ML17209A183

Review of Temp Sensor Response Time Measurement Using Loop Current Step Response Technique

ML17209A183
Person / Time
Site:	Saint Lucie
Issue date:	08/16/1978
From:	Ackermann N TECHNOLOGY FOR ENERGY CORP.
To:
References
NUDOCS 8010060267
Download: ML17209A183 (31)

Text

REGULAT~ INFORMATION DISTRIBUTIO YSTEM (RIDS)

ACCESSION NfkR:,BQjl0060267 DOC ~ DATE; 78/06/16 NOTARIZED:

NO FACIL:50-355't. Lucia Plantg Unit lg Florida Power 8 Light Co.

AUTH ~ NAME AUTHOR AFF'IL'IATION ACKERMANN<N.J.

Technology for Energy Corp.

REC IP. NAME RECIPIENT AFF IL'IATION DOCKET" 4'5000335

SUBJECT:

"Review of Temp Sensor'esponse Time Current Step

Response

Technique."

Measurement" Using Loop ENCL~

SIZE':

DISTRIBUTION CODE:

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REVI EH OF TEMPERATURE SENSOR

RESPONSE

TIME MEASUREMENT USING LOOP CURRENT STEP

RESPONSE

TECHNIQUE 4

FOR NUCLEAR REGULATORY COMMISSION BY NORBERT J ACKERNANNg JR JULIAN E MOTT AuGUsT 16,'978 801006o QQ,7

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Customer Bulletin Technology Ior Energy Corporation 10431 Lexington Drive Knoxville, Tenneaeee 37922

<e1s) ssasase SURVEILLANCE QF SAFETY/RELIEF VALVES CAN IMPROVE PLANT AVAILABILITY Displays hourly RMS levels and variance for each channel on request and automatically if tripped TEC 1400 program-controllable 16 channel multiplexer TEC 1408 programmable filters: 1-15 kHz Over 100 days of data, including all trip records for all channels, stored on one diskette

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Alert light indicates channel trip Keypad selection of channel and function. for viewing TEC 910/911 signal conditioning amplifier system with charge-converter drivers Microcomputer uses TEC's custom software, for safety/relief, valve monitoring A TEC Model 1400 microprocessor-controlled surveillance system is being used to continuously monitor and process the acoustic noise within BWR safety/relief valves, so that valve leakage can be recognized long before a malfunction results. A commonly used safety/relief valve in BWR plants is a pilot-operated type, having a two-stage pilotvalve section and a main valve section. The pilot-disc seat is vulnerable to deteriorating processes which lead to increasing leakage across the seat into the chamber of the second stage. A small leak has no immediateadverse

effect, because the pilot valve discharge line can accomodate the flow without substantial pressure buildup. However, as a small leak grows, the second-stage disc opens; even though the pilot disc was not lifted. Since valve malfunction does not occur until a leak worsens to that critical leak rate, early detection of leakage can allow corrective measures to be scheduled, thereby reducing the loss of plant availability. Also, the surveillance data provide criteria for selecting valves which should be inspected during the next outage.

'I Serving the Energy Production Industry

Several types of surveillance techniques have been considered for detection of the valve leakage.

Sensing the temperature near the discharge line is one possibility. This approach is generally considered to have poor sensitivity. Direct measurement of the pressure in the second stage chamber could be accomplished by fitting the valve with a pressure transducer. Although this invasive technique can be accommodated in a laboratory experiment, its implementation for plant use would require substantial additional safety analysis and testing of the valve's integrity. The monitoring of the leak noise transmitted to the external wall of the pilot stage is a highly sensitive non-invasive method.

A valve having a leaking pilot-disc seat was tested under laboratory conditions in order to determine the correlation of the leak noise with leak rate or second-stage, pressure. As the second stage pressure increased from 40 to 200 psi, the leak rate increased 59%,

the temperature increased 9% and the acoustic RMS voltage increased 370%. Therefore, the sensitivity of the acoustic detection is excellent. Furthermore, if the leak were intermittent, the, acoustic detector would respond accordingly while the thermocouple would not. These measurements provided additional encouragement for utilization of the acoustic detection method.

The basic components of the TEC Model 1400 surveillance system are a multiplexer, signal conditioner, microprocessor and display. Under a combination of pushbutton and software control, the system displays data recalled from computer memory through front-panel keypad commands. Additional data handling and processing are provided through an optional floppy-disc data storage device, terminal and hard copy unit.

The RMS values of each input signal are sampled at a typical rate of 1 per second. Each sample consists of two values: namely, the RMS value (x) in bandwidth A and the RMS value (y) in bandwidth B. The bandwidths of the programmable filters are selectable over the range 1 kHz-15 kHz via TTYor terminal keyboard control. The computer memory stores the last 60 values of x and y for each channel, as well as the last 100 hourly averages of x, y, and the variance (a') in x. In addition, every hourly average value is preserved on the disk forevery channel. One disk can store up to 120 days worth of hourly records.

Using the keypad, the last one-minute or 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> history of x, y, and a'or any channel can be displayed on the system's built-in CRT. Also, whenever an x value exceeds a preselected warning level, an automatic display mode is activated.

Ordihary operation is returned only upon acknowledging the warning display from the keypad.

Detailed technical specifications and prices are available upon request.

FOR FURTHER INFORMATION CONTACT'echnology for Energ'y Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 (615) 966-5856

~

~

Customer Bulletin Technology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 (615) 966-5856 TEC 900/901 SIGNAL CONDITIONINGAMPLIFIER SYSTEM i

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TEC

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TEC

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TEC

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.4$

TEC

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TEC

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.4 FEATURfS.

~ Ultra-Low Noise, Ultra-Low Drift

~ Differential or Single Ended Input

~ Bandwidth DC to 50 kHz

~ Total Gain 1 to 100,000

~ AC Coupling from.001 Hz

~ Variable DC Offset The TEC 901 amplifier, designed to satisfy a wide range of linear amplifications, provides high or low amplification of either dc or ac signals with excellent linearity, low drift, and fast recovery. Control features on the front panel include differential or single-ended operation, first-and second-stage gain, bandwidth control, and overload indications. The modular design using high-quality integrated circuits makes the TEC-901 a low cost, compact, and highly versatile signal-conditioning amplifier.

lp The TEC 900 Pow'er Bin is designed to accommodate eight (8) TEC 901 plug-in amplifiers.

The bin measures 5/4I'igh, 19" wide, 12" deep. Power is supplied to reserved connector pins from three separate regulated supplies sharing a common source.

An.optional eight (8) coaxial cable signal harness that connects directly to the power bin front panel and terminates with BNC connectors is available. The standard harness is ten feet in'ength.

Different lengths are available.

'I Serving the Energy Production Industry

MODEi 901 LOW-PASS OVL 5'UTPUT TEC

~

TEC 901 AMIQFIER SPECIFICATIONS

~

Inputs Differential or Single-ended Impedance Single-ended:

1 megohm (min)

Differential: 2 megohms (min)

Maximum Input Signal Single-ended:

+15 V Differential: +10 V Common Mode Rejection 80 dB (min), 90 dB (typ) at 1st stage gain = 10 Settling Time 30usec N Gain = 100 for+10 V 0

TAIM 2nd GAIN

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CPUT TEC 900 POWER BIN SPECIFICATIONS Output Voltage.

+15 VDC Output Voltage Accuracy........a1%

Line Regulation

...........................02%

(max)

Output Current............................ 600 ma Output Ripple 2.0 mv rms (max)

Temp Coefficient........................ 0.2%'C Operating Temp..........................-15'C,

+ 71'C Source Voltage............................105 to 125 or 205 to 240 VAC 50 to 400 Hz Input Power Cable...................... Standard 3 Prong Plug Gain 1st Stage:

1, 2, 5, 10, 20, 50, & 100 2nd Stage:

1, 2, 5, 10, 20, 50, 100, 200, 500, &

1000 Accuracy better than 1%

Frequency Response DC: to 50,000 Hz AC:.001 to 50,000 Hz Filters High Pass:

0.001, 0.01, 0.1, 1, 10, & 100 Hz (switch selectabie on board)

Low Pass:

10, 20, 50, 100, 200, 500, 1,000, 2,000, 5,000, 10,000, 20,000, & 50,000 Hz Output Linear:

110 V Impedance:

c10 ohm Overload Indications Adjustable from 1 to 10 V 1st Stage Noise G = 100 (referred to input) 0.01 to 10 Hz: 2 Ijv p-p (max) 10 to 10,000 Hz: 3 Ijv rms G = 1 (referred to output) 0.01 to 10 Hz: 40 pv p-p (max)

'0 to 10,000 Hz: 50 pv rms 2nd Stage Noise G = 100 (referred to input) 0.01 to 10 Hz: 40 pv p-p (max) 10 to 10,000 Hz: 3 pv rms FOR FURTHER INFORMATION,CONTACT:

Marketing Manager Technology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 (615) 966-5856

0 Customer Bulletin Technology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 (B15) 958-585B THE TEC MODEL 1430 LOOSE-PART DETECTION SYSTEM Th'e TEC Model 1430 Loose-Part Detection System (LPDS) was developed not only to meet the requirements of NRC Regulatory Guide 1.133, but also to provide for special diagnostic proce-dures which enable confident evaluation of data. The Model 1430 Loose-Part Detection System is based upon the TEC Model 1400 Surveillance System pictured below. The modular system con-tains complete signal conditioning and data processing instrumentation needed for a quality-assured Loose-Part Detection Program.

Meets NRC Requirements Automatic Display of Pertinent Data Special Diagnostics Available h

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4 A~~Ay Vi VVVVVV 4 Microprocessor Controlled Trend Analysis Minimizes False Alarms Data Records on Floppy Disk 11-CHANNEL VERSION OF..TEC MODEL 1400 SURVEILLANCE SYSTEM In addition to supplying the hardware and software that comprises the 1430 system, TEC offers consulting and field measurement services to assist the customer in implementing the fullLoose-Part Detection Program.

Serving the Energy Production Industry

FEATURES:

~ Monitoring of Event Related Parameters The peak signal amplitude and the rms signal level foreach channel are monitored, read into the microprocessor, statistically correlated, and stored on disk for subsequent trend analysis. This eliminates the need for analog-tape recording of signals.

~ Sensor Channel Performance Checks Microprocessor controlled signal trend analysis is used to test for and identify degraded channel performance.

This approach greatly simplifies the "once every 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> channel checks" required by NRC Regulatory Guide 1.133.

~ System Sensitivity The system sensitivity is commensurate with the goals established by the NRC Regulatory Guide 1.133.

~ Alert Level The alert level is optimized for each channel by digital analysis of the signal history at all oper-ating conditions. The system, therefore, remains operable during start-up periods when loose-part impacting is most likely to occur. The signal histories aid the operator in meeting the "at least once per 92 days" requirement for verifying that the alert-level is consistent with the "normal" background noise as called for in Regulatory Guide 1.133.

~ False Alarm Minimization A Deliberate-Plant-Maneuver Monitor informs the microprocessor that plant operating condi-tions are changing and momentarily disables the alarm. Because the system remains active, detection of impacts resulting from these maneuvers serve as an automatic check of the sys-tem's operability.

~ Records Alldata records (time, events, peak amplitudes, rms levels, etc.) are stored on a floppy-disk that can be periodically removed, filed, and replaced with a new disk. By using this simple and inexpensive method, a permanent history of the plant's LPDP is maintained in a compact form.

~ Visual Display of Recorded Data A visual display of the recorded data for each channel is obtained by entering the channel number and file record of interest on the front panel keyboard. The information is automatically displayed on the CRT.

~ Options a)

A switch selectable audio monitor allows the operator'to listen to the output of any channel.

'i')

Custom'oftware for additional diagnostic capability.

c)

Automatic impacting devices for system checkout and calibration.

FOR FURTHER INFORMATION CONTACT'echnology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 (615) 966-5856

Customer Bulletin t

Technology for Energy Corporation 10431 Lexington Orive Knoxville, Tennessee 37922 (615) 966-5856 Sensor Time Response Testing Time response testing is required by the Nuclear Regulatory Commission through Regulatory Guide 1.118 for all components in reactor protection systems including the plant sensors.

Technology for Energy Corporation (TEC) offers",complete consulting engineering services, field measurement services, and special instrumentation to assist thc electric utilities in meeting these testing requirements.

TEC is the nuclear reactor industry leader in the implementation of advanced measurement technology, particularly in th<<surv<<illanc<<and diagnosis ol'plant anomalous performance and component malfunction.

From this broad experiential

base, we have developed a complementary set of measurement techniques and instrum<<ntatinn for pcrfnrming low cost quality-assured sensor time response testing on RTD's and pressure sensors in nuclear power reactors.

RTD We have implemented three measurement techniques and the related instrumentation for in-situ RTD time rcsponsc tcstin

~ in a>>u<<l<<ar power plant:

noise analysis, loop current step

response, and self-heating.

Hence, we can help you choose thc measur<<m<<nt technology that best matches your nccds l'rom the standpoint ol'ensor design, instrumentation channel <<rrangc-

ment, and operations philosop)>>.

Th<<basic principles of these measurement techniques arc as follows.

Noise Analysis.

Noise analysis uses the naturally occurring random fluctuations from the sensor to determine its response time.

These fluctuations are spectrally analyzed to construct thepower spectral density (PSD) which is related to the sensor transfer function. The PSD is then transformed by autoregression analysis to give the equivalent "plunge test" result.

Loop Current Step Response.

The loop cur-rent step response technique, developed under EPRI auspices, involves the measurement of the RTD output when its current is cxtcrnally increased rapidly from its normal value of a few milliamperes to a level of tens of milliamperes.

I.

The resulting resistive heating in the RTD causes a temperature rise of a few degrees.

The RTD time response may be 'etermined then by observing the response of the sensor to this perturbation and transforming the results to an equivalent "plunge test" result.

Self-Heating.

This test is just the steady-state version of the loop current step response method.

Thc current in the RTD is externally increased, but in this case measurements arcn't made until steady state is attained.

Using this procedure, thc change in thc RTD's resistance is measured such that a characteristic resistance-versus-cur-rent curve can be constructed whose slope is related to the sensor time response.

Pressure Sensor We have implemented an extension of the pressure sensor testing technique that was developed under EPRI auspices.

This technique involves the introduction of an externally applied pressure perturbation by an hydraulic signal generator.

Following this perturbation, the response of the pressure sensor under scrutiny is intercompared with that of a reference fast-response pressure sensor to confirm adequate response time..

For furth'er sensor time response testing information or for details about other TEC technical services or instrumentation, contact:

Norbert J. Ackermann, Jr.

Technology for Energy Corporation 10431 Lexington Drive Knoxville, Tennessee 37922 61 5/966-5856 Serving the Energy Production Industry

Customer Bulletin Technology for Energy Corporation 10770 Dutchtown Aoad Knoxville, Tennessee 37922 (615) 966-5856 IN-SITU RESPONSE TIME TESTING OF TEMPERATURE SENSORS

>EC qgTEC

~QT EC iQ TEC MODEL 1100 LOOP CURRENT STEP RESPONSE MEASUREMENT SYSTEM FEATURES:

~ Determine response time without removing RTD

~ Meets recommendations of NRC Regulatory Guide 1.118

~ Constant current source cannot damage RTD

~ Adjustable for any RTD resistance

~ Automatic or manual testing capability TEC offers the Model 1100 system to utilities making RTD sensor response time measurements in accordance with NRC Regulatory Guide 1.118. The Loop Current Step Response (LCSR) technique uses technology which was developed under DOE funding at the Oak Ridge National Laboratory and further refined under EPRI Research Project 503-3. The LCSR method is the measurement of an RTD's response when its current is externally stepped from its normal value of a few milliamperes to a level of tens of milliamperes. The resulting resistive heating in the RTD causes a temperature rise of a few degrees. The RTD response time is determined by observing the response of the RTD to this external current and transforming the observed result to that of an equivalent plunge test.

TEC offers a full set of instrumentation, test procedures, and analysis software to accurately and efficiently perform and interpret the LCSR measurement.

TEC offers supporting field measurement and consulting engineering services to further assist the utility in planning, performing, interpreting, and reporting the measurements.

Serving tbe Energy Production Industry

MODEL 1100 SYSTEM DESCRIPTION The Model 1100 system is housed in a bin which measures 5/~" high, 19" wide and 18" deep. The LCSR testing unit is incorporated in the four right hand modules. Blank panels cover positions that are available for other TEC instrumentation modules. A half wide bin is also available which contains only the LCSR testing unit.

Model 1101 Floating Wheatstone Bridge/AmplifierModule. The bridge/amplifier is balanced via front panel controls and has selectable amplification of the true bridge imbalance voltage of 20, 50, 100, 200, and 500.

TEC's design has several notable features. The most important is that self-heating of the LCSR instrument does not affect the measurement accuracy.

A unique design approach resulted in a bridge resistive temperature coefficient less than 0.1 ppm/mw-'C. The bridge is floated above ground so that inadvertent disconnecting of the RTD at any stage in the test willnot damage the bridge amplifier. For RTDs in the 102 ohm to 547 ohm range (expected range for reactor applications) the pre-test nulling of the bridge has been simplified by a 31 position coarse adjustment coupled with a 10 turn, locking fine adjustment. Another feature is that TEC includes with each bridge the calibration data necessary for determining in the test the actual resistance of the sensor. This is accomplished by nulling the bridge, reading the coarse and fine settings, and consulting the calibration data.

Model 1131 Constant Current Source Module. The Model 1100 uses a constant current supply because a

variable voltage supply could lead to oversupply of power and possibly damage the RTD when testing it cold. The constant current source has an output range that is fullyadjustable from less than1 ma to 100 ma and is preselectable at both low and high levels to provide a consistent, well-defined step function.

Model 1121 Control Module. The control module can be operated in a manual mode via front panel switch-ing or an automatic mode via remote TTL compatible logic from a computer or signal generator.

In the automatic mode, the test is initiated by providing a TTL logical high level (+5V) at the "Auto Step" input terminal on the front panel. This effectively closes a relay which increases the current to the bridge from a few milliamperes to some desired current level (typically tens of milliamperes) chosen by the user and dependent upon the design limitations of the sensor being tested. The return of the voltage level at the "Auto Step" input to a logical low(<0.8V) terminates the test. The manual mode performs the same func-tions, but the test is initiated via the front panel switch. In either mode, an adjustable output (0 to+5 VDC) is provided by the control unit when the test is initiated and is removed when the test is terminated. This output signal feature allows the user to identify when the test started and stopped; it also provides a means of remotely controlling digital analysis equipment if so chosen. If a recording of the LCSR test results is made, this output signal would also be recorded to give a timing reference forthe initiation and the termin-ation of the test.

Model 934 Power Bin Module. Three power supplies provide separate power to each ofthe above modules.

1 FOR FURTHER INFORMATION,CONTACT:

Marketing Manager Technology for Energy Corporation 10770 Dutchtown Road Knoxville, Tennessee 37922

'615) 966-5856

LCSR HISTORY 1.

BASIC DEVELOPMENT ORNL/DOE R. L. Shepard R.

M. Carroll 2.

LWR APPLICATION RESEARCH EPRI/UT T.

W. Kerlin 3.

COMMERCIAL APPLICATION TEC J.

E. Mott J.

C. Robinson J.

E. Jones R,

K. Fisher M. V. Mathis

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results, (2) Determine Al.

TIME CONSTANT DEPENDENCE ON hR k

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SENSOR TESTING RESULTS Yew sensor and well plunged 180'F, 3 Ft/Sec 2.89 Sensor installed in plant Good Fit {6 = 0) v ~ 1.70 sec.

Poor Fit (8

=.001")

v

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= 3.70 sec.

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9.6 sec.

air gap'latinua

" sensing element oxide sheath and well

COMPARISON OF PLUNGE SENSOR TESTING METHODS hR/k for Various Test Conditions Sensor Reactor Conditions 3 Ft/Sec 180'F Water 1

I t/Sec 500 F Lead-Comments Combustion 300 27 115 Internal Resistance dominates for all tests.

Westinghouse 3.8

0. 34 1.5 3 Ft/Sec has wrong mechanism dominating, even liquid metal does not simulate well.

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0 10 20 30 40 50 60 Time in Seconds FiS ~ 5.l Typical Output of an RTD Follovire a Sten Change in Current from 2.2 ma to 35 ma.

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0 12 15 18 21 24 27 30 Time in Seconds Fig. 5.2 Average LCSR Test Results for 14 steps.

II

LUMPED PAIUQKTER TRANSFORMATION 1.

Requires No Knowledge of Sensor 2.

Has Non-Conservative Bias i.e.

One Eigenvalue A

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Two Eigenvalues 1

1 1-Al Eigenvalues Gives exact value of Al for center located sensing element 3.

Does not give credit for sensing element near surface

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CONTINUOUS MODEL (1)

Requires Knowledge of (a)

Thermal properties of sheath and well (b)

Sensor dimensions and corresponding uncertainties (2)

Requires Two Eigenvalues (3)

No Bias Error (4)

Calculable Error (5)

Accounts for Sensing Element Location

TABLE 5.1 EFFECT OF 'to (INITIAL TIME FOR ANALYSIS )

ON THE TIME CONSTANT TTrue

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/ Error T

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