2.3 Potential Regulatory Impact .. . . 40

3.3 Fuel Mimic Power Monitor (or Constant-Temperature Power Sensor) .................................... 41

3.3.1 Basic Principles of the Technology .41

3.3.2 Maturity of the Technology ............................ 43

3.3.3 Potential Regulatory Impact ............................ 43

3.4 Johnson Noise Thermometry .......................... 43

3.4.1 Basic Principles of the Technology .43

3.4.2 Maturity of the Technology .......................... 46

3.4.3 Potential Regulatory Impact . . . 46

3.5 Magnetic Flowmeter for Primary Coolant Flow Measurement ................................................ 46

3.5.1 Basic Principles of the Technology .46

3.5.2 Maturity of the Technology .......................... 47

3.5.3 Potential Regulatory Impact .47

3.6 Fabry-Perot Fiber-Optic Temperature Sensors ...................................... 47

3.6.1 Basic Principles of the Technology .47

3.6.2 Maturity of the Technology ........................ 48

3.6.3 Potential Regulatory Impact .49

3.7 Fiber-Optic Pressure Sensors ......................... 49

3.7.1 Principles of the Technology .49

3.7.2 Maturity of the Technology ........................ 51

3.7.3 Potential Regulatory Impact .52

3.8 Hydrogen Sensors ................. 52

3.8.1 Basic Principles of the Technology .52

3.8.2 Maturity of the Technology ........................ 53

3.8.3 Potential Regulatory Impact .53

3.9 Smart Sensors .............. 53

3.9.1 Sensor Fusion and Enhanced Diagnostics .53

3.9.2 Maturity of the Technology ........................ 54

3.9.3 Potential Regulatory Impact .54

4. CONCLUSIONS AND RECOMMENDATIONS . . . 56

5. REFERENCES . . . 65

viii
LIST OF FIGURES

Figure Page

2.1. OPC, a communication technology standard for process control .................................................... 14

2.2. EnLight256 ............................................................ 16

2.3. Schematic of a nanotriode ........................................................... 18

2.4. OSEK/VDX standards and implementation in 'POS ........................................................... 21

2.5 OSEKtime-based system architecture ............................................................ 22

2.6. Thermal scan of a mechanical component showing a bad bearing on a shaft of an

electrical motor ........................................................... 24

2.7. Generic classical centralized control system architecture ........................................................... 26

2.8. Generic decentralized control system ........................................................... 27

2.9. Buses and processors in a generic industrial plant ............................................................ 27

2.10. TELEPERM XP Subsystems .28

2.11. General-purpose and open network technologies can be used to configure a compact,

human-friendly supervisory control system .28

2.12. Example of control and monitoring system with human-system interface .31

2.13. System architecture of a virtual collaborator .31

2.14. Iris scanning at Heathrow Airport, London .32

3.1. Silicon carbide Schottky diode radiation detector ............................................................ 37

3.2. Detection of neutrons via charged particle production by the 6Li(n, a) reaction in a

converter foil ............................................................ 38

3.3. General concept of solid-state flux monitor ........................................................... 40

3.4. Fabrication concept of the solid-state fuel monitor ............................................................ 40

3.5. Constant-temperature power sensor Wheatstone bridge control circuit .......................................... 42

3.6. Cylindrical sensor configuration of the CTPS ........................................................... 42

3.7. :Planar sensor configuration of the CTPS ........................................................... 42

3.8. Basic components of a Johnson noise thermometer ............................................................ 44

3.9. Schematic for automatic recalibration of RTD from Johnson noise measurement ......................... 45

3.10. [illustrating the relationship between the PSDs of the individual channel voltages and

the CPSD between them ............................................................ 45

3.11. Schematic diagram of a dual fiber-optic Fabry-Perot temperature sensor .48

3.12. Fiber-optic pressure transducer .......................... 49

3.13. Sensor head design .50

3.14. Sensor block diagram..................................................................................................................... 50

3.15. abry-Perot cavity........................................................................................................................... 51

ix

EXECUTIVE SUMMARY

The Nuclear Regulatory Commission (NRC) Digital System Research Plan forms the framework for

identifying research areas that the NRC performs to update the tools used in assessing the safety of digital

Instrumentation and Controls (I&C) applications in U.S. nuclear power plants. NRC Digital Research

Plan fcr FY 2001-FY 2004 [NRC 2001] identified Emerging Technologies as an area of research. This

includes areas that have been shown to be likely to be applied in the future and areas that have the

potential to raise safety issues but have not been addressed. By becoming informed of emerging I&C

technology and applications, the NRC "...is better prepared to make future regulatory decisions in th se

areas" [NRC 2001].

Oak Ridge National Laboratory (ORNL) has been tasked to perform the Emerging Technologies stud.y,

the first report of which was published in March 2003 as NUREG/CR-6812, "Emerging Technologies in

Instrumentation and Controls." This current report is an update of NUREG/CR-6812. This update (1)

discusses the current state of development of the technology focus areas identified in NUREG/CR-68 12,

(2) identifies advanced sensors as an emerging technology that can affect safety and operating margins

and provides a detailed investigation of the topic, and (3) identifies I&C areas that should continue to be

monitored in an effort to improve the NRC I&C review process. The methods employed for this

emerging technology update survey consisted of literature reviews (in particular, recent scientific and

technical journals), Internet searches, vendor contacts, and discussions with technology experts.

This report focuses on the following eight technology focus areas that were identified previously in

NURE(G/CR-6812:

1. Sensors and Measurement Systems,

2. Communications Media and Networking,

3. Microprocessors and other Integrated Circuits,

4. Computational Platforms (computers, programmable logic controllers, application specific

integrated circuits, etc.),

5. Diagnostics and Prognostics,

6. Control and Decision,

7. Human-System Interactions, and

8. High-Integrity Software.

In the following paragraphs, excerpts of technologies under various development stages, as well as their

regulatory impact, are described. More detailed information is provided in the report body.

For the sensors and measurement systems technology focus area, some of the sensors and sensing

techniques that were initiated as a result of the research stimulus provided by the U. S. Department of

Energy (DOE) programs [New England Research Institutes (NERI), International Nuclear Energy

Research Initiative (INERI), and Nuclear Engineering Education Research (NEER)] have progressed from

concepts and laboratory prototypes to becoming potentially commercial products.

One notable example of sensors that are close to becoming commercially available is the silicon carbide

neutron-flux monitor. This sensor has the potential to combine the functions of current three-range flux

monitors into a single system. However, data on important parameters such as drift, accuracy,

repeatability, and degradation over time could not be ascertained for this update. It is important that a

combined neutron monitor based on this technology not only exhibits the full dynamic range from startup

to 100%/ power, but it should also be shown to not degrade over the long term when at 100% power. The

improved operating and safety margins that such detectors will provide, should they also meet all the

criteria mentioned above, certainly warrant continued monitoring of progress in their development.

xi
An example of a sensor with potential for commercialization in the near future (within 5 years) is the fuel

mimic power monitor (or constant-temperature detector). The instrument represents a unique sensing

technology in that it provides a direct measurement of the nuclear energy deposited into a fuel mimic

mass. This type of sensor will have the advantage of providing an accurate and direct measurement of

reactor power. This may provide licensees a basis to, for example, apply for increase in their licensed

operating power level. A significant problem found with the current version, however, is signal drift. In

fact, comprehensive testing and characterization of the second-generation constant-temperature power

sensor (CTPS) design has yet to be performed. Commercialization of the technology is still a few years

away and should be monitored over the long term.

Another sensor that could be commercially available for nuclear power plant applications within 5 years

is the Johnson noise thermometer (JNT).' The attraction of JNT is that it is inherently drift free and

insensitive to the material condition of the sensor. As a result of the latter characteristic, a sensor based

on Johnson noise is immune to the contamination and thermo-mechanical response shifts that plague

thermocouples and resistance thermometers. This advantage should improve operating as well as safety

margins in nuclear power plants. However, problems that have hampered commercial utilization of

Johnson noise thermometers include a relatively long response time because of the long integration time

required to make a temperature measurement. An ORNL implementation addresses this problem in a

dual-mode thermometer by making the temperature measurement as a simple resistance measurement

whose resistance to temperature conversion is quasi continuously updated using Johnson noise. Thus, a

practical implementation of the JNT in nuclear power plants could be as an on-line, self-calibrating

resistance temperature detector (RTD). The regulatory implication of self-calibration is that required

calibration intervals could be relaxed.

At the other end of the spectrum in terms of commercial availability of the sensor technology are

scintillation-based sensors for in-core temperature and flux measurements and vacuum nanotriodes. In

the case of scintillation-based sensors, the primary deficiencies in the technology preventing its use for incore measurements have been the lack of an effective technique for measuring light within reactor core

environments and the rapid darkening of fiber-optic light pipes in high radiation fields. Additionally,

scintillation materials darken too rapidly to be useful in bulk form near a nuclear reactor core. For the

purposes of this update, no significant progress in overcoming these problems could be identified.

Advances in some integrated circuit (IC) technologies are also summarized in this report. These

technologies include radiation-hardened ICs and system-on-a-chip (SoC) devices. The potential impact

toward facilitating smart sensors and sensor networks in containment applications in the long term

suggests the value of maintaining awareness of developments for radiation-hard ICs. Likewise, the

potential for sensing applications using SoC circuitry that can be located in harsh environments at future

reactors and then changed out (perhaps robotically) on a periodic basis provides motivation for

monitoring the long-term trends in SoC development.

Variability in the radiation response of commercial off-the-shelf (COTS) devices is a significant radiation

hardness assurance (RHA) issue. Approaches such as radiation-hard technologies and improved

manufacturing processes may resolve this impediment. These improvements are most likely to be seen

first in space applications. Therefore, it is warranted to monitor special-purpose applications while

confirming the radiation tolerant characteristics of commercial ICs. Considerable progress has been made

in radiation-hardened integrated circuit development using materials such as silicon-on-insulator (SOI).

State-of-the-art-radiation-hard IC technologies are exemplified by the SCS 750 single-board computer,

' Although Johnson noise thermometry has been around for over 50 years [Garrison 1949, Brixy 1971], several

technical challenges have hampered its commercial application in nuclear power plants.

xii
which is Maxwell Technologies' innovation for space applications. This next-generation supercomputer

uses SOI technology fabricated in a radiation-tolerant 0.13-pIm complementary metal-oxide

semiconductor (CMOS) process. Some of its performance characteristics include (1) one upset every 300

years in a geostationary (GEO) orbit; (2) space-qualified performance at 1800 MIPS; (3) Triple Modular

Redundant Processing; (4) use of SOI processors; and (5) use of advanced error corrected synchronous

dynamic random access memory (SDRAM).2 Another innovation in radiation-hardened chip technology

is the integration of chalcogenide material with radiation-hardened CMOS process to produce memozy

arrays. Chalcogenide-based memory is highly radiation resistant, and its importance in space I&C

applications is well recognized. Four megabit C-RAMs represent the current state of the art. The

regulatory implication of these advances in radiation-hardened IC technology is that equipment such as

smart transmitters could find their way into containment environments in the near future.

In the field of nanoelectronics, advances in the development of nanotriodes deserve mention because of

the technology's potential influence on nuclear I&C. In particular, this reinvention of the vacuum tube

may show promise for high-radiation and high-temperature environments. Nanotriode technology is still

in its infancy, but advances continue to be made. For example, nanotriodes developed at Cambridge

University have reached a density of 109 per cm2, comparable to the density of metal-oxidesemicociductor (MOS) transistors. Nanotriodes are advantageous over MOS technology in radiation

resistance and temperature tolerance. A current research issue is the reproducibility and longevity of

nanotriodes. Although the technology is not likely to be deployed in nuclear power plant environments in

the nea future, progress in their development should continue to be followed over the long term, given

that this technology could enable smart sensors to migrate into the most inhospitable areas within the

reactor containment.

For SoC devices, most of the current research is focused on the application to the field of communicadion

and computer science. The specialized applications are challenged by the high degree of on-chip

integration for complex systems, power consumption, and manufacturability, including testability and

reliability. The application of SoC to small systems is already mature. Monitoring the special application

of the SoC technique to nuclear instrument development and control performance improvement is

appropriate.

In sensor fusion, data reconciliation and gross error detection has recently received attention by the

nuclear electric utilities in Europe. This technique takes advantage of the plant-wide mass balance and

energy balance equations to reconcile plant measurements such that the balance equations are satisfied.

Because the easily developed models provide additional functional redundancy to the plant

measurements, the reconciled values will be much more accurate than the raw measurements. This

technique is mature enough for application in nuclear power plants at steady-state conditions to improve

plant performance and provide a sensor calibration standard when digital systems are applied. Additional

research is focusing on dynamic data reconciliation for better control.

The trend in the use of data networks to serve plant personnel, as well as in the application of digital I&C

in some system upgrades, is likely to increase. The current control and protection products on the market

(e.g., TELEPERM XP and TELEPERM XS) make use of specialized Ethernet or proprietary protocols for

networked microprocessor-based systems. Fieldbus standards continue to proliferate (in the non-nuclear

environment) and networked field devices are likely to see increasing application as part of I&C upgrades

for plant life extension-with smart sensors becoming more prominent.

2 A type of dynamic random-access memory (RAM) that can run at much higher clock speeds than conventional

memory.

xiii
High-integrity softwareCan area of considerable importance to the application of computer-based systems

in nuclear power plants for obvious reasons Ocontinues to be an important area of research and is briefly

reviewed in this report. Considerable progress has been made over the past 15 years or so in increasing

the state space capacity of model checkers, to the point where specifications containing hundreds of state

variables can often be verified automatically in a few hours. However, realistic designs often contain

thousands or millions of state variables, far exceeding the reach of current model checking algorithms.

Another class of verification tools called theorem provers can be used to overcome the capacity

limitations of model checking. A theorem prover does not search the state space of a specification

directly, but instead searches through the space of correctness proofs that a specification satisfies for a

given correctness property. In general, model checking and theorem proving are complementary

technologies and should be integrated to successfully tackle realistic system designs.

An important aspect of the Emerging Technologies series of reports is to identify research needs as well

as I&C areas that should continue to be monitored in an effort to improve the NRC review process. An

underlying enabling technology that will facilitate reliable nuclear plant digital I&C operation is the

implementation of a robust communication protocol. Unfortunately, the unwary use of digital

communication in the plant (for example, communication between control, safety, and offsite) has the

potential to raise safety and cyber security concerns. A set of best practices in digital communication in

nuclear power plant safety I&C systems could be developed to support the review of digital I&C system

upgrades in current generation plants, as well as in Generation III and Generation IV plants.

Communications media (e.g., cables, fibers, wireless bands) and network systems provide the pathways

by which data and information are distributed among the field devices, processing components, and

display systems in a plant. In nuclear power plants, traditional direct-wired, point-to-point connections

between analog equipment have been the norm. However, the trend in the use of data networks to serve

plant personnel, application of digital I&C in system upgrades, and communication between safety and

nonsafety systems, is likely to increase. Institute of Electrical and Electronic Engineers (IEEE) Std 7-

4.3.2 does not specifically prohibit two-way communication between safety and nonsafety systems.

Communication pathways between safety and nonsafety systems are generally acceptable as long as

failure of the communication system does not impair the safety function, and the safety function does not

rely on nonsafety system inputs to operate. While current NRC regulatory guidelines [e.g., Regulatory

Guide (RG) 1.152-2005] do not endorse the guidance provided in IEEE Std 74.3.2 for communication

independence because it "provides insufficient guidance," they do not specifically prohibit it. RG 1.152

points to additional guidance provided in Appendix 7.0-A, "Review Process for Digital Instrumentation

and Control Systems," Appendix 7.1-C, "Guidance for Evaluation of Conformance to IEEE Std 603," and

Section 7.9, "Data Communication Systems," in NUREG-0800.

While in agreement with the additional guidance provided in RG 1.152, allowing communication between

digital systems in general does introduce the potential for compromising safety. One example is the

disabling of a safety parameter display system at the Ohio Davis-Besse nuclear power plant that occurred

in January 2003 [Davis-Besse, 2003]. The slammer worm first penetrated the unsecured network of a

Davis-Besse contractor, then worked its way through a Ti line bridging that network and Davis-Besse's

corporate network. The TI line was one of multiple ingresses into the Davis-Besses's business network

that completely bypassed the plant's firewall. The plant was reported to have been offline when the

incident occurred, thus the breach did not affect the operation of the plant. However, the case does

illustrate an important issue: that a cyber security breach can compromise a safety system where

interconnection is allowed between plant and corporate networks (or any other network).

xiv
ABBREVIATIONS AND ACRONYMS

ABWR

ADC

ALAR A

AIN

ALWR

ASI

ASIC

AVS

BWR

CAN

CCD

CENELEC

CMOS

COTS

CPSD

CPU

CRAM

CTPS

DAC

DCS

DER

DF

DM

DMIPS

DNA

DOE

DP

DSP

EM

EMI

EPRI

FFPI

FFT

FMS

FPI

GEO

GSD

HEMT

HMI

HTGR

I&C

110

IC

IEEE

INERI

IR

ISO

IT

advanced boiling-water reactor

analog-to-digital converter

as low as reasonably achievable

aluminum nitride

advanced light water nuclear reactor

actuator sensor interface

application-specific integrated circuit

automated visual surveillance

boiling-water reactor

controller area network

charge-coupled device

European Committee for Electrotechnical Standardization (Comit6 Europ6en de

Normalisation Electrotechnique)

complementary metal-oxide semiconductor

commercial off-the-shelf

cross power spectral density

central processing unit

chalcogenide-based random access memory

constant-temperature power sensor

digital-to-analog converter

distributed control system

distributed energy resources

distribution function

dissimilarity measures

Dhrystone million instructions per second

deoxyribonucleic acid

U.S. Department of Energy

decentralized periphery

digital signal processing/processor

electromagnetic

electromagnetic interference

Electric Power Research Institute

fiber-optic Fabry-Perot interferometer

Fast Fourier Transform

fieldbus message specification

Fabry-Perot interferometer

geostationary

A file extension used to identify a PROFIBUS-DP/PA device

high-electron mobility transistor

human-machine interface

high-temperature gas-cooled reactor

instrumentation and controls

input/output

integrated circuit

Institute of Electrical and Electronics Engineers,

International Nuclear Energy Research Initiative

infrared

International Standards Organization

information technology

xv
JAD

JNT

KAERI

KTA

LC

LED

LPRM

MEM

MEMS

MFM

MIS

MMI

MMU

MOS

NASA

NEER

NERI

NIST

NPP

NRC

OLE

OPC

ORNL

OS

OSEK

OSEKtime

PA

PC

PETS

PETS

PLC

PSD

PWR

RAD

RAM

RF

RG

RHA

ROC

ROM

RTB

RTD

RTOS

RUP

SCADA

SCIIB

SDLC

SDM

SDRAM

SDS

SER

joint application development

Johnson noise thermometer

Korean Atomic Energy Research Institute

German Nuclear Safety Standards Commission

inductor-capacitor

light-emitting diode

local power range monitor

microelectromechanical

microelectromechanical system

multilevel flow model

metal-insulator-semiconductor

man-machine interface

memory management unit

metal-oxide semiconductor

National Aeronautics and Space Administration

Nuclear Engineering Education Research

Nuclear Energy Research Initiative

National Institute of Standards and Technology

nuclear power plant

U.S. Nuclear Regulatory Commission

object linking and embedding

OLE for Process Control

Oak Ridge National Laboratory

operating system

Open systems and the corresponding interfaces for automotive electronics

OSEKIVDX time-triggered operating system

process automation

personal computer

Performance Evaluation of Tracking Surveillance

performance evaluation of tracking surveillance

programmable logic controller

power spectral density

pressurized-water reactor

rapid application development

random-access memory

radio frequency

Regulatory Guide

radiation hardness assurance

receiver operating characteristics

read-only memory

remote terminal block

resistance temperature detector

real-time operating system

rational unified process

supervisory control and data acquisition (system)

self-calibrating interferometer/intensity-based

system development life cycle

system development method

synchronous dynamic random access memory

smart distributed system

Safety Evaluation Report

xvi
SEU single-event upset

SiC silicon carbide

SoC system on a chip

SOI silicon-on-insulator

SPACEe specification and coding environment

SSFM solid-state flux monitor

TEMPO Thermal Performance Monitoring and Optimization

TTP time-triggered protocol

TXS TELEPERM XS

UML unified modeling language

UT University of Tennessee

VC virtual collaborator

VDX Vehicle Distributed eXecutive

VME VersaModule Euro card (as in VME bus)

VSIC vertically stacked integrated circuit

xvii
I

I
1. INTRODUCTION

1.1 Scope of Study

The purpose of this report is to provide an update on the instrumentation and controls (I&C) technolcgy

survey documented in NUREG/CR-6812, Emerging Technologies in Instrumentation and Controls,

published in 2003. This report is the second in the series designed to provide periodic reports on the

status of specific technologies that have potential applicability for safety-related systems in nuclear power

plants amd pose emerging research needs. NUREG/CR-6812 provided a broad-brush overview of I&C

technologies and served as the baseline for the series of periodic reports specified in the U. S. Nuclear

Regulatory Commission (NRC) Plan for Digital Instrumentation and Control (SECY-01-0155). There

have been several advances in I&C since NUREG/CR-6812 was published, and this report provides a

summary of the state of the art in the technology areas identified in the previous report. From the

findings, we develop suggestions for prospective research needs.

1.2 Research Approach

The research approach taken in this survey closely follows that used in NUREG/CR-6812. The set of

technology focus areas identified in NUREG/CR-6812 was used as the starting point. Then, based or.

these focus areas, the multidisciplinary expertise at Oak Ridge National Laboratory (ORNL) and the

University of Tennessee (UT) was employed to review the state of the art in these technologies.

Investigations were conducted that consisted of literature reviews (in particular, recent scientific and

technical journals), Internet searches, vendor contacts, and discussions with technology experts. Input

was also solicited from nuclear industry representatives such as the Electric Power Research Institute

(EPRI).

On the basis of the results from this combined expertise, the study provides a summary update on each of

these technologies. Sensors are identified as one of the areas in which developments have the greatest

likelihood of maturing into commercial deployment in power plants. Additionally, sensors offer the

greatest benefits in improving safety and operating margins. Thus, sensor technology is singled out for a

detailed discussion after a summary update of the other technologies is provided. Finally, general

observations and conclusions are drawn about safety-related issues posed by the expected application of

these technologies for upgrades at existing nuclear power plants and for near-term deployment of

advanced reactors. The study then suggests confirmatory research approaches that may need to be

sponsored by the NRC to promote an understanding of any claimed capabilities of these technologies and

their suitability or unsuitability for the nuclear power plant environment.

1.3 Structure of Report

The information presented in this report consists of the findings from the emerging technology update

survey and observations regarding specific state-of-the-art capabilities, techniques, and components that

are candidates for near-term deployment of nuclear applications in existing and evolutionary reactors or

may eventually be candidates for deployment in long-term advanced reactor concepts.

Using the technology focus areas identified in NUREG/CR-6812 as a basis, Chapter 2 provides a

summary update of each technology focus area. Issues addressed are (1) any advantages the particular

technology will have in improving the operation economy and safety of nuclear power plants, (2) any new

safety is sues the new technology will bring about when applied to nuclear power plants, and (3) the

impact of the technology on NRC's license review.

1
Chapter 3 provides a more detailed discussion of advanced sensors, the latter having been identified as an

area with significant safety impact and in which developments have the greatest likelihood of maturing

into commercial deployment in power plants. In addition, issues discussed include basic principles of the

technology and its maturity (e.g., commercial availability or potential for commercialization in the next 5

years).

Finally, Chapter 4 presents observations and conclusions about emerging technologies identified in the

survey, suggesting confirmatory research approaches that may need to be sponsored by the NRC to

promote an understanding of any claimed capabilities of these technologies and their suitability for the

nuclear power plant environment.

2
2. SUMMARY UPDATE OF INSTRUMENTATION AND CONTROLS (I&C)

TECHNOLOGIES

2.1 Sensors and Measurement Systems

Given the range of sensing techniques in existence within the various process industries (e.g.,

petrcchemical, steel, pharmaceutical), NUREG/CR-68 12 [Wood 2003] limited the Sensors and

Meas;urement Systems focus area primarily to those measurement systems that relate to the traditional

measured variables within the nuclear power industry. We follow a similar approach in this report and

provide a summary update on the following sensors in the measurement systems technology focus area.

* silicon carbide flux monitors

* solid-state neutron flux monitors

• fuel mimic power monitors

• scintillation-based measurements for temperature and flux

* Johnson noise thermometry

• magnetic flowmeters for measurement of primary coolant flow

* Fabry-Perot fiber optic temperature sensors

* optic pressure sensors

* gamma ray tomographic spectrometry

* hydrogen sensors

* smart sensors

While we provide summary updates for the other technology focus areas in this chapter, we have selected

the sensors and measurement systems technology focus area for a more detailed study in the next chapter

for the following reasons: (1) sensors are likely to have the greatest safety impact because they have a

direct bearing on operating and protection margins; (2) some new sensor designs have the likelihood of

maturing into commercial deployment in power plants in the near term; and (3) some of the most

significant advances in the technology focus areas are in the area of sensors. Thus, we have devoted

Chapter 3 to discuss sensor developments in more detail.

Table 2.1 provides a summary of the sensors identified above. In this table, the status column signifies

the general time frame for implementation as follows:'

* Category A - Ready for use. The technology is either commercially available now or could be

available within a year.

* Category B - Confirmatory testing required. Commercial availability is at least a couple of

years away.

* Category C - Some additional development required. Commercial availability is possible

within the next 3 to 5 years.

* Category D - Significant development required. Commercial availability is not likely within the

next 5 years.

* Category E - Fundamental research required. Commercial availability may be possible in 5-1')

years.

¢ The category designation is somewhat subjective. It is based on the authors' assessment of available information

and, in some cases, from discussions with experts.

3
2.1.1 Silicon Carbide Flux Monitor

The most likely commercial application of the silicon carbide flux monitor is for ex-core neutron

monitoring with no gamma compensation. Prototypes have been tested under research reactor conditions.

The test results show that the key features, such as linear pulse-mode operation without gamma

compensation, are comparable to the presently used gas-filled, ex-core detectors. It is anticipated that a

wide-range silicon carbide neutron detector can now be designed to replace the combined functions of the

multiple power range detectors in current use. This technology is past the developmental stage and is

essentially ready for use.

2.1.2 Solid-State Neutron Flux Monitor

The most likely commercial application of the solid-state neutron flux monitor is for in-core flux

mapping. The solid-state flux monitor (SSFM) functions both as a neutron-pulse monitor and a dosesensitive resistive element. Generation 1I SSFM prototype sensors have been tested at ORNL to

characterize the stability and leakage current at room temperature where no incident gamma radiation is

present. The results showed that the leakage current is comparable to the presently used gas-filled fission

chamber. Design improvements are required to reduce the leakage current to enable potential deployment

of the device at core temperatures that are higher than the temperatures of water reactors. The stability of

the device also requires further investigation because device polarization appears to be significant [ORNL

2005]. In addition, the long-term survivability of this device under in-core environments has not been

demonstrated. In general, commercialization of this device is still several years away, and the technology

should continue to be monitored.

2.1.3 Fuel Mimic Power Monitor (or Constant Temperature Nuclear Power Sensor)

The fuel mimic power monitor or constant temperature nuclear power sensor (CTPS) represents a unique

sensing technology that provides a direct measurement of the nuclear energy deposited into a fuel mimic

mass, rather than simply neutron flux, as with other detectors. Thus, the most likely commercial

application of the technology is for the direct measurement of nuclear power inside the core. Arrays of

CTPS sensors could provide an extremely accurate picture of core power distribution. It is also possible

to incorporate a CTPS into a fuel rod so that power distribution could be determined with much greater

resolution than is currently achievable.

Tests on the first-generation, controlled-calorimetric, in-core instrument prototypes and subsequent

modeling showed three existing problems: lack of proportionality in the relative neutron and photon

response, a relatively low bandwidth due to nonuniform distribution of nuclear and electrical energy

deposition, and drift due to heat transfer through the sensor power leads. The second-generation sensor

design forces the temperature gradient into a thin metal axial region that gives a uniform energy

distribution from all sources. It also provides better control of thermal leakage and contact resistances

and improves the prediction with increased bandwidth and better proportionality. Comprehensive testing

and characterization of this second-generation design has not yet been performed. Commercialization of

the technology is still a few years away and should be monitored over the long term.

4
Table 2.1 Summary of state of the art of sensor technology focus area

Technolo2y Description of principle Foreseeable application New progress Status4 Conclusions

6LiF deposited on top of a thin

SiC neutron flux SiC layer converts neutrons to Ex-core neutron

monitor charged particles via the monitoring with no Prototype tested under A Essentially ready for

mllr*3*.research reactor conditionsAEseta yrad fo Li(n,a)3

H reaction. Charge is gamma compensation use

collected under a voltage bias

Flux-induced change in electric The stability and leakage

Solid-state neutron flux resistance of polycrystalline In-core flux mapping current tested at room B Needs further testing

monitor aluminum o y tnrf a temperature with no incident gamma radiation

Second-generation

Control the input electric energy prototype with improved

to a fuel pellet to maintain bandwidth and (1) Restricted to steadyFuel mimic power constant temperature when Direct measurement of proportionality has been state operation

monitor (or constant reactor is at some steady state the nuclear energy constructed. However, B (2) Needs

temperature power power level. The electrical power deposition comprehensive testing and demonstration testing at

sensor) required to maintain constant characterization had yet to reactor operation

temperature is a measure of the be performed at the time of conditions

nuclear power level writing

Requires radiation- and

Sl-airtnreitne (1) Sensitivity to thermally-hardened

Johnson noise Electronic vibration due to Self-calibrating resistance electromagnetic (EM) noise C preamp. Improvements

thermometry thermal agitation of atoms (RTDs) (2) Complexity of in signal processing and

implementation rad-hard electronics are

still needed

Currently tested for Determination of how to

Conductor passes through primary flow Needs to solve problem

Magnetic flowmeters magnetic field generates voltage measurement in connect liner to electrode Neof radiat on

prop to velocity pressurized-water reactors and select proper lier for susceptibility of liner _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (PW Rs)ma n tcfo

Needs results of

Tested for irradiation .caused by radiation exposure Fabry-Perot fiber-optic Principle of superposition of effects, high temperature, irradiation observed testing; exaD more

temperature sensor waves and pressure exhaustive tests may be

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _r e q u i r e d

5
Table 2.1 Summary of state of the art of sensor technology focus area (continued)

Technology Description of principle Foreseeable application New progress Statusa Conclusions

(1) Pressure measurement

in high-temperature, highpressue, corosive(1) DemonstratedNedtimrv

Detects the change in optical environment application in harsh durability and

Optical pressure sensor guiding path defined by a (2) Optical Fabry-Perot radiation environment C demonstrate

compressible medium interferometer to detect (2) Experimental study is performance

pump cavitation and flow performed

instabilities

Expect widespread

(1) mageof pbblebedapplication of the

Gamma ray Use energy and time of Compton coating structure bedchnior In use after the improved ore scatter event and photon electric c s I u efficient

tomographic absorption event to project arrival (2) Real-time cadmium zic tellurde A implementation of the

spectrometry angle of an incident Gamma ray characterization of production as low as reasonably

y radiation field achievable (ALARA)

principle

Uses palladium as catalyst to Robust hydrogen sensors wtNeeds to be able to

Hydrogen sensor allow hydrogen to diffuse into a Post-accident hydrogen have been integrated onto a C withstand the harsh

metal and change the resistance monitoring single chip post-accident ____ _ ____ ___ _____ _____ _____ __ __ ___ ___ ___ ___ environm ent

Could be integrated into

Use functional redundancy for On-line instrument Demonstration testing has distributed control

Ssensor fault diagnosis calibration and fault been done B generation nuclear

power plants (NPPs)

Rea-tie dgnsisthrughbuit-On-line instrument Ultra-sensitive capacitive Etnieueo h

Enhanced diagnostics Real-time diagnosis through bult- calibration and fault pressure sensor with built-in C principle in NPPs

in softwareandh_ ardware testig_ diagnosis temperature compensation _in_____ principle 

'A = ready for use; B = confirmatory testing required; C = some additional development required; D = significant development required; E = ftndamental research

required.

6
2.1.4 Scintillation-Based Measurements for Temperature and Flux

The purpose of scintillation-based measurement is to obtain more accurate, reliable, and cost-effective

determination of in-core power density that will facilitate higher fuel bum-up, more efficient core

loadings, and uniform power distributions. Although the probe would be generally applicable to any

reactor technology, it is being specifically targeted to accommodate the higher core temperatures of hightemperature gas-cooled reactors (HTGRs). The primary deficiencies in the technology preventing its use

for in-core measurements are the lack of an effective technique for measuring light within reactor core

environments and the rapid darkening of fiber-optic light pipes in high radiation fields. For the purposes

of this update, no significant progress in overcoming these problems was identified.

2.1.5 Johnson Noise Thermometry

Of the two basic types of Johnson noise thermometer (JNT) under development-inductive JNTs and

conductive JNTs-the conductive JNT is closest to being commercialized. The complexity of

implementing this type of sensor has been one of the most significant drawbacks in its development. Fcr

example, until recently, sensitive analog band pass filters were used as part of signal processing in JNT

systems in Europe and in the United States, and these filters were often difficult to stabilize, even by

skilled operators. Other problems that have hampered commercial utilization include (1) a relatively long

response time because of the long integration time required to make a temperature measurement to with.n

an acceptable uncertainty and (2) sensitivity to electromagnetic noise. To address the system complexity

issue, scientists at the National Institute of Standards and Technology (NIST) report that now the

extensive use of digital signal processing (DSP) techniques makes it possible to avoid the use of analog

band pass elements. The new system, with state-of-the-art digital circuitry, makes the system easier to

use. To address the problem of long response time, researchers at ORNL have developed a dual-mode

thermometer. This sensor makes the temperature measurement as a simple RTD resistance measurement

whose resistance to temperature conversion is quasi continuously updated using Johnson noise. To

address electromagnetic interference (EMI) issues, DSP methods are used to quantitatively evaluate the

magnitude of any periodic interference in the noise spectrum and subtract it from the signal, thus

minimizing the interference effect as much as possible. The JNT system at NIST utilizes Fast Fourier

Transform (FFT) cross-correlation noise power spectra with 1-Hz resolution and periodic interference are

readily distinguished from the thermal noise or reference system pseudonoise.

It appears that the most significant hurdle left to be overcome is the need for radiation- and thermally

hardened preamplifier electronics for containment use. Thus, JNT is a potential temperature

measuarement system for the commercial nuclear marketplace in the near future (3-5 years) and should

continue to be monitored.

2.1.6 Magnetic Flowmeter for Measurement of Primary Coolant Flow

Until recently, the susceptibility to radiation of the liners in magnetic flowmeters has limited their use.

Researchers at ORNL [Holcomb 2002, Holcomb 2003] are studying the behavior of these liners in

radiation fields that result in a lifetime exposure dose of 2.4 x 108 rads. This level of expected exposure is

based on coolant system data from Generation II PWRs, and test plans for magnetic flowmeter liners in

this type of environment are being developed. The development of materials for a liner that can survive

high-radiation environments is a primary objective. This effort includes production of liners with an

internal electrode structure and electrical feed-through test pieces. Current-generation flowmeter

electronics could utilize the new liner technology. Progress in radiation-resistant liner technology should

continue to be monitored.

7
2.1.7 Fabry-Perot Fiber-Optic Temperature Sensor

The Fabry-Perot fiber-optic temperature sensor is a technology likely to be deployed in nuclear power

plants in the near term. Fiber-optic sensors have several advantages which make them attractive for use

in harsh environments-immunity to electromagnetic and radio-frequency interference, resistance to

corrosive environments, high reliability, and relatively high accuracy. However, recent studies have

shown this type of sensor to exhibit some offset in mixed high-neutron/gamma fields, which nevertheless

anneals after the temperature is increased. Other research has suggested that the temperature offset may

also be reduced by improved welding methods. If these shifts in calibration can be compensated for with

an on-line sensing or calibration model, the Fabry-Perot temperature sensor, or a similar fiber-optic

technology, will be suitable for applications in nuclear power plants. The technology should continue to

be monitored.

2.1.8 Optical Pressure Sensors

Optic pressure sensors have demonstrated their successes in combustion applications such as pressuresensing spark plugs, glow plugs, and fuel injectors. They have also been used in noncombustion

applications, such as monitoring pressure in natural gas pipeline compressors, plastic melt pressures, and

pressure control in a pharmaceutical plant. The survivability of fiber Bragg grating-based optic sensors

has been demonstrated for radiation levels up to 2 x 10'9 fast neutrons/cm2 and 87 Grad (0.87 Giga Gy)

gamma in a combined neutron and gamma environment.

One application of fiber-optic sensing technology that deserves attention is the use of fiber-optic FabryPerot interferometers (FFPIs) to detect cavitations and flow instabilities in centrifugal pumps in nuclear

power plants. The dynamic pressure resulting from the pump suction and discharge effects, cavitations,

vane-pass pulsations, and excessive-wear ring leakage for a high-energy process may cause large dynamic

axial forces, leading to premature thrust-bearing failures. Continuously monitoring the dynamic pressure

provides a useful indicator of unsafe operation of pumps. Standard pressure transducers are limited to

processes below about 3000C, but this FFPI sensing system is able to extend the operating temperature up

to 8000C and to improve the sensitivity by two orders of magnitude.

Ongoing development of fiber-optic sensor technology is directed toward improving sensor performance

and long-term durability. Many applications for nuclear power plants should be available in the next

decade.

2.1.9 Gamma Ray Tomographic Spectrometry

Gamma ray imaging techniques were not successfully applied for real-time characterization of radiation

fields in nuclear power plants until the end of 1990s, primarily because of the requirements for large size

and special shielding. The newly designed GammaCamTM has a compact, portable package with the

potential of overcoming these limitations. The output from the GammaCam is in the form of color visual

images of the scanned area, overlaid with a scaled color representation of the radiation field(s) present.

The GammaCam system is particularly useful for obtaining information on the location and intensity of

radiation fields, which can be used to locate hot spots.

The current system allows for the reliable acquisition of gamma ray images in high-radiation

environments, has a field of view of 250, permitting radiation mapping of large areas, and is able to cover

most of the energies of interest in nuclear power plants. The performance of this system has been

demonstrated in field experiments to help health physicists rapidly perform a preliminary characterization

of an area and identify the precise location of the strongest sources while minimizing the exposure.

8
It is reasonable to expect widespread application of the gamma ray imaging technique for more efficient

implementation of the ALARA principle in nuclear power plants in the near term. This tool is well suited

for ALARA programs, as it enables remote characterization of radiation source areas.

2.1.10 Hydrogen Sensor

Hydrogen sensors have nuclear power applications both in the near term as monitors for hydrogen

accumulation in reactor systems, and in the long term as an essential element of a nuclear hydrogen

production plant. Indeed, as hydrogen technology has emerged as a clean, abundant energy source, many

hydrogen sensor technologies have been developed by different industries in the past 5 years.

Catalytic bead sensors can measure hydrogen concentrations of I to 5% with a 10- to 30-s response time.

Semiconductor and electrochemical hydrogen sensors have very fast response times (less than several

seconds), but they are not appropriate for post-accident measurements in nuclear power plants because

oxygen concentrations also affect the resistance and the chemical reaction. Palladium alloy sensors,

which have rapid responses and are robust in varying environments, would be effective monitors in

nuclear applications.

A robust, wide-range hydrogen sensor has been developed by Sandia National Laboratories. This

hydrogen sensor uses (1) catalytic palladium nickel (PdNi) gate metallization on field-effect transistor

sensors for detecting low concentrations of hydrogen (part per million), (2) PdNi resistor sensors for

detecting higher concentrations of hydrogen (up to 100%), and (3) on-chip microthermometers and

microheaters for maintaining constant chip temperature. The design is aimed at addressing the drawbacks

of current hydrogen sensors: limited dynamic range; poor reproducibility and reversibility; unacceptable

frequency of false alarms; and the tendency to be slow, unreliable, and difficult to use. Some additional

issue; for nuclear application include the ability to remove sulfur-bearing contaminants from the

palladium surface for accurate measurements and functionality in nonuniform hydrogen distribution and

the harsh environment of high temperature, high pressure, and high humidity in the containment after an

accident.

Aluminum nitride (AIN)-based hydrogen sensors are also under development. This unique sensor is

based on a palladium/AIN/silicon structure, which behaves similarly to a metal-insulator-semiconductor

(MIS) device. The device is reported to be highly selective, showing no response to oxygen, propane, or

carbon monoxide, and capable of detecting hydrogen concentrations down to I ppm in the surrounding

flow. While this device holds a lot of promise, much work is needed before it can be commercialized.

Ongoing work has focused on characterizing the electrical properties of the device, characterizing the

exact nature of the sensing mechanism, and optimizing the performance by varying palladium and AIN

thicknesses and employing various palladium-based alloys.

Hydrogen sensor technologies should continue to be monitored as continued improvement is very likely.

2.1.1]1 Smart Sensors

Sensor Fusion

In sernsor fusion, data reconciliation and gross error detection has recently received attention by the

nuclear electric utilities in Europe. This technique takes advantage of the plantwide mass balance and

energy balance equations to reconcile plant measurements, such that the balance equations are satisfied.

Because the easily developed models provide additional functional redundancy to the plant

measurements, the reconciled values will be much more accurate than the raw measurements. This

technique is mature enough for application in nuclear power plants at steady-state conditions to improve

9
plant performance and provide a sensor calibration standard when digital systems are applied. Additional

research is focusing on dynamic data reconciliation for better control.

Enhanced Diagnostics

An alternative approach to smart sensors is for the sensors to have the capability to realize the diagnosis

and report on their own conditions through built-in software- and hardware-testing capabilities. Because

this technique depends on individual sensor design, it is difficult to completely review this topic.

However, the trend toward sensors with the capability of self-checking and calibration as well as

intelligent and automatic failure diagnosis is certain to increase, and such sensors will find greater

application in nuclear power plants. This technology will reduce personnel costs and increase equipment

reliability by detecting a fault at its incipient stage. For instance, Integrated Sensing Systems, Inc., has

developed an ultrasensitive capacitive pressure sensor that has built-in temperature compensation and

provides features such as self-testing and self-calibration.

2.2 Communication Media and Networking

Communications media (e.g., cables, fibers, wireless bands) and network systems provide the pathways

by which data and information are distributed among the field devices, processing components, and

display systems in a plant. In nuclear power, traditional direct-wired, point-to-point connections between

analog equipment have been the norm. However, the trend to use data networks is likely to increase,

serving plant personnel and the application of digital I&C in some system upgrades. The current control

and protection products on the market (e.g., TELEPERM XP and TELEPERM XS) [TELEPERM (1)]

make use of specialized Ethernet or proprietary protocols for networked microprocessor-based systems.

Fieldbus standards are maturing, and networked field device are likely to see increasing application as

part of I&C upgrades for plant life extension-with smart sensors becoming more prominent. As pointed

out in NUREG/CR-6812, it is to be expected that new plants, both in the near term and the long term, will

take advantage of the advances in communications technologies to facilitate highly integrated,

autonomous control and information systems. In addition, future nuclear power plants may not

necessarily have complete separation of safety systems from control systems [Wood 2003].

2.2.1 Sensor Buses

The availability of bus systems has made communication between programmable controllers and personal

computers very effective with devices such as limit switches, pushbuttons, and motor starters. There are

about a dozen of these so-called device-level networks. The most widely used buses-actuator sensor

interface, control area network, Device Net, smart distributed system, Interbus-S, LonWorks, Profibus,

and Seriplex-are discussed below.

Actuator Sensor Interface

An actuator sensor interface (ASI) is a wiring system that connects power and signal (input and output)

from a programmable logic controller (PLC) to devices on a machine or process. In its basic form, the

ASI features only one cable (a simple pair) that runs from the PLC input/output (1/0) card for up to 300

meters (with repeaters), connecting proximity switches, photo sensors, motor starters, push buttons, signal

columns, solenoids, valves, and switches. Safety devices can be connected to the same networks. Each

of these field devices can have an integrated ASI connection or be connected to an I/O node. One master

PLC controls up to 31 nodes (62 with ASI 2.1), and each node can be up to 41/40 (or 8 inputs or 8

outputs). So the maximum I/O per ASI master is 248 (465 with ASI 2.1). A master PLC will normally

need a power supply, an ASI output module, and possibly a communications module to interface with a

higher field bus (e.g., Profibus or Devicenet) known as a gateway. ASI (ASI bus) is a simple bus system

10
that connects intelligent sensors using a mechanically keyed two-wire cable. This cable is responsible for

transmitting control and device data, powering the devices, configuring the system architecture, and

monitoring the network. In many installations, an ASI bus can replace more complex systems and

drastically simplify wiring and diagnostics. ASI is also universal, with devices from different

manufacturers being 100% compatible with one another.

Cont-roller Area Network

A controller area network (CAN) is a common small-area-network solution that supports distributed

product and distributed system architectures. The CAN bus is used to interconnect a network of

electronic nodes or modules. Typically, a two-wire, twisted-pair cable is used for the network

interconnection. The CAN protocol is a set of stringent rules implemented in silicon that supports the

serial transfer of information between two or more nodes. CAN has the following features:

* A multimaster hierarchy. This allows constructing intelligent and redundant systems. If one

network node is defective, the network is still able to operate.

* Broadcast communication. A sender of information transmits to all devices on the bus. All

receiving devices read the message and then decide whether it is relevant to them. Because all

devices in the system use the same information, data integrity is guaranteed.

* Sophisticated error-detection mechanisms and retransmission offaulty messages. This feature

also guarantees data integrity.

CAN is the International Standards Organization (ISO) standard for automotive networking and is used in

virtually all industries (e.g., automotive, manufacturing, agricultural, medical, building controls, marine,

aerospace).

Device Net

Device Net is an open, low-cost communications link based on the reliable CAN technology to

interconnect industrial devices (such as limit switches, photoelectric sensors, valve manifolds, motor

starters, process sensors, panel displays, operator interfaces) via a single network. This technology

eliminates expensive wiring and failure due to the increase in number of connections. It also reduces the

cost 2nd time to wire and install industrial automation devices while providing reliable interchangeability

of components from multiple vendors. The direct connectivity provides improved communication

between devices as well as important device-level diagnostics not easily accessible or available through

hardwired VO interfaces.

This technology is used extensively in the United States, Australia, New Zealand, Japan, and China; and

it is rapidly gaining popularity in Europe. Device Net is based on the ISO CAN standard for automotive

networking. Device Net is now an official European Committee for Electrotechnical Standardization

(CENELEC) standard (EN50325).

Smart Distributed System

The Smart Distributed System (SDS), developed by Honeywell's Micro Switch Division, is described by

the manufacturer as an advanced bus system for intelligent sensors and actuators. This CAN-based

network, open at both the control and device levels, streamlines installation, optimizes machine

applications, and empowers inputs and outputs to operate at various levels. Combining the power of

CAN technology, Honeywell personal computer (PC) control, and intelligent I/O devices, the smart

distribution system (SDS) provides an integrated solution. Over a single four-wire cable, SDS can

interfiice with up to 64 nodes with a maximum of 126 addresses. These intelligent sensor and actuator

I1I
devices do more than just turn on and off; they have advanced device-level functions and system and

device diagnostics.

Interbus-S

Interbus-S is a ring-based distributed device network for manufacturing and process control. An

Interbus-S system consists of a controller board installed into a PLC or computer (PC, VME, etc.) that

communicates to a variety of IO devices. This device is available on the Series 90-30 PLC (Homer

Electric modules), Series 90-70 PLC (VME Solution from Phoenix), and Field Control I/O (Homer

Electric BIU). It treats data as a shift register and is supported by a variety of third-party devices.

LonWorks

The LonWorks network communicates using LonTalk, the standardized language of the network.

LonTalk consists of a series of underlying protocols that allow intelligent communication among various

devices on a network. The protocol provides a set of services that allow the application program in a

device to send and receive messages from other devices over the network without needing to know the

topology of the network or the names, addresses, or functions of other devices. The LonWorks protocol

can optionally provide end-to-end acknowledgment and authentication of messages and priority delivery

to provide bounded transaction times. Support for network management services allows remote network

management tools to interact with devices over the network to reconfigure network addresses and

parameters, download application programs, report network problems, and start, stop, or reset device

application programs. LonTalk-and thus LonWorks networks-can be implemented over any medium,

including power lines, twisted pair, radio frequency (RF), infrared (IR), coaxial cable, and fiber optics.

PROFIBUS

PROFIBUS is one of the most widely used field bus architectures for industrial control and automation in

Europe and the United States. It is well developed and is supported by large companies such as Siemens.

Each device is described in a profile file called a GSDd file created by the manufacturer. Baud rate can be

selected from 9.6 kB/s up to 12 MB/s, with up to 126 devices on the same bus. The PROFIBUS family is

composed of three protocols:

• PROFIBUS-Fieldbus Message Specification (FMS): a peer-to-peer messaging format that allows

masters to communicate with one another. An example is PLC-to-PLC communication. It also

supports data exchange with field devices. FMS can thus be used for a wide variety of

applications, operating at average transmission speeds. However, this ability to provide a wide

variety of functions also makes it more complex to implement compared to the other variants.

* PROFIBUS-Decentralized Periphery (DP): This is the high-speed solution of PROFIBUS. It is

optimized especially for communication between automation systems and decentralized field

devices (e.g., sensors). It uses a master-slave protocol, in which the master periodically scans the

slaves. Multiple masters are possible, in which case, each slave device is assigned to one master.

Multiple masters can read input from a device, but only one master can write outputs to that

device. PROFIBUS-DP communicates via cyclic data traffic exclusively. Each field device

exchanges its I/O data with the automation device, the master, within a cycle time.

d A GSD file is used to identify a PROFIBUS-DP/PA device (master or slave). It contains data making it possible to

have manufacturer independent configuration tools. Typical information in a GSD file is vendor information, baud

rates supported, timing information, options/features supported, and available 1/0 signals. A GSD file must be

available for every decentralized periphery (DP)/process automation (PA) slave.

12
PROFIBUS-Process Automation (PA): This device is similar to PROFIBUS-DP, with diagnostic

functions. It is often used in intrinsically safe environments required by chemical and

petrochemical process applications. Unlike the automated applications in manufacturing

engineering, which require short cycle times of a few milliseconds, other factors are important in

process automation, including (1) intrinsically safe transmission techniques, (2) ability of field

devices to be powered over the bus cable, (3) reliable data transmission, and (4) interoperability

(standardization of device functions). The aspects of "intrinsic safety" and "bus supply" were

neglected at first when PROFIBUS was standardized. The PROFIBUS-PA specification

published in March 1995 included this transmission technique for intrinsically safe installations

and field devices powered over bus cables [PROFIBUS-PA].

Seriplex

The Seriplex network, which is supported by Schneider Electric, offers a lot of flexibility. It has been

designed to effectively and efficiently network the basic bit-level devices on the plant floor. Unlike mos;t

networks, which require a large investment in software and training, the Seriplex network technology is

easy to use and has lower installation and maintenance costs. The Seriplex control bus includes cable

runs of 5000 ft or more. System throughput time is 0.4 ms for 32 sensors and the same for actuators (5

ms for 510 1/0). It supports more than 255 inputs and 255 outputs. The design eliminates overhead

communications and offers system flexibility without system reconfiguration. It uses any wiring

configuration (e.g., star, loop, tree, trunk, or daisy chain) consisting of a small, four-wire cable that

provides both communication and power and connects directly to over 510 devices. The system

eliminates the thousands of parallel wires that usually run through a conduit between local control

cabinets and devices. The Seriplex control bus offers the advantages of distributed I/O, plus fast

performance, easy configurability, and lower installed cost. Recently, Leviton Manufacturing introduced

a new surge protection device designed to provide transient voltage surge suppression for products

operating on Seriplex control bus networks. The Class 9999 Type SPXF Seriplex module simplifies

motor monitoring and network control of contactors, starters, and overload relays. It reduces the cost of

control and power wiring, allowing controls to be linked by a single Seriplex sensor bus cable. The input,

output, alarms, and trip indicators are available to the host controller and each module's LED display,

providing local and remote status monitoring. It has two settable current threshold alarms, two cause-oftrip data signals, an overload relay trip status signal, and remote reset capability.

Seriplex and ASI have markedly similar characteristics. They are fast, with transmission speeds

exceeding 100 kB/s. Both use a low-cost application-specific integrated circuit (ASIC) embedded in the

sensor or in a nearby terminal block. Both buses supply power to the devices connected to them; both are

designed to be easy to use. The complexity is buried in the ASIC, so the user has little concern about

network details.

2.2.2 OLE for Process Control

Object linking and embedding (OLE) is Microsoft's protocol for creating compound documents. With

OLE, it is possible to dynamically link files and applications together. An object is a combination of data

and the application needed to modify that data. Objects can be embedded in or linked to documents

created with a different application. For example, an Excel spreadsheet can be embedded within a

Microsoft Word document using OLE. Double-clicking the embedded spreadsheet will launch Excel and

allow the user to modify the sheet.

OLE for Process Control (OPC) is a new technology designed to bridge various data sources [e.g., from

PLCs, pressure and temperature gauges, and distributed control systems (DCSs)] from different vendors

13
through a common communication technology standard. Typically, vendors connect these data sources

via serial, Ethernet, wireless, or even radio links to various applications, using Windows, UNIX, or VMX

operating systems. OPC defines a common standard interface that allows applications to access data from

these various process control devices. The applications must implement one OPC-compliant driver to

access data from any OPC-compliant server (see Fig. 2.1). Thus, the data access method remains the

same regardless of the type and source of data. This means that users are free to choose the software and

hardware that meet their primary production needs, without having to consider the availability of

proprietary drivers.

OPC components fit into two categories: OPC clients and OPC servers. A client is typically a data sinkan application that uses data in some way, such as a man-machine interface (MMI) or supervisory control

and data acquisition (SCADA) package. A server is a data source-a device-specific program that

collects data from a field device, then makes it available to an OPC client. A client interacts with a server

using a well-defined OPC interface. Therefore, any OPC client can communicate with any OPC server,

regardless of the type of device from which the server is designed to collect data. OPC is built using

Microsoft's OLE technology. Also, the OPC specification was designed by an open foundation to meet

the general needs of industry, not the specific needs of a few software or hardware manufacturers. The

specification also provides for a robust evolution of functionality over time, so that OPC components can

meet the emerging needs of industry.

Trender)

MISpreadsheet

Fig. 2.1. OPC, a communication technology standard for process control.

2.3 Microprocessors and Other Integrated Circuits

2.3.1 Radiation-Hardened Integrated Circuits

Considerable progress has been made in radiation-hardened integrated circuit development using

materials such as silicon-on-insulator (SOI). State of the art radiation-hardened integrated circuit (IC)

technologies are exemplified by the SCS750 single-board computer, which is Maxwell Technologies'

innovation for space applications [Maxwell Technologies 2004]. This single board computer uses SOI

technology fabricated in a radiation-tolerant 0.1 3-jim complementary metal-oxide semiconductor

(CMOS) process. Its performance characteristics include (1) one upset every 300 years in a geostationary

14
orbit (GEO), (2) space qualified performance at 1800 MIPS, (3) triple modular redundant processing, (4)

use of SOI processors, and (5) the use of advanced error corrected synchronous dynamic random access

mernory (SDRAM). In addition, power consumption is selectable from 5 - 20W. This next-generation

supercomputer will dramatically increase on-board data processing, mission planning, and critical

decision making.

ATMIEL Corporation has manufactured a radiation-hard 0.1 8-tum CMOS-cell-based ASIC for highreliability space applications. The ATMEL ATCI 8RHA [ATMEL 2004] is fabricated on a proprietary

0. I 8-.tam with six-layer metal CMOS process intended for space use.

Another innovation in radiation-hardened chip technology is the development of chalcogenide-based

random access memories (C-RAM). The term "chalcogen" refers to Group VI elements of the periodic

table, and "chalcogenide" refers to an alloy with at least one of the Group VI elements. An example of a

chalcogenide material is Ge2Sb2Te5. Chalcogenide is a proven phase change material used in rewriteable

CDs and DVDs. This material changes phases, reversibly and quickly, between an amorphous state that

is dull in appearance and electrically high in resistance, and a polycrystalline state that is highly reflective

and low in resistance. Chalcogenide-based memory is highly radiation resistant, and its importance in

space I&C applications is well recognized. Serious attempts to develop chalcogenide-based nonvolatile

memory technology for space applications began with the successful integration of chalcogenide material

(Ge2Sb2Tes) from Ovonyx with BAE Systems' 0.5pm radiation hardened CMOS to produce 64-kB arrays.

Follcwing the success of this project, the next generation of C-RAM fabricated was a 4M-bit product

implemented in 0.25gm radiation-hardened CMOS. Four megabit C-RAMs represents the current state of

the adt.

2.3.2 System on a Chip

System on a chip (SoC) could eventually lead to a sensor on a chip application that could be located in

harsh environments and changed out (perhaps robotically) periodically. This would facilitate new

measurements of monitoring capabilities at remote or harsh locations over the lifetime of a nuclear power

plant without requiring expensive cabling or qualification for an extended life.

Most of the current research is focused on applying technologies currently in use in the fields of

comrmunication and computer science. The specialized applications are challenged by the high degree of

on-chip integration for complex systems, power consumption, and manufacturability, including testability

and reliability. The application of SoC to small systems is already mature. The National Aeronautics arid

Space Administration (NASA) has developed a remote I/O (TRIO) chip that can interface to 32

transducers with current- and voltage-sensing capability, a read-out chip, and a precise time-interval

chip--all of which are incorporated into a particle spectroscopy instrument [Paschalidis 2003].

Monitoring the special application of the SoC technique to nuclear instrument development and control

perfo mance improvement is appropriate.

2.3.3 Optical Processors

An Israeli company, Lenslet, Ltd., claims that its optical DSP [Lenslet 2004], which runs up to 8 tera

operations per second (a thousand times faster than existing products) will open the door for new

applications for the defense, homeland security, multimedia, and communications fields. The company

claims to have developed the world's first commercial optical DSP, which includes wireless and cellular

communications, software-defined radio, real-time video compressions, radar and electronic warfare, and

biotechnology, and data mining.

15
The potential benefits of the optical DSP, known as the EnLight256 (see Fig. 2.2), include better

communication in noisy channels, multichannel interference cancellation, multiprotocol receivers,

improved resolution and images for synthetic aperture radar, digital beam formation, enhanced signal

detection in electronic warfare and radar warning receiver systems, and multichannel video compression

and procession at high image resolutions. This new optical DSP could replace multiple-DSP boards.

EnLight256 can be used as either a system-embedded accelerator or a stand-alone processor for

computationally intensive applications.

Fig. 2.2. EnLight256.

The optical DSP uses light to form basic fixed-point calculations quickly. Its interface is standard and

electronic, like existing DSPs. Optical processing involves analog processing, which introduces

inaccuracies. The company says it has developed calibration algorithms and conversion techniques to

reduce such inaccuracies. The current EnLight256 is on several chips, but Lenslet reportedly plans to

reduce that prototype to a single chip in about 5 years. The current test model is about the size of a

personal digital assistant. The company expects that this technology could be mainstream in about a

decade. Optical processors are well known for their speed of communication. The latest development is

highly uniform, InP-based, high-electron-mobility transistor (HEMT) technology [Naoki 2003] for highspeed optical communication system ICs. High frequency is the special feature of HEMTs. The

technology is implemented with a cutoff frequency of 175 GHz after interconnection, which is

sufficiently high for applications in 40-GB/s optical communication ICs. The standard deviation of the

threshold voltage was only 13 mV across a 3-in. wafer. The new technology enables fabrication of ICs

with over 1000 transistors with a 0.1 micro m-class gate length and operated at over 40 GB/s.

Furthermore, the technology uses a 2:1 multiplexer with more than 200 transistors and an operating speed

of 90 GB/s. Thus, HEMT technology can be applied to fabricate high-speed ICs for optical

communication systems.

2.3.4 Vertically Stacked Integrated Circuits

A vertically stacked integrated circuit (VSIC) is a method to circumvent the physical limits imposed by

the single-layer approach to integrated circuit fabrication. As an example, the Pentium 4 processor has

seven layers of wiring, but only on the bottom layer of pure silicon do the active semiconducting regions

lie. In VSIC design, active semiconducting layers are stacked on top of each other, much like the floors

of a skyscraper.

VSICs continue to face challenges in updating the current two-dimensional design tools to minimize the

number of wires so that the distances traveled by signals, which are combinatorial, are minimized. In the

end, the design still has physical limits because the heat produced by the layers must be dissipated [Das

16
2003]. Developments should continue to be monitored to determine whether the achievable technology

can satisfy the needs of nuclear application. As pointed out in NUREG/CR-6812, use of this technology

in the nuclear industry is likely to occur after its uses are well established for other applications (e.g.,

telecommunications). Thus, the potential impact on nuclear power applications would be similar to that

of resent evolutionary improvements in IC technology. For safety-related applications, the main issues to

be considered for the new stacked processors and memory devices would probably be overall reliability

and environmental compatibility if implemented in other than controlled environments.

2.3.5 Nanotriodes

Nanctechnology has experienced significant progress in nanosensors, nanoactuators, nanoelectronics, arid

micro-electromechanical devices (MEMs) in the past several years. In the case of nanoelectronics,

advances in the development of nanotriodes deserve particular mention because of the technology's

potential influence on nuclear I&C. In particular, this reinvention of the vacuum tube may show promise

for high-radiation and high-temperature environments. The flow of electrons in a vacuum should be

unaffected by radiation bombardment.

Nanctriode technology is still in its infancy with advances continuing to be made. For example,

nanoiTiodes developed at Cambridge University have reached a density of 109/cm2, comparable to the

density of metal-oxide semiconductor (MOS) transistors. Nanotriodes are advantageous over MOS

technology in radiation resistance and temperature tolerance. A current research issue is the

reproducibility and longevity of nanotriodes [Schewe 1999]. Figure 2.3 shows the schematic of an

encapsulated nanotriode fabricated at Cambridge University. Tungsten is used to form the cathode layer

(15 nm thick), the gate layer (20 nm thick), and the anode layer (15 nm thick). Silicon dioxide is used tc

separate the two electrode layers (40 nm on each side). An additional masking layer of titanium (15 nm

thick) is deposited on top of the tungsten anode. Electrons are field-emitted from tungsten nanopillars on

the cathode having tip radii of I nm and heights of 10 nm. The current is collected at the anode controlled

by the gate electrode. The turn-on gate voltage for field emission is 8 V, and the field-emitted currents of

up to 10 nA are collected at the anode.

Progress in development of nanotriodes should continue to be followed over the long term, given the

potential that this technology could enable smart sensors to migrate into the most inhospitable areas

within the reactor containment.

2.3.6 Microelectromechanical Systems (MEMS)

Progress continues to be made in MEMS (also known as micromachines) technology. For example, a

high-t:emperature, low-power silicon tunnel diode oscillator transmitter with an on-board optical power

converter is under development for harsh environment MEMS sensing and wireless data telemetry

applications [Suster 2004]. The prototype sensing and transmitting module employs a MEMS silicon

capacitive pressure sensor performing pressure-to-frequency conversion and a spiral loop serving as an

inductor for the inductor-capacitor (LC) tank resonator and also as a transmitting antenna. A GaAs

photodiode converts an incoming laser beam to electrical energy for powering the prototype design. The

system covers a distance of 1.5 m. Telemetry is achieved up to 250'C with transmitter power

consumption of about 60 jiW. Such a system can be useful in a harsh environment in which sensing and

data communications are always a challenge.

Thus, MEMS technology bundled in a SoC package shows promise for eventual use in nuclear power

plants for sensing (wireless or wired) applications. The long-term progress in the development of this

technology should continue to be monitored.

17
Thantu=n

*SilICOn dlotkiol

100 nm

100nm Nanopiars

Fig. 2.3. Schematic of a nanotriode (http://www.aip.org/png/html/nanotriodes.html).

2.3.7 Molecular-Scale Electronics

Molecular electronics involves designing, fabricating, and applying molecular-level or nano-scale

electronic systems such that drastic improvements in computational speed and density can be expected.

There are at least three major approaches to the development of this technology.

The first approach is chemical computing, which builds calculations upon the chemical reactions and

stores the answers in the resulting chemical structures. Adleman utilizes sequences of deoxyribonucleic

acid's (DNA's) molecular subunits to represent vertices of a graph. Thus, combinations of these

sequences formed randomly by the massively parallel action of biochemical reactions in test tubes

represent the random paths through the graph. Using the tools of biochemistry, Adleman was able to

extract the correct answer to the graph theory problem out of the many random paths represented by the

product DNA strands [Adleman 1994, Adleman 2002].

The second approach is quantum computing, which performs massively parallel computations through the

natural mechanism of interference among the quantum waves associated with the nanoscale components.

In a quantum computer, each bit of information is represented by a quantum state of some component,

such as the spin orientation of an atom, which can be manipulated in nanoscale. By carefully setting up

the states, a desired computation can be performed through the wave interference among the quantized

components.

The third approach is nanoelectronic-based computing, which is a natural extension of conventional

integrated circuit technology. Quantum dots and single-electron transistors, which can now be made as

small as 30 nm, have shown switching and amplification properties. Hewlett-Packard demonstrated in

1999 that a monolayer film of molecules between two electrodes could act as a switch. In 2001, Bell

Laboratories used a monolayer to mimic the properties of a transistor. These molecular-scale devices

have the potential of turning into working computational units with extremely high bit densities and

switching speeds.

Despite advances in molecular electronics since the publication of NUREG/CR-6812, numerous

challenges remain to be overcome before a molecular device that operates analogously to a transistor is

feasible. Therefore, although the technology is interesting, it is not likely to develop to the point that it

would migrate into nuclear applications within the foreseeable future.

18
2.4 Computational Platforms

NUREG/CR-68 12 noted various PLC-based and microprocessor-based computational platforms for

operations, control, and safety applications available for I&C upgrades in existing nuclear plants or

foundational I&C systems for near-term deployment of future nuclear plants. Two key technologies were

iden ified: ASICs and real-time operating systems. These technologies were identified for two reasons:

The possibility exists for long-term expansion for ASIC-based components in nuclear power

safety applications. Awareness of progress in this technology is therefore recommended,

especially in light of the potential costs for dedicated commercial software-based systems.

Operating systems provide the fundamental interface between software and hardware in most

digital applications. Thus, their performance and reliability characteristics should be well

understood.

For the purposes of this update, we reviewed the literature to assess progress in ASIC implementations in

safety systems. In the area of real-time operating systems, we provide an example of a real-time

operating system that has been in use for safety-critical applications such as aircraft. We also discuss in

some detail the open system and the corresponding interfaces for automotive electronics (OSEKI'l)

operating system, and OSEKtimel" in particular, in order to provide an understanding of the general

requirements of an operating system for safety critical applications.

2.4.1 Application-Specific Integrated Circuits (ASICs) and Application-Specific Software

The NRC reviewed the Westinghouse 7300A ASIC-based replacement module and issued a Safety

Evaluation Report (SER) on February 2001 [EPRI, 2003b]. Siemens (Framatome ANP) received

approval in May 2000 from NRC to install safety I&C systems based on the TELEPERMm XS (TXS)

platform for safety-related automation tasks in U.S. nuclear power plants [TELEPERM (1)]. TXS is the

first digital system to be awarded generic approval under NRC's standard in NUREG-0800. Although tfe

TXS is not implemented with ASICs, it does have unique characteristics in architecture and software

implementation. First, the system architecture and all I&C application functions are engineered by means

of a graphical specifications tool called Specification and Coding Environment (SPACE). The modular

struc ure of TXS has been optimized during system development such that the application-specific

functions designed for TXS using the SPACE engineering tool are independent of the version of hardware

components and system software [TELEPERM (2)]. TXS software is designed so that there is effective

decoupling of the process engineering tasks from the response of the I&C system. This is based on the

fact that faults and accident conditions in the process are required to not influence the response of the

safety I&C under any circumstances. Thus, event-driven software is not used in the TXS. All parts of tae

software involved in initiating automatic measures are deterministic. That is, the measured signals are

read, limit signals are formed, and control commands are output in the same fixed sequence independent

of what may be happening in the plant or on other computers.

Note that the TELEPERM family includes not only TELEPERMTh' XS, for safety I&C equipment, but

also TELEPERM XP, for process control systems [TELEPERM (3) (4), Lochner 2002]. Recent

applications include the replacement of the turbine control system and the turbine protection equipment

for German and Swedish plants.

19
2.4.2 Real-Time Operating Systems

Of the different categories of operating systems available today, a hard real-time operating system (OS) is

the only obvious choice for safety system applications in nuclear power plants.' One such specification is

LynxOS-178, introduced in 2003. LynxOS-178 is a commercially available DO-178B level A certifiable

(FAA standard), real-time operating system (RTOS) that meets the stringent standards for safety-critical

systems. It includes support for POSIX interfaces, which saves time and cost associated in developing

and maintaining applications based on the POSIX open standards.

Another hard real-time embedded operating system standard is OSEKtime, which is an extension of the

OSEKNVDX operating system standard. In this update we discuss OSEKtime in some detail in order to

help understand the performance and reliability requirements for hard real-time operating systems.

OSEKIVDX and OSEKtime

OSEK IDistributed eXecutive (OSEK/VDX) is a specification for event-triggered operating systems. It

was originally developed for the automotive industry but has found its way into many applications such

as aerospace, industrial control, building control, public transportation, robotics, and medical electronics.

OSEKtime, an extension of OSEK/VDX, defines a strictly time-triggered operating system [based on the

time-triggered protocol (TTP)], including a communication protocol for fault-tolerant applications. This

specification is extremely important because the control units of embedded systems in the automotive

industry are expanding into safety-critical applications such as braking and steering. Figure 2.4 shows the

various specifications of OSEK/VDX [TTTech 2004]. 'TOS is an actual operating system with TTPI

support based on the OSEKtime specification. It meets all the requirements of a hard real-time operating

system. These requirements are the following [Tanzer 1999]:

* Dependability - reliability due to fault tolerance and fault detection. The replica deterministic

behavior of time-triggered architectures supports the implementation of fault-tolerant systems by

active redundancy. This facilitates the construction of highly dependable systems.

* Predictability - deterministic behavior even at peak load and in case of failure. The system

behavior is controlled by the progression of time based on a periodic pattern making the temporal

system behavior predictable. This eases system validation and verification considerably.

* Composability - a clean modular concept as the basis for an improved diagnosability, testability,

and certifiability. The various components of a software system can be developed independently

and integrated at a late stage of software development. This is possible because the interface

between all components is strictly defined both in the value and time domain. The smooth and

painless integration of components facilitates the management of the ever increasing complexity

of embedded real-time systems.

'An operating system is said to be "real-time" if it provides some mechanisms to give predictability to task

execution times. Soft real-time operating systems meet timing requirements most of the time but are allowed to

occasionally miss deadlines. Hard real-time operating systems provide the facilities necessary to meet timing

requirements under worst-case conditions. This is clearly the most desirable performance characteristic for safety

systems.

fTTPO is a communication technology developed at Vienna University of Technology and refined in several

European Union (EU)-funded research projects. It addresses the specific requirements of dependable embedded

systems and supports the partitioning of a large system into a set of nearly autonomous subsystems with small and

testable interfaces.

20
* Reusability of components - In a time-triggered distributed architecture the "glue logic" needed

to interconnect existing components into a new system is physically separate from the application software in the component. Existing components may therefore be reused in a new context

without any modification of the tested and proven application software.

* Efficiency - The operating system takes up a minimum of random-access memory (RAM), readonly memory (ROM), and central processing unit (CPU) processing power.

* Support for fault-tolerant hard real-time systems - The OS supports fault detection and

deadline monitoring.

OSEKNDX

OS

Operating System

COM

Communication

NM

Network Management

OIL

Implementation

Language

ORTI

Runtime interface

OSEKtime

Time-Triggered OS

FT-COM

Fault-Tolerant

Communication Layer

Fig. 2.4 OSEKIVDX standards and implementation in TTPOS

{Permission to use this copyrighted material is granted by TTAutomotive Software GmbH ITTTech 20041}

Figure 2.5 shows a typical structure of an OSEKtime-based system OSEK was designed for systems with

small hardware resources such as 8-bit processors with no memory management unit (MMU). On the

other hand, RTLinux is an example of an operating system especially designed for mid-range to highrange processors and is based on the POSIX standard. For nuclear power plant safety systems, the

overriding requirement is safety (i.e., ability of the circuit or subsystem to perform its safety function

when required) rather than processing power per sec. This is achieved through redundancy, diversity of

hardware and software, and fault handling. Also, the applications using the operating system should be

safe in the sense that they cannot defeat the operating system's protection mechanisms. These

characteristics are achieved by considering the reliability requirement at every phase of system design. In

general, development of hard real-time operating systems is still dynamic, and continued participation in

standards activities to provide technical support to the NRC is recommended. In addition, near-term

research into the performance and reliability characteristics of real-time operating systems is suggested.

21

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l l l unit,

Display (ECU)

--------------------------!-: 7N:~ ::

Fi.25OEtm-ae sytearhtcu.

r-- - - - ----- --- -- - - - - -- _ Network_ 

, (ECU)

r-- - --- --- - ---- - --- --- _-__-____

Fig. 2.5 OSEKtime-based system architecture.

2.5 Surveillance, Diagnostics, and Prognostics

2.5.1 Model-Based Techniques

The Thermal Performance Monitoring and Optimization (TEMPO) system is designed to support plant

personnel in identifying and correcting problems that cause small decreases in plant efficiency over long

periods of time [TEMPO 2004]. TEMPO has three basic function modules: modeling, monitoring, and

optimization. The modeling module allows users to create and maintain a plant model. The monitoring

module receives the measured data and fits the plant model calculations, using a few key parameters, to

the measurements. The optimization module solves a nonlinear optimization problem to optimize the

specified objective functions and free variables. In optimization mode, the user has the opportunity to

select predefined, constrained optimization options (e.g., steam fraction to reheater vs. water

temperature). Typically, the model will be initiated with the current state of the plant, but it is possible to

load different initial plant states. Then the model is started for optimization, and the user can see the new

parameters compared with the old ones. The user is allowed to put different weights on the objective

function parts and modify constraint parameters.

The TEMPO system, still being developed, will be able to address plant operation efficiency problems

due to fouling, leaking valves, pump degradation, flowmeter drifting, and ambient condition changes such

as sea water temperature or plant parameters. The major issues regarding optimization of plant efficiency

are related to steady-state assumptions on plant-measured data and how to deal with model uncertainty

22

UD7-?
such as pipe leakage and equipment heat loss, so the technology needs to be demonstrated on its

applications to real nuclear power plants. The technology deserves monitoring for near-term deployment.

2.5.2 Fault Detection for Field Devices

For aiutomated monitoring and testing of field devices, smart sensors and final control elements that can

report their health to the logic solver are increasingly available. This increases plant availability because

an unhealthy sensor can be replaced promptly or its input ignored for a voting strategy. Also, problems

with final control elements can be diagnosed more rapidly, thus averting dangerous situations. The

advanced diagnostics present in today's smart transmitters, when combined with open digital protocols

and asset management software, allow the user to remotely diagnose field devices and go beyond

alarming transmitter failures to actually predict impending failures in the complete measurement system.

This significantly reduces unscheduled outages and improves overall plant availability. In addition to

detecting failures, today's smart transmitters allow the user to easily diagnose application, configuration,

and installation errors.

2.5.3 Forewarning of Failure in Critical Equipment

The state of the art is exemplified by the work of Hively and others [Hively et al. 2003]. In this work,

methodologies were developed for the forewarning of machine failures in critical equipment in nextgeneration nuclear power plants. New nonlinear methods were developed and applied successfully to

extract forewarning trends from process-indicative, time-serial data for timely, condition-based

maintenance. The approach used was a multitiered, model-independent, and data-driven analysis that

used an ORNL-developed nonlinear method to perform the extraction of the requisite information from

the data. The first tier of the analysis provides a robust choice for the process-indicative data. The

second tier rejects data of inadequate quality. The third tier removes signal artifacts that would otherwise

confound the analysis, while retaining the relevant nonlinear dynamics. The fourth tier converts artifact.

filtered time-serial data into a geometric representation that is then transformed to a discrete distribution

function (DF). This method allows for noisy, finite-length datasets. The fifth tier obtains dissimilarity

measures (DM) between the nominal-state DF and subsequent test-state DFs. Forewarning of a machine

failure is indicated by several successive occurrences of the DM above a threshold, or by a statistically

significant trend in the DM. This paradigm yields robust nonlinear signatures of degradation and its

progression, allowing earlier and more accurate detection of a machine failure.

2.5.4 Control Loop Performance Monitoring

In the past 10 years, controller performance assessment has become an active research area in the process

industry, and several commercial software packages are available [Harris 1999]. The embedded

algorithms in these programs enable users to obtain accurate controller quality metrics without

performing plant tests and to monitor all the aspects of control loops. The principle of the algorithms is to

compare the predefined metrics calculated from the historic data with some standards characterizing the

best possible control performance. The control loop performance assessment also enables identification

of the root causes of poor controller performance. For example, the phase shift in the process 110 cross

correlation plot can be examined to differentiate whether an oscillation is due to valve stiction or

improper controller tuning. For digital control systems with fast sampling speeds, the control loop

performance assessment algorithms can be easily implemented. The demonstration research needs to be

an intagral part of advanced I&C development for nuclear power plants and deserves monitoring in the

near term.

23
2.5.5 Vision-Based Diagnostics

Currently, machine vision diagnostic techniques, especially IR imaging, have been widely used in

monitoring bearings, misaligned motor shafts, bad couplings, heat exchangers, steam traps, pumps, etc.

The thermal patterns that arise prior to catastrophic failure can be continuously monitored to prevent

sudden equipment failure and localize the problem. Figure 2.6 is a thermal scan on a mechanical

component showing a bad bearing on a shaft of an electrical motor. This nonintrusive diagnostic

technique allows impending failures to be detected and replacements made during scheduled outages.

Overheated bearing

Fig. 2.6. Thermal scan of a mechanical component showing a had

hearing on a shaft of an electrical motor [ATV 20011.

2.5.6 Laser-Based Alignment Monitoring

On-line monitoring of the shaft alignment of rotating machines is very important in reducing the vibration

and extending the lifetime of machines in nuclear power plants. The most primitive approach is to rely on

theoretical calculations of the thermal expansion so that operators can compensate for the positional

change from a cold condition to nominal operation. Other methods such as using well-designed support

arms with dial indicators, eddy current pickups, or linear variable displacement transformers have been

used to monitor positional change in real time. However, these methods are susceptible to inappropriate

operator interpretation. Laser technology enables measurement of the relative movement between two

laser transducers across long distances with very high resolution. The Permalign system has been

mounted to a Westinghouse 23,700-HP turbine coupled to a Pacific Dresser pump operated at 45,000 psi.

It is reported that the vibration level was reduced by up to one-half after the laser alignment system was

used [Perry 2001 ]. The development of laser shaft alignment for on-line machine monitoring still needs

to address several other issues, such as the insensitivity of the laser transducer to adjacent vibrations and

thermal disturbances. Because this technique can provide a preventive maintenance strategy for rotation

machinery in nuclear power plants, it warrants long-term monitoring.

24

CQO¶/LI-
2.6 Control and Decision

2.6.1 Data Acquisition and Control in Industrial Plants

Methods for data acquisition and control have evolved during the past 40 years, and competition among

companies has led to several variations in implementation. Digital data acquisition and control was

implemented during the 1960s through integration software with analog-to-digital converters (ADCs) and

digital-to-analog converters (DACs). To communicate directly with ADC and DAC boards, assembly

language coding was written, and selected sections of coding were executed based on receipt of

interrupts. It was generally necessary to turn off all interrupts during the processing of computational

routines and to turn them on when the processing was complete. Interrupts could be clock- or eventdriven. This was the general protocol followed in programming data acquisition and control for the

NERVA project during the 1960s and early 1970s.

The development of systems for data acquisition and control today is accomplished through the use of

much higher-level computer software and programming languages. Data transfer rates continue to

increase, as do communication protocols from various major commercial companies that provide

hardware and software for data acquisition and control systems.

Kirman [2004] provides a good overview of a number of data acquisition and control system

architectures. He emphasizes in his presentation that data acquisition and control systems must fit the

system and not vice versa. Figure 2.7 shows the classical centralized control system architecture, in

which the central computer monitors and forwards commands to PLCs. Figure 2.8 shows a decentralized

system, in which all controllers can communicate as peers (without going through a central master),

restricted only by throughput and modularity considerations. Figure 2.9 shows a PLC-based process

control system for a generic industrial plant. In general, start-up sequencing of simple equipment that

invokes discrete (binary) steps is well accomplished by PLCs; however, complex machinery, which may

have the possibility of multiple start-up paths depending on internal and external conditions, operates

beyond the fixed programming of PLCs. A modern, process control system for (both nuclear and

nonnuclear) power plants is exemplified by the TELEPERM XP [TELEPERM (4)], as shown in Fig.

2.10. The TELEPERM XP is designed for new plants as well as for retrofits during which the old plant

I&C is largely replaced! The TELEPERM XP is an example of a hierarchical architecture of a

distributed control system.

Distributed systems are typically organized in hierarchies in order to reduce cognition, communication,

and control complexity, as well as to enhance scalability. The TELEPERM XP consists of the following:

subsystems.

* The AS 620 Automation System. This subsystem collects measured values and statuses from the

process, carries out open- and closed-loop control functions and passes the resulting commands

to the process.

* The OM 650 Process Control and Management System. This is the human-machine interface

(HMI) and is the operating and monitoring window to the process.

* The ES 680 Engineering System. This is used for the configuration of subsystems. These

include all plant-specific automation, process control and process information software

functions, communication between subsystems and entire control system hardware.

g The TELEPERM ME is designed for retrofitting an existing plant (e.g., expanding the control room or replacing

obsolete control systems and, primarily, to modernize the user interface in the control room).

25
* The DS 670 Diagnostics System. This subsystem is used to perform detailed system status

evaluation and system analysis by providing informational and diagnostic functions. Information

on faulty components and all I&C faulty alarms can be provided on this diagnostics subsystem.

* The CT 670 Commissioning Tool. This is used for commissioning and maintenance tasks. The

CT 675 software is accessed using a Windows-compatible PC.

* The SIMATIC NET Industrial Ethernet Bus System. Communication between the I&C system

components AS 620, OM 650, ES 680 and DS 670 systems are carried out via this plant bus.

Central computer

(Mainframe)

IGroup control,

(PLC)I

I Group control

I ;:0(PLC)

:Group control

(PLC)

I I

Sensors and actuators Sensors and actuators Sensors and actuators

P L A N T

Fig. 2.7. Generic classical centralized control system architecture.

26

C~05..
Fig. 2.8. Generic decentralized control system.

Fig. 2.9. Buses and processors in a generic industrial plant.

27
IDS G70 I

0:=L: I A:i _=s _' , 8~stem

I II

r SIMATIC MET indistrial eth-n bus system

i__ .Ing

LoLL_ _

Fig. 2.10. TELEPERM XP subsystems.

2.6.2 Supervisory Control System

The main function of a supervisory control system is to manage all monitoring and operational tasks,

placing top priority on reliability. Recent supervisory models offer advanced maintenance functions and

greater cost efficiency. Figure 2.1 1 presents a schematic of a supervisory control system. Hitachi has

developed advanced digital and electronic technologies to improve supervisory capabilities in nuclear

power plants while maintaining reliability. Hitachi's totally digital system NUCAMM-90 (Nuclear

Power Plant Control Complex with Advanced Man-Machine Interface 90), providing centralized and

supervisory control systems for advanced boiling water reactors (ABWRs), has made possible the

application of such technologies to supervision and operation from the viewpoint of improving

performance and reliability [Takehiko 2001].

McHaOE h mer

MB: -f e ild

Fig. 2.11. General-purpose and open network technologies can be used to

configure a compact, human-friendly supervisory control system.

2.6.3 Intelligent Agent-Based Control

The Infotility Company has recently conducted a U.S. Department of Energy (DOE) research project to

develop intelligent software components that run at distributed locations on the energy network to

28

C(l7
improve the reliability, efficiency, security, and stability of the U. S. electrical transmission and

distribution network (Cohen 2003). This design uses intelligent agents on the power delivery

infrastructure to support multiple operational criteria and a coordination and grid protection scheme. The

first phase of the project, begun in September 2003, established a detailed software development plan iE

April 2004. The second phase of the project, still under way, will create a commercialized version of the

software and conduct proof-of-concept testing in a real-world environment with actual distributed energy

resources (DER) devices connected to a major U. S. electrical system. The project, if successful, may

have a significant impact on the operation of nuclear power plants. For instance, an energy company wi th

multiple plants in one region may be able to allocate its energy output to the national electric grid on a

flexible schedule.

2.6.4 NonMathematical Flow Methods

A multilevel flow model (MFM) is able to incorporate a deep model structure of means and ends and a

quantitative representation of goals and functions, while an expert system and fuzzy logic cannot perfonn

this task. On the other hand, MFM uses discrete and more abstract representation, more appropriate for

plant-wide reasoning and higher-level decision making than for statistical and control theory methods.

The first MFM model of the main systems of nuclear power plants was developed by Ingstrom based on a

nuclear simulator facility at the Nuclear Training and Safety Center (KSU), Studsvik, Sweden, in 1998

and demonstrated in 2000 [Larsson 1998]. However, MFM modeling is still costly to develop and subject

to error. Because the use of computerized emergency operation procedures is a trend to avoid human

error!. the research needs to be monitored in the long term.

2.7 Human-System Interface

2.7.1 Control and Monitoring Systems

To address the key issues of implementing advanced technology and reliability, Hitachi has developed a

client-server architecture to realize efficient plant monitoring and operating functions. The system was

installed to control radioactive waste treatment equipment at Tohoku Electric Power Company, Inc.,

Onagawa Nuclear Power Plant No. 3. Hitachi's NUCAMM-90 employs the latest technology to achieve

plant supervision [Takehiko 2001]. The interface continuously monitors the plant because most of the

operation is done automatically (sequential control). To further enable a clear understanding of plant

operations, operators are provided with system diagrams, trend graphs, and alarm status. The highly

reliable NUCAMM-90 was applied to a control network that links all controllers and HMI servers, and

sufficient responsiveness and reliability were obtained through the architecture and the use of a highspeed duplex optical fiber loop network. The system's remote terminal block (RTB), a direct-cableconnected process 1/0 device, has analog signal conversion functions, an internal low-power circuit, and

separate high-power process signals. Thus, it does not require a buffer circuit. It contains a circuit that

can directly interface, for example, the air-operated valves that make up the most of the device's control

equipment, enabling the amount of internal wiring to be greatly reduced and the number of control panel

indicators to be halved.

Figure 2.12 shows an example of a control and monitoring system with a good HMI. By clicking with the

mouse on any control equipment device (pump, valve, etc.) at the top of the system diagram, the operator

obtains (in a pop-up display) an operation switch window modeled after an actual hard switch. Multiple

displays can be shown with this switch window. In addition, trend graphs can be displayed on the same

screen, enabling operations such as valve opening or closing to be performed while monitoring the tank

level.

29
2.7.2 Software Agent-Based Operational Support System

Agent-based systems continue to receive considerable attention. Operators/users can delegate to a society

of software agents tasks that are either too time-consuming or mundane to perform themselves or that

cannot be accomplished by humans in the available time frame. An agent may be defined as a component

of software and/or hardware that is capable of acting exactingly in order to accomplish tasks on behalf of

its user. The characteristics of an agent include such attributes as autonomy, learning, and cooperation.

Agents may also possess an internal symbolic, reasoning model, and they engage in planning and

negotiation in order to achieve coordination with other agents.

One application of software agents in the power plant environment is in the area of security. In the

ongoing research to boost the security of nuclear installations, scientists at ORNL have developed special

software popularly called "special agents" [SpaceDaily 2004] that work 24/ to uncover threats to

national security. Special agents are intelligent software programs that scan the Internet, satellite images,

and massive amounts of electronic information for anything that hints of a plot. By using computers to

gather data and reduce the information to what is relevant, the intelligence community can concentrate on

analyzing just the meaningful information. Such software agents can definitely play a crucial role in

homeland security and should be considered for long-term deployment in power plant security.

2.7.3 Virtual Collaborators

The ongoing research in the development of a virtual collaborator (VC) [Ishii 1999] has resulted in a

prototype VC developed at Kyoto University that can behave just like a power plant operator in a nuclear

power plant (see Fig. 2.13). At present, the VC can detect an anomaly, diagnose the root cause, and

operate the control panel according to the operation manual in virtual space, where the control room of

the nuclear plant is visualized. The prototype is a distributed simulation system that comprises of four

subsystems:

* a nuclear power plant simulator,

* a man-machine interface simulator,

• a human model simulator, and

* a human body motion simulator.

Researchers are now focusing on developing the functions to estimate human internal states and

communicate with real people in the next phase of research.

30
S;XAAd- * - ._.ct- n

2 _

Fig. 2.12. Example of control and monitoring system with human-system interface.

Fig. 2.13. System architecture of a virtual collaborator.

31
2.7.4 Biometrics

Biometrics is widely used as a very reliable technology for security. Iris scanning has already been

implemented in Heathrow Airport at London (see Fig. 2.14). The United States, too, began using

biometrics at its airports and seaports in January 2004. Under the new US-VISIT program [Ross 2004],

all foreigners entering on visas will have their hands and faces digitally scanned. American citizens will

also be affected, as new passports with a chip that contains biometric data are scheduled to be issued in

2005.

Fig. 2.14. Iris scanning at Heathrow Airport, London.

In California, a retired employee association has employed biometrics to secure software-based assets.

Novell and Identix, Inc., have installed fingerprint scanning to replace computer passwords [Emigh

2003]. This eliminated the need for the staff to change passwords every month. The fingerprint reader

was also cost-effective-a mere $150. Such low-cost systems can be adapted for security purposes in

highly secure nuclear installations.

2.7.5 Automated Visual Surveillance for Facility Monitoring

For decades, surveillance through closed-circuit TV has been popular, but the problem is always too

many cameras and too few personnel to monitor them. In the current global climate where guaranteeing

security to high-risk buildings and nuclear facilities is a requirement, automated visual surveillance

(AVS) may be a good solution. An AVS monitors an area, takes video, and then takes appropriate action.

Because surveillance systems are generally domain-specific, the best test of the system is in the

environment in which it is to be used; however, such testing is not always possible. Quantitative testing

has been performed using receiver operating characteristics (ROC) curves [Dicks 2003] with varying

parameters on a single test bed. Surveillance particularly benefits from a standard set of test data using a

database like performance evaluation of tracking surveillance (PETS). The test sequence provided for

PETS2000 [Dicks 2003] represents a suitable test bed because it contains different moving objects and

thus confronts the system with the challenge of tracking a specifically selected object in the presence of

other objects that are moving across the entire image frame and are even intersecting with the trajectories

of other objects in the sequence.

Advances in AVS systems will enhance deployment in nuclear power plants. An example is face

recognition at access control points. If coupled with additional access controls (e.g., palm or iris

scanning, coded badges, or keypads), AVS can be used to replace security personnel at some access

32
poin-:s. Video-based face recognition can be used in conjunction with other personnel tracking

mechanisms, such as radio-tagged badges, to enhance security in nuclear power plants.

2.7.6 Virtual Reality

According to EPRI, large-scale, cost-competitive advanced nuclear power plants calls for stabilization of

atmospheric greenhouse gas concentrations. Also, during the capital investment recovery period,

cons ruction costs for advanced nuclear reactors must be reduced for them to compete economically with

other sources of energy. EPRI has collaborated with Westinghouse to develop advanced construction

visualization tools for the first 9 months of construction of the AP600 plant [EPRI 2003]. This is one of

the three advanced light water nuclear reactor (ALWR) designs certified by NRC for further deployment.

The benefits of using virtual reality include

• optimization of construction sequencing and labor deployment,

• verification of accurate and achievable construction schedules,

* identification and elimination of problems before they are encountered, and

* preparation and training of the workforce.

2.8 High-Integrity Software

2.8.1 Software Development Technologies, Methodologies, and Tools

The term "high integrity" implies a specific characteristic of the software in terms of reliability or

dependability that requires that the software must be developed using special techniques. The safety

requirements of military, aerospace, and transportation applications, due to the consequences of software

failure, continue to drive development of ever-increasing levels of quality and reliability for software. In

general, however, advances in software engineering have not kept pace with hardware. While there are

several system development life cycle (SDLC) methodologies available, the basic processes remain

similar. The SDLC is a conceptual model that describes the stages involved in an information system

development project, from an initial feasibility study through maintenance of the completed application.

Various SDLC methodologies have been developed to guide the processes involved, including the

waterfall model (which was the original SDLC method); rapid application development (RAD); joint

application development (JAD); the fountain model; the spiral model; build and fix; and synchronize and

stabilize. Several models may be combined into a hybrid methodology such as the rational unified

process (RUP) which is currently widely used. Documentation is crucial regardless of the type of model

chosen or devised for any application, and it is usually done in parallel with the development process.

Some: methods work better for specific types of projects, but in the final analysis, the most important

factor for the success of a project may be how closely the particular plan was followed.

In general, an SDLC methodology follows the following steps:

1 . The existing system is evaluated. Deficiencies are identified. This can be done by interviewing

users of the system and consulting with support personnel.

2. The new system requirements are defined. In particular, the deficiencies in the existing system

must be addressed with specific proposals for improvement.

3. The proposed system is designed. Plans are laid out concerning the physical construction,

hardware, operating systems, programming, communications, and security issues.

33
4. The new system is developed. The new components and programs must be obtained and

installed. Users of the system must be trained in its use, and all aspects of performance must be

tested. If necessary, adjustments must be made at this stage.

5. The system is put into use. This can be done in various ways. The new system can be phased in,

according to application or location, and the old system gradually replaced. In some cases, it may

be more cost-effective to shut down the old system and implement the new system all at once.

6. The system should be exhaustively evaluated after it is up and running for a while. Maintenance

must be kept up rigorously at all times. Users of the system should be kept up-to-date concerning

the latest modifications and procedures.

Waterfall Model

The waterfall model is a popular version of the SDLC model for software engineering. Often considered

the classic approach to the SDLC, the waterfall model describes a development method that is linear and

sequential. Waterfall development has distinct goals for each phase of development. Imagine a waterfall

on the cliff of a steep mountain. After the water has flowed over the edge of the cliff and has begun its

journey down the side of the mountain, it cannot turn back. It is the same with waterfall development.

After a phase of development is completed, the development proceeds to the next phase, and there is no

turning back.

The advantage of waterfall development is that it allows for departmentalization and managerial control.

A schedule can be set with deadlines for each stage of development, and a product can proceed through

the development process like a car in a carwash, and theoretically, be delivered on time. Development

moves from concept, through design, implementation, testing, installation, troubleshooting, and ends with

operation and maintenance. Each phase of development proceeds in strict order without any overlapping

or iterative steps.

The disadvantage of waterfall development is that it does not allow for much reflection or revision. After

an application is in the testing stage, it is very difficult to go back and change something that was not well

thought out in the concept stage.

Spiral Model

The spiral model, also known as the spiral lifecycle model, is a systems development method (SDM) used

in information technology (IT). This model of development combines the features of the prototyping

model and the waterfall model. The spiral model is favored for large, expensive, and complicated

projects.

The steps in the spiral model can be generalized as follows:

I. The new system requirements are defined in as much detail as possible. This usually involves

interviewing a number of users, representing all the external or internal users and other aspects

of the existing system.

2. A preliminary design is created for the new system.

3. A first prototype of the new system is constructed from the preliminary design. This is usually

a scaled-down system and represents an approximation of the characteristics of the final

product.

34
4. A second prototype is evolved by a fourfold procedure: (I) evaluating the first prototype in

terms of its strengths, weaknesses, and risks; (2) defining the requirements of the second

prototype; (3) planning and designing the second prototype; (4) constructing and testing the

second prototype.

5. At the customer's option, the entire project can be aborted if the risk is deemed too great. Risk

factors might involve development cost overruns, operating-cost miscalculation, or any other

factor that could, in the customer's judgment, result in a less-than-satisfactory final product.

6. The existing prototype is evaluated in the same manner as was the previous prototype, and, if

necessary, another prototype is developed from it according to the fourfold procedure outlined

above.

7. The preceding steps are iterated until the customer is satisfied that the refined prototype

represents the final product desired.

8. The final system is constructed, based on the refined prototype.

9. The final system is thoroughly evaluated and tested. Routine maintenance is carried out on a

continuing basis to prevent large-scale failures and to minimize downtime.

Rational Unified Process

The rational unified process [RUP 2001] is currently one of the most popular SDLC methodologies. It is

a hybrid model utilizing features of the waterfall, spiral, and rapid application development models. The

unified process has four basic principles: (1) the software should stress use cases (which show how it

interacts with users), (2) the process is architecture centric, (3) it is iterative, and (4) it is incremental. It

uses :,ix industry-recognized best practices for software development:

1. Develop software iteratively

2. Manage requirements

3. Use component-based architectures

4. Visually model software

5. Verify software quality

6. Control changes to software

The methodology is used to apply these principles and practices to the software development process,

which involves everything from gathering system requirements to analysis, design, implementation, and

testing. The documentation is developed as a model of the system using the industry standard unified

modeling language (UML).

The UML document types (like use cases, class diagrams, and state transition diagrams) are then

connected with various models used throughout the software development process.

Formal Methods

Improvements in formal methods - mathematically-based techniques with the goal of ensuring that

complex hardware and software designs and protocols behave correctly for all possible behaviors -

continue to be the focus of research in software engineering. They include formal specification

languages, model checkers, theorem provers, as well as development of domain-specific logical theories

and proof techniques relevant to high-performance hardware systems.

35
To a large extent, the high-level architectures of hardware and software systems are described as a

mixture of informal English text and diagrams. It is common for such descriptions to be longer than the

code itself, and for ambiguities and misinterpretations to creep in. These specifi cation errors often result

in subtle design defects, especially when the implementer and the specifier are different people. Formal

specification languages are an alternative to English. Such languages are akin to programming languages,

except at a higher level of abstraction. They can be used to specify how architecture is required to

behave, as well as high-level design decisions. These attributes allow architectures to be described

unambiguously, and yet are often an order of magnitude more concise than the corresponding English.

While it is possible to construct pencil-and-paper proofs that a design satisfies its specification, model

checkers provide the ability to automate correctness reasoning-the ability to check whether a design is

correct and to report meaningful diagnostics when a specification is violated.

Considerable progress has been made over the past 15 years in increasing the state space capacity of

model checkers, to the point that specifications containing hundreds of state variables can often be

verified automatically in a few hours. However, realistic designs often contain thousands or millions of

state variables, far exceeding the reach of current model checking algorithms. Another class of

verification tools called theorem provers can be used to overcome the capacity limitations of model

checking. A theorem prover does not search the state space of a specification directly, but instead

searches through the space of correctness proofs that a specification satisfies a given correctness property.

In general, model checking and theorem proving are complementary technologies and should be

integrated to successfully tackle realistic system designs.

2.8.2 Object-Oriented Language: Real-Time Java

Aonix Company announced its plans for delivering safety- and mission-critical JavaTM technologies to its

mainstream markets on March 29, 2004. The first generation of the safety-critical Java product Jraven

built on the strong foundation of the Aonix SmartKernel, a memory and time-partitioned kernel designed

to provide safety and security protection. Jraven has already proven its success in a number of

commercial deployments. The new-generation product JRTKTh will offer increased generality and

flexibility in the software and greater ease of use to be efficiently integrated into the industrial missioncritical soft-real-time virtual machine [Aonix 2004]. The influence of the product on developing digital

control of safety system in nuclear power plants needs to be monitored.

36
3. DETAILED INVESTIGATION OF ADVANCED SENSORS

Sensors and sensor systems were identified in Chapter 2 as a technology focus area that deserves more

attention in the near term because of the following characteristics: (1) they are likely to have the greatest safety impact because they have a direct bearing on operating and protection margins; (2) many new

designs have the likelihood of maturing into commercial products ready for deployment in power plants in the near term; and (3) some of the most significant advances in the technology focus areas are in the

area of sensors. Thus, this chapter is devoted to a more detailed treatment of sensors and sensor systems.

3.1 Silicon Carbide Flux Monitor

3.1.1 Basic Principles of the Technology

In the basic detector, an n-epitaxial silicon carbide layer of 3-100 pim is grown on top of a silicon carbide

substrate (300 gum) as shown in Fig. 3.1. When a negative reverse bias is applied to the Schottky contact,

the n-epitaxial layer becomes depleted of charge carriers. When an ionizing particle passes through this

depleted layer, the charge produced is collected under the influence of the reverse bias and, with proper pulse-shaping electronics, detected as a current pulse. By depositing a layer of neutron-sensitive material

(e.g., 6LiF), as shown in Fig. 3.2, incident neutrons are converted to charged particles [e.g., Li(n, a)3H]. Both thermal and epithermal neutrons can be detected using the neutron-to-charged particle conversion

technique.

SclcAttky Contact\

Epitaxia SiC Layep 3 - 100,jm

sIC ConductigSubsrae

(-1 Os Nitogen atoms per cmrh 300ptm

Back Ohmic Contact/

2i0-pm to 6-mm diameter

Fig. 3.1. Silicon carbide Schottky diode radiation detector.

37

0c6l~
6LiF converter layer

Fig. 3.2. Detection of neutrons via charged particle production

by the 6Li(n, a) reaction in a converter foil.

3.1.2 Maturity of the Technology

To date, neutron response calibrations have been performed for miniature SiC semiconductor detectors

based on a Schottky diode design in neutron fields maintained at NIST [Dulloo 2003, Ruddy 2004]. The

neutron response was calibrated at fluence rates from 1.76 x 104 to 3.59 x 10'0 /cm2 /s in NIST neutron

fields. The maximum deviation from linearity of the fit of the neutron response of the SiC detectors to the

NIST-measured fluence rates is much less than 5%, which is the estimated uncertainty in the measured

fluence rates. A direct comparison of the SiC count rates to count rates obtained with a NIST double

fission chamber over limited ranges where the detector positions and configurations remain unchanged

shows a relative precision of ±0.6%. In a separate set of calibrations, a SiC neutron detector that had been

previously irradiated with a fast (E>1 MeV) neutron fluence of 1.3 x 1016 cmr2 was found to have an

absolute neutron fluence rate response that was indistinguishable from that of a previously unirradiated

detector.

Neutron sensitivity for this type of detector was found to be 1 .3e °

3 cps/cm2/nv/micron LiF. The LiF

enrichment corresponding to this sensitivity is 90%. The neutron sensitivity is proportional to LiF

thickness up to about 10 pm. For higher thickness values, the sensitivity starts to level off and becomes

constant at about 25 ptm.

Prototype SiC ex-core neutron detectors have also been tested under research reactor conditions [Ruddy

2002]. The test results show that the key features, such as the linear pulse-mode operation without

gamma compensation, are comparable to the presently used gas-filled ex-core detectors. It is anticipated

that a wide-range SiC neutron detector can now be designed to replace the combined functions of the

multiple power range detectors in current use.

38

cod

J
3.1.3i Potential Regulatory Impact

Because of its larger band gap compared to conventional semiconductors such as silicon or germanium,

SiC :radiation detectors are not as susceptible to thermally generated noise and are capable of operation at

high temperatures. These detectors have also been shown to be much more resistant to detrimental

radiation effects (from gamma rays, neutrons, or charged particles) than silicon or germanium detectors.

They are reported to operate well in fast neutron fluences up to I1'' n/cm2 (E,>l MeV)] as well as high

temperatures up to 8000C. These detectors are capable of monitoring thermal, epithermal, and fast

neutron fluences, and offer the potential of combining the functions of current three-range flux

monitoring into a single system. In addition, the detectors have a highly linear response as a function of

gamma-ray dose rate. Furthermore, the neutron response can be completely separated on the basis of

pulse height from the gamma-ray response. Therefore, gamma dose rate and thermal or epithermal

neution fluence rate can be measured simultaneously with a single detector. It is likely that a wide-range

silicon carbide neutron detector can now be designed to replace the combined functions of the multiple

power range detectors in current use. However, data on important parameters such as drift, accuracy,

repeatability, and degradation over time could not be ascertained for this update. It is important that a

combined neutron monitor based on this technology not only exhibits the full dynamic range from startup

to 100% power, but it should also be shown to not degrade over the long term when at 100% power. The

improved operating and safety margins that such detectors will provide, should they also meet all the

critetia mentioned above, certainly warrant continued monitoring of progress in their development.

3.2 Solid-State Neutron Flux Monitor

3.2.1 Basic Principles of the Technology

The solid-state flux monitor (SSFM) is being developed at ORNL as part of an International Nuclear

Energy Research Initiative (INERI) project sponsored by DOE and the Korean Ministry of Science and

Technology [Wood 2003]. The monitor is based on the flux-induced change in electrical resistance of an

AIN solid with evaporated metal contacts. The detector functions by intercepting a small fraction of

incident neutrons in the '

4N(n, p)'4C reaction.

The i n-core version of the SSFM is based on a polycrystalline AIN compact with evaporated metal

contacts (see Fig. 3.3). The electrical resistivity of AIN at temperatures of 300 K is typically over 10'4 C!-

cm. Even at 1300 K, AIN remains a very good insulator. The reaction imparts a net kinetic energy to the

energetic daughters of 627 keV. As the energetic daughters slow down in the nitride matrix, they excite

electrons into the conduction band. The excited electrons are free to move under an applied bias,

resulting in a neutron-flux-induced electrical current. The detector is intended to be operated in current

mode, and it will also be sensitive to gamma rays. Thus, the SSFM will be limited to operation in reactor

power-range fluxes. Figure 3.4 shows the current fabrication concept.

3.2.2 Maturity of the Technology

The SSFM has been tested to characterize stability and leakage current at room temperature with no

incident radiation to establish baseline sensor performance and electrical characteristics. Leakage currert

for all samples tested was in the range of 0.3 to 0.4 nanoamperes (nA) [Holcomb 2002]. This is in the

range of conventional neutron detectors, such as miniature fission chambers used in local power range

monitor (LPRM) assemblies used in boiling-water reactors (BWRs). LPRMs often exhibit leakage

current in the range of 0.1 to 0.2 nA, using an integral mineral-insulated cable assembly of about 15-ft in

length. Radiation testing of the sensor, including both mixed neutron-gamma and gamma irradiation at

ambient temperature for extended periods of time, is being performed to fully characterize the SSFM for

inexpensive, in-core flux measurement.

39
Design improvements are required to reduce the leakage current to enable potential deployment of the

device at core temperatures above that of water reactors. The stability of the device also requires further

investigation as device polarization appears to be significant [Holcomb 2005]. In addition, the long-term

survivability of this device under in-core environments has also not been demonstrated.

3.2.3 Potential Regulatory Impact

The SSFM technology is interesting in that it is the first known use of a solid-state resistive type device as

a flux/dose monitor under in-core reactor type environments. Future tests in radiation environments need

to be evaluated relative to the robustness and cost of the SSFM when placed in service in an operating

reactor. In general, commercialization of this device is still several years away, and the technology

should continue to be monitored.

3 Nd

Nitride Crysta!

- - I

Contacts

Fig. 3.3. General concept of solid-state flux monitor [Source: Wood 20031.

Silver Paint Contacts

\ \ A115N

Bias Voltage \

4 \ _

Nideel WinngCeramic Cemn

Evaporated Nickel Contacts

Fig. 3.4. Fabrication concept of the solid-state fuel monitor.

40
3.3 Fuel Mimic Power Monitor (or Constant-Temperature Power Sensor)

3.3.1 Basic Principles of the Technology

The fuel mimic power monitor has been developed and demonstrated through the Nuclear Engineering

Education Research (NEER) program and EPRI funding. The instrument represents a unique sensing

technology in that it provides a direct measurement of the nuclear energy deposited into a fuel mimic

mass [Radcliff 2000]. This constant-temperature power sensor (CTPS) works by controlling a resistive

device in thermal contact with a uranium fuel pellet or fuel analogue. The measure produced by this

system is nuclear power generation rather than a more classic quantity such as neutron flux.

To illustrate the CTPS concept, imagine a fuel pellet in which fission events are occurring with the

temperature at steady state. The pellet will maintain an equilibrium temperature somewhat higher than

the bulk coolant temperature, with the temperature difference dependent on the heat transfer coefficient.

If the heat transfer coefficient is known, it is possible to calculate energy deposition by measuring the

equilibrium temperature difference between fuel and coolant. At steady-state this relationship is

Qdep = Qremoved = UA (Tfi,,l - T,. d* (3. 1)

where

Qremoved= Energy loss by convection to surroundings,

Qdep = Energy deposited (nuclear, electrical, etc.),

UA = Overall heat transfer coefficient,

Tt = Temperature of fissile element,

T = Bulk coolant temperature.

If a resistance-heating element is placed inside this fuel pellet, it is possible to alter the temperature of tle

pellet. By passing a current through this resistance element, heat is deposited that can raise the pellet

temperature well above the equilibrium temperature due only to nuclear heating. The electrically

deposited power can be controlled because the resistance of the heat element is linearly related to

temperature. If UA and Tc,,0i0,remain constant, and the temperature (resistance) of the fuel pellet is

maintained by some control routine, it is possible to use a measurement of the electrical power input as

the inverse measurement of nuclear power input. In this case the nuclear and electrical power deposited

in the pellet are given by the following equation:

Qdep. nuclear + Qdep. electrica = UA (A T) = Constant (3.2)

or

Qdep. nuclear = Constant - Qdep. etrIcal.. (3.3)

In practice, the resistance sensor element can be made part of a Wheatstone bridge for an accurate

measurement of resistance (and therefore electrical power). Figure 3.5 shows a schematic of a CTPS

Wheatstone bridge control circuit [Mills 2004].

41
Heated Element (Re)

Fig. 3.5. Constant-temperature power sensor Wheatstone bridge control circuit.

Figures 3.6 and 3.7 show a cylindrical sensor configuration and a planar sensor configuration,

respectively.

Pt leads

Al 203 cap

U235 core

,,BeO layer

* gSS shell

* , Pt socket

Fig. 3.6. Cylindrical sensor configuration of the CTPS.

Sapphire or A12

03 Alumina Cover

/Uraniam Oxid~e 6\i Pt hae 6Le Pt Pt heater

Alumina

Substrate

0.65rcm

r 0.50cm

Fig. 3.7. Planar sensor configuration of the CTPS.

42

Cut '
3.3.2. Maturity of the Technology

Tests on the first-generation, controlled-calorimetric, in-core instrument prototypes and subsequent

modeling showed three existing problems: (1) lack of proportionality in the relative neutron and photon

response, (2) a relatively low bandwidth due to the non-uniform distribution of nuclear and electrical

energy deposition, and (3) drift due to heat transfer through the sensor power leads. The secondgeneration sensor design forces the temperature gradient into a thin metal axial region, which gives a

uniform energy distribution from all sources and better control of thermal leakage and contact resistances

and improves the prediction with increased bandwidth and better proportionality [Radcliff 2002].

Different configurations (i.e., planar and cylindrical prototypes) of second-generation CTPS have been

tested for linearity, sensitivity, and bandwidth [Mills 2004]. The response of resistance of the CTPS to

temperature was very linear for the planar configuration up to 500CC, with a slope of 0.02250/0C. The

sensitivity was found to be 0.5 mW of CTPS detector power per kilowatt of reactor power, and bandwidth

was Sound to be about 3.5 Hz. A significant problem found with this type of sensor was signal drift, and

future work includes addressing this problem.

3.3.3 Potential Regulatory Impact

This type sensor will have the advantage of providing an accurate and direct measurement of reactor

power. This may provide licensees a basis to, for example, apply for an increase in their licensed

operating power level. A significant problem found with the current version, however, is signal drift. In

fact, comprehensive testing and characterization of the second-generation CTPS design has yet to be

performed. Commercialization of the technology is still a few years away and should be monitored over

the long term.

3.4 Johnson Noise Thermometry

3.4.1 Basic Principles of the Technology

The components of a Johnson noise thermometer are shown in Fig. 3.8. JNT is based on the noise voltage

associated with a resistor at some temperature T(Nyquist's theorem). For frequencies below I MHz and

temperatures above 25 K, the power spectral density FT2 of the noise voltage is given (to an accuracy of

more than 0.0001%) by

V2 =4KTRAfJ (3.4)

where i is Boltzmann's constant, Af is the bandwidth over which the noise is measured, and R is the

resistance of the sensor. Equation 3.4 is the basis for all noise thermometry, although it is generally not

used directly because of several technical difficulties. First, the amplifier gain needs to be both known

and soable. Second, the amplifier passband and filtering effects of connection cabling must be known to

within the required measurement accuracy. Finally, the resistance of the sensor must be independently

and accurately measured. Early Johnson noise thermometers worked around these difficulties by

performing a ratio of two noise voltage measurements. One noise voltage measurement was made with a

resistor at the unknown temperature, and the other with a resistor at a reference temperature, switched

onto a single amplifier channel. The unknown temperature T is then given by

T=T '(3R()5)

43
where it is assumed that the bandwidth is constant. Equation 3.5 shows that a noise thermometer is

absolute, i.e., a primary thermometer. The problem with the method, however, is that changing the

connection of the sensor to the high-gain measurement circuit introduced noise and decreased reliability

[Garrison 1949, Kisner 2005].

Preamplifier , ~Transmission L~ine

IBatt=as Detector Intc.gmrtor

Sensor t7Filltr

Fig. 3.8. Basic components of a Johnson noise thermometer.

One alternative approach being investigated by ORNL to minimize the difficulties in previous designs

follows the work of Pepper and Brown [Pepper 1979], in which a resistive sensor is connected in series

with an inductor and a capacitor forming a tuned circuit. In this approach, the ideal mean squared noise

voltage is given by

fokB T f S,,(f)df= S= 4k2 TR (3.6) 2Q C 36

where S, is the spectral density, fo is the resonant frequency, Q is the resonance quality factor, and C is the

capacitance of the capacitor. A significant advantage of this measurement technique is that for lossless

inductors and capacitors (if the measurement bandwidth is greater than the tuned circuit bandpass), the

measured voltage output is independent of the sensor resistance and the inductance. In practice, however,

there are losses associated with real inductors, and this limits the overall accuracy obtainable with a tuned

circuit implementation of Johnson noise thermometry.

One disadvantage with Johnson noise thermometry is the relatively long response time because of the

long integration time required to make a temperature measurement. In particular, because of the

statistical nature of the voltage measurement, there is uncertainty in the solution, which is progressively

decreased by increasing the integration time of the measurement. To overcome this problem, another

approach to Johnson noise thermometer design has been developed at ORNL [Kisner 2005] in

collaboration with the Korean Atomic Energy Research Institute (KAERI), through an INERI program.

As shown in Fig. 3.9a, Kisner et al.'s implementation first measures the actual resistance value of the

RTD, using a resistance-to-temperature transfer to compute the temperature as is conventionally done for

reading an RTD's temperature. This temperature readout has a fast response time, and overcomes the

comparatively slow response of the Johnson-noise-derived temperature value, due to the statistical

processes from which the value is calculated. The transfer function of the RTD, however, drifts over time

requiring periodic recalibration. The nondrifting Johnson noise temperature is used to periodically

recalibrate the RTD resistance to temperature-transfer function. Thus, the temperature measurement in

this dual-mode thermometer is made as a simple resistance measurement whose resistance to temperature

conversion is quasi continuously updated using Johnson noise.

44
In the measurement of the Johnson noise temperature (performed in the box marked "Measure Johnson

Noise" in Fig. 3.9), the concept of cross correlation is used. In this concept, the measured noise voltage

from one amplifier channel is Fourier-transformed and correlated with that from the other channel to form

a cross power spectral density (CPSD) that effectively eliminates the noise contribution from the

amplifier electronics. This is shown in Fig. 3.10. The figure shows the power spectral density (PSD)

function of each amplifier channel containing both correlated and uncorrelated noise and the CPSD

function from both amplifiers containing only correlated noise. The CPSD function has units of volts

squared per hertz and expresses the voltage-squared content per unit frequency of the measured voltage

signal. CPSD provides mean square noise voltage, and the resistance is independently measured. The

amplifier gain as a function of frequency and frequency bandwidth is required to obtain temperature from

the voltage measurements. The technique used to obtain gain bandwidth product is to initially calibrate

the measurement using a known temperature and treat both properties as a single constant.

RM TrvThour F0ry

UeFast

Joh~nsoni slow

I~ TempValue

Fig. 3.9. Schematic for automatic recalibration of RTD from Johnson noise measurement

[Source: Kisner 20051.

V 2

PSSD 1

ff

a"tr (K T 

Fig. 3.10. Illustrating the relationship between the PSDs of the individual channel

voltages and the CPSD between them.

45
3.4.2 Maturity of the Technology

Some of the more significant problems that have hampered commercial utilization are (1) relatively long

response time because of the long integration time required to make a temperature measurement and (2)

sensitivity to electromagnetic noise and complexity of implementation (i.e., the need for skilled

operators). Kisner et al.'s [2005] implementation addresses this dual-mode thermometer problem by

making the temperature measurement as a simple resistance measurement whose resistance to

temperature conversion is quasi continuously updated using Johnson noise. The second problem has also

been addressed by the implementation by NIST, in which DSP methods are used to quantitatively

evaluate the magnitude of any periodic interference in the noise spectrum and subtract it from the signal,

thus minimizing the interference effect as much as possible. The JNT system at NIST utilizes FFT crosscorrelation noise power spectra with l-Hz resolution and periodic interference are readily distinguished

from the thermal noise or reference system pseudo-noise. Kisner et al. [2003] also address

electromagnetic interference issues using the following methods:

* shielding the sensitive element from electromagnetic noise by placing the RTD in a stainless steel

sheath coated on the inside with highly conducting metals such as aluminum, copper, or silver;

and

* developing software to remove electromagnetic spikes from the spectrum.

The ORNL scientists plan a demonstration of conductive JNT at a nuclear facility within 2 years. Based

on the review of the state of the art of Johnson noise thermometry, we expect that deployment of Johnson

noise thermometry in nuclear power plants should be possible within the next 3 to 5 years.

3.4.3 Potential Regulatory Impact

Considerable progress has been made to date in JNT to make it a viable technology in the near future for

primary flow-loop temperature measurement. The attraction of JNT is that it is inherently drift free and

insensitive to the material condition of the sensor. As a result of the latter characteristic, a sensor based

on Johnson noise is immune to the contamination and thermo-mechanical response shifts that plague

thermocouples and resistance thermometers. This advantage should improve operating as well as safety

margins in nuclear power plants. The technology should continue to be monitored.

3.5 Magnetic Flowmeter for Primary Coolant Flow Measurement

3.5.1 Basic Principles of the Technology

When a conductor is passed through a magnetic field, a voltage is generated that is proportional to the

velocity of the conductor. This principle is used in the magnetic flowmeter, where the flowing primary

coolant becomes the moving conductor. Physically, a magnetic flowmeter consists of signal-processing

apparatus (the transmitter), magnetic coils, and electrodes (to measure the potential across the coolant).

The magnetic coils and electrodes are typically implemented as part of a short segment of pipe made of

nonmagnetic material that has a nonconductive inner surface containing or pierced by electrodes. Nonwetted, capacitively coupled models are available to allow operation with very low conductivity fluids

such as pure water. The advantages of magnetic flowmeters include high accuracy (±0.25% under ideal

conditions) and linear response. In addition, they are obstructionless (no fouling, no pumping power

consumption) and can be designed to have minimal sensitivity to a flow profile. Also, the capability to

directly measure flow rather than rely on inferring flow from measurement of primary coolant pump

speed could impact operational margins.

46
3.5.2, Maturity of the Technology

This technology has been in use for several years in the process industry and is a mature technology.

However, the radiation sensitivity of the nonconductive inner pipe liner in magnetic flowmeters is the

major impediment to the application of the magnetic flowmeter to flow measurements in light-water

reactors. Solutions to this problem have been proposed [Wood 2003, ORNL 2003, Holcomb 2003]. In

particular, work under an INERI project [ORNL 2003] involves the application of advanced digital sigral

processing as well as state-of-the-art fabrication technologies for the ceramic liner. To date, work has

focused on the challenges of producing a radiation-resistant liner and evaluating its survivability. A target

lifetime exposure dose of 2.4 x I 08 rads, based on Generation II PWR coolant systems has been

ideni ified, and preliminary radiation test plans for the new magnetic flowmeter liner are being developed.

3.5.3 Potential Regulatory Impact

Improvements in flow measurement accuracy can significantly improve operating margins and over

power occurrencesh For example, on a per-unit basis, errors in feedwater flow measurement have the

greatest impact on the accuracy of thermal power calculations - more than any of the other

measurements necessary to make the heat balance calculations to confirm operation at 100% power.

(Utilities have historically used calculation of heat balance around the reactor vessel or steam generator as

a secondary method to periodically compute reactor thermal power to confirm operation at 100% rated

thermal power). In addition, flow measurements are typically used to demonstrate that safety-related

component performance is adequate to meet the demands indicated by the accident or transient analyses.

Therefore, obtaining accurate flow measurements is important to safety.

Ultrasonic and magnetic flowmeters are theoretically among the most accurate instruments for flow

measurement. However, experience with transit-time flowmeters in some nuclear power plants show that

these instruments may not be as accurate as they are claimed to be [NRC 1995]. This may especially be

true in complex flow situations, such as in a nuclear power plant environment. It is important, therefore,

to pursue further development work on magnetic flowmeters for application in nuclear power plants.

3.6 Fabry-Perot Fiber-Optic Temperature Sensors

3.6.1 Basic Principles of the Technology

Of the many types of fiber-optic temperature sensors, the most sensitive is the interferometric type.

Fiber-optic interferometric techniques are applicable for measuring almost any physical quantity. Since

interferometry yields high-resolution measurements of length, fiber-optic techniques have been developed

where a measurand is converted into a change of displacement. Temperature is one such measurand, and

for high-precision temperature measurements, fiber-optic interferometers are an important alternative.

Fiber-optic versions are available for all the well-known interferometers: Michelson, Fabry-Perot, Sagnac

and, perhaps most common, Mach-Zender.

Interferometric fiber-optic sensors are phase- (or wavelength-) modulated, have high accuracy and

sensitivity, and may be independent of the absolute light intensity transmitted or detected. The basic

principle of the Fabry-Perot fiber-optic temperature sensors idea is simple: send light through two fibers,

a reference fiber and a sensing fiber (Fig. 3.11). As the physical dimensions of the sensing fiber are

changed by the measurand (temperature), there will be a phase difference between the light travelling

h Overpower events are periods during which plants are operated above their licensed power level.

47
through the two fibers. The phase difference can be measured by "counting fringes," transformed into a

physical dimension change which, in turn, gives information about the measurand.

'Cu er.

Power o't.

Reference

Fig. 3.11. Schematic diagram of a dual fiber-optic Fabry-Perot temperature sensor.

The sensor uses two Fabry-Perot interferometers (FPI), one for sensing and one for reference. Similar

sensors using other types of interferometers also exist. Light from the light-emitting diode (LED) is

modulated by reflection, first by the sensing FPI and then by the reference FPI. It can be shown that the

power output is proportional to I + 0.5 cos(Aqp), where AOp is the phase shift due to the perturbation

applied to the sensor interferometer. Measurements show that the phase shift is linearly dependent on

temperature in a range of 26 to 1080C.

Although the sensitivity obtained with this dual FPI sensor is somewhat less than that of a single FPI

sensor using a laser source, excellent performance is still possible: sensitivity of the order of 0.0002

degrees is calculated at the maximum sensitivity point.

3.6.2 Maturity of the Technology

Fiber-optic sensors in some form have been commercially available for the process industry since the

1980s. Systems with improved sensitivities, such as the Fabry-Perot type discussed above, have been

available since the 1990s.

The performance of two Fiso Fabry-Perot fiber-optic temperature sensors have been evaluated for

potential application in nuclear power plants [Hanying 2003]. This type of sensor employs a Fizeau

interferometer and a charge-coupled device (CCD) array to locate the position of the maximum

interference fringe intensity, which is directly related to the environmental temperature. Consequently,

the basic sensing mechanism is independent of the absolute transmitted light intensity, which is the

parameter most likely to be affected by external harsh environments such as nuclear irradiation, high

pressure or temperature, and cyclical vibration.

The first sensor exhibited no failure or degradation in performance during and following gamma-only

irradiation in which a total dose of 1500 krad (15 kGy) was delivered at a dose rate of 250 krad/h

(2.5 kGy/h). However, intermittent behavior was observed throughout the latter portions of subsequent

tests performed in a thermohydraulic environment in accordance to IEEE Std. 323-1983 [IEEE Std. 1983]

procedures. Degradation in performance occurred after the test. Visual evaluation after opening the

sensor head indicated that the method used in internal welding was the primary contributor to the

observed behavior during this test. Further consultation with the vendor showed that the robustness and

reliability of Fiso sensors can be substantially improved by modifying the internal welding methods.

48
The second Fiso temperature sensor was tested in a mixed neutron/gamma environment in which the total

neutron fluence was 2.6 x 1016 neutrons/cm2 and the total gamma dose was 1.09 x 1 0 rads. During the

initial calibration following completion of the test, the sensor exhibited a fixed temperature offset of

18.93C (34 0F) but responded linearly to change in temperature. Annealing was observed as the

temperature increased, which reduced the offset by -63%. This observed phenomenon was very valuable

in subsequent model building for on-line maintenance and calibration of the Fiso temperature sensor in a

mixed neutron/gamma irradiation field. Conclusions from these tests are that if the observed shifts can be

compensated for in an on-line sensing or calibration model of the Fiso sensor, then this type of fiber-op tic

sensor will be competitive in nuclear power plant applications.

3.6.3 Potential Regulatory Impact

Fibe; optic sensors are among the most sensitive and accurate sensors available. Thus, they also benefit

from the same regulatory advantages associated with improved sensors, as previously mentioned. The

major problem hampering their widespread use in nuclear power plant containment environments is the

degradation caused by gamma radiation. Ongoing development of fiber-optic sensor technology is

directed toward improving sensor performance and long-term durability. Many applications for nuclear

power plants should be available in the foreseeable future.

3.7 Fiber-Optic Pressure Sensors

3.7.1 Principles of the Technology

There are several basic designs for fiber-optic pressure sensors. The optical pressure transducer based on

correlation of reflected light works as the impulse is applied on the surface of diaphragm. When the light

focus es on the diaphragm, the angle with which the light reflects varies with the deflection of the

diaphragm. A bundle of optical fibers point toward the diaphragm. Some of the fibers in the bundle

direct light towards the diaphragm, and the remainder of the fibers capture a portion of the reflected light.

The intensity of the reflected light is proportional to the diaphragm deflection that is caused by the

pressure applied to the diaphragm, as shown in Fig. 3.12.

Sensor

LED Sensor Housing, ,

Drive

Electronicsr i -C ( 3v - Fibers L

Photodiode Pressure Sealz f Diaphragm

Fig. 3.12. Fiber-optic pressure transducer.

The sensor response to pressure results from the displacement of the diaphragm, which in turn changes

the optical signal transmitted from the sending to the receiving fiber upon reflection from the diaphragm.

In a two-fiber design, the light intensity collected by the receiving fiber may either decrease or increase

with increasing diaphragm deflection. For a given diaphragm displacement due to a full-scale pressure

change, the sensor response can be adjusted by a suitable choice of optical fiber core diameters and

numerical apertures, as well as by the relative position of the fibers with respect to the diaphragm. In a

robust and durable design, the sensor head consists of a metal housing with a welded sensing diaphragm,

a fiber-holding ferrule, and two fibers bonded inside the ferrule, as schematically shown in Fig. 3.13.

49
DIAPHRAGM

WELD

Fig. 3.13. Sensor head design.

The diaphragm is one of the most critical elements of the sensor. Sensor diameters typically range from

1.7 to 8 mm, covering the pressure range from 100 to 30,000 psi. Small diaphragm diameters create a

significant design challenge due to the simultaneous requirement for large deflection (for high signal-tonoise ratio) and low stresses (required for infinite lifetime).

As shown in Fig. 3.14, the fiber-optic sensor developed by Optrand consists of three basic components: a

sensing head with a metal diaphragm directly exposed to combustion pressure, a cable containing two

multimode fibers, and an opto-electronic signal conditioner containing all optical and electronic

components.

LED

- BectFbnics -

-Photoiode

Sigrml Conditioner

Fig. 3.14. Sensor block diagram.

Opto-electronic conditioning circuitry contains a photodiode, an infrared LED, and an analog electronic

circuitry. Two input electrical leads are for power supply and ground while one output pin is for pressure

output and the other for sensor fault diagnostics. The electronic circuitry controls light intensity,

amplifies and filters the photodiode signal, and provides the auto referencing function. The baseline light

intensity in fiber-optic sensors may vary due to optical link transmission fluctuations resulting from

connector mechanical and thermal instabilities, fiber bending, light source, or detector temperature

dependence, or aging over time. The auto-referencing approach not only corrects for offset drift but also

for sensor gain error. A side benefit of the technique, not possible with other combustion pressure

sensors, is the availability of sensor-health monitoring output. By continuously monitoring the LED

current level or its rate of change, one can identify a potential sensor failure before it occurs. This ability

is particularly important in control applications where sensor failure may cause malfunction or even

failure of the controlled device.

Another type fiber-optic pressure sensor is based on Fabry-Perot interferometry. The basic principle is

shown in Fig. 3.15.

50
Incoming Fiber

Strain - Strain

Cavity Length

Fig. 3.15. Fabry-Perot cavity.

Two partially silvered surfaces are placed close together, creating an optical cavity. When light is

injected from outside the cavity, a portion of it is reflected and a part of it passes through the first mirror

to be reflected from the second mirror. The second mirror is attached to the pressure diaphragm so that its

position will vary with the applied pressure. Multiple reflections are created between these two surfaces,

and these reflections interfere with each other, either constructively (peaks) or destructively. The light that reflects back up the fiber is wavelength-modulated in proportion to the cavity length. A partially silvered wedge passes light into the cavity, and a CCD array on the other side of the cavity detects the

light. The CCD array is calibrated such that when it detects the peak wavelength from the two surfaces of

the sensor's Fabry-Perot cavity, the data are correlated to the absolute length of the cavity, which is a

function of the pressure.

A third type of pressure sensor based on fiber optics uses a quartz tuning fork attached to the end of a

Bourdon tube. As pressure increases inside the Bourdon tube, it attempts to uncoil. This places tension

on the quartz tuning fork, thereby increasing the resonant frequency of the tuning fork. If an LED or laser

diode excites the tuning fork via a fiber, a second fiber can detect the change in resonant frequency.

3.7.2 Maturity of the Technology

Fiber-optic pressure sensors have been used for several years in the process industry, and may also find

increasing use in nuclear power plants. Their advantages include excellent stability, high accuracy, and

very low maintenance requirements. In addition, they have significant advantages for application in harsh

environments due to their immunity to the effects of high-temperature, high-electromagnetic interference,

high corrosion, and high-radiation environments. These sensors have demonstrated their successes both

in combustion applications, such as pressure-sensing spark plugs, glow plugs, fuel injectors, and

noncombustion applications, such as monitoring pressure in natural gas pipeline compressors, plastic melt

pressures, and pressure control in a pharmaceutical plant. Luna Innovations demonstrated that their

Bragg grating-based optic sensors can survive up to 2 x 10'9 fast neutrons/cm2 and 87 GRad gamma in a

combined neutron and gamma environment. These sensors have been demonstrated to measure pressure

up to 500 psi at 8000C. Sampling frequencies up to 1.0 MHz are available [Luna Innovations 2004].

One application of fiber-optic sensing technology that deserves attention is the application of the fiberoptic Fabry-Perot interferometer (FFPI) to detect cavitations and flow instabilities in centrifugal pumps in

nuclear power plants [Perez 1998]. The dynamic pressure resulting from the pump suction and discharge effects, cavitations, vane-pass pulsations, and excessive wear ring leakage for a high-energy process may

cause large dynamic axial forces, leading to premature thrust-bearing failures. Continuously monitoring the dynamic pressure provides a useful indicator of unsafe pump operation. The FPPI technology also

has the added advantage of being able to operate at temperature ranges of up to 8000C (typical pressure transducers are limited to processes below about 3000

C) and two-orders-of-magnitude improvement in

sensitivity over typical pressure transducers.

51

CV?'
Above 8000C, conventional quartz glass fiber-optic sensors fail to measure pressure reliably. Singlecrystal sapphires have been used extensively for high-temperature measurements (above 1000IC), but

very few data have been reported for pressure measurement applications. In order to extend the operating

temperature of fiber-optic pressure sensors, a fiber-optic pressure sensor utilizing single-crystal cubic

zirconium as a structure material has been developed [Peng-Wei 2004]. The pressure response of the

sensor has been measured from 0 to 1700 psi. Additional experimental results from 23 to 10261C show

that cubic zirconium could be used for pressure sensors at temperatures over 1 000C.

Work is being done to improve fiber-optic pressure and temperature sensors for oil down-hole

applications [Qi-Bing 2001]. The air gap in the sensor head changes with the pressure and temperature.

The sensor head is an interferometer-based fiber-optic senor. For high-speed applications, a novel selfcalibrating interferometer/intensity-based (SCIIB) scheme that compensates for both light-source drift and

the fiber-loss variation is used to demodulate the pressure (or temperature) signals. Experimental results

show that the SCIIB system achieves 0.1 % accuracy with a range of 0 to 8000 psi for the pressure sensor

and a range of 0 to 6000C for the temperature sensor.

Measurement of pressure in an explosive air blast requires an electrically isolated sensor having high

bandwidth and high spatial resolution. Researchers have developed an optical-fiber-based pressure sensor

that meets these requirements [MacPherson 2000]. Tests that subject the sensor to experimental

explosive-blasts show a high degree of reproducibility in sensor performance and are consistent with a

contemporary theoretical model. A rise time of 3 Us was achieved in response to a 100-Kpa shock, and a

resolution of I Kpa was demonstrated.

3.7.3 Potential Regulatory Impact

The preponderance of fiber-optic pressure sensor research is toward improving long-term durability and

extending the operating temperature range. Several applications of the technology are anticipated, with

benefits as discussed in the previous section.

3.8 Hydrogen Sensors

3.8.1 Basic Principles of the Technology

Currently, hydrogen sensors are based on the property changes after hydrogen is absorbed into a material

through physical or chemical mechanisms. Catalytic bead sensors consist of two beads surrounding a

wire with one bead inert to hydrogen molecules and the other highly reactive to hydrogen molecules. The

increase in the resistance of the catalytic bead is used as a signal for hydrogen detection. Catalytic bead

sensors can measure hydrogen concentrations ranging from I to 5% with 10 to 30 s of response time.

Semiconductor and electrochemical hydrogen sensors have very fast response times (less than several

seconds), but they are not appropriate for post-accident measurement in nuclear power plants because

oxygen concentration also affects the resistance and the chemical reaction. The hydrogen sensor

technology deserving of monitoring for nuclear application is the palladium alloy sensor, which has rapid

responses and is robust in environment variations [Jardine 2002].

The basic type of resistive palladium alloy sensor uses the palladium surface as a catalyst to break the HH bond and allow the monatomic hydrogen to diffuse into the metal such that the changes in the electric

resistivity of the metal can be used for hydrogen detection. Palladium can also be used as the gate

material for a standard field effect transistor; the large changes in the current-voltage characteristics of the

field-effect transistor are then used for hydrogen detection.

52
3.8.2. Maturity of the Technology

Hydrogen sensors have nuclear power applications both in the near term as monitors for hydrogen

accumulation in reactor systems and in the long term as an essential element of a nuclear hydrogen

production plant. Indeed, as hydrogen technology has emerged to provide a clean, abundant energy

source, many hydrogen sensor technologies have been developed by different industries in the past 5

year;.

A robust wide-range hydrogen sensor technology has been developed by Sandia National Laboratories

[SNI, 2004]. The hydrogen sensor uses (1) catalytic palladium nickel (PdNi) gate metallization on field&

effect transistor sensors for detecting low concentrations of hydrogen (parts per million), (2) PdNi resistor

sensors for detecting higher concentrations of hydrogen (up to 100%), and (3) on-chip microthermnometers and micro-heaters for maintaining constant chip temperature. The design is aimed at

addressing the drawbacks of current hydrogen sensors: a limited dynamic range, poor reproducibility and

reversibility, an unacceptable frequency of false alarms, and the tendency to be slow, unreliable, and

difficult to use. Some additional issues for nuclear application include methods to remove sulfur-bearing

contaminants from the palladium surface for accurate measurements; nonuniform hydrogen distribution;

and the harsh environment of high temperatures, high pressure, and high humidity in the containment

after an accident occurs.

Aluminum nitride-based hydrogen sensors are also under development [Auner 2004]. This unique sensor

is based on a Pd/AIN/Si structure which behaves similarly to a MIS device. The device is reported to be:

highly selective, showing no response to oxygen, propane, or carbon monoxide, and can detect hydrogen

concentrations as low as 1 ppm in the surrounding flow. While this device holds a lot of promise, a

considerable amount of work still needs to be performed before it can be commercialized. Ongoing work

has focused on characterizing the electrical properties of the device, characterizing the exact nature of the

sensing mechanism, and optimizing the performance by varying palladium and AIN thicknesses, and

employing various palladium-based alloys.

3.8.3 Potential Regulatory Impact

Continued interest in following progress in hydrogen-sensor technology is warranted. Continued

development of hydrogen sensors is needed not only for current plants, but more so for entrained gas

moni':oring and for facility or process monitoring as part of nuclear-driven hydrogen production. In either

case, monitoring the evolution of these technologies is suggested.

3.9 Smart Sensors

3.9.1 Sensor Fusion and Enhanced Diagnostics

Data reconciliation and gross error detection methods have recently received attention among nuclear

electric utilities in Europe [Grauf 2004, Sunde 2003]. The sensor fusion technique takes advantage of the

plant-wide mass balance and energy balance equations to reconcile plant measurements such that the

balance equations are satisfied in a strict manner. Because the easily developed models provide

additional functional redundancy to the plant measurements, the reconciled values will be much more

accurate than the raw measurements. This technique is mature enough for application in nuclear power

plants at steady-state conditions to improve plant operation performance and provide a sensor calibratiom

standard when digital systems are applied. Additional research currently focuses on dynamic data

reconciliation for better control.

53
An alternative approach to smart sensors is to realize the diagnosis and report of their own conditions

through built-in software and hardware testing capabilities. Because this technique depends on individual

sensor design, it is difficult to completely review this topic. However, the trend toward sensors with the

capability of self-checking and calibration as well as intelligent and automatic failure diagnosis is certain

to increase in order to reduce personnel costs and increase reliability by detecting a fault at its incipient

stage. For instance, Integrated Sensing Systems, Inc., has developed an ultra-sensitive capacitive pressure

sensor that has built-in temperature compensation and provides such features as self-testing and selfcalibration [Adrian 2000].

3.9.2 Maturity of the Technology

While implementation of the technologies outlined above is not as widespread in the power industry,

smart sensors and transmitters themselves have long proliferated in the non-nuclear industry and are also

in use in nuclear power plants in noncontainment applications. Smart transmitters can offer improved and

safer plant operation through remote communications and because of their self-diagnostics capabilities.

Specific benefits include (1) greater transmitter accessibility in difficult access locations, (2) simplified

transmitter and loop verification, (3) self identification of the failure mode, and (4) ease of

troubleshooting and diagnostics from the control room. The most significant hindrance to their

application in a containment environment continues to be susceptibility of the CMOS electronics to

radiation. However, with advances in radiation-hardened electronics (e.g., C-RAMs and SOI

technology), and the likelihood of such electronics increasingly being applied in commercial off-the-shelf

(COTS) systems, it is highly likely that smart transmitters can be qualified for containment applications in

the foreseeable future.

3.9.3 Potential Regulatory Impact

Current standards and regulations for qualifying microprocessor-based I&C may be adequate for

qualifying smart transmitters for use in containment environments. However, advances in radiationhardened electronics should continue to be monitored to identify any need for independent verification of

claimed performance in containment. For example, system response time may be critical in some

applications, but temporary (several milliseconds) degradation in performance may preclude a smart

transmitter's use in containment, even though for less time-critical applications the transmitter may pass

qualification.

54
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55
4. CONCLUSIONS AND RECOMMENDATIONS

This update survey of emerging I&C technologies in the nuclear power plant environment provides an

opportunity to assess recent advances in the I&C discipline since the first publication in the series

(NUREG/CR-6812). While the technology focus areas identified in NUREG/CR-6812 have essentially

been maintained in this update, we have focused on sensors for a more detailed discussion. One reason is

that improved and more accurate sensors provide the best opportunity for increased safety and operating

margins. In this chapter, we provide a summary of our observations and offer recommendations for

confirmatory research and continued monitoring of progress.

Table 4.1 provides a summary of the state of the art of the technology focus areas discussed in this

update. The "Status" column in the table has the same definition as in Table 2.1, that is

* Category A-Ready for use. The technology is either commercially available now or could

be available within a year.

* Category B - Confirmatory testing required. Commercial availability is at least a couple of

years away.

* Category C - Some additional development required. Commercial availability is possible

within the next 3-5 years.

* Category D - Significant development required. Commercial availability is not likely within

the next 5 years.

• Category E - Fundamental research required. Commercial availability may be possible in 5-

10 years.

For the sensors and measurement systems technology focus area, some of the sensors and sensing

techniques that were initiated as a result of the research stimulus provided by the DOE programs (NERI,

INERI, and NEER) have progressed from concepts and laboratory prototypes to becoming potential

commercial products:

1. One notable example of sensors that are close to becoming commercially available is the silicon

carbide neutron flux monitor. One important advantage of this type detector is that, because of its

larger band gap compared to conventional semiconductors such as silicon or germanium, SiC

radiation detectors are not as susceptible to thermally generated noise and are capable of operation at

high temperatures. This technology is past the developmental stage and is essentially ready for use.

However, data on important parameters such as drift, accuracy, repeatability, and degradation over

time could not be ascertained for this update. It is important that a combined neutron monitor based

on this technology not only exhibits the full dynamic range from startup to 100% power, but it should

also be shown not to degrade over the long term when at 100% power. The improved operating and

safety margins that such detectors will provide, should they also meet all the criteria mentioned

above, certainly warrant continued monitoring of progress in their development.

2. A sensor that could be commercially available for nuclear power plant applications within 5 years is

the Johnson noise thermometer. The attraction of JNT is that it is inherently drift free and insensitive

to the material condition of the sensor. As a result of the latter characteristic, a sensor based on

Johnson noise is immune to the contamination and thermo-mechanical response shifts that plague

thermocouples and resistance thermometers. This advantage should improve operating as well as

safety margins in nuclear power plants.

56
Table 4.1. Gennern] Otnfin of emergina t~ehnoenloes

Technology Status' Description _________ ____ 

of 

____ 

principle _____ 

Typical or foreseeable New progress Conclusions ____ap p lication _ _ _ _ _ _ _ _ _ _ _ _ _ _

'LiF deposited on top of a thin SiC

SiC Neutrn layer converts neutrons to charged Ex-core neutron Fl NuxtMonioA particles via the Li(n,a)3

Flux Monitor A Charge H reaction monitoring with no Prototypje tested underEsetalradfoue is collected under a voltage gamma compensation research reactor conditions. Essentially ready for use

._.__Thestabias andleakage

Solid-state Flux-induced change in electric In-core flux mapping at The stability and leakage neutron flux B resistance of aluminum nitride power range fluxes, since current tested at room Need further testing monitor solid 

I_ 

detector is sensitive temperature with no incident Ne ute etn gamma radiation

Control the input electric energy to

Fuel mimic a fuel pellet to maintain constant The

power monitor temperature when reactor is at Direct measurement of seondpenertion Resrtion tsed (Constant B some steady-state power level The the nuclear energy bandwidth and proportionality demonstration testing at temperature 

power sensor) 

electrical 

maintain power required to deposition has been tested reactor operation conditions constant temperature is a

measure of the nuclear power level

(I) Pressure

Movement of diaphragm due to measurement in highOptical pressure C pressure causes changes in temperature, pressure, Demonstrated application in Need to improve the durability reflected light Source of light may corrosive environment harsh radiation environment. and demonstrate its sensors bea ih-mtigdoe(E) (2) Optical Farbry-Perot Experimental studies arepefrac band lgt-emitting diode( eD interferometer to detect continuing and detector may be a photodiode pump cavitation and flow

___ _instabilities

. (I) Applied to obtain Use the energy and time of ape o obtain Gamma ray Compton scatter events and image of pebble bed In use after improvements in tomographic A photoelectric absorption events to (2) Real-time cadmium zinc telluride Expect extensive use spectrometry. project the arrival angle of an characterization of production. incident gamma ray radiation field

Hydrors Hydsroge _ C Use H to palladium diff-use into as 

a 

catalysts metal and to Post-accident monitoring hydrogen Robust hydrogen sensors have Need to stand the post- chenintgae noasnl accident harsh environment s n o schange the resistance _ _ __ _ _ _ _ chip__ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _

57
Table 4.1. General status of emerging technologies (continued)

Technology Status Description of principle Typical or foreseeable New progress Conclusion application

Electronic vibration due to thermal Temperature Sensitivity to electromagnetic Requires radiation-hardened

Johnson noise agitation of atoms (noise) This measurement wi (EM) noise; complexity of preamp Improvements in

thermometry noise voltage is a function of contion implementation is being signal processing and rad-hard

temperature T calibration addressed electronics are still needed

Mature technology in

Conducting fluid passing through non-nuclear industry Radiation sensitivity of inner

Magnetic D magnetic field generates voltage Currently tested for pipe liner is the major Liner problem needs to be

flowmeter proportional to velocity of flow primary flow measure- challenge Work to overcome solved

ment in pressurized this problem is still in progress

water reactors (PWRs)

Send light through a reference

fiber and a sensing fiber.

Fabry-Perot Temperature causes change in Tested for irradiation

fiber-optic D physical dimension, causing a effects, high temp and Degradation caused by Results awaited for radiation

temperature phase difference between the light , irradiation observed exposure testing

sensor travelling through the two fibers. pressure

The phase difference can be

measured by "counting fringes"

Total dose hardness,

. Materials/processes that are latch-up immunity, and Maxwell-SCS 750, radiationRadiation- radiation resistant (e.g., SOI, upset error mitigation. tolerant 0.13 pm, hardened B chalcogenide) and compatible with Should enable use of complementary metal-oxide read for y testing

cintgrte IC manufacturing processes are commercial off-the-shelf semiconductor (CMOS) circus used (COTS) systems in harsh process.

environments

Optical B Optical digital signal processing Better communications Thousand times faster than Lenslet Ltd.-Enlight 256

processors (DSP) for analog processing in noisy channels and conventional electronic commercially available interference cancellation processing

Supervisory Manage all monitoring and Advanced man-machine Advanced boiling water HITACHI-NUCAMM-90

control A operational tasks interfac Nueatrs (ABWRs), Onagawa commercially available

58
Table 4.1. General status of emerging technologies (continued)

Technology Status' Description of principle Typical or foreseeable

I application New progress Conclusions

. Use functional redundancy On-line instrument Could be integrated into Sensor fusion sensor fault diagnosis for calibti and fault Demonstration testing has distributed control systems iao been done (DCS) for next generation tiagnosis dnuclear power plants

Enhanced 

diagnostics Real-time diagnosis through built On-line instrument Ultrasensitive capacitive Extensive use of the principle in software and hardware testin calibration and fault pressure sensor with built-in in nuclear power plants ____diagnosis_________temperature compensation

(l) Protection of (1) Wide application in

System on a C Integration of intellectual property telecommunication Need to address high degree of all components on (2) Save circuit board (2) A remote input-output chip integration for complex chip one chip space with 32 transducers of voltage systems (3) Sensors-on-a chip and current sensing _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~~a p p lic a tio n _ _ _ _ _ _ _ _ _ _ _ _ _ _ Vertically (1) New 3D design tools are stacked E Three-dimensional (3D) design to Advanced chip developed Fundamental research integrated increase transistor density technology. (2) Heat removal is still a circuits constraint

Nanotriodes E Reinvention Renventionof of vacuum tubes using High-radiation and (1) 1 00-nm size nanotriodes

nanotechnology tesi gradiapplication are developed Fundamental research temperature a(2) High operating voltage

Proof-of-principle research on

Molecular-scale E electonic improve iprov E computation 

comutaton speed sped and ad Associated with high- DNA-based computing, Fundamental theoretical electronics density sped speed cmputtion computation quantum computing, and rsac nanoelectronics-based research

_computing

Applicationspecific Design-for-test concept Westinghouse 7300A (ASIC- integrated A Integrated circuits for specific allows safety system based) digital replacement Already in extensive use circuits (ASIC) function applications module and ASIC

software

Model-based Use real-time simulation and Nuclear power plant Need demonstrating techniques _ 

B optimization performance to improve operation operation performance TEMPO software is completed application improvement

59
Table 4.1. General status of emerging technologies (continued)

Technology Status' Description of principle Typical or foreseeable New progress Conclusions ____ ___ ____application ____ ____ 

Control-loop Compare the metrics calculated

performn ce-o from historical data with some Real-time controller Application in other process Need to have a demonstration

performance standards of the best possible performance assessment industries research for NPPs

monitonngIperformance

Laser-based Able to measure the relative Demonstrated for the Need to address the sensitivity

alignment B movement between two laser Shaft alignment of alignment monitoring of a to the adjacent vibration and

monitoring transducers across long distance thermal disturbances

Intelligent The concept of software agent is Proof-of-concept development

agent-based D used to support autonomous Autonomous control of and testing to support the grid Long-term monitoring

control control nuclear power plants coordination and protection of distributed energy resources

The achieved control is

Incorporate into control the case dependent, so An multilevel flow model

Multilevel flow structured graphic representation computerized operation (MFM) model of nuclear main MFM modeling is time

model of system goals, functions, and procedure can be system has been developed consuming and still subject to

their relationships developed using this and demonstrated error

method

Object-oriented Safety-critical Java product using May have application to Product release (JRTKTm) has

language: real D memory- and time-partitioned the control of safety beenProduned Long-term monitoring

time Java kernel systems

Multiple agents that can take May have applications in

Software agents D situational actions interact to power grid distribution Demonstrated application t Long-term monitoring and coordinated plant distributed data management Lntm ooi achiee sel-orgaizinggoal control ______________

60
Table 4.1. General status of emerging technologies (continued)

Technology Status' Description of

principle

Typical or foreseeable

application New progress Conclusions

Human-system Enable operation with ABWRs, Onagawa Nuclear HITACHE-NUCAMM-90 interface _ _ _ 

A 

_ _ _ _ _ Client server architecture system diagrams and Power Plant commercially available e _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ t r e n d s P o w e _ P l n t _ o m m rc i a l y _ v a i a bl

Software agentbased B Software search engines Security of nuclear Works 24/7, sorts out only Used in ORNL for homeland operational installations relevant information security support system

Virtual 

collaborator Can behave like a Detect anomaly, diagnose the Second-phase research started Software with hardware nuclear power plant root cause, and operate control with focus in interaction with

operator panel humans

Identification using biological Safety of nuclear power Biometrics C traits such as iris and face plants and strategic US-VISIT program For homeland security recognition installations

Automated

visual Monitors area, takes video, and Safety of nuclear Tested using performance surveillance for D takes action installations evaluation of tracking system Focus on moving objects facility (PETS) 2000

monitoring

Optimize construction

Virtual reality A Software sequence, eliminate Implemented in AP600 plant Commercially available problems, reduce cost, (ALWR)

and train workforce

'Category A - Ready for use. The technology is either commercially available now or could be available within a year. Category B - Confirmatory testing required. Commercial availability is at least a couple of years away. Category C - Some additional development required. Commercial availability is possible within the next 3-5 years. Category D - Significant development required. Commercial availability is not likely within the next 5 years. Category E - Fundamental research required. Commercial availability may be possible in 5-10 years.

61
However, problems that have hampered commercial utilization of Johnson noise thermometers

include a relatively long response time because of the long integration time required to make a

temperature measurement. An ORNL implementation addresses this problem in a dual-mode

thermometer by making the temperature measurement as a simple resistance measurement whose

resistance to temperature conversion is quasi continuously updated using Johnson noise. ORNL

scientists plan a demonstration of JNT at a nuclear facility within 2 years. Thus, a practical

implementation of the JNT in nuclear power plants could be as an on-line, self-calibrating RTD. The

regulatory implication of self-calibration is that required calibration intervals could be relaxed. It is

recommended that progress in this technology should continue to be monitored.

3. At the other end of the spectrum in terms of commercial availability of the sensor technology are

scintillation-based sensors for in-core temperature and flux measurements and vacuum nanotriodes.

In the case of scintillation-based sensors, the primary deficiencies in the technology preventing its use

for in-core measurements have been the lack of an effective technique for measuring light within

reactor core environments and the rapid darkening of fiber-optic light pipes in high radiation fields.

Additionally, scintillation materials darken too rapidly to be useful in bulk form near a nuclear reactor

core. For the purposes of this update, no significant progress in overcoming these problems could be

identified. In the case of vacuum nanotriodes, the technology is also still in relative infancy.

However, because of the advantages that advances in both technologies could provide for nuclear

power plant I&C, both scintillation-based sensors and vacuum nanotriodes should continue to be

monitored.

4. Variability in the radiation response of COTS devices is a significant radiation hardness assurance

(RHA) issue. Approaches such as radiation-hard technologies and improved manufacturing processes

may resolve this impediment. These improvements are most likely to be seen first in space

applications. Therefore, it is warranted to monitor special-purpose applications while confirming the

radiation-tolerant characteristics of commercial ICs. Considerable progress has been made in

radiation-hardened integrated circuit development using materials such as SOI. State-of-the-artradiation-hard IC technologies are exemplified by the Maxwell Technologies' single board computer,

the SCS750. It uses SOI technology fabricated in a radiation-tolerant 0.13-[um CMOS process.

Performance characteristics include (1) one upset every 300 years in a GEO orbit, (2) space qualified

performance at 1800 MIPS; (3) triple modular redundant processing, (4) use of SOI processors, and

(5) use of advanced error-corrected SDRAM. Another innovation in radiation-hardened chip

technology is the integration of chalcogenide material with radiation-hardened CMOS process to

produce memory arrays. Chalcogenide-based memory is highly radiation resistant, and its

importance in space I&C applications is well recognized. Four megabit C-RAMs represent the

current state of the art. Advances in radiation-hardened ICs should continue to be monitored to

facilitate the review of safety instrumentation such as smart transmitters for containment applications.

5. Advances also continue to be made in other, more exotic technologies such as nanotriodes and

molecular electronics. This technology could have a significant impact on nuclear I&C because of its

high tolerance for high-radiation and high-temperatures. Despite advances in the development of

these devices, numerous challenges remain before working devices become commercially available.

In the case of molecular devices, although the technology is interesting, it is not likely to develop to

the point that it would migrate into nuclear applications within the foreseeable future. Although this

is not likely that nanoelectronics and nanotriodes be deployed in nuclear power plant environments in

the near future, progress in their development should continue to be followed over the long term,

because this technology could enable smart sensors to migrate into the most inhospitable areas within

the reactor containment.

62
One important aspect of the Emerging Technologies series of reports is to identify research needs as

well as I&C areas that should continue to be monitored in an effort to improve the NRC review

process. In a memo to the NRC by the Advisory Committee on Reactor Safeguards [ACRS 20001,

the latter indicates that the National Research Council recommended Emerging Technologies as a

research area for inclusion in the NRC research plan for instrumentation and control. It also

recommended that the output of the research should include "specific anticipated output or

product... and the way in which this output or product meets the Agency needs...."

6. The authors of this report believe that an underlying enabling technology that will facilitate reliable

nuclear plant digital I&C operation is the implementation of a robust communication protocol.

Unfortunately, the unwary use of digital communication in the plant (for example, communication

between control, safety, and offsite) raises safety and cyber security concerns. The authors

recommend confirmatoryv research to develop a set of recommendations for best practices in digital

communication in nuclear power plant safety T&C systems. This will support the review of digital

I&C system upgrades in current generation plants, as well as in Generation III and Generation IV

plants. Communications media (e.g., cables, fibers, wireless bands) and network systems provide the

pathways by which data and information are distributed among the field devices, processing

components, and display systems in a plant. In nuclear power plants, traditional direct-wired, pointto-point connections between analog equipment have been the norm. However, the trend in the use of

data networks to serve plant personnel, application of digital I&C in system upgrades, and

communication between safety and nonsafety systems is likely to increase. Current federal and NRC(

regulation limit, but not specifically prohibit, two-way communication between safety and nonsafety

systems. Communication pathways between safety and nonsafety systems are generally acceptable as

long as failure of the communication system does not impair the safety function, and the safety

finction does not rely on nonsafety system inputs to operate. However, allowing such

communication introduces the potential of compromising safety. One example is the disabling of a

safety parameter display system at the Ohio Davis-Besse nuclear power plant in January 2003. This

was done by the penetration of a slammer worm' through a private computer network that was being

used by a contractor to access the plant network. This occurred in spite of the presence of a firewall

that plant personnel believed would protect the network. The plant had been offline when the

incident occurred, thus the breach did not pose a safety hazard. However, the case does illustrate two

significant safety issues: (I) a cyber security problem, where interconnection between plant and

corporate networks (permitted by federal safety regulations) could compromise the safety system and

(,2) the potential problem is posed by allowing communication between control and safety systems.

'A computer worm, like a computer virus, is a program that replicates functional copies of itself to other computer

systems via network connections, often with the intent of adversely interfering with the normal use of a computer

program. The difference between a virus and a worm is that unlike viruses, worms exist as separate entities. They

do not attach themselves to other files or programs. There are several strains of worms (e.g., slammer worm).

63

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68
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(9-2004) (Assigned by NRC, Add Vol., Supp., Rev.,

NRCMD 3.7 and Addendum Numbers, If any.)

BIBLIOGRAPHIC DATA SHEET

(See nstrctions on the reverse)NUREG/CR-6888 ORNLIrM-2005-75

2. TITLE AND SUBTITLE 3. DATE REPORT PUBLISHED

Emerging Tecinologies in Instrumentation and Controls: An Update MONTH YEAR

Januarv | 2006

4. FIN OR GRANT NUMBE:R

JCN Y6932

5. AUTHOR(S) 6. TYPE OF REPORT

Kofi Korsah, e: al Technical

7. PERIOD COVERED (Inmusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (II NRC, provide Division, Office or Region. US. Nuclear Regulatory Commission, and maiing address; it coitractor.

provide name and mflling address.)

Oak Ridge National Laboratory

PO Box 2008, MS 6010

Oak Ridge, Th\1 37831

9. SPONSORING ORGANIZATION -NAME AND ADDRESS (If NRC, type 'Same as above;ifcontractor, provide NRCDhvsion, Office or Region, U.S NudearRegulatoty Commission,

and maiing address.)

Division of Engineering Technology

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

10. SUPPLEMENTAFY NOTES

Christina Antcnescu, NRC Prolect Manager

11. ABSTRACT (200 words or less)

This report is a summary of advances in eight instrumentation and control (I&C) technology focus areas that have applications

in nuclear power plant digital upgrades as well as in new plants. It is the second in a series of planned update reports (the first

one was NUREG/CR-6812) in an NRC-sponsored Emerging Technologies study. NUREG/CR-6812 provided a broad-brush

overview of I&C technologies and served as-the baseline for the series of periodic reports specified in the U. S. Nuclear

Regulatory Commission (NRC) Plan for Digital Instrumentation and Control (SECY-01-0155). There have been several

advances in I&C since NUREG/CR-6812 was published, and this report provides a summary of the state of the art in the

technology areas identified in the previous report. From the findings, we develop suggestions for prospective research needs.

12. KEY WORDS/DESCRIPTORS (List words orphrases that wifl assist researchers In locating the report.) 13. AVAILABILRTY STATEMENT

communications unlimited

diagnostics 14. SECURInY CtA;SIFICATION

human-system interaction (This Page)

instrumentation and controls (I&C) unclassified

integrated circjit (This Report)

measurement

microprocessc r unclassified

sensor 15. NUMBER OF PAGES

software

regulatory impact 16. PRICE

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Federal Recycling Program