ML19319C107
| ML19319C107 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/31/1975 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Schwencer A US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8001310471 | |
| Download: ML19319C107 (8) | |
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DESCRIPTION:
ENCLOSURES:
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Response to our, concernin; secticn o et Rev 14 to BAW-10003
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MCDONALD MCORE (L)
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EXTEriNAL O!STRICUTION
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December 31, 1975
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s Director of Nuclear Reactor Regulation Attention:
A.
Schwencer, Chief Light Water Reactor Branch 2-3 Division of Reactor Licensing U.S. Nuclear Regulatory Commission Washington, D. C.
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Dear Mr. Schwencer:
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In response to your letter dated November 11, 1975, regarding the topical report BAW-10003, Revision 4,
" Qualification Testing of Pro-tection System Instrumentation", the attachment addresses Section 6 of your evaluation of BAW-10003.
Yours very truly, i
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THE TCLEDO ECISCN CCMPANY EC:SCN PLAZA 3CC MACISCN AVENUE TCLECO CHIC 13652 l
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s DB-1 RESPONSES TO NRC LETTER OF NOVEMBER 11, 1975 RPS QUALIFICATION, ITEM 6 i
6.a.
The still air temperature range of 40 to 110 F applies to the ambient 3
temperature range at the inlet to the system cabinet's ventilation system. This range will be maintained in the areas containing the system cabinets in order for the systems to perform within specifications.
The still air humidity of 50 percent R.H. represents a typical operating value and should be specified at the full range of 10 to 80 percent R.H.
continuous with excursions to 90 percent R.H. for not more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The upper values, which are the critical values for equipment operability, are documented in Table 2-2 of BAW 10003.
The range of 10 to 80 percent with 90 percent R.H. for not more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> will be maintained in the areas containing the system cabinets in order for the systems to perform within specifications.
6.b.
The interconnecting wiring and connectors used with the Bailey Meter Company systems were qualified during environmental and seismic qualifi-cation tests. Test fixtures used during the tests included wiring and connectors used on BMCo systems (see page 6-4 of BMi-10003, " Test fixtures... duplicate... normal application").
6.c.
The electrical power sources for the instrumentation have been tested and will maintain input to the cabinets within the voltage range of 107 to 127 V ac at a frequency range of 58 to 62 Hz.
i 6.d.
The accident analysis is based on the design R.C. flow rate; R.C. flow measurement errors are less than the excess flow fraction which is required by the R.C. flow acceptance criterion. For all other entries in 6.d., the applicant's Chapter 15 analysis is based on assumed "end-to-end" instrument string errors which are greater than or equal to, but not less than those errors listed.
6.e.
The technical specifications will require that calibration of the Motorola j
pressure sensors be performed at each refueling outage.
Comparative readings between the like variables in the four channels would indicate i
any deviation and, thus, the need for calibration if it should occur prior to the refueling outage. The use of a two-out-of four voting logic between channels ensures that an out-of-calibration sensor will have no adverse effect on the syerem.
Calibration not less frequently than once every four months is not possible in that calibration of these pressure sensors, which are located inside the containment vessel, during operation was not a design basis for Davis-Besse.
Calibration during operation would require unwarranted excessive occupational radi-ation exposure as some of the equipment is located in radiation zones D and E, which are described in Chapter 12 of the FSAR.
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The response time values as stated in Criteria 6.f.,
represent time constants for sensors and step response times for individual modules as 4
confirmed during laboratory tests and reported in BAW-10003. However,
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safety analysis uses end-to-end string responses which cannot be calcu-lated by summation of the individual module response times listed in Criteria 6.f.
Instead of such a summation, the safety analysis in j
Chapter 15 is based on the addition of the sensor's time constant, used as a pure delay, which is then added to the cabinet mounted modules' 3
string response time (also assumed as a pure delay). The time constant is used as a pure delay since the dynamic response of the plant variable has a time constant greater than the instrument string including sensor.
Only those modules utilized in trip strings are tested for string response.
Other equipment, while housed in the same cabinet but whose functions 1
are not utilized in safety analysis, is not tested for string response.
The required trip string response for cabinet mounted modules is specified to the equipment vendor and is verified prior to shipment of every system leaving the factory. The actual values obtained during such l
response tests are documented in the QA data manual.
I Table 1 entitled " Sensor Time Constants", tabulates the required values j
as assumed in Chapter 15 by Safety Analysis along with typical values i
obtained during tests of the sensors.
Table 2 entitled " Cabinet Equipment String Response" tabulates the i
required values as assumed in Chapter 15 by Safety Analysis along with typical values of string response obtained during checkout of each trip string of the cabinet mounted modules.
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A simulated step input is utilized with the starting value being repre-l sentative of a normal operating plant variable and the end value above i
(or below) the trip setpoint value.
The string response (from input t
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terminal to reactor trip module output) is recorded and documented in the QA data manual.
6.g.
Table 1 shows the sensor delay requirement while Table 2 shows the RPS system requirement, as utilized by Safety Analysis.
l The R.C. pump status monitors only supply input to the R.C. pump i
status / flux trip function. Conversion of the digital R.C. pump monitor j
signal to an analog voltage is accomplished with an accuracy of 0.88 l
percent in the resulting flux trip setpoint. The R.C. pump monitor l
input to the RPS has a total delay of no more than 240 ms from the time power to the R.C. pump is interrupted until the digital signal from the R.C. pump monitor reaches the RPS.
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Individual modules in the RPS cabinets will be calibrated as per IC 2001.00.
Instrument F ilibration Procedure (attached).
This procedure requires the individu modules to be calibrated in accordance with the appropriate instrue ton manuals for the modules and requires that this calibration be doct +nted.
After the individual modules have been calibrated by IC 2001.00, the complete instrumentation strings in the RPS will be tested in accordance with IP 305.01, RPS Pre-Operational Calibration. This procedure will test the strings in the RPS by using the installed test modules. This procedure is presently being written and uses B&W's TS 305.01 (attached) as a guide. The tolerances used in TP 305.01 are as conservative, and in some cases more conservative, than those specified in B&W's TS 305.01.
Af ter the completion of TP 305.01, the field inputs to the RPS are calibrated by the following procedures. Note that the tolerances used in these calibrations are in accordance with those given in B5W's TS 205.01 unless otherwise stated.
A.
Reactor Coolant Pressure: The RPS RCS pressure strings are cali-brated per TP 300.02, Reactor Pressure Instrument Pre-Operational Calibration (RPS) Test Procedure (attached), which requires simu-lating pressure signals by means of a pneumatic tester at the pressure transmitter. Voltages and indications are verified such that overlap will exist between TP 300.02 and TP 305.01.
B.
Reactor Coolant Flow: The RPS RCS flow strings are calibrated per TP 300 04, Reactor Coolant Flow Instrumentation Pre-Operational Calibration (attached), which requires simulating flow signals by means of a pneumatic tester at the D/P transmitters.
Indications are verified such that overlap will exist between TP 300.04 and TP 305.01.
C.
Reactor Coolant Temperature: The RPS RCS temperature strings are calibrated per TP 2400.21, Reactor Temperature Instrumentation Pre-Operational Calibration Instrument Strings RC 3A and 33 Test Procedure (attached), which requires simulating temperature signals by varying the resistance at the inputs to the RPS temperature strings.
Indicators and voltages are verified such that overlap will exist between TP 300.04 and TP 305.01.
D.
Reactor Building Pressure: The RPS Reactor Building Pressure strings are calibrated per TP 2400.25, Containment Pressure to SFAS and RPS Pre-Operational Calibration Test Procedure (attached),
which requires simulating presaure signals by means of a pneumatic tester at the pressure swite'ies.
Indications are verified such that overlap will exist between IP 2400.25 and TP 305.01.
E.
Reactor Coolant Pump Status Monitor: The procedure for testing the RPS RCP Power Monitors has not been completed but is presently being developed. l l
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Neutron Monitoring: Total Flux to the RPS is calibrated by TP 800.02, NSS Heat Balance Check Test Procedure, in conjunction with ST 5058.02, RPS Dailey Heat Balance Check Procedure (both procedures attached). These procedures require that the total flux instrumentation be calibrated if the calculated and indicated core power differs by more than + 2%.
Flux Imbalance: At the present the procedures requiring the imbalance instrumentation to be calibrated have not been completed.
When completed these proceudres will require that the out-of-core imbalance instruments be calibrated whenever out-of-core imbalance differs from incore imbalance by more than i 5%.
Please note the procedures that are attached are two to three years old.
These procedures will be reviewed and revised prior to their use in order to incorporate changes in the procedure writing philosophy, changes in equipment, changes in the Technical Specifications, etc.
Although these changes will be made, the procedures will follow the basic outlines given by the NSS vendor and will assure that the accuracies as discussed in part 6.d. above will be met.
4 At the present time, we do not have procedures for determining the response time of individual module < within the RPS cabinets. We are presently working on a Response Time Program such that the response time of the complete channel will be h armined to be within the limits as specified in the Technical Specifications. We feel that this total response time for the channel is sufficient to insure that the safety analysis assumptions are met.
To date, the applicant's procedures allow for field tests for accuracy and response time measurement of the cabinet mounted equipment. However, field tests for sensors require that the sensors be tested on an individual component basis for obtaining a time conctant from a simulated step input. Field testing of the sensors is difficult due to:
a.
Limited plant variable simulation using present state-of-the-art on-line or in-situ testing techniques.
b.
Inability to simulate a step change in the plant variable compatible to the laboratory test simulation.
i For cabinet mounted equipment, the periodic field tests for accurancy i
and response time can be accomplished by simulating sensor inputs or using actual sensor inputs at the input terminals of the cabinet-mounted equipment The input signal as well as the resulting trip action and system response time can be determined and recorded.
TECo intends to follow and support industry and research related programs such as is being pursued by EPRI to determine acceptable methods for determining sensor response times. TECo also intends to follow and evaluate the techniques and experiences of nuclear power plants presently committed to verifying response time for sensors.
If these techniques are successful and practical, they will be used as a basis for the preparation of test procedures to comply with the requirements of the Technical Specifications... -.
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i DB-1 TABLE 1 SENSOR TIME CONSTANTS Trip String Plant Variable Required Typical 1
Sensor Simulation Value Tested Value l
Pressure (Motorola)
Decrease pressure 250 ms 25 ms Temperature Increase temperature 1
177 GY 3.0 sec
- 3.25 sec 377 HW 5.0 sec 5.25 sec i
R.C. Flow Decrease flow 240 ms 110 ms R.C. Pump Monitor **
Loss of pumps 240 ms 160 + 16 ms****
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C.V. Pressure ***
Increase pressure 240 ms 40 ms (Mercoid)
Neutron Flux Increase flux 10 ms (Ionic delay not tested) i l
- The required value is based on a 60 f t/sec flow, whereas the tested value is based on 3 ft/see flow which is conservative.
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- The R.C. pump monitor provides a digital (on-of f) signal.
- The containment vessel pressure switch provides a digital (on-off) signal.
- This is a calculated value based on the circuit design and vendor standard product information.
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J DB-1 tap;E 2 CABINET EQUIPMENT STRING RESPONSE Trip String Plant Variable Required Typical Function Simulation Value Test Value overpower Increase flux 150 ms 105 t 10 ms Power / Delta Increase flux 150 ms 105 1 20 ms Flux / Flow Decrease flow 240 ms 160 1 20 ms Power /No. of Pumps Loss of pumps 150 ms 90 1 15 as High Pressure Increase pressure 150 ms*
85 1 10 ms Low Pressure Decrease pressure 150 ms*
85 1 10 ms High Temperature Incrc de temperature 150 ms 105 1 10 ms Pressure / Temperature Decrease pressure 150 ms 80 1 10 ms R.B. Pressure Incre.ise pressure 150 ms 901 15 ms
- The required value is 140 ms if monofilar stators are used.
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