PLA-3396, Forwards Rev 1 to SEA-EE-183, Evaluation of Unit 1 Computer Class 1E - Non-Class 1E Interfaces & Rev 1 to SEA-EE-184, Evaluation of Unit 1 Annunciator Class 1E - Non-Class 1E Interfaces
| ML18030A072 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/19/1990 |
| From: | Keiser H PENNSYLVANIA POWER & LIGHT CO. |
| To: | Butler W Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17157A218 | List: |
| References | |
| PLA-3396, NUDOCS 9006290155 | |
| Download: ML18030A072 (7) | |
Text
ACCELERATED DISTRIBUTION DEMONSTPA,TION SYSTEM 0
0 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR: 9006290155 DOC. DATE: 90/06/19 NOTARIZED:
NO FACIL:50-387 Susquehanna Steam Electric Station, Unit 1, Pennsylva 50-388 Susquehanna Steam Electric Station, Unit 2, Pennsylva AUTH.NAME AUTHOR AFFILIATION KEISER,H.W.
Pennsylvania Power 6 Light Co.
RECIP.NAME RECIPIENT AFFILIATION BUTLER,W.R.
Project Directorate I-2 DOCKET 05000387 05000388
SUBJECT:
Forwards "Evaluation of Potential High Voltage Sources Into Unit 1 6
2 Computers."
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Pennsylvania Power & Light Company Two North Ninth Street ~ Allentown, PA18101-1179 ~ 215/770-5151 Harold W. Keiser Senior Vice President-Nuclear 21 5/770 4194 June 19, 1990 Director of Nuclear Reactor Regulation Attention:
Dr.
W. R. Butler, Project Director Project Directorate I-2 Division of Reactor Projects U.S. Nuclear Regulatory Commission Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION CLASS 1E/NON 1E ISOLATION
SUMMARY
REVISION PLA-3396 FILES R41-2 A28-3B Docket Nos.
50-387 50-388
Dear Dr. Butler:
The purpose of this letter is to provide you with the Pennsylvania Power
& Light Company's reports which closeout the commitment made during our meeting with your Staff on January 18, 1990 and revised reports resulting from additional design changes.
- Also, a revised summary is provided.
Attached is a copy of Pennsylvania Power
& Light Company's
- report, "Evaluation of Potential High Voltage Sources Into Unit 1 and 2 Computers".
This evaluation shows that there are no in
.plant potential high voltage sources, not previously evaluated, that could migrate through the plant computers to safety systems and prevent these safety systems from performing their minimum requirements.
High voltage cables (480 VAC and higher) are not potential sources since these cables do not come in contact with the computer input cables.
Rotating machine and distribution transformer temperature sensors are not high voltage sources into the computer since one lead of these devices is connected to ground or through insulating film disc devices preventing high voltages from developing at a sensor outputs.
9006290155 900619 PDR
'RDOCKK05000387 P
June 19, 1990 SSES FILE R41-2, A28-3B PLA-339 6 Attached is a copy of Pennsylvania Power
& Light Company's
- report, "Evaluation of Welded Contacts of Class 1E Circuit Breaker Auxiliary Switches and Limit Switches Used for Unit 2 and Common Annunciator Inputs".
This evaluation shows that the Westinghouse auxiliary switches used for annunciator inputs are from the Engineered Safeguard System 4 kV Buses normal and alternate source incoming circuit breakers.
These auxiliary switches are in series with undervoltage time delay relay contacts.
When the circuit breaker is closed and its incoming line voltage is less than 924 of rated for more than 10 seconds the annunciator input circuit closes exposing the Westinghouse auxiliary switch contact to potential welding until the low voltage problem is corrected.
This low voltage will be promptly corrected (within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) by transfer of loads to an alternate source.
- Thus, exposure of the auxiliary switch contact to potential welding is eliminated and, therefore, affects of welded contacts do not require further consideration.
Analysis of the Class lE valves which use Namco limit switches for annunciator inputs shows that these valves will meet their minimum performance even if their annunciator input limit switches should weld shut.
This conclusion is based upon the evaluation that shows:
o The limit switches are used for alarm and indication only and are not used in Class 1E circuits.
or o
The limit switches are in affiliated circuits and are not used in Class 1E circuits.
Analysis of the Unit. 2 Class 1E motor-operated valves shows that these valves, except for the RHR Minimum Flow Valves HV-E11-2F007A and HV-E11-2F007B, will meet their minimum performance requirements even if the annunciator input limit switches should weld shut.
This is based upon an evaluation that shows:
The valves change position and meet their m'inimum performance requirements before the annunciator input switches are exposed to potential welding, i.e. the valve limit switches are normally open and they close when the valves change to their isolation position.
The HV-21210A and HV21210B valves meet their minimum performance requirements even with annunciator input limit switches welded shut, i.e. the valves can open to throttle RHR service water flow with the annunciator input switches welded shut.
June 19, 1990 SSES FILE R41-2, A28-3B PLA-339 6 In the event annunciator input limit switches for HV-Ell-2F007A and HV-E11-2F007B weld shut, the limit switch main drive shafts could perhaps break loose internal to the valves causing the valves to jam, thus potentially preventing full closure of the valves.
More than likely, the welded shut limit switches would cause damage to the limit switch gearing, but would not prevent the subject valves from closing.
A copy of Pennsylvania Power
& Light Company's report, "Evaluation of Welded Shut Class 1E Limitorque Limit Switches Used for Unit 2 Computer Inputs," is attached.
This evaluation shows that the Unit 2 Class 1E motor-operated
- valves, except for Main Steam Line Drain Isolation Valves HV-B21-2F016 and HV-B21-2F019 and the Reactor Water Cleanup Isolation Valves HV-G33-2F001 and HV-G33-2F004, will meet their minimum performance requirements even if the computer input limit switches should weld shut.
This conclusion is based upon an evaluation that shows:
The valves change position and meet their minimum performance requirements before the computer input limit switches are exposed to potential contact welding, i.e. the valve limit switches are normally open and they close when the valve changes position to its isolation position.
OR The valves are in affiliated (associated) circuits and contacts from these devices are not used in Class 1E circuits, i.e. operation of the valve is not required for design basis event conditions.
In the event computer input limit switches for HV-G33-2F001, HV-G33-2F004, HV-B21-2F016 and HV-B21-2F019 weld shut, the limit switch main drive shafts could perhaps break loose internal to the valves causing the valves to jam, thus potentially preventing full closure of the valves.
More than likely the welded shut limit switches would cause damage to the limit switch gearing, but would not prevent the subject valves from closing.
The above referenced reports complete the open items on this issue.
The following reports were revised
- 1) to recommend that the computer input contacts for HV-B21-1F016, HV-B21-F019, HV-G33-1F001 and HV-G33-1F004 be changed to open contacts when the valves are open instead of adding isolation devices; and 2) placed valves HV-E41-1F075 and HV-E41-1F079 in Group 2 (valves requiring automatic closure).
These changes prevent the annunciator limit switches from being exposed to potential welding during normal plant line-up:
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June 19, 1990 SSES FILE R41-2, A28-3B PLA-3396 o
Evaluation of Unit 1 Computer Class 1E Non-Class 1E Interfaces Revision 1
o Evaluation of Unit 1 Annunciator Class lE Non-Class 1E Interfaces Attachment 1 provides a summary of the reports which are applicable to this issue.
Attachment 2 provides a summary of the Design Change Packages (DCP) of physical work which needs to be completed.
It is our conclusion that except for the modification listed in, the existing design of the Class 1E Non-Class 1E interfaces is in conformance with our FSAR commitments.
Very truly yours, H.
W. Keiser CTC/nl plag3396.ctc cc:
~NRC Document Control Desk (original)
NRC Region Mr. G. S. Barber, NRC Sr. Resident Inspector Mr. M. C. Thadani, NRC Project Manager
ATTACHMENT 1 SEA-EE-180 Rev.
0 "Evaluation of General Electric Nuclear Steam System for Compliance to IEEE279-1971 SEA-EE-181 SEA-EE-182 SEA-EE-183 Rev.
0 "Evaluation of Open CT Secondary Voltages on the Unit 1 and Unit 2 Computer Input Circuits" Rev.
0 "Evaluation of Potential Transformers Used to Develop Unit 1 and 2 Computer Inputs" Rev.
1 "Evaluation of Unit 1 Computer Class 1E-non Class 1E Interfaces" SEA-EE-184 Rev.
1 "Evaluation of Unit 1 Annunciator Class 1E-non Class 1E Interfaces" SEA-EE-204 SEA-EE-221 Rev.
0 Rev.
0 "Evaluation of Units 1
& 2 Main Turbine Generator Field Computer Inputs" "Evaluation of Unit 1 Analog Computer Class 1E-non Class 1E Interfaces" SEA-JNPE-150 Rev.
1 "Isolation Capabilities of BOP Isolators" SEA-EE-226 Rev.
1 "Evaluation of Welded Shut Class 1E Limitorque Limit Switches Used for Unit 2 Computer Inputs" SEA-EE-231 Rev.
0 "Evaluation of Welded Contacts of Class 1E Circuit Breaker Auxiliary Switches and Limit Switches Used for Unit 2 and Common Annunciator Inputs"
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ATTACHMENT 2 ELECTRICAL ISOLATION
SUMMARY
The results of PP&L's investigation for electrical isolation showed that the following modifications are needed to assure that the plant design is in conformance to the analysis for isolation (separation):
DCP Descri tion 90-9001 90-9002 90-9007 90-9008 89-3038 89-3039 89-9175 Add CT protectors to the Unit 1 Main Generator CT's used to develop computer inputs.
Add CT protectors to the Unit 2 Main Generator CT's used to develop computer inputs.
Add electrical isolation or rewire eleven (11) circuits in Unit 1, used to develop computer or annunciator inputs.
Add electrical isolation or rewire eleven (11) circuits in Unit 2, used to develop computer or annunciator inputs.
Add electrical isolation to the Unit 1 RCIC and RHR Sys.
A flow circuits.
Add electrical isolation to the Unit 2 RCIC and RHR Sys.
A flow circuits.
Add electrical isolation to the Unit 1 Main Steam Line Log Rad monitor outputs to computer and recorders.
89-9176 Add electrical isolation to the Unit 2 Main Steam Line Log Rad monitor outputs to computer and recorders.