ML17303A183

Suppls 860314 Responses to NRC SPDS Isolator Questions to Reflect Results of Addl Isolator Testing,Per 860929 Commitment.Test Results Also Reviewed & Accepted by NRC During Nov 1986 SPDS Site Audit & Meeting on 861209

ML17303A183
Person / Time
Site:	Palo Verde
Issue date:	12/19/1986
From:	Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Knighton G Office of Nuclear Reactor Regulation
References
ANPP-39451-JGH, TAC-56654, TAC-62796, TAC-64581, NUDOCS 8612300237
Download: ML17303A183 (38)

Text

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ACCESSIQN NBR: 8612300237 DOC. DATE: 86/12/19 NOTARIZED: NQ DOCKET 0 FACIL: STN-50-528 Palo Vev de Nuclear Stati one Uni t ii t

STN-50-529 Palo Vev de Nuc leav Stations Uni 2> Av'izona Pub Av'i zona Pub li li 05000528 05000529 STN-50-530 Palo Verde Nuclear Stationi Unit 3> Arizona Pub li 05000530 AUTH. NAKE AUTHOR AFFILIATION HAYNES> J. 0. Av izona Nucleav'ouer ProJect i (formev lg Av zona Public Serv RECIP. NANE RECIPIENT AFFILIATION KNICHTON> C. W. PWR Prospect Directorate 7

SUBJECT:

Submits suppl responses to SPDS isolator questions reflecting v esults of addi isolatov testing.

DIBTRIBUTION CODE: *OOOO COPIEB RECEIVED: LTR ~ ENCL Q BIIE:

TITLE: OR/Licensing Submittal: Supp 1 1 to NUREQ-0737(Generic Ltv'2-33)

NOTES: Standardized plant. N. Davis> NRR: 1Cg. 05000528 Standardized plant. N. Davis. hfRR: 1CM. 05000529 Standardized plant. N. Davis'RR: iCg. 05000530 REC I P I ENT COPIES RECIPIENT COPIES ID CODE/NANE LTTR ENCL ID CODE/MANE LTTR ENCL PWR-B ADTS 1 1 PWR-B EB 1 PWR-B PEICSB 2 2 PWR-B FOB 1 1 PWR-B PD7 LA 1 1 PWR-B PD7 PD 7 7 LICITRA> E 1 1 PWR-B PEICSB 1 PWR-B RSB 1 1 INTERNAL ADN/LFNB 1 0 IE/DEPER/EPB 3 3 NRR BWR ADTS 1 NRR PAULSQN> W 1 1 NRR PWR-B ADTS 1 NRR/DSRO ENRIT 1 1 IB 1 NRR/DSRO/RSIB 1 1 RE FIL S 1 RGN5 1 1 EXTERNAL: LPDR NRC PDR 1 1 NSIC NOTES: 1 1 TOTAL NUBBER OF COPIES REQUIRED: LTTR 32 ENCL 31

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Arizona Nuclear Power Project P.o. BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 December 19, 1986 ANPP-39451-JGH/MAJ/98.05 Director of Nuclear Reactor Regulation Attention: Mr. George W. Knighton, Project Director PWR Project Directorate ¹7 Division of Pressurized Water Reactor Licensing B U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2 and 3 Docket Nos. STN 50-528 (License NPF-41)

STN 50-529 (License NPF-51)

STN 59-530 Response to NRC Safety Parameter Display System (SPDS) Isolation Questions File: 86-A-056-026

Reference:

(1) Letter from J. G. Haynes, ANPP, to G. W. Knighton, NRC, dated September 29, 1986 (ANPP-38447).

Subject:

Response to Perform Maximum Credible Fault Testing on SPDS Isolation Devices.

(2) Letter from E. E. Van Brunt, ANPP, to G. W. Knighton, NRC, dated March 14, 1986 (ANPP-35548).

Subject:

Response to Six NRC Questions on SPDS Isolation Devices.

Dear Mr. Knighton:

In Reference (1), ANPP committed to perform additional SPDS isolation device testing and supplement the responses to the staff's isolator questions (Reference

2) to reflect the results of the additional testing. Attached are the ANPP supplemented responses to the isolator questions reflecting the results of the additional isolator testing. The ANPP test results were also reviewed and accept-ed by the staff during the November, 1986, PVNGS SPDS Site Audit and at a meeting held on December 9, 1986, in Bethesda, Maryland.

If you have any questions, please call Mr. William F. Quinn of my staff at ext.

4087.

Very truly yours, J. G; Haynes Vice President Nuclear Production JGH/MAJ/rw.

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Mr. George W. Knighton

Subject:

Response to SPDS Isolation Questions ANPP-39451 Page 2 CC: 0. M. De Michele E. E. Van Brunt, Jr.

E. A. Licitra (w/a)

A. C. Gehr (w/a)

R. P. Zimmerman (w/a)

L. Beltracchi (w/a)

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For each type of device used to accomplish electrical isolation, describe the specific testing performed to demonstrate that the device is acceptable for its application(s). This description should include elementary diagrams where necessary to indicate the test configuration and how the maximum credible faults were applied to the devices.

ANPP RESPONSE As previously discussed in ANPP-35548 dated March 14, 1986, a "hi-pot" and "surge withstand" test were performed. In addition to this testing the following additional tests were performed by ANPP to satisfy the NRC staff request.

To demonstrate that the SPDS isolation devices are acceptable for their application, an isolation barrier qualification test was performed. This test was based on the guidance provided in IEEE 279-1971 and IEEE 384-1981.

The test was completed with the purpose of collecting data on the performance of the SPDS isolation devices when the isolators were subjected to:

(A) A maximum credible voltage/current transient applied to the isolations device non-Class 1E side; (B) Shorts, grounds and open circuits occurring on the isolators non-Class 1E side.

These tests were performed and documented per the procedure titled "Procedure For Testing The Energy Incoxporated Class IE Analog Model 80798-58 and Digital Model 80643 Isolation Devices As Used In The ERFDADS System (SD)", Revision 0 and Errata sheets.

The test procedure was created to define test methodology, test setup, test criteria and documentation of performed actions.

The general methodology of the test procedure is as follows:

(A) Perform a functional test of each channel of the isolator cards prior to performing either the MCF, open or short testing to prove that the channels to be tested function properly:

(B) Perform a short/open test which places a short and open at the isolators output while monitoring the isolators input signal to prove that there is no breakdown of the isolation barrier of the specific cards.

(C) Perform an applied transient test that applies a voltage/current

'ransient which is similar to that defined by the maximum credible fault transient'. The, transient was applied 'to the output leads of the isolator channel 'while monitoring, the isolators input (Class 1E) side of the channel under test, to prove the isolator fulfills

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(D) Perform an applied transient test that applies a voltage/current transient which is similar to that defined by the maximum credible fault transient. This transient was applied to the power supply terminals while monitoring the isolators input (Class 1E) side of the channel under test, to prove the isolators fulfill their intended function.

The test procedure also included sections regarding test prerequisites, test acceptance criteria, test equipment required, methods of documenting test results, figures for test rig setup and detailed instructions for executing the test in a safe and orderly manner.

Elementary diagrams '(Figures 1C, 1D, '1E, 1F, 1G, and 1H) that indicate the open/short/maximum credible fault test configuration and how the maximum credible fault was applied to the isolation devices are attached.

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Provide data to verify that the maximum credible faults 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.

ANPP RESPONSE To determine the magnitude of the MCF that the PVNGS SPDS isolation devices would be exposed to, several bolted-fault scenarios were considered. Scenarios that are not in the plant design bases due to very low probability of occurrence were eliminated.

The SPDS isolation device MCF calculation was performed to determine the MCF voltage/current available at the isolation devices non-1E side (output). The results of the calculation which considered the case of two bolted-faults (Faults 81 and 82 on Figure 2A) at the SPDS (ERFDADS) isolation cabinet. Figures 2B and 2C indicate that a MCF of 9:5 amps at 120 volts are credible through the isolation device non-Class lE output signal cables and a MCF of 207 amps at 120 volts at the isolation device power supply, respectively.

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Provide data to verify that the maximum credible fault was applied to the output of the device in the transverse mode (between signal and return) and that other faults were considered (i.e., open and short circuits).

ANPP RESPONSE The signal transient fault (Fault 81) was applied to the output leads (power source) of the isolator channel while monitoring the isolation input (Class 1E) side of the channel under test. The test configuration is shown on Figures lE and 1F.

The power supply transient (Fault 82) was applied to the power supply terminals while monitoring the isolators input (Class 1E) side of the channel under test. This application of this MCF is shown on Figures 1G and 1H.

Open and short circuits to the isolation device outputs are as shown on Figures 1C and 1D.

(4) NRC QUESTION Define the pass/fail acceptance criteria for each type of device.

ANPP RESPONSE The pass/fail acceptance criteria used for evaluating the digital and analog SPDS isolators under test conditions is:

(a) That there is, no barrier breach of the non-lE system through the isolator to the 1E system, or, (b) If there is a barrier breach, the breach does not significantly impact the class lE system from meeting is minimum performance requirements as specified in the PVNGS design basis.

The ANPP acceptance criteria is defined in the context of and is consistent with Regulatory Guide 1.75, Revision 1 and IEEE standards 384-1974 and 279-1971. The utilization of the acceptance criteria is described below.

Test Results:

(a) Si nal Transient Fault Test (Fault 81)

Analog Isolator Model 649-1 These isolators were tested and promptly opened internally after a brief period (2 ms.) of current flow. Overall results show that no breakthrough of the individual channels isolation barrier occurred.

Analog Isolator Model 798-58 These analog isolators are similar in design to the Model 649-1 but each output of each channel provided a 18 volt varistor for protection. Overall results show that no breakthrough of the isolation barrier occurred on any of the channels tested.

Digital Isolator Model 643-1 At the application of the 120VAC transient signal, the output capacitor (1 ufd/35V) fails in the short mode because of excessive voltage application beyond the dielectric rating.

The isolator integrated circuit isolation barrier is then faulted due to excessive heat dissipation of the output transistor causing the voltage remaining on the output (Non QlE) terminals to appear on the input. In this specific test, 120VAC was applied . through a simulated 13 ohm line resistance to the isolator output terminals. A current of approximately 8.0 amps was then flowing through the shorted output capacitor causing a voltage drop of approximately

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0.5V. As the isolation barrier was breached, this 0.5V appears across a 2000 ohm resistance in the test jig which results in a fault energy of 0.125 mw. This voltage appeared on all channels as the failure mode was similar on all tested channels.

(b) Power Su 1 Transient Fault Test (Fault //2)

Analog Isolator Model 987-58 The application of the transient quickly rendered the isolator integrated circuit inoperative with no physical damage or no isolation barrier breakthrough.

Analog Isolator Model 649-1 The application of the transient voltage quickly rendered the isolator integrated circuit inoperative with no physical damage or no isolation barrier breakthrough.

Digital Isolator Model 643-1 The application of the transient voltage caused the output transistor to short subsequently impressing 120VAC across the output capacitor resulting in the breakdown of the dielectric. This breakdown of both the output transistor and capacitor resulted in flow of high current, high heat dissipation within the isolator and subsequent breakdown of th'e isolation barrier. At this time, the voltage drop across the shorted 'output capacitor was observed across the input (QlE) terminals of the isolator card. The transient lasted from 1/4 to 1 cycle in duration applying a maximum of 0.4 volts across the input (QlE) terminals.

(c) 0 en/Short Fault Test The results of the open/short tests were documented by oscilloscope photographs showing the switching transient of the load switching and the magnitude of the applied signal. During the test of card type 643-1, serial 165, a small spike appeared simultaneously with the switching transient. The appropriate test steps were re-performed a number of times with no re-occurrence. The small spike was deemed noise due to external interference.

RESULT ACCEPTANCE:

(a) During the transient testing the analog isolators did not allow a fault signal to migrate into the isolator Class lE side. Therefore, the analog isolators are acceptable for their intended application and no additional circuit analysis was performed.

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(b) During the transient testing the digital isolators did allow an average signal of 0.5 volts into the isolator Class lE side. A detailed digital circuit analysis was performed and identified that the 1E field contact inputs are rated at 120 volts, and at least 1 amp, therefore the breakthrough voltage into the isolator Class lE side will not significantly impact the field contact input. It should also be noted that the normal voltage across the contact input is 48 volts at 0.5 ma while the contacts have a minimum rating of 125 VAC at 1 amp. Even though the digital isolators did pass a small voltage across the isolation barrier, the impact upon the Q1E circuit was insignificant within the guidelines of R.G. 1.75 and IREE 384 and therefore are acceptable for their SPDS application.

(c) In conclusion, the testing and analysis performed by ANPP shows that both the digital and analog isolators used in the PVNGS SPDS application meet the guidelines of R.G. 1.75, Revision 1, IREE standards 384-1974 and 279-1971 and are acceptable for use.

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