ML20203N840
| ML20203N840 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/19/1986 |
| From: | Randazza J Maine Yankee |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20203N842 | List: |
| References | |
| 72061-SEN, IEIN-86-003, IEIN-86-3, MN-86-29, NUDOCS 8605060107 | |
| Download: ML20203N840 (21) | |
Text
t i
RMWlE HARHEE,;AmmmPOWER00mPARHe v.o nox 408 g
/
Wiscasset, Maine 04578 207-882c21 g
February 19, 1986 MN-86-29 Region I United States Nuclear Regulatory Commission Office of Inspection and Enforcement 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention:
Dr. Thomas E. Murley, Regional Administrator
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b)
IE Information Notice No. 86 USNRC Letter to MYAPCo dated January 17, 1986 (c) MYAPCo Letter to USNRC dated February 4, 1986 (MN-86-23)
(d) " Performance Qualification Tests of Four Valve Motor Operators," Franklin Research Laboratories Test Report No. F-C4124, dated April, 1975 (e) " Test of Limitorque Valve Operator to Meet General Requirements of an Electric Valve Actuator in Nuclear Reactor Containment Environment," Limitorque Test Report No. 600198 dated November, 1968
Subject:
Maine Yankee Limitorque Valve Operators Gentlemen:
On February 13, 1986, representatives of the NRC and Maine Yankee Atomic Power Company participated in a telephone conference regarding Limitorque valve operators. This letter is in response to a request from your staff during this telephone conference.
Limitorque valve operators are used at Maine Yankee and at many other nuclear power plants.
The majority of the Limitorque valve operators at Maine Yankee are original equipment and were purchased before 1970.
The Limitorque valve operators which fall under the requirements of 10 CFR 50.49 are tracable to qualification testing performed by Limitorque. Maine Yankee maintains qualification documentation reports (QDRs) for these valve operators.
In January of 1986, Maine Yankee retained DiBenedetto Associates of North Andover, Massachusetts, to conduct an independent audit of our Equipment Qualification Program. During the course of this audit, members of the audit team brought to our attention a problem other licensees had identified with internal jumper wire in Limitorque valve operators.
They had determined that in some cases the jumper wire supplied by Limitorque had been replaced with wire of unknown qualification. Similar problems were later documented in IE Information Notice No. 86-03, Reference (b).
8605060107 860219 7206L-SEN PDR ADOCK 05000309 G
PDR l E V
l
United States Nuclear Regulatory Commission Page Two Attention: Dr. Thomas E. Murley, Regional Administrator MN-86-29 Upon notification of this concern, we implemented a program to inspect the jumper wire of the Limitorque valve operators subject to 10 CFR 50.49 at Maine Yankee. As discussed in Reference (c), we have completed an inspection of these Limitorque operators which could be inspected during power operation.
Some of the jumper wire found installed appeared to be wire which was originally supplied by Limitorque and other wire appeared to be fleid installed.
Each type of wire appeared to be designed to operate under harsh environmental conditions. Since we could not precisely identify the wire, we replaced all jumper wires with Rockbestos Firewall SIS wire for which Maine Yankee holds a qualification documentation report, QDR #0840.
As discussed on February 13, two valves, RH-M-1 and RH-M-2, are only required during cold shutdown operation, and as such, are not covered by 10 CFR 50.49.
Two other valves, PR-M-16 and PR-M-17, were purchased directly from Limitorque in 1982.
Limitorque has informed us that these valve operators were supplied with quallfled Rockbestos Firewall SIS wire.
Furthermore, since Maine Yankee's 1981 refueling outage, all fleid installed jumper wire has been quallfled Rockbestos Firewall SIS wire.
Therefore, qualification of these valve operators is not in question.
The nine remaining Limitorque valve operators subject to 10 CFR 50.49, which can not be inspected during power operation are described in Attachment 1. indicates, to the best of our knowledge, the number and type of internal jumper wires in each of the valves remaining to be inspected.
Attachments 3 through 6 describe and summarize the qualification information available for each type of jumper wire installed in these valves. Attachment 7 provides an operability analysis of the valves considering postulated jumper wire insulation failure modes.
It concludes that failure of the jumper wire insulation is extremely unlikely.
In any event, failure of the jumper wire insulation should not prevent the valve from performing its intended safety function.
Except for CH-M-1 and CH-M-87, operation of any of the valves yet to be inspected is not essential to permit operation of a safety system such as emergency core cooling, emergency feedwater, or containment spray.
In most cases these valves serve as one of the redundant valves required by 10 CFR 50, Appendix J.
Additional redundant valves are available down stream which could be operated if the Limitorque valve operators were considered inoperable.
CH-M-1 and CH-M-87 are located outside containment and, as such, experience a harsh environment only in the form of potential high radiation exposure during long term recirculation cooling.
These valves operate early in a postulated accident sequence (are positioned by SIAS) and are therefore not subject to a harsh environment at the time of operation.
Therefore, even if these valve operators were not environmentally qualified, continued operation would not pose a threat to public health and safety.
7206L-SEN
United States Nuclear Regulatory Commission Page Three Attention: Dr. Thomas E. Murley, Regional Administrator MN-86-29 Maine Yankee plans to inspect the installed jumper wire in the remaining valve operators.
These inspections can only be conducted when the plant is shut down and conditions permit deenergizing and testing the valve operators.
At this time, Maine Yankee's next scheduled shutdown is for refueling in February of 1987. Should a shutdown be scheduled prior to that time, Maine Yankee plans to inspect as many valve operators as possible.
In our opinion, the Limitorque valve operators at Maine Yankee meet the requirements of 10 CFR 50.49.
However, as discussed with members of your staff, we have initiated an evaluation in accordance with 10 CFR Part 21 because of the information provided by our consultant and the IE Information Notice No. 86-03.
Please contact me if you have any questions in this matter.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY
}"
J. B. Randazza Executive Vice President J8R/bjp Attachments:
- 1) Summary of Limitorque Valves to be Inspected
- 2) Limotorque Internal Hiring
- 3) Rockbestos Firewall SIS Hire 4)
ITT Silicone Rubber / Glass Braid Wire
- 5) PVC (Limitorque Installed)
- 6) PE/PVC (Fleid Installed Jumpers)
- 7) Operability Analysis
- 8) Plant System Drawings (FM-90A, 91A, and 92A) cc: Mr. Ashok C. Thadant Mr. Cornelius F. Holden Mr. Pat Sears 7206L-SEN
ATTACHMENT 1
SUMMARY
OF LIMITORQUE VALVE OPERATORS TO BE INSPECTED 1
7206L-SEN
.=_
Valve:
RC-M-15 Valve
Description:
2 inch motor operated valve Safety Function:
Fill Header Isolation Valve. One of three fill header isolation valves (RC-M-15, 25 or 35), must be able to open 20-24 hours into an accident for switchover to hot leg.
injection.
Hot leg injection is only required following a 1
major cold leg break to reduce the boric acid concentration in the core.
Normal Position:
Closed Safety Position:
Open j
Internal Wiring:
Limit switch wires - qualified Rockbestos Firewall SIS wire.
i Torque Switch to Limit Switch Wires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Wire - Field installed jumper.
Installation Date: Original plant equipment Required Time for Operation: Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Sufficient documentation is available on the internal wiring, with the exception of one torque switch wire, to demonstrate full qualificaticn for the postulated accident environment. A failure of the torque switch wire insulation will not affect operation of the valve (See Attachment 6).
Additionally, only one fill header isolation valve, of three available (RC-M-15, RC-M-25, or RC-M-35), is required for a major cold leg break in the reactor coolant system. This is an extremely low probability event.
If this valve were inoperable either of two similar valves provides the same function.
1 e
7206L-SEN w-
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. v.
Valve:
RC-M-25 Valve
Description:
2 inch motor operated valve Safety Function:
Fill Header Isolation Valve. One of three fill header isolation valves (RC-M-15, 25 or 35), must be able to open 20-24 hours into an accident for switchover to hot leg injection.
Hot leg injection is only required following a major cold leg break to reduce the boric acid concentration in the core.
Normal Position:
Closed Safety Position:
Open Internal Hiring:
Limit switch wires - qualified Rockbestos Firewall SIS wire.
Torque Switch to Limit Switch Hires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Hire - Field installed jumper.
Installation Date: Original plant equipment Required Time for Operation: Hithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Mode 1/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Sufficient documentation is available on the internal wiring, with the exception of one torque switch wire, to demonstrate full qualification for the postulated accident environment. A failure of the torque switch wiro insulation will not affect operation of the valve (See Attachment 6).
Additionally, only one fill header isolation valve, of three available (RC-M-15, RC-M-25, or RC-M-35), is required for a major cold leg break in the reactor coolant system.
This is an extremely low probability event.
If this valve were inoperable either of two similar valves provides the same function.
7206L-SEN
Valve:
RC-M-35 Valve
Description:
2 inch motor operated valve Safety Function:
Fill Header Isolation Valve. One of three fill header isolation valves (RC-M-15, 25 or 35), must be able to open 20-24 hours into an accident for switchover to hot leg injection.
Hot leg injection is only required following a major cold leg break to reduce the boric acid concentration in the core.
Normal Position:
Closed Safety Position:
Open Internal Wiring:
Limit switch wires - qualified Rockbestos Firewall SIS wire.
Torque Switch to Limit Switch Wires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Wire - Field installed jumper.
Installation Date: Original plant equipment Required Time for Operation: Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Mode 1/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Sufficient documentation is available on the internal wiring, with the exception of one torque switch wire, to demonstrate full qualification for the postulated accident environment. A failure of the torque switch wire insulation will not affect operation of the valve (See Attachment 6).
Additionally, only one fill header isolation valve, of three available (RC-M-15, RC-M-25, or RC-M-35), is required for a major cold leg break in the reactor coolant system.
This is an extremely low probability event.
If this valve were inoperable either of two similar valves provides the same function.
7206L-SEN
' Valve:
SL-M-29 Valve
Description:
1 1/2 inch motor operated isolation valve Safety Function:
Seal Water Return Isolation Valve - Used to isolate reactor coolant pump seal water return on Containment Isolation Signal (CIS).
Reopening of valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Wiring:
Limit Switch Hires - Quallfled Rockbestos Firewall SIS wire.
Torque Switch to Limit Switch Hires - ITT Silicone rubber /
glass braid (200*C) wire.
Torque Switch Hire - Field installed jumper.
Installation Date: Original plant equipment.
Required Time for Operation: Hithin 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Sufficient documentation is available on the internal wire, with the exception of one torque switch wire, to demonstrate full qualification for the postulated accident environment. A failure of the torque switch wire insulation will not affect operation of the valve (See Attachment 6).
Valve SL-M-29, a CIS valve, operates very early in the accident, such that the conditions within the operator would not be expected to be sufficiently harsh to prevent the valve from accomplishing its safety function. Also, based on our evaluation, no subsequent environmental related failure mode is capable of re-opening the valve (See Attachment 7).
Furthermore, in the highly unlikely event the valve did not operate, its redundant containment isolation valve, SL-A-53, would be available.
In addition, an alternate method of accomplishing the safety function is also available, in that manual valve SL-57 may be closed to provide further assurance of containment integrity.
The valve location has been reviewed and found to be accessible following worst case accident conditions.
7206L-SEN
Valve:
SL-M-40 Valve
Description:
1 1/2 inch motor operated isolation valve Safety Function:
Seal Water Return Isolation Valve - Used to isolate reactor coolant pump seal water return on Containment Isolation Signal (CIS). Reopening of valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Hiring:
Limit Switch Hires - Qualified Rockbestos Firewall SIS wire.
Torque Switch to Limit Switch Hires - ITT Silicone rubber /
glass braid (200*C) wire.
Torque Switch Hire - Field installed jumper.
Installation Date: Original plant equipment.
Required Time for Operation: Hithin 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Mode 1/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Sufficient documentation is available on the internal wire, with the exception of one torque switch wire, to demonstrate full qualification for the postulated accident environment. A failure of the torque switch wire insulation will not affect operation of the valve (See Attachment 6).
Valve SL-M-40, a CIS valve, operates very early in the accident, such that the conditions within the operator would not be expected to be sufficiently harsh to prevent the valve from accomplishing its safety function. Also, based on our evaluation, no subsequent environmental related failure mode is capable of re-opening the valve (See Attachment 7).
Furthermore, in the highly unlikely event the valve did not operate, its redundant containment isolation valve, SL-A-53, would be available.
In addition, an alternate method of accompIlshing the safety function is also available, in that manual valve SL-57 may be closed to provide further assurance of containment integrity.
The valve location has been reviewed and found to be accessible following worst case accident conditions.
7206L-SEN
Valve:
SL-M-51 Valve
Description:
1 1/2 inch motor operated isolation valve Safety Function:
Seal Water Return Isolation Valve - Used to isolate reactor coolant pump seal water return on Containment Isolation Signal (CIS).
Reopening of valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Hiring:
Limit Switch Hires - A combination of Limitorque supplied PVC and fleid installed jumpers.
Torque Switch to Limit Switch Hires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Hire - Field installed jumper.
Installation Date: Original plant equipment.
Required Time for Operation: Within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Valve SL-M-51, a CIS valve, operates very early in the accident, such that the conditions within the operator would not be expected to be sufficiently harsh to prevent the valve from accomplishing its safety function. Also, based on our evaluation, no subsequent environmental related failure mode is capable of re-opening the valve (See Attachment 7).
Furthermore, in the highly unlikely event the valve did not operate, its redundant containment isolation valve, SL-A-53, would be available.
In addition, an alternate method of accomplishing the safety function is also available, in that manual valve SL-57 may be closed to provide further i
assurance of containment integrity.
The valve location has been reviewed and found to be accessible following worst case accident conditions.
i 7206L-SEN
Valve:
LD-M-2 Valve
Description:
2 1/2 inch motor operated isolation valve SafetyFNnction:
RCS Letdown Isolation Valve - Used to isolate letdown line on a Safety Injection Actuation Signal (SIAS).
Reopening of the valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Wiring:
Limit Switch Wires - A combination of Limitorque supplied PVC and fleid installed jumpers.
Torque Switch to Limit Switch Wires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Wire - Field installed jumper.
Installation Date: Original plant equipment Required Time for Operation: Within I hour Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB within Containment Qualification Documentation Report:
0531-1 Safety Evaluation Valve LD-N-2, an SIAS valve, operates very early in the accident, such that the conditions within the operator would not be expected to be sufficiently harsh to prevent the valve from accomplishing its safety function. Also, based on our evaluation, no subsequent environmental related failure mode is capable of re-opening the valve (See Attachment 7).
Furthermore, in the highly unlikely event the valve did not operate, its redundant containment isolation valve, LD-T-5, provides redundant automatic isolation.
In addition, alternate methods of accomplishing the safety function are also available in that several manual valves may be closed to provide further assurance of containment integrity.
7206L-SEN
Value:
CH-M-1 Valve
Description:
4 inch motor operated isolation valve Safety Function:
Volume Control Tank Outlet Isolation Valve - This valve is required to isolate the volume control tank upon a Safety Injection Actuation Signal (SIAS).
Reopening of valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Wiring:
Limit Switch Wires - A combination of Limitorque supplied PVC and field installed jumpers.
Torque Switch to Limit Switch Wires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Wire - Fleid installed jumper Installation Date: Original plant equipment Required Time for Operation: Within I hour Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB in Containment Qualification Documentation Report.
0531-2 Safety Evaluation Valve CH-M-1 is located in an area of the Primary Auxiliary Building which does not initially experience any accident environments. A high radiation environment only results during the recirculation phase of the accident, which is not initiated until, at the earliest, 10-15 minutes after SIAS. Valve CH-M-1 has, therefore, completed its safety function prior to exposure to the accident environment.
In addition, based on our evaluation, no subsequent environment related failure mode is capable of re-opening the valve (See ).
7206L-SEN
Valve:
CH-M-87 Valve
Description:
4 inch motor operated isolation valve Safety Function:
Volume Control Tank Outlet Isolation Valve - This valve is required to isolate the volume control tank upon a Safety Injection Actuation Signal (SIAS).
Reopening of valve is not required.
Normal Position:
Open Safety Position:
Closed Internal Hiring:
Limit Switch Hires - A combination of Limitorque supplied PVC and fleid installed jumpers.
Torque Switch to Limit Switch Hires - ITT Silicone rubber / glass braid (200*C) wire.
Torque Switch Hire - Field installed jumper Installation Date: Original plant equipment Required Time for Operation: Within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> Model/ Type:
Limitorque SMB-00 Accident:
LOCA/MSLB In Containment Qualification Documentation Report:
0531-2 Safety Evaluation Valve CH-M-87 is located in an area of the Primary Auxiliary Building which does not initially experience any accident environments. A high radiation environment only results during the recirculation phase of the accident, which is not initiated until, at the earliest, 10-15 minutes after SIAS. Valve CH-M-87 has, therefore, completed its safety function prior to exposure to the accident environment.
In addition, based on our evaluation, no subsequent environment related failure mode is capable of re-opening the valve (See
- ).
t 7206L-SEN
ATTACHMENT 2 LIMITORQUE INTERNAL WIRING Jumper Hire
- LS LS TS TS (Limitorque)
(Fleld)
(Fleld) (Limitorque or Field) 1 2
3 4
5 6
7 8
9 RC-M-15 R
R R
N/A R
F I
I I
RC-M-25 R
R R
N/A R
F I
I I
RC-M-35 R
R R
N/A R
F I
I I
SL-M-29 R
R R
R R
F I
I I
SL-M-40 R
R R
R R
F I
I I
SL-M-51 P
P F
F F
F I
I I
LD-M-2 P
P F
F F
F I
I I
CH-M-1 P
P F
F
,f F
I I
I CH-M-87 P
P F
F F
F I
I I
R = Rockbestos Firewall SIS Wire (See Attachment 3)
I - ITT Silicone Rubber / Glass Braid (200*C) Wire (See Attachment 4)
P = PVC (Limitorque Installed) (See Attachment 5)
F = PE/PVC (Fleld Installed Jumpers) (See Attachment 6)
- Jumper numbers indicate usage of jumper as either Limit Switch (LS) or Torque Switch (TS) and whether the jumper was installed by Limitorque or in the field.
7206L-SEN
ATTACHMENT 3 ROCKBESTOS FIREWALL SIS WIRE During the 1985 refueling outage, Rockbestos Firewall SIS wire (Product Code A83-0146) was installed as limit switch jumpers in the following Limitorque actuators:
RC-M-15 RC-M-25 RC-M-35 SL-M-29 SL-M-40 Rockbestos Firewall SIS wire is environmentally quallfled for.this application by Maine Yankee Qualification Documentation Review (QDR) Package
- 0840.
In addition, QOR #0840 is supplemented by the following additional Rockbestos tests:
1.
Report #QR-5805, " Report on Qualification Test for Firewall III Irradiation Cross-Linked Polyethylene Constructions for class IE Service in Nuclear Generating Stations," October 8,1985.
2.
Report #QR-5804, " Report on Qualification Tests for Firewall III Chemically Cross-Linked Polyethylene Constructions for Class IE Service in Nuclear Generating Stations," August 27, 1985.
3.
Report #QR-4802, " Qualification Analysis Report on Firewall III Chemically and Irradiation Cross-Linked Polyethylene Insulation Cables and Firewall III Solid Dielectric and Cellular Dielectric Coaxial Cables," August 1984.
7206L-SEN
ATTACHMENT 4 ITT SILICONE RUBBER / GLASS BRAID WIRE During the inspection of outside containment valve actuators supplied under Limitorque Shop Order #346674, it was noted that they all used the same type of wire for the limit switch to torque switch jumpers.
This wire has been identified as "ITT-C SEW-2 and SF-2 200*, 600V." The SF-2 and SEW-2 designations are Underwriters Laboratory (UL) and Canadian Standards Association (CSA) specifications for silicone rubber insulated, glass braided 200*C, 600V fixture wire. Maine Yankee believes that this type of wire is suitable for its application and have on file a letter from ECOTECH, Inc. #ET 86.2.14.2, " Maine Yankee Plant Interim Assessment of Braided Cabling in Contactor Circuit of Limitorque Actuators" which provides additional qualification documentation.
The Limitorque operators inside containment were purchased under the same shop order, therefore, it is believed that the limit switch to torque switch jumpers are identical as those outside containment. As previously discussed, inspections will be performed to provide verification. Additionally, Maine Yankee has a photograph of RC-M-25 which substantiates our belief of in-containment use of this wire.
7206L-SEN
ATTACHMENT 5 PVC (LIMITORQUE INSTALLED)
During the inspection of outside containment Limitorque actuators, #16 AWG stranded wire with black insulation and no identification marking was found.
Conversations with Limitorque indicate that during the time frame in which the Maine Yankee actuators were supplied, Limitorque was using type TH wire (PVC insulation) for jumper wires.
Type TW wire was included in a qualification test of 4' valve actuators for Consumers Power Company, Franklin Institute Research Laboratories Test Report,
- F-C4124 " Performance Qualification Tests of Four Valve Motor Operators,"
Reference (d).
It has been established through telephone discussions between Engineering Planning and Management, Inc. (EPM) and Consumers Power Company that the valve actuators used in this test were removed from service, decontaminated, and not rewired in preparation for testing. Subsequent to testing the actuators were refurbished (which did not include rewiring) and returned to service. Consumers Power has verified that the present wiring is still type TW.
4 In addition to the Consemer Power testing, telephone converations with Limitorque suggest that type TH wire was included with the actuators covered by Limitorque Test Report #600198 " Test of Limitorque Valve Operator to Meet General Requirements of an Electric Valve Actuator in Nuclear Reactor Containment Environment", dated November, 1968 (Reference (e)).
In spite of a test anamoly involving the geared limit switch assembly (not a result of wire failure), the actuators successfully operated for 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> in a steam and chemical spray environment at elevated temperature and pressure.
For these reasons, Maine Yankee considers this wire suitable for use inside containment.
l 7206L-SEN
ATTACHMENT 6 PE/PVC (Field Installed Jumpers)
During the inspection of outside containment Limitorque actuators, several 2"-3" pieces of #12 AWG, Collyer PE/PVC (1000V) wire were observed in each limit switch compartment. This wire was added to convert the actuator control scheme to the Maine Yankee standard.
Maine Yankee Qualification Documentation Review (QDR) Package QDR #0815 qualified Collyer PE/PVC (1000V) cable for outside containment use.
The Collyer cable used at Maine Yankee is #12 AWG, 7 strand, rated 1000 Volts, and j
has a 15 Mils PVC jacket over 30 Mils of PE insulation. Collyer PE/PVC is believed to be used as limit switch jumpers in the following 4 valve control circuits:
LD-M-2 SL-H-51 CH-M-1 CH-M-87 l
l l
The first two valves are containment isolation valves which are only l
l I
required to close very early in the design basis accident scenario.
The second two are outside containment valves which complete their safety function before exposure to the accident environment.
Proper operation of these valves is expected for the following reasons:
1.
The control wiring it located within the limit switch compartment and protected from direct exposure to the environment - unlike cable qualification tests.
2.
The 1000V rated cable has 50% more insulation and jacket material than comparable qualified 600V rated cable such as Rockbestos Firewall SIS wire.
The Collyer PE/PVC is also believed to be used as a 1-2" torque switch jumper for the following valves:
RC-M-15 RC-M-25 RC-M-35 LD-M-2 SL-M-29 SL-M-40 SL-M-51 CH-M-1 CH-M-8' This short length of wire connects 'We Jj+. nt terminals on the torque switch, and is not in close proximity ta ny r - r wire which could cause a short or ground. An uninsulated piece or wire or jumper would perform equally as well, therefore, degradation or failure of tnis wire's insulation does not impact valve operation.
7206L-SEN
ATTACHMENT 7 Page 1 of 3 OPERABILITY ANALYSIS Control Circuit Loading During Normal Operation The MOV starting contactors are the principal control circuit loads.
These starting contactors are energized only during the actual stroking time of the MOV which is-typically on the order of approximately I minute or less.
The remaining circuit loads, which include valve position indicating lights, may conservatively be assumed to be continuous.
This results in control circuit currents of less than 1 ampere.
These loads produce very little, if any, self-heating of the MOV control wire for typical control circuit appilcations.
The MOV environmental ambient temperature, therefore, can be applied as the normal control wire insulation temperature. As a result, little insulation degradation should occur during normal operation.
jr*
Control Wire Failure Modes: Opens, Shorts, Grounds Open circuits, and high resistance connections, may be caused.by the incorrect termination of control circuit wiring.
However, the use of multistranded wiring and terminal lugs adequately prevents these types of failures from occurring. Open circuits or control wire conductor separation are not expected to occur because of the low electrical currents encountered in M0V control circuit applications.
Circuit shorts and grounds (including both high and low impedance conditions) may occur as a result of gross electrical insulation breakdown.
For the control voltage levels in question, such gross electrical breakdown could only occur due to. direct conductor-to-conductor, or conductor-to-ground contact.
Such direct shorts are possible only where conductor breakthrough This requires the cable insulation be damaged to the degree necessary occurs.
to expose the inner conductor to direct contact with adjacent conductors, or other metallic components, at ground potential. Conductor breakthrough will typically only occur (n.two cases.
In the first case, conductor breakthrough could occur when substantial insulation embrittlement due to radiation or
~
thermal damage combines with mechanical abrasion or agitation of the wire causing insulation material to crumble and drop from the conductor.
In the second case, conductor breakthrough could occur when extremely high, temperatures, or for' certain materials high radiation, cause the trisulation material to soften. This softening when combined with mechanical pressure may permit the conductor to become exposed.
I 7206L-SEN
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ATTACHMENT 7 Page 2 of 3 Under the operational and environmental stresses which may be experienced by the MOV control circuit wiring, conductor breakthrough is not expected to occur.
Extensive and severe thermal and radiation degradation would be required to cause gross insulation embrittlement which would permit insulation loss when combined with minor vibration forces experienced during valve operation. Control wire insulation softening is not expected to occur because of the type of cable insulation normally used at Maine Yankee. Only Butyl based insulations are susceptible to sufficient molecular scission to cause softening due to high radiation conditions.
The type of control wire in use when the plant was constructed was not of this type.
Additionally, the temperatures expected to be found in the limit switch compartments inside containment are lower than the material softening temperatures of any control wire normally used at Maine Yankee.
The configuration of the individual control wire within the limit switch compartment greatly minimizes the probability of the individual conductors achieving contact with grounded components or other exposed conductors.
The use of individual insulated wires, rather than multiconductor cables, creates insulating air spaces between the wires.
These spaces greatly minimize the potential for the intimate conductor-to-conductor contact which is necessary to cause direct shorting or grounding.
Although conductor breakthrough will not typically occur, sufficient insulation degradation, if postulated, may cause changes in individual wire insulation resistances. While such changes, particularly insulation cracking, could result in a wire's inability to adequately pass the high voltage testing performed as part of most cable qualification, these changes are unlikely to cause the low conductor-to-conductor or conductor-to-ground insulation resistance (IR) values necessary to cause failure of the MOV control circuit.
l Because of the control circuit configurations involved, the IR values required must be sufficient to cause shunt resistances around otherwise open contacts I
which prevent contactor dropout when required.
The physical wire separation which results from the use of single conductor control wire creates long leakage paths which effectively ensure that such low IR values will not exist.
In summary, operability of the Limitorque valve operators is ensured because of (1) the wire configurations within the limit switch compartment, (2) the wire types normally used at Maine Yankee for this type of application, (3) the level of protection provided by the limit switch compartment and (4) the limited severity of environmental conditions experienced for the DBAs under consideration (e.g., LOCA and MSLB).
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ATTACHMENT 7 Page 3 of 3 Control Circuit Analysis Motor operated valves (MOVs) which are required to operate during LOCA and MSLB events can be divided into two groups based on control circuit
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design. These groups are as follows:
1.
Circuits receiving automatic actuation signals, and 2.
Circuits which are repositioned by operation of control room control switches.
Maine Yankee control circuits are designed so that valves receiving automatic actuation signals cannot be erroneously repositioned by control circuit shorts which occur in the limit switch compartment. A relay contact located outside the harsh environment effectively blocks actuation of the incorrect valve contactor.
Similarly, for valves positioned by operation of control switches, contactor energization cannot occur due to shorts in the limit switch compartment.
In these circuits, energization of both the open and close contactors is prevented by the normally open control switch contacts utilized in both circuit legs.
This inherent circuit protection against shorts results from use of a momentary spring-return-to-normal control switch.
Therefore, for both of these cl. cult types, incorrect repositioning of MOVs will not be caused by limit switch compartment shorts. MOVs which are actuated and properly positioned, prior to any insulation degradation, cannot be repositioned because of degradation of the control wiring.
Valves which require actuation, either automatic or manual, during accident environmental conditions, can potentially be adversely impacted only by extremely low cable insulation resistance (IR) values. As discussed above, this condition is not expected to occur due to wire configuration, wire type, inherent protection provided by the limit switch compartment, and the limited severity of environmental conditions.
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