ML20116D023
| ML20116D023 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/18/1985 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19269B447 | List: |
| References | |
| NUDOCS 8504290255 | |
| Download: ML20116D023 (17) | |
Text
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SOUTH CAROLINA ELECTRIC & GAS COMPANY post orrict ts4 COLUMBlA. SOUTH CAROLINA 29218 l
- o. w. DinoN. Ja-Vice pnesiDENT NUCLEan OPEnATIONs April 18,1985 Mr. Harold R. Denton Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Safety Parameter Display System
Dear Mr. Denton:
In a letter from the NRC Staff dated October 4,1984, South Carolina Electric and Gas Company (SCE&G) was requested to provide additional information related to the Safety Parameter Display System (SPDS) for the Virgil C. Summer Nuclear Station. The attachments to the letter provide the response to the NRC request for information.
This submittal contains information proprietary to Westinghouse Electric Corporation and is supported by the enclosed affidavit signed by Westinghouse.
The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.790 of the Code of Federal Regulations (CFR).
Accordingly, it is respectfully requested that the information which is proprietary to Westinghouse be withheld from public disclosure ir accordance with 10 CFR Section 2.790.
Correspondence with respect to the proprietary aspect of this application for withholding or the supporting Westinghouse affidavit shou ld reference CAW-85-30 and shou ld be addressed to R. A. Wiesemann, Manager, Regulatory and Legislative Aff airs, Westinghouse Electric Corporation, Post Office Box 355, Pittsburgh, Pennsylvania 15230.
Enclosed are 10 copies each of the proprietary and non-proprietary versions of WCAP-10170, Supplement 2, " Westinghouse Technical Support Complex Design and V&V Process for the V. C. Summer Nuclear Station." This WCAP is referenced by SCE&G in the enclused responses to the NRC Staff questions.
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I Mr. Harold R. Denton Office of Nuclear Reactor Regulation Page 2 April 18,1985 t
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MDB/vb Enclosure cc:
V. C. Summer C. A. Price T. C. Nichols, Jr./0. W. Dixon, Jr.
C. L. Ligon (NSRC)
E. H. Crews, Jr.
K. E. Nodland E. C. Roberts R. A. Stou gh W. A. Williams, Jr.
G. 0. Perciva' D. A. Nauman C. W. Hehl J. N. Grace J. B. Knotts, Jr.
Group Managers NPCF
- 0. S. B rad h an, File l
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1 Attachment A Digital Isolators Page 1
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Question 1.
Isolation Devices a.
"For each type of device used to accomplish electrical isolation, describe the specific testing performed to demonstrate that the device is acceptd)1e for its application (s). This description should include elementary diagrams when necessary to indicate the test configuration and how the maximum credible f aults were applied to the devices.
b.
Data to verify that the maximum credible f aults applied during the test were the maximum voltage / current to which the device could be exposed, and define how the maximum voltage / current was determined.
c.
Data to verify that the maximum credible f ault was applied to the output of the device in the transverse mode (between signal and return) and other f aults were considered (i.e.,
open and short circuits) d.
Define the pass /f ail acceptance criteria for each type of device.
e.
Provide information regarding the extent to which the isolation devices comply with the environmental qualifications and with the seismic qualifications which were the basis for plant licensing.
f.
Provide a description of the measures taken to protect the safety systems from electrical interference (i.e.,
Common Mode and Crosstalk) that may be generated by the SPDS."
Answer:
Digital Isolators The Virgil C. Summer Nuclear Station application uses digital isolators in 120 volt AC circuits and 125 volt DC circuits. The maximum f au lt postulated is a short from a 120 volt AC circuit to the isolated circuit within cable trays. The following tests performed by Rochester Instruments and the additional analysis demonstrate that even with no current limiting in the non-lE circuits, the isolator itself will clear the fault and will not affect the lE portion of the circu it.
h Attachment A Digital Isolators
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Page 2 FAULT CURRENT TEST The objective of this test was to assess the ability of the EI4400 series isolator module to maintain isolation between the IE input and non-lE output during a short circuit f ault condition at the output of the module. This test provides data supporting f au lt currents of very short duration.
TEST SET-UP 1.
Test set-up simulated an installation in which the isolator output was a series element in a 3 amp fused circuit powered by a 24VDC power supply. The equipment was connected as shown in Figure 1.
Both relay contacts and associated circuitry were subjected to the short circuit condition.
2.
Test Equipment DVM Model Fluke 8050A T.E. # TV0-151 Cal. due date 05/85 Scope - Model HP-1727A T.E. # T0-46 Cal. due date 10/85 Power Supply - AC/DC Electronics, Model EC24N10 Power Supply - Health / Zenith PSI Rated 24 VDC,10A continuous output PS2
- Model P-2718 Precautions were taken to limit excessive lead lengths between the isolator module output and the power supply.
Lead lengths and wire gauge type were recorded.
Total Length 21" Wire Gauge 12 Gauge Stranded Test Description 1.
Test #1 - Power supply connections were terminated at module pins 6 & 7 (KlC).
A.
Opened SW1.
B.
Applied 24VOC to module (Pins 6 & 7)
C.
Closed SW1 (simulating the presence of an input signal).
Simultaneously measured the waveform on the scope and recorded the resu lts. The DVM was also monitored to check the isolation condition.
D.
Inspected the module for trace of component damage and isolation breakdown.
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Attachment A Digital Isolators Page 3 2.
Test #2 - Power Supply connections were terminated at module pins 7 & 8 (KID).
A.
Replaced fuse and checked that SW1 was in the closed position.
B.
Applied 24VDC to module (pins 7 & 8).
C.
Opened SW1.
Sinultaneously measured the waveform on the scope and recorded the results. The DVM was monitored to check the isolation condition.
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C1 added to boost short circuit current 2.
F1 - Littlefuse Series 312; 3A/250V fast acting.
3.
Scope across R measured wavefonn.
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R consisted of three.1 ohm resistors. Total measured resistance =
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(Measurement taken on Fluke 8520A with 4 wire esistance setting).
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Attachment A Digital Isolators Page 4 Test Results 1.
Test #1 Current Waveform RA Ilv f +1.9a,-:'
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I eI. sao I8E Module Condition - No evidence of isolation breakdown or trace / component damage was noted.
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Test #2 Current Waveform ECA a
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Module Condition - No evidence of isolation breakdown or trace component damage was noted.
Attachment A Digital Isolators Page 5 HI-P0T AND TUNCTIONAL TEST PROCEDURES Test equipment required (or equivalent) a.
Rochester Instnament Systems Test Set TMM34.
(Figure 2) b.
Digital Voltmeter.
c.
Hi-Pot Test Set.
Hi-Pot Test A.
The aJtput connector had all pins wired together, and the two input terminals at the end of the module were wired together.
Attached the Hi-Pot Terminal block to the module. Applied 4000 VAC RMS between input and output with a 1 ma trip point.
The Hi-pot test was performed by Rochester Instruments to the relay contacts since open and short circuits tests are not applicable to these contacts. The isolators successhJ lly passed these tests.
Functional Test A.
Prior to installing the module in the test set, selected the required field contact voltage per the suffix table below:
Suffix Field Contact Voltage
-X 24 VDC
-J 48 VDC
-0 125 VDC
-S 117 VAC (Note 1)
Note:
The 117 VAC connection was via the jacks on the panel and an external variac was used to generate this voltage.
l B.
Selected the output load using switches SW1 and SW2 per the table below:
Module Output 1 Output 2 l
l El 4401 100 MA (Relay Contact Out) 10 MA (High Speed l
Iso. out) l El 4402 100 MA (Relay Contact Out) 10 MA (Relay Contact Out)
El 4403 10 MA (High Speed Iso. Out) 10 MA (High Speed Iso. Out)
El 4404 10 MA (High Speed Iso. Out) 10 MA (High Speed Xistor Out)
El 4405 100 MA (Relay Contact Out) 10 MA (High Speed Xistor Out)
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Attachment A Digital Isolators Page 6 C.
Turned power on.
Installed module in the test set and attached the terminal block to the module input.
Go-No-Go Test A.
Verified that the green light emitting diodes (LEDs) illuminated and the red "10MA" LEDs were off when switch SW3 was "0N."
Full Test A.
With the module installed and SW3 "0N," set the input voltage over the range of input voltage as shown below. Verified that the green LEDs illuminated over the full range of the modules specified input voltage.
Nominal Voltage Range 24 VDC 20 to 30 VDC 48 VDC 38 to 60 VDC 125 VDC 105 to 140 VDC 117 VAC 105 to 132 VAC B.
Measured the matput voltage at the Output 1 and Output 2 terminals, referenced to the aJtput return test point. The voltage, when on, was tested to be less than 1.5 volt DC.
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Attachment A Digital Isolators Page 8 QUALIFICATION AND SEISMIC TESTING Results of qualifications tests show that environmental conditions for the Virgil C. Summer Nuclear Station were met or exceeded as follows:
REQUIRED QUALIFIED Tempt. ature 77*F lll.9'F Humidity 50%
50%
Radiation
<500 Rads 2 x 104 Rads Seismic tests show that the isolators could withstand the safe shutdown earthquake and operating basis earthquake conditions postulated for their location in the control building.
Bypass capacitors at the output tenminals are provided to bypass interference to ground and output wiring is shielded to provide further protection.
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Attachment A Digital Isolators Page 9 ADDITIONAL FAULT CURRENT ANALYSIS The f ault current test outlined on pages 1 through 3 of this attachment demonstrates the isolator's ability to clear a f ault of very short duration. For higher f aults of longer duration the following analysis supports the use of the isolators of the Virgil C.
Summer Nuclear Station.
The class 1E input to the isolator card is connected to an optical isolator located at the front of the isolator board near the class IE input terminals and isolates both current and voltage between the lE and non-lE circuits.
Additionally, at the opposite end of the isolator board near the non-lE aatputs, there is a relay which provides the contact output to the non-lE circuits and serves as an additional isolation device. Thus, two isolators are present.
If a high f ault current across the relay contacts is postulated, one of four actions can be expected to occur:
- 1) The non IE circuit connectea to the isolator card opens and the f au lt clears.
- 2) The circuit trace on the isolator circuit board opens and the f ault clears.
- 3) The card edge connectors vaporize and the f ault clears.
- 4) The relay contacts melt and open which clears the f aalt.
It is anticipated that the most likely (and worst case) ocaJrances will be a f ailure of the circuit trace on the board to the relay contacts or the f ailure of the contacts themselves. Either f ailure will not affect the safety related circuitry on the circuit board.
Low f ault currents insufficient to fuse circuitry as described above could result in heating on the circuit board. Because the board material is non flammable glass epoxy with 6 inches separation between l
the lE and non-lE portions, any burning on the non-lE end of the board will not propogate to the lE end of the board.
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Attachment A Digital Isolators Page 10
SUMMARY
The preceding tests were performed on an EI4401 Isolator Module which is identical to the EI4402 module used at the Virgil C. Summer Nuclear Station with the exception that the EI4401 module contains single pole double throw relay aJtput circuitry in lisJ of a double pole double throw aJ tpu t.
The circuit paths for each output are comparable; therefore, it is logical that the test results would be similar. The results of these tests and analyses indicate that the isolator module will perform its isolation function during the conditions as described in the tests for all postulated f ault conditions.
In addition, to provide further protection to safety systems from electrical interference that may be generated by the Safety Parameter Display System, bypass capacitors at the output terminals are provided to bypass interference to ground and output wiring is shielded.
i Attachment A Analog Isolators Page 11 Answer:
Analog Isolators s.
Analog inputs to the TSC computer which require isolation originate from the Westinghouse 7300 Process Racks. Those protection grade /IE analog signals are isolated using voltage-to-voltage and voltage-to-current isolation cards within the 7300 Process Racks before they are routed to the TSC Computer. These are the same isolaticin cards used to provide isolation between the protection and control system required by IEEE-279.
The answers to questions 1.a through d and f for;.these analog isolation devices are addressed in the Virgil C. Summer Final Safety 1
Analysis Report (FSAR) (Section 7.2.2.2.3.7 - Control and Protection System Interaction) and referenced WCAP
- _Siroky, R.M. and Marasco,.F.W., "7300 Series Pr%892A (Reference 5:
ccess'Controi System Noise Tests," June,1977.) This WCAP provides' bases information, test configurations and details, diagrams, f aJit conditions, acceptance criteria, and conclusions. The tests outlined in the WCAP demonstrate that the protection systems are not degraded by credible f elt
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conditions which could be postulated in non-protection systems used for control and display of information, including the TSC computer.
These test conclusions have been preifiously accepted by the Staff.
Seismic qualification (question 1.e) for these ardlog isolation devices is addressed in the Virgil C. Summer FSAR (Section 3.10.2.2 -
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, Nuclear Steam Supply System Equipment) and Referenced WCAP-7817, Supplement 4 (Reference 7: Reid, J.B., " Seismic Testing of Electrical and Control Equipment'(Westinghouse NUCANA 7300 Series), (Lpw 5eismic Plants)," November,1972.), and is consistent with the licensing basis
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Th'e 7300 Process Racks containing these analog isolation devices are s
.; located in a mild ' environment which-Is controlled by redundant safety
'related HVAC Systems. For this reason they cannot be exposed to a
% harsh environment as a result of ~any oesign basi's event. The environmental qualification of the 7300 Process Racks which contain these analog isolation devices is ' addressed _ir Section 3.11 of the Virgil C. Sunaner FSAR and is consistent with the licensing basis for the plant.
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Question 2.
Human Factors Program
" Provide a description of the display system, its human f actored
design, and the methods used and results from human f actors programs s
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to ensure that the displayed information can be readily perceived and comprehended so as not to mislead the operr.or."
Answer:
On February 2,1984, a Safety Evaluation Report (SER) for the Westinghouse Generic Safety Parameter Display System was issued by the NRC (letterTLS05-84-02-009). The same functional requirements, design basis doajments and human f actors programs that were the subject of the SER wer'e applied to the Virgil C. Summer TSC system. A description >of the Virgil C. Summer display system and human f actors considerations is presented in the enclosed WCAP-10170, Supplement 2, dated January 1935.
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Attachment C Page 1 Question 3.
Data Validation
" Describe the specific methods used to validate data displayed in the SPDS. Also describe how invalid data are defined to the operator."
Answer:
The Redundant Sensor Algorithm (RSA) processes redundant sensor inputs and (when possible) returns a group value of the valid sensor for use in upper level displays. Valid signals are selected by first eliminating those values which result from known bad input points (either by aJtomatic hardware checking or by operator input), those values which are not periodically updated (removed from scan), and those values which have previously f ailed the sensor consistency check.
The remaining signals are then examined for consistency within a predetermined tolerance. If no more than one of these signals f ails to agree within the tolerance, the average value of those signals within the tolerance will be used to represent the group value. Sensors outside the tolerance will be given a quality code of P00R and will not be considered in subsequent evaluation cycles until the value returns within the acceptable tolerance.
In the case where only a single sensor value is presented to the consistency checking routine, that sensor value will be used for the group value.
If no sensors reach the consistency check, or if more than one of the signals reaching that check do not pass the test, then no value is assigned to the group value and the group value will be given a data quality of BAD.
The following quality codes will be used for individual sensor values.
QUALITY CODE DESCRIPTION BAD 3
Signal missing, or removed from scan with no value entered, or from an I/O point which was detected by system diagnostic routines.
"B" is displayed after the data.
P00R 2
A signal which has f ailed the group consistency check.
"P" is displayed after the data.
MANUAL 1
Signal has been removed from scan and a value has been manually entered.
"M" is displayed after the data.
GOOD 0
A sensor value that is neither BAD, P00R, nor MANUAL
e Attachment C Page 2^
For redundant sensor, the following group quality codes will apply:
QUALITY CODE DESCRIPTION BAD 3
No GOOD sensor inputs for the group are found in the signal consistency checking.
"B" is displayed after data.
P00R 2
Group quality is not BAD, but one or more of the individual group sensors has a quality other than G000.
"P" is displayed after data.
MANUAL 1
Not applicable -- a manually entered group value will not be utilized.
GOOD 0
A group value which is neither BAD, nor P00R.
Attachment D Page 1 Question 4.
Parameter Selection
" Provide the basis for the selection of parameters which are sufficient to provide information to plant operatcrs about:
a.
Reactivity control b.
Reactor core cooling and heat removal from the primary system c.
Reactor coolant system integrity d.
Radioactivity control e.
Containment conditions."
Answer:
The basis used for the selection of parameters for the Virgil C.
Summer TSC is the same as the one described in Section 2.3 of the NRC SER referenced in the question 2 response. A list of the parameters used for the Virgil C. Summer TSC data base is included in the enclosed WCAP-10170, Supplement 2.
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