ML20206U681

Part 21 & Interim Deficiency Rept Re Potential for Hydrogen Embrittlement Failure of Valcor Solenoid Valve Springs. Initially Reported on 860702.Valcor Recommends Retrofitting Valves W/Suitable Matl

ML20206U681
Person / Time
Site:	Vogtle
Issue date:	09/17/1986
From:	Foster D GEORGIA POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-86, REF-PT21-86-330-000, RTR-NUREG-0302, RTR-NUREG-302 GN-1077, IEIN-86-072, IEIN-86-72, PT21-86-330, PT21-86-330-000, NUDOCS 8610080100
Download: ML20206U681 (8)

Text

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,. ', Georgia Power Company

.,3 Post Office Box 282 Waynesboro. Georgia 30830 Telephone 404 554-9961, Ext. 3360 404 724-8114, Ext. 3360

0. 0. Fost., GeorgiaPower I ect ite s u} elec:nc sptem September 17, 1986 M

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m United States Nuclear Regulatory Commission .,_.,

Region II File: X78G03-M120 Suite 2900 Log: GN dO77 101 Marietta Street, Northwest ro Atlanta, Georgia 30323

Reference:

Vogtle Electric Generating Plant-Units 1 and 2; 50-424, 50-425; Valcor Solenoid Valves; Letter GN-1023 dated July 31, 1986 Attention: Mr. J. Nelson Grace In previous correspondence, Georgia Power Company informed the USNRC of a potentially reportable condition involving the potential for hydrogen embrittlement failure of Valcor solenoid valve springs.

This condition is the subject of USNRC I&E Information Notice 86-72.

Georgia Power Company has completed its evaluation and has concluded that this condition is reportable pursuant to the requirements of 10 CFR 21 and 10 CFR 50.55(e).

While in the process of evaluating the sprina failure concern, another condition involving Valcor solenoid valves was detected during Unit 1 preoperational testing. This second condition involves the failure of reed-type position switches mounted on the valves. The failure was caused by the use of an inappropriate control circuit design which caused the switches to be exposed to currents in excess of their rating. This condition is also reportable pursuant to 10 CFR 21 and 10 CFR 50.55(e).

Based upon guidance in NUREG-0302, Revision 1, and other USNRC correspondence, Georgia Power Company is reporting both of these conditions pursuant to the reporting requirements of 10 CFR 50.55(e).

A summary of our evaluations for both conditions is attached.

This response contains no proprietary information and may be placed in the NRC Public Document Room.

8 Your truly ph00 100 860917 S OcK 0500o424 PDR

• V D. O. Foster REF/D0F/tdm (Distribution on Page Two) t

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, 'xc: U. S. Nuclear Regulatory Commission

, Document Control Desk Washington, D. C. 20555

! J. H. Miller R. A. Thomas L. T. Gucwa l J. P. O'Reilly D. R. Altman C. W. Hayes G. F. Head P. R. Bemis G. A. McCarley

R. E. Conway J. A. Bailey D. S. Read J. T. Beckham 0. Batum Sr. Resident (NRC)

R. H. Pinson G. Bockhold- C. C. Garrett (0PC)

P. D. Rice C.~ E. Belflower J. E. Joiner (TSLA)

B. M. Guthrie J. F. D'Amico D. Feig (GANE)

D. E. Dutton E. D. Groover NORMS 1

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EVALUATION OF A P0TENTIALLY REPORTABLE CONCERN VALCOR SOLEN 0ID VALVES Initial Report: On July 2,1986, Mr. R. E. Folker, Vogtle Project Quality Assurance Engineer, informed Mr. E. F. Christnot of the USNRC Region II of a potentially reportable condition concerning Valcor Solenoid Valves. Valcor Engineering Corporation informed Georgia Power Company that solenoid valve springs could fail when exposed to high temperature reactor coolant containing hydrogen.

Background Information: On August 19, 1986, the USNRC issued Information Notice 86-72; Failure 17-7 PH Stainle:s Steel Springs in Valcor Valves Due to Hydrogen Embrittlement. Valcor Engineering Corporation had in-formed the NRC that valve springs may fail when exposed to high tempera-ture reactor coolant containing hydrogen. h this information notice, it was indicated that spring failures had occurred at three operating reactors. It also stated that the manufacturer had concluded that hydro-gen embrittlement of stainless steel springs was a complex function of high temperatures, water chemistry, water flow conditions, and time of exposure to the service conditions. All springs made of 17-7 PH (precipitation-hardened) stainless steel used in Valcor valves in nuclear power plants may be susceptible to this failure mode under these condi-tions and should be considered for replacement. A copy of Information Notice 86-72 is included as Attachment 1.

Valcor process solenoid valves were supplied on the Vogtle Project on Specification X5AC07. Bechtel Power Corporation identified the following six valves in each unit that could be subjected to conditions identified in the information notice:

t Tag Number Service i

HV-3520 Residual Heat Removal - Train A Sample HV-3521 Residual Heat Removal - Train B Sample HV-3526 CVCS - Downstream of Letdown Heat Exchanger HV-8208 PASS - Liquid Sample Return HV-8209 PASS - Liquid Sample Return HV-8220 Reactor Coolant System - Hot Leg Sample Bechtel Power Corporation requested Valcor's assistance to determine which valve springs could potentially fail. Valcor rewmmended that the springs of valves HV-8208 and HV-8209 (Units 1 and 2) be replaced.

Valcor's response indicated that valve HV-8220 (Units 1 and 2) was shipped

with spring material (Elgiloy) that was not susceptible to hydrogen embri ttlement. The other valves were acceptable as supplied for their service conditions.

Subsequent to the report to the NRC of the potential deficiency concerning the hydrogen embrittlement of Valcor solenoid valve spring 3, another condition was encountered associated with the use of underrated seal-in contacts on Valcor valves (0perational Deficiency Reports T-1-86-1932,

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4 T-1-86-1970). This condition concerned - direct-acting process solenoid operat.i valves, also manufactured by Valcor Engineering Corporation,

-which have been used in various safety-related process systems. A listing of these valves appears in Table 1.

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} The control circuits for these solenoid valves use reed switches for-i seal-in contacts to maintain the solenoid in an energized condition after initial manual energization has been performed by an operator.

One design utilized a safety signal to automatically de-energize the solenoid causing the valve to close. The other design utilized a manually

] actuated handswitch to break the seal-in circuit and close the valve.

> The reed switches are rated at 0.5 amps at 125V DC. A review of this

' condition indicated that the reed switches were carrying a solenoid current of 1.5 amps at - 125V DC, which exceeded their rated capability.

j A test was conducted that demonstrated that after a short period .of i time (approximately 15 minutes), the switch overheated and the reed switch contacts tialded together, which prevented the switch contacts

from opening when required.

i i The switch contacts can fail in one of two ways: either by burning l open or by burning closed. The effect on plant safety for each of these i failure modes is as follows.

! 1. Burning Open

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If the handswitch (HS) associated with the valve is in the " normal" position, swith contact failure by burning open will result in the de-energization of the solenoid. Since these valves utilize a fail-safe design, the valves move to their safe position. The valve can be opened by an operator moving the handswitch to the "open" position, but it will go closed when the handswitch is released to its spring-return-to-normal ' position. Therefore, this 2 switch failure mode cannot degrade plant safety.

2. Welding Closed l Switch contact failure by burning closed, which has been experienced

! during preoperational testing, could result in a loss of control i

of these valves. Since these valves utilize other contacts which ,

i open in response to the safety signal or operation of the associated I handswitch, the solenoid would be de-energized allowing the valve

! to close as long as these other contacts are open. However, after

! reset of the safety signal or release of the spring-return-to-normal I handswitch, the valve (s) with welded closed seal-in contacts would j re-open, resulting in an uncontrolled change in plant status. This j could result in an inadvertent loss of containment isolation.

l Engineering Evaluation: An engineering evaluation was conducted to i determine if an unsafe condition could occur as a result of a failure <

! of Valcor solenoid valve springs due to hydrogen embrittlement. Valves 4

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3 Page Three HV-8208 and HV-8209 are used in the post-accident sampling system liquid return line. These valves are active containment isolation valves that receive a containment isolation signal' for closure. One of these valves is also a break point between safety-related and nonsafety-related piping.

These process solenoid valves were' designed to return by spring action to the closed position (fail-closed). A condition in which the spring

. fails could render the solenoid valves inoperable 'and in an unsafe (open) position resulting in a potential containment atmosphere leak during a design basis event.

An engineering evaluation was also conducted to determine the cause for the failure of the seal-in contacts. The root cause of this condition was determined to be the use of a control circuit scheme by Bechtel Power Corporation that is normally used for pilot solenoid valve applica-tions. Pilot solenoid valve current is typically 0.1 to 0.2 amps, which is within the rating of the seal-in contact. The Valcor valves are i

direct-acting solenoid valves and have significantly higher coil current.

This difference in coil current requirements was overlooked during the design process, thereby allowing underrated reed switch and seal-in contacts to be used.

As a result of this condition, Bechtel Power Corporation conducted a review of other direct-acting solenoid valves. Five other safety-related Valcor valves were found to have circuit designs that used adequately j rated seal-in contacts using auxiliary relays instead of the reed t switches. Other valves, all of which were supplied under the NSSS i contract, either properly addressed the high coil currents or did not use seal-in contacts. Therefore, this problem is limited to the valves listed in Table 1.

A review of this condition indicated that it could also result in an inadvertent loss of containment isolation. In fact, valves HV-8208 and HV-8209 were affected by both conditions.

I Evaluation of Quality Assurance Program Breakdown: A quality assurance program review has concluded that a significant quality assurance program breakdown did not occur because:

1. The valve spring deficiency had been previously reported to the NRC and, subsequently, passed on to the industry by Information Notice 86-72. Valcor appears to be acting responsibly since the valve spring problem was passed on to customers along with recommended corrective action.

2. The design problem associated with the use of underrated seal-in contacts occurred only in isolated instances and applications as verified by a complete review of all similar Valcor valves used in the plant. Furthermore, the error was discovered as part of the quality assurar.ce program preoperational testing.

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Conclusion:

Georgia Power Company has evaluated the condition associated with the potential failure of the valve springs of Valcor solenoid valves due to hydrogen embrittlement and has concluded that a reportable condi-i tion does exist as defined . by the reporting criteria of Part 10 CFR 50.55(e). A Part 10 CFR 21 notification is not required since the NRC 4

has been adequately informed of the existence of this condition. (See Information Notice 86-72.)

Georgia Power Company has also evaluated the condition associated with the use of underrated seal-in contacts by Bechtel Power Corporation.

Georgia Power Company has concluded that this condition is reportable per the reporting criteria of Parts 10 CFR 21 and 10 CFR 50.55(e). Based upon guidance in NUREG-0302, Revision 1 and other NRC correspondence, l Georgia Power Company is reporting this condition pursuant to the reporting requirements of Part 10 CFR 50.55(e).

4 Corrective Action:

1. For the - condition associated with the potential hydrogen embrittle-j ment of the springs:

Valcor recommends retrofitting the valves with a spring material suitable for the intended service. Bechtel has initiated change control package D10284J to replace the existing springs in valves HV-8208 and HV-8209 from 17-7 PH to Elgiloy.

For Unit 2 valves, a Field Equipment Change Order will be issued.

This action will be tracked by PCW' action item 2B1509 for startup system RP03.

2. For the condition associated with the use of underrated seal in i

contacts:

Project Field Engineering -

Operations (PFE-0) has issued Field l

Change Requests (FCR's) to implement the necessary control circuit

changes for all valves indicated in Table 1.

Unit 2 valves will be corrected by the issuance of Design Change Notices by Bechtel Power Corporation and PFE-0.

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TABLE 1 VALVES WITH UNDERRATED SEAL-IN CONTACTS

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I#TATETY RfLfffD APPLICATIONS

- TSpecification fifC67)

Associated Startup Elementary System & Normal /

Valve Diagram P&ID Failure Scheme Type) (X4DB-) Mode Function Signal Number ,_

GS00 NC/FC Cont H2 None HV-2790A 1X3D-BG-B05B (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2790B 1X3D-BG-B05B (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2791A 1X3D-BG-BOSE (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2791B 1X3D-BG-3053 (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2792A 1X3D-BG-305E (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2792B 1X3D-BG-905E (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-2793A 1X3D-BG-305E (2) 213-2 Monitor GS00 NC/FC Cont H2 None HV-27933 1X3D-BG-BG53 (2) 213-2 Monitor RP02 NC/FC PASS liq. CI-A HV-8208 1X3D-BH-YO2C rtn to ctat.

(1) 110(F-8)

RP02 NC/FC PASS lig. CI-A HV-8209 1X3D-BH-YO2D (1) 110(F-8) rtn to etmt.

RP02 NC/FC PASS gas CI-A HV-3211 1X3D-SH-Y02D rtn to ctat.

(1) 110(C-7)

RP02 NC/FC PASS gas CI-A HV-3212 1X3D-BH-YO2C rtn to ctat.

(1) 110(C-7)

BC00 NC/FC PASS ctmt. CI-A HV-8986A 1X3D-BD-E02L sump (1) 122(B-4)

BC00 NC/FC PASS ctmt. CI-A HV-8986B 1X3D-BD-E02M sump (1) 122(B 4)

RCO2 NJ/FC S/G #1 AFW star-HV-9451 1X3D-BC-007F Sample signa:

(1) 159-3 851MLC

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S TABLE 1 (CONTINUED)

- Associated Startup Elementary System & Normal /

Valve Diagram P&ID Failure (Scheme Type) (X4DB-) Mode Function Signal Number HV-guS2 1X3D-BC-007E RCO2 N0/FC S/G #2 AFW start (1) 159-3 Sample signal HV-9453 1X3D-BC-Q07E RCO2 N0/FC S/G #3 AFW start (1) 159-1 Sample signal HV-9454 1X3D-BC-Q07F RCO2 N0/FC S/G #4 AFW start (1) 159-1 Sample signal BJ02 NC/FC Acc. tank CI-A HV-10950 1X3D-BD-D0aW (1) 120 1 sampling 1X3D-BD-D0nX BJ02 NC/FC Acc. tank CI-A HV-10951 2 sampling (1) 120 CI-A BJ02 NC/FC Acc. tank HV-10952 1X3D-BD-D04W 3 sampling (1) 120 1X3D-BD-DouX BJ02 NC/FC Acc. tank CI-A HV-10953 4 sampling (1) 120 851MLC

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