ML20058N417
| ML20058N417 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/13/1993 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-M84327, TAC-M84328, NUDOCS 9312210393 | |
| Download: ML20058N417 (33) | |
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Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401-1927 1 Telephone (612) 330-5500 l
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December 13, 1993 10 CFR Part 50 Section 50.63(c)(d)
U S Nuclear Regulatory Commission Attn: Document Control Desk ,
Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Reply to Requests for Information on the Station i Blackout / Electrical Safeguards Upgrade Project '
(TAC Nos. M84327 and M84328) i Referencess (1) Letter from Thomas M Parker, Northern States Power Company, ;
to U S Nuclear Regulatory Commission dated December 23, 1991 .
titled " Design Report for the Station Blackout / Electrical Safeguards Upgrade Project," Revision 1 (2) Letter from Marsha Gamberoni, U S Nuclear Regulatory Commission, dated October 1, 1992 titled " Request for Additional Information - Station Blackout / Electrical Safeguards Upgrade Project for Prairie Island Nuclear !
Station, Units 1 and 2 (TAC No. M84327 and M84328) i On December 23, 1991, we submitted for NRC Staff review the Design Report (Reference 1) for our project to add two safeguards emergency diesel
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generators, to upgrade the safeguards electrical distribution system, and to !
upgrade the #121 cooling water pump to become a swing safeguards pump.
In preparation for an Instrumentation and Control System Branch on-site audit of this project, we received a Request for Additonal Information (Reference 2). Due to the large amount of documentation required to answer the request, we provided the necessary information during the ensuing audit. Attachment 1 to this letter documents the answers provided during the audit and references the documents which were provided to the auditors on-site.
During the audit (conducted November 16 through 20, 1992), in response to questions, we committed: "That we would provide a copy, when complete, of the evaluations being performed to assess the impact of the new load sequencers on ]
the current accident analyses." Attachments 2, 3, and 4 to this letter
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9312210393 931213 -
PDR P
ADOCK 05000282 e, i PDR a
e i Northem States Power Company U S NRC December 13, 1993 l Page 2 of 2 ;
l provide the evaluations discussed in commitment #1, above. j I
Please contact Jack Leveille (612-388-1121,. Ext. 4662) if you have any l I
questions related to this letter.
N .!
Roger O Anderson <
Director l Licensing and Management Issues c Regional Administrator - Region III,.NRC Senior Resident Inspector, NRC i NRR Project Manager, NRC J E Silberg Attachments: (1) Response to Request for Additional Information . l (2) NSP Internal Correspondence from Peter Wildenborg to Marcia Thompson, dated January 4, 1993 (3) Westinghouse Letter from T A Hawley to K E Higar, Northern ,
States Power Company, dated January 8,.1993, titled: !
" Station Blackout / Electrical Safeguards Upgrade Time. ]
Delays - Final Report" (4) NSP Internal Correspondence from Keith E Higar to Marcia Madson, dated December 31, 1992 i l
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l RESPONSE TO REOUEST FOR ADDITIONAL INFORMATION
- 1. Validation and Verification Process
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- a. Provide the Verification and Validation Plan and all related documentation for the load sequencer.
See References 8 through 15 and 17 through 20.
- b. Describe the acceptance criteria for hardware and software.
See References 10, 11, and 15.
- c. Provide the acceptance criteria and procedures for, and results of, the hardware / software integration testing.
See References 10, 11, and 15.
- d. Provide the procedures and results for the startup testing.
Prerequisite Test Procedures SBO-SEQ-501, SBO-SEQ-601, SBO-SEQ-502, and SBO-SEQ-602, and Preoperational Test Procedures SBOP-SEQ-501, and SBOP-SEQ-601 were made available during the site audit of load sequencer implementation. The test results for the prerequisite tests were also available during the site audit.
- e. Discuss any differences with IEEE 7.4.3.2.
The load sequencer programmable logic controller system Verification &
Validation Plan has been implemented to be in accordance with ANSI /IEEE-ANS-7-4.3.2-1982. Northern States Power believes there are no differences between the Verification & Validation Plan and the standard.
- f. Provide a listing of all software errors and their ensuing corrections.
Documentation for all software errors and corrections was provided during the site audit of load sequencer implementation.
- g. Describe the process for future modification to this system.
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See Reference 3.
- 2. IE/Non-1E Isolation
- a. Explain the " contact-to-contact separation" terminology and list all j l applications where this methodology is used.
All outputs from the load sequencer, both 1E and non-1E, are controlled i by Asea Brown Boveri Type RIMH2 auxiliary relays. The coil of the relay I
Attachment 1 Page 2 of-9 is energized by the programmable logic controller, and' the eight pairs .
of contacts in each relay provide the output. Some of the contacts provide signals for breaker permissives, and.these outputs are II. Other contacts on the same relay provide signals for indication or annunciators, and these outputs are non-1E. These relays have heavy duty contacts which are rated to carry 10 amperes of 125VDC_ current continuously and 135 amperes for 200 milliseconds for an already closed contact (fault duty).
The non-safety related circuits which'are connected to the' contacts off j these isolation relays fall into three categories; 1) plant computer inputs which are wired to a remote multiplexor unit, 2) inputs to the plant annunciator system, and 3) contacts that operate main control board indicating lights which have been' classified as non-15.
- b. Provide the electrical wiring diagrams which show the non-class 1E connections to the load sequencer.-
The following drawings are provided
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i Bus 15 sequencer Wiring Diagram NF-156973 )
Bus 16 sequencer Wiring Diagram NF-156974 l Bus 25 Sequencer Wiring Diagram NF-120722 Bus 26 Sequencer Wiring Diagram NF-120723 1E cables are terminated along the back section of cabinet 2 and non-1E l cables are terminated along the right side'section of cabinet 2 as shown on the key plan' on these drawings.
For Unit 2,'the 1E cables are those cables listed as top entry and the non-1E cables are listed as bottom entry on the far right side of the Unit 2 drawings. For Unit 1, this convention was not followed.
- a. Describe the audit and audit results of'the vendor's QA program and procedures for commercial grade dedication of the programmable logic controllers.
See Reference 4.
- b. What are the vendor's recommendation and bases for the shelf life of-the sequencer's spare parts?
- c. Provide the standards and procedures used to dedicate the Allen-Bradley commercial grade PLCs. ,
Standards are listed in Reference 13, Section 2.2 and Reference 15, section 3.0. Procedures are in References 10 and 15, Appendices.
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- d. Describe the criteria governing the successful completion of the l Allen-Bradley commercial grade PLC t'edication.
See Reference 15.
- e. Identify the methods and acceptance criteria for verifying the-critical characteristics. ;
i See Reference 15. l 5
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- 4. EMI/RFI
- a. Provide the methodology and the results of the electromagnetic j interference site survey.
l The electromagnetic interference site survey was performed in'accordance-with IEEE Standard 473-1985, IEEE Recommended Practice'for an l Electromagnetic Site Survey (10kHz to 100Es); NIL-STD-461C, l
Electromagnetic Emission and Susceptibility. Requirements for the. control of Electromagnetic Interference; and MIL-STD-462, Electromagnetic Interference characteristics, Measurement of. The survey for the .I frequency range from 10 kEs to 10 GEu was ccepleted for the normal j operating ambient on October 24, 1992. A spacial survey was completed on l
November 13, 1992, in Bus 16 Room during welding activity.to determinec the Electromagnetic Interference environment in the bus room. Additional ambient surveys for the frequency range from 30 Es to 10_ kEs were ; i performed during the Outage Integrated Safeguards testing on January 1 ;
l and January 4, 1993. !
l 1 The results of the site surveys are described below: I 1
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l The radiated emissions testing in the frequency range from 10 kEs to
, 10 GE: found the highest emissions (other than two-way radio l emissions) to be less than 0.1 Volt /seter. This is a- factor of ' 100 l less than the level to which the load sequencer cabinets were tested.
Two-way radio testing was also performed during this site survey.
The results of this survey indicate that some of the portable radios used on site emit more than 10 Volts / meter, which is the level to l
which the sequencer was tested. Therefore, in order to insurs that the load sequencer is not subjected to higher emissions levels than allowed, portable radio use near,the load sequencers will be restricted by administrative controls.
i The radiated emissions testing in the frequency range from 30 Es.tm' i 10 kHz was performed twice; once during ambient conditions on the bus, and, then, during the Integrated Safeguards test while source breakers and load breakers were cycling. A comparison of the emissions plots indicates negligible changes in the magnetic field ;
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Attachment 1 i Page 4 of 9 .
strength inside the load toquencer cabinets due to the Integrated j Bafeguards test. i I
The conducted emissions testing of the AC power lines'for the I programmable logic controller in the frequency range from 30 55 to 15 kHz indicated the highest emissions to be 127.8 dBpA, or 1.7 amps RMS. This maximum occurred at 60 Es, which is the operating I frequency of the progrs===hle logic controller,: and the current j corresponds to the power requirements of the load sequencer cabinet. ,.
Smaller peaks occurred.at harmonics of this operating frequency, j primarily, at 180 Es, 300 Es, and 420 Es. The highest emissions in j the frequency range from 15 kEs to 50 MHz was 66.0 dBpA. j 1
Additional site testing for radiated emissions and conducted; r emissions was completed while welding activities were taking place in the Bus 16 room. This welding resulted in increased emissions in the frequency range from 10 MHz to 50 MEs for.the conducted ,
'l emissions, and in the frequency range _from 10 kEs.to 1 GEs for the radiated emissions. The increase in conducted emissions while ;
welding was approximately 10 dSpA with a peak emission of.49.4 dSpA l st 41.5 MHz. The highest levels for the radiated emissions was 105.5 dByV/m (0.19. Volt / meter).
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- b. Provide the evaluations of the vendor's EMI/RFI testing methodology i and the results of the factory testing.for' radiated and conducted v susceptibility.
l Northern States Power arranged the Electromagnetic Interference / Radio Frequency Interference testing rather than the sequencer vendor.
Northern States Power approved the Test Procedure 42014-20 prior to the testing and witnessed the testing. See Reference 21 for the procedure and results.
- c. Provide the results of the licensee's comparison between the onsite and factory EMI/RFI testing.
The results of the factory tests versus onsite tests for electromagnetic interference were reviewed and discussed during the' site audit of load ~
j sequencer implementation. The only testing which was not completed at that time was the radiated emissions testing in'the frequency range from 30 Bs to 10 kHz. As discussed in 4.a'above, the performance'of the Integrated Safeguards test had little effect on the levels of electromagnetic interference observed at the sequencer cabinet. The interference levels measured before and during the safeguards test. wore well below the limits specified in MIL-STD-461C for RE01, Radiated Emissions, 30 Es to 30 kHz, Magnetic Field.
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- d. List the EMI/RFI testing frequencies and provide justifications for i any frequencies not tested.
j Factory Testing l
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Attachment 1 j Page 5 of 9 l i
C801: 30 Es to 50 kEs {
Cs02: 50 kEE to 400 MEs C806: spikes at 200 V peak and 10 microsec width l RS03: 20 MEs to 1 GEs l site Testing:
Transient monitors see question 4.e.
Electromagnetic Interference- survey:
Radiated Emissions: 30 Es to 10 kBs Radiated Emissions: 10 kEs to 10 GBs l Radiated Emissions: 10 kEs to 10 GHz with welding activity l Conducted Emissions, Power Leads: '30 Es_to 15 kEs' l' l
Conducted Emissions, Power Leads: 30 Es to 15 kEs with
- welding activity Conducted Emissions, Power Leads: 15 kEs to 50 MEs conducted Emissions,1 Power Leads: 15.kEs to 50 MEs with' ,
- welding activity' l 1 l l e. During the pre-operational test, are there any transient monitors. I installed? If any, what are the parameters being monitored?'
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L Transient monitoring was performed for extended periods of time on :
each load sequencer.. Monitoring was performed while the plant'was. f shutdown, while Integrated Safeguards testing was in progress, and while the plant was at full power. The 120 VAC supply for each progr===mble controller was monitored with a Dranets Model 626A Power Line Disturbance Analyser. The monitor provides information on ove rvoltage, unde rvoltage, frequency shifts, surges, and impulses.
- f. Provide the surge transient susceptibility testing specifications for ,
the programmable controllers.
See Reference 21. '
- 5. Operation
- a. Describe the alarms being provided in the control room and at tho' local panel.
Annunciator system alarms provided by the_ sequencer _in the main
, control room are shown on Reference 7 at locations in Column 01 l
(typical) in rows 02, 03, 07, 08, 09, and 10. In addition, the-sequencer provides the main control room information about its operation on a status light box at the G panel. See Reference 6 for a front view.
Locally, the load sequencer provides indication for testing and alarm messages for testing.
Attachment 1 Page 6 of 9
- 6. Power Supolv
- a. Discuss the effects of degraded voltage and loss of UPS to the PLC; specifically address the operations of the back-up battery and any failure modes pertaining to the operational software after the power has been restored. .
The programmable logic controller power supply can operate at voltages ;
as low as 98 VAC, as shown in Reference 5. Below that voltage the ;
power supply will shut down and the load sequencer will also shutdown. l When power is lost to the load sequencer, all output relays which control load shedding, load sequencing, and source breakers will fail 3 to the doenergized position. The doenergized position allows the control room operator to manually control all breakers through normal ;
panel switches (see question 8.b).
t The programmable logic controller in the load sequencer does not rely I on the controller back-up battery for operation. ' All operating i
software is contained on non-volatile electrically erasable progr==mahle read-only memory modules (EEPROMs), and following a~ power-outage, the operating software is reloaded into the controller memory.
Following a loss of uninterruptable power supply power to the sequencer, when power is restored to the controller, the operational software will resume in the operating mode. On power-up of the controller, the ' operating
- node is entered, even if the sequencer had been in the ' test' modo prior to the loss of power. Note that this response is different from the original Northern States Power response to the NRC Request for Additional Information, question #4, which was provided on July 10, 1991.
- b. What is the lowest power at which the PLC can operate 7 see Reference 5.
- c. What is the expected life of the back-up battery?
see Reference 5.
- 7. Surveillance
- a. Is the PLC a multi-sequence or a single-sequence load sequencer? If it is a multi-sequence load sequencer, 1) describe the different sequences, 2) describe the methods by which a sequence is selected.
The programmable logic controller is a single sequence load sequencer.
- b. Describe the manual scenario testing sequences to be performed in the monthly surveillance.
See Reference 18.
Attachment 1 Page 7 of 9
- c. Does the programmable logic controller have a self-test mode? If it does, how long is the test duration?
The programmable logic controller's self-test functions are described in the Allen Bradley literature. The self-test functions used by the load sequencer are:
- Key in remote position
- Battery low
- Watchdog timer elapsed (250 usec)
- Fault routine because of a PLC 5/10 failure
- 8. System Intecration
- a. Where do the following signals to the load sequencer come from?
degraded voltage safety injection loss of off-site power Refer to the following drawings for wiring and schematic information on these signals.
DEGRADED VOLTAGE gl LOOP Bus 15 NF-40155-4 NF-40291-4 NF-40155-3 NE-40006-4 I-H-1-992 NF-40156-6 I-H-1-993 NE-40006-3 NE-40006-12 Bus 16 NP-40156-4 NP-40291-8 NF-40155-3 NE-40006-10 I-H-1-992 NF-40156-6 I-H-1-993 NE-40006-3 NE-40006-12 Bus 25 NF-120705-43 NF-40246-4 NF-120705-39 NE-116785-11 I-H-1001-885-7 NF-120705-42 I-H-1001-885-8 NE-ll6785-4 NE-116785-10 Bus 26 NF-120706-43 NF-40626-8 NF-120706-40 NE-116786-12 I-H-1001-885-7 NP-12070 -42 I-H-1001-885-8 NE-116786-3 NE-116786-9
- b. Describe all provisions for "back-up" provision to the digital load sequencer.
Whenever there is a problem with the load sequencer it can be placed in manual at the main control room G panel. In this condition, the effects are as follows:
_ _ _ . _ _ ._ - ._. . _ - _ =_
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- - a Attachment 1 Page 8 of 9 LOADS
- The permissive contacts that'the load sequencer provides to loads are in their. permissive position (normally closed) so all loads-can be operated manually.from the control room or at their local stations and they can-be controlled by their normal automatic control circuits. The only control which is-lost is the ability to?
. automatically sequence loads onto the bus.
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, SOURCES: The voltage restoration scheme does not function in:this' l condition. Loss of a source to the bus will require manual operator action to recover the bus.
INDICA:" ION and ALARNS: The following main control room alarms are.
operabl6 with the sequencer in manuals j - degraded voltage
- under/.',oss of voltage
- channel alert
- 9. Desion Basis Consideration
- a. Provide the assersment and documentation on the development of the-design modificatian with respect to the design basis.
The System Requirements Document (Reference 17) gives the'< load, j sequencer design basis, and the Fluor Daniel / Northern States Power j review and approval of the design are documented in formal review and
- approval submittals at Fluor Daniel and Spectrum.-
1 The original design requirements are presented in the load sequencer i specification (Reference 1). As the design progressed'a more and more j detailed logic was developed through'several iterations of review (Reference 2). Other requirements for hardware, testing, troubleshooting, and modification were agreed upon and documented in )
project meetings and correspondence and submitted through Fluor' Daniel l to spectrum. Requirements for the logic have evolved for the past.two )
years and have been reviewed by the Northern States Power Design Basis
, Group and Northern States Power Nuclear Analysis Group (and' Westinghouse) and the architect / engineer for the project (Fluor Daniel) for impact on the original plant design basis. These reviews j are documented in several project correspondence and in one formal
, calculation. The final review of the project by the Design Basis Group and the Nuclear Analysis Department (and Westinghouse) is still l outstanding. This review is required by the Northern States Power' )
l Design Change process and is a NOLD required to be satisfied prior to leaving Cold Shutdown.
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Attachment 1 '
Page 9 of 9 Reference Documents:
- 1. Load Sequencer Specification X-Hiaw-02713.
- 2. Load Sequencer logic diagrams dated 4-28-92 and brief description dated 5-1-92.
- 3. Draft 5AWI 3.19.2 PLC Configuration Management.
- 4. FDI/NSP Audit reports of Spectrum Technologies, Inc.
- 5. Allen-Bradley product specification sheets.
- 6. Bus 25 status light box sketch (8.5 X 11).
- 7. Annunciator Box 47524/47024 SBO U2 Tie-In Layout (11 X 17).
- 8. Verification and Validation Plan (VVP9000520/1)
- 9. Verification and Validation Report (VVR9000520/1)
- 10. System Software / Hardware Acceptance Test Report (SHTR9000520/1)
- 11. Software Unit Testing (SUT9000520/1)
- 12. Ladder Logic Diagram (LLD9000520/1)
- 13. Qualification Test Report (QTR9000520/1)
- 14. Commercial Grade Dedication of Software (CGDS9000520/1)
- 15. Acceptance Test Procedure (AP9000520/1), Revision 3
- 16. Seismic Test Procedure (SP9000520/1)
- 17. System Requirements Document (SRD9000520/1)
- 18. Software Requirements Specification (SRS9000520/1)
- 19. Computer Software Quality Plan (SQP9000520/1)
- 20. Software Configuration Management (SCM9000520/1)
- 21. Wyle Labs Electromagnetic Interference Test Report on the j Safeguard Load Sequencer dated 9-26-91. j
- 22. Software Design Description (SDD9000520/1)
- 23. Allen-Bradley PLC-5/10 Status File l
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ATTACHMENT 2 NSP Internal Correspondence from Peter Wildenborg to Marcia Thompson, dated January 4, 1993 2 Pages (excluding this cover page)
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l INTERNAL CORRESPONDENCE NSP Date January 4, 1993 To Marcia Thompson Location PRAIRIE ISLAND From Peter Wildenborg Location PRAIRIE ISLAND ,
Subject Effect of SBO/ESU Additional SI Delay Times on the Dose Consequences of a Steam Generator Tube Rupture This analysis determines the effect of the additional SBO/ESU source searching and load sequencing delays on the dose consequences from a steam generator tube rupture.
The addition of the DS/D6 diasels as part of the Station Blackout ,
project introduces additional time delays for initiation of the Safety Injection (SI) pumps. Specifically, there is an additional 5 seconds source search time delay and 2 seconds load sequence time delay. The effect of these time delays on the dose consequences of the steam generator tube rupture accident, as described in USAR section 14.5.4, requires consideration.
Only the time delays are considered for evaluating an effect on offsite dose. Westinghouse states in its evaluation of the SBO/ESU time delays that these have no effect on the thermohydraulic response of the reactor systems. Therefore the USAR source term from the steam generator tube rupture accident will not be affected since fuel integrity is not affected.
USAR section 14.5.4 describes the tube rupture accident and associated environmental consequences. This section analyzes the dose effects of a steam generator tube rupture followed by an immediate loss of offsite power where the activity in the steam generator is released through the atmospheric steam dump rather than being routed to the condenser. One of the bases for activity release to the environment is that operator action terminates the release within 30 minutes of accident initiation.
The additional 7 seconds delay in initiating'the SI pumps could be added to the 30 minutes estimated time for release termination. The 30 minutes was used in the USAR as a maximum release duration, with the actual duration expected to be shorter. In the vorst case, the 7 additional seconds to start the SI pumps would add to the 30 minutes maximum duration and increase the dose consequences by the incremental fraction of time which is:
1 + [7 sec / (30 min
- 60 sec)) - 1.0039 i
When the thyroid and whole body doses calculated in USAR section l 1
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14.5.4 are multiplied by this fraction, they do not change after rounding to the same number of significant figures presented in the USAR.
It is concluded that the additional 7 seconds delay time for SI pump start due to D4/D5 implementation has no significant effect on the steam generator tube rupture dose calculation.
Prepared by: ,
@ete Wildenborg (/
Plant HP If Reviewed by: , /97 [ / -
D6n Schuelke General Supt. Radiation Protection & Chemistry
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ATTACHMENT 3 i
Westinghouse Letter from T A Hawley to K E Higar, j
Northern States Power Company, dated January 8, 1993, Titleds." Station Blackout / Electrical Safeguards Upgrade Time Delays - Final Report" ;
15 Total Pages (excluding this cover page)
This attachment consists of: !
i a one page letter with one attachment:
" Evaluation of SBO/ESU Time Delays, Prairie Island Units 1 and 2", ,
S pages itself, with also one attachment:
NSP letter from Keith E Higar to Jeff Usem, Westinghouse, dated-November 23, 1992, 2 pages itself, and also two attachments: ,
Internal NSP letter from Marcia Thompson to Cliff Bonneau, '
dated November 9, 1992, 2 pages'itself, and also one-attachment:
ATTACHMENT ONE, which describes the changes in cequence logic due to the proposed modification,.4-pages Prairie Island Blanket Purchase Order Release No. PB8825, 1 Page
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f 10950 Ren Roa@t WestinEhouse Minnetonta Minnesota 55343 Electric Corporation sia sas $323 -
I January 8,1993 NSP-93-501 ET-NSL-OPL-I-93-006 :
Mr. K. E. Higar
- Nuclear Analysis Department !
Northern States Power Company l Renaissance Square - 8th Floor 414 Nicollet Mall '
Minneapolis,MN 55401 NORTHERN STATES POWER COMPANY' \
PRAIRIE ISLAND UNITS 1 AND 2 :
Station Blackout /ElectricalSafeguards Upgrade Time Delays - FinalReport i
Dear Mr. Higar:
j In response to Northern States Power's request, Westinghouse has completed the evaluation -
of the source searching time delay. The final version of this effort is attached for your review and comment. This document was previously sent via NSP-92-181 for your '
comment. ,
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If you have any questions concerning this issue, please contact Mr. Tim Kitchen on !
(412)374-4153.
i Sincerely, ;
'C ,
, a - i a L ~c', '
T. A. Hawley '
Inside Salesman (612) 939-5230 l TAH/lmr Attachment cc: T. M. Parker, IL. l A R. O. Anderson, IL, I A C. A. Bonneau, IL, I A i
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i EVALUATION OF SBOIESU TIME DELAYS PRAIRIEISLAND UNITS 1 AND 2 l
l BACKGROUND l
l Northern States Power (NSP) is currently performing a Station Blackout / Electrical Safeguards Upgrade (SBO/ESU) project at the Prairie Island Units. NSP has determined that the SBO/ESU project will introduce an additional time delay for all loss of offsite power -
(LOOP) scenarios. Previously NSP indicated that there was a two second delay from the time the diesel generators are up to speed to the time that power is available to certain safety related equipment due to the load sequencing. The initial evaluation indicated that there was ,
no impact on the current Prairie Island safety analyses. The initial evaluation was performed and transmitted via Westinghouse Project letter NSP-92-136 dated 2/28/92 (Reference 1).
Upon the final review of the SBO/ESU modifications an added 5 second time delay was determined to exist in addition to the sequencer loading delay. The added 5 second time delay 2s evident in the under voltage case due to loss of some or all off-site power. This is due to the off-site source searching and causes a delay in the diesel start of 5 seconds. The description of the final SBO/ESU modification was provided to Westinghouse via Reference ;
2 and is included as an attachment to this evaluation in Appendix A.
Northern States Power requested Westinghouse to re-evaluate the time delays utilized for the LOCA and Steam Generator Tube Rupture (SGTR) analyses. This assessment addresses the l effects of the time delay on the Prairie Island Units 1 and 2.
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EVALUATIONS !
1 LOCA and LOCA-Related Evaluations l l l Laree Break LOCA l l
l l The current LBLOCA PCT on record is 2109F (Reference 3) and is based upon no LOOP. The analysis must be reviewed to ensure that the LBLOCA with LOOP does not become limiting in PCT. An "S" signal was assumed in the analysis of record.
However, an "S" signal is not concurrent with LOOP. The "S" signal is generated at a setpoint which is about 2 seconds after the LOOP according to the analysis of )
record and follows the undervoltage time line. Therefore, the evaluation discussed below is for the under voltage case with LOOP.
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Northern States Power Company PrairieIsland Units I and2 NSP-93-501 - Attachment Evaluation ofSBOIESU Time Delays Page 2 Safety injection (SI) cases with no LOOP and with LOOP are not affected by the additional 5 second delay. The initial evaluation (Reference 1) is still valid for the SI with LOOP and the information provided in Reference 2 shows that the no LOOP SI scenario is not affected by the SBO/ESU modification.
From the information in Reference 2, due to the 5 second delay in the off-site source searching, the diesel generator will be on the 4160 V bus within 15 seconds. After that, a 2 second load sequencing delay time is introduced. The MOV stroke times are 10 seconds. That is, the longest possible HHSI delay time for the LOOP scenario is :
27 seconds.
Based on the current WCOBRA/ TRAC LBLOCA analysis on record, the end of bypass time is 26.23 seconds for the no LOOP case. The HHSI flow is bypassed (considered to flow out of the break and not into the core) for the first 26.23 seconds of the transient time. As a result of the modification an increase of 0.77 second (i.e.
27-26.23 = 0.77) in the bypass time and the subsequent effect on PCT must be addressed. 'Ihe current LBLOCA analysis heatup rate between 26 and 27 seconds of the transient time is 9.6F per second. The additional 0.77 second would increase the PCT by 7.4F. A previous LOOP versus no LOOP sensitivity study result showed that the no LOOP scenario was more limiting as documented in Reference 4.
Additional information concerning the effect of RCP coast down on this evaluation j can be found in Reference 6. As a result, the 7.4F PCT increase determined from the LOOP case is no more limiting and it can be concluded that the no LOOP condition is still limiting in terms of LBLOCA PCT.
Small Break LOCA The current small break LOCA analysis (with LOOP) of record was performed with the Westinghouse Small Break LOCA (SBLOCA) ECCS NOTRUMP Evaluation Model. This analysis resulted in a PCT of 1077F, as documented in Reference 5.
The SBLOCA analysis assumed a 25 second safety injection (SI) time delay. The anticipated HHSI delay time of 27 seconds for the under voltage case with LOOP, which is 2 seconds longer than the current calculations on record. For the 6 inch break (limiting case), the analysis of record shows that the SI signal is at 5.62 sewnds. With a 27 second time delay, the earliest possible time for the SI flow to come in is 32.62 seconds.
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'Nonhern States Power Company Prairie Island Units 1 and2 NSP-93-501 - Attachment Evaluation ofSBOIESU Time Delays Page 3 l
However, the current calculations ou record indicate that the SI flowrate is still zero at 150 seconds of the transient time. Unlike the large break, se rector vessel-pressnre is gradually reduced during the small break LOCA. For the 6 inch break at -
150 seconds, the reactor vessel pressure is still at 744.5 psia which prevents SI flow. ;
Therefore, the SI flow is zero for extended periods of time in the transient. Thus, changing the SI delay time from 25 to 27 seconds will have no impact on the current l PCT result. The other break sizes were also reviewed.
For the 8 inch break, the SI signalis at 5.16 seconds. With a 27 second time delay, l the earliest possible time to obtain the SI is at 32.16 seconds of the transient time.
The calculations on record show that there is no SI flow at 50 seconds of the transient '
time. Therefore, there is no impact on the cutrent PCT result.
For the 4 inch break, the SI signal is at 7.95 seconds. With the 27 second time delay, the earliest possible time to obtain the SI flow is 34.95 seconds. - The current calculations on record show that the integrated SI flow during the first 50 seconds of. ;
the transient time is 50.1 pounds. It is estimated that the additional 2 second SI time ;
delay would reduce the integrated SI flow by 5.9 pounds. Based on a sensitivity !
study,5.9 pounds shortfall in SI flow would result in a PCT penalty of 0.1F. The' j analysis on record for the 4 inch SBLOCA PCT is only 833.9F. ' This increase is :
insignificant when compared to the huge margin remaining for this break. _!
I Based on the discussion above,it is concluded that changing the SI delay time from !
25 seconds to 27 seconds will have no effect on the Prairie Island Units 1 and 2, i SBLOCA PCT result. I LOCA Hydraulic Forces l The hydraulic forces resulting from a LOCA will have peaked and subsided well l before the first possible actuation of safety related equipment.' 'Ihus, the additional- l five second delay will have no effect on this analysis or the results of this analysis. ,
Post-LOCA Lone Term Cooline and iIot Lee Switchover i
This calculation is performed to ensure that the core remains subcritical after a l LOCA has occurred, and is based upon system volumet and boron concentrations. !
Since this is a long term calculation, any delay in safety related equipment actuation )
are unimportant. Therefore, the results of this calculation will be unaffected. ;
i 4
Northern States Power Company PrairieIsland Units I and2 NSP-93-501 - Attachment i Evaluation ofSBOIESU Time Delays Page 4 Steam Generator Tube Ruoture Evaluation The increased time delay does not affect any SGTR analysis input assumptions. As such there is no impact on the Westinghouse portion (the thermal-hydraulic response) of the SGTR. The effect of the increase in time delay for the SGTR dose. analysis must be considered by Northern States Power.
Containment Inteerity LOCA Mass and Enerev There is no impact on the current limiting case LOCA Mass and energy releases due to the additional 5 second source searching time delay. The analyses assume an "S" signal is generated coincident with the LOOP. The current FSAR M&E releases remain bounding.
LOCA Doses Radioloeical Evaluation Upon review of FSAR Section 14.9.4, the calculation of the environmental releases consider a one minute delay in the containment spray actuation. The assumption of the one minute delay will bound the additional sequence delay. Therefore, the additional delay will not impact the current radiological analysis.
CONCLUSIONS The additional delay time has been evaluated for the analysis areas discussed in the l Evaluation section. Westinghouse has determined that these analyses will be unaffected by the additional delay and that the no Loss of Offsite Power condition is still limiting with respect to the LBLOCA PCT. Additionalinformation concerning the evaluations presented can be found in Reference 6.
REFERENCES
- 1. NSP-92-136, " Increased Time Delay Due to Load Sequencing After SBO",
G. Goldberg to K. E. Higar, February 28,1992
' NortSern States Power Company PrairieIsland Units I and 2 NSP-93-501 - Attachment l Evaluation ofSBOIESU Time Delays Page5 i I
I
- 2. Letter from K. E. Higar of Northern States Power to J. Usem of Westinghouse l Electric Corporation, "SBO/ESU Re-evaluation of Time Delays Utilized in LOCA :
Analyses", November 23,1992
- i
- 3. Westinghouse Large Break LOCA Best Estimate Methodology, WCAP-10924, Volume 1. Addendum 4, Proprietary-i
- 4. Westinghouse Large Break LOCA Best Estimate Methodology, WCAP-10924, !
Volume 2, Revision 2, Addendum 1 Proprietary l t
- 5. NSP-92-106, " Northern States Power Company, Prairie Island Units 1 and- 2, i l
Transmittal of SBLOCA Updated USAR Sections", J. Goldberg, January 17,1992 l
- 6. NSP-92-183, "Resoludon of Comments on Draft SBO/ESU Report", T. Hawley to .
K. E. Higar, December 31,1992 l i !
! i 1
APPENDICES i I
i Aopendix A Letter from K. E. Higar of Northern States Power to J. Usem of Westinghouse Electric -
Corporation, "SBO/ESU Re-evaluation of Time Delays Utilized in LOCA A'nalyses".. '
November 23,1992 (8 Sheets)
L l
-t I
i l
Northem States Power Company 414 Nicollet Man Minneapolis, Minnesota $5401-1927 Telephone (612) 330 5500 November 23rd, 1992 l
Mr. Jeff Usem Westinghouse Electric Corporation 10950 Bren Road East Minnetonka, MN 55343 j
(612) 939-5226 RE: Station Blackout / Electrical Safeguards Upgrade (SBO/ESU)
Re-evaluation of time delays utilized in IDCA Analysis Mr. Usem This letter serves as a request for Westinghouse to re-evaluate the time delays utilized for the LOCA analyses, and to ensure that the time delays used in the analyses bound the SB0/ESU imposed time delays.
Attachment 1 is a memorandum from Marcia Thompson to Cliff Bonneau dated November 9*, which identifies four major changes from the previously reviewed SBO/ESU configuration.
Marcia's letter is quite complete, so I will not reiterate what is already stated; however, I will point out item #2, pg.1, and the 'undervoltage' diagram, attachment 1, page 2. Previously, the Diesel vould have started at the U.V.
(time =ero), but now the Diesel vill start at 5 seconds due to the off-site source searching as stated in item #2. Therefore, there will be an additional 5 second delay to safety equipment functionality (plus the 2 see sequencing delay).
As before, the Diesel vill start automatically on an 's' signal (SI). For the LOCA analyses, if an 's' signal is generated at the time of LOOP, then the additional five second delay is not applicable. The Diesel vill start immediately on the 's' signal, and the five second source searching time delay does not apply.
Northern States Power Company requests that Westinghouse re-evaluate the impact ;
i of the ' new' SB0/ESU imposed time delays upon the LOCA analyses by December 42, 1992, as was previously performed (before the changes) in Westinghouse letter NSP-92-136 dated February 28 *, 1992.
Also note paragraph 4 on page 2 of Marcia's memorandum, please respond to this question in your documentation for this new review.
Attachment 2 is the Prairie Island Blanket Purchase Order Release form.
_2- November 23rd, 1992 gg y,,,
f If you have any questions concerning the correct maximum time delays for the l different scenarios or if comply with the requested due date is improbable, l
please call me at (612) 337-2001. 1 Sincerely
[
^ eith E. Higar Nuclear Analysis Department Engineer I l
cc: R O Anderson (NSP) l l
C A Bonneau (NSP) l M A Thompson (NSP) l T Kitchen (U) l M Emery (V)
ATTACHMENT 1: Memorandum ESU-3025 from Marcia Thompson to Cliff Bonneau dated November 92, 1992.
i I ATTACHMENT 2: Prairie Island Blanket Purchase Order Release No. PBB825.
i l
I
r Internal Correspondence h((d i
i Date: November 9, 1992 To: Cliff Bonneau, Supt Safety Analysis Location: Ren Sq 8 From: Marcia Thompson, SBO/ESU Proj Eng Location: PI NPD SBO
%t I
i
Subject:
STATION BLACKOUT / ELECTRICAL SAEIGUAP.DS UPGRADE ER4V476 DIESEL GENERATOR PLANT INTERFACE SBO/ESU Project Design Review
! ESU-302S During our Design Change Package review by the plant staff, it was identified on the Plant Specific Reviews sheet that NSF Nuclear Analysis must review the project design changes. Nuclear Analysis has reviewed specific areas of concern for the project in the past such as PRA for the 121 Cooling Water Pump and the PRA, Transient, and LOCA review for the 480V system 2 second time delay imposed by the voltage regulators. Now the design as a whole must be reviewed.
The SBO/ESU project Architect Engineer has performed the safety evaluation for the project but there are areas which only NSF Nuclear Analysis Department can review. We request your department review the changes for the PRA, Transient, and LOCA Analyses.
Attachment one to this letter is a summary of changes to the l
safeguards bus logic due to the SBO/ESU Project. Also transmitted l
to you is the Plant Design Change Review Package. The SBO/ESU Project Design Report Rev. 1 was previously transmitted to your department and to Nuclear Support Services if you need it for reference. There are four major changes which we would like to bring to your attention:
- 1. The step assignment for loads on Units.1 and 2 has changed as shown in page 4 of attachment one.
l 2. The diesel will no longer get the undervoltage start signal at the time of detection of 4160V bus undervoltage. Instead it will wait until both offsite sources have This beentime determined to be delay will be the same unacceptable, then it will start.
for train A and B on both Units 1 and 2. See pages 1 through 3 of attachment one.
- 3. 121 Cooling Water Pump will be powered from a " swing" safeguards bus (Bus 27). The pump was previously refurbished as a safeguards pump and this repowering will complete the upgrade of the pump as The start logic for the pump has either a Train A or Train B pump.
l been modified to give a start on SI from either Unit 1 or Unit 2.
- 4. Last November, your group (coordinat@d by Mr. Iteith Higar)
' evaluated a change in the 480V Step 1 loads which will be delayed by I
2 seconds when we install 480V voltage regulators in 1993 and 1994.
When performing the evaluation of the changes mentioned in 1, 2, and j 3 above, the delays in Step 1 480V should be assumed to be in effect so that the final configuration is represented in one evaluation.
Page 4 of the attach =ent shows the final sequence.
The evaluation requested above must be complete before either Unit can leave Cold Shutdown this December. Unfortunately, this is rather late notice, however, the logic has just recently been
' finalized due to many last minute changes on the project so it may work out to be the most efficient time to do the evaluation. Please let me know if there is anything we can do to help speed your review i
or the Westinghouse review.
i Also, there is one question about the Westinghouse LOCA evaluation
]
(letter NSP-92-136) from last year's 480V evaluation. When
}
evaluating a LB or SB LOCA with LOOP in Sections 2.1.1 and 2.1.2, 1
why isn't the time ~ spent searching through offsite sources included 1 in the time for HHSI to start? Is the to g> seconds spent
- searchingthroughthesourcesevaluated{4)tooccurwithinthe10 seconds that the diesel is starting? This time delay is important to understand in order to evaluate our disel start logic changes.
~
For SI with LOOP the diesel start logic change is not significant
, since the diesel starts on SI too. However, if there is some i
analysis that addresses the time to reenergize the bus during a run-SI LOOP, it may be affected.
If you have any questions on the attached summary please call me at 5276. It may be necessary to have a meeting to go over the correct ,
- maximum time delays for the different scenarios because the logics for these systems are very complex.
1 Sincerely, 1 Marcia Thompson i SBO/ESU Project Engineer cc: Without Design Change Review Package '
R Pond R Peterson R Woodling J Pryatel J Ruether P Hellen J Maki J Leveille r J Goldsmith K Albrecht M Reddeman E89Yd76 D000 i
ATTACHMENT ONE Locic before SBO/ESU Mods:
Safety Injection (SI):
SI initiation causes immediate diesel start, load rejection, and Diesel starts, load sequencing with the bus on the offsite source.
accelerates to required speed and voltage in 10 seconds and sits
' idling in standby.
UndeJvoltage: sensed on Undervoltage (2 +/- 2 second duration causes valid signal) 4160V bus causes diesel start and source tripping. The scheme closes in another offsite source to power the bus. If a source does not successfully repower the bus, source tripping occurs again and the scheme repeats until it finds a source. If none of the offsite sources successfully repowers the bus, load rejection occurs, then the diesel closes onto the bus, and then load sequencing occurs. In the case of a complete LOOP, the other offsite sources do not have adequate voltage so the scheme will not try them and will wait for the diesel.
Safety Injection with LOOP:
SI initiation causes immediate diesel start, load rejection, and load sequencing (sequencing will not occur until a source is restored). The LOOP causes source tripping, The bus sequences through the other offsite sources and when none of them successfully repower the bus (because of LOOP), the diesel closes onto the bus and load sequencing occurs.
Locic after SBO/ESU Mods:
Safety Injection:
SI initiation causes immediate diesel start, load rejection, and immediate load sequencing with the bus on the offsite source.
Diesel starts, accelerates to required speed and voltage in 10 seconds and sits idling in standby. This is'the same as before SBO/ESU mods.
Undervoltage:
Undervoltage (4 second duration causes valid signal) sensed on 4160V bus causes source tripping and load shedding. The' bus tries the other offsite source and load sequencing occurs. If it does not successfully repower the bus then the diesel is started and load !
shedding occurs, the diesel closes onto the. bus within 10 seconds of the diesel start signal, and then load sequencing occurs. In the case of a complete LOOP, the other offsite source does not have adequate voltage so the scheme will not try it and will start the diesel and wait for it.
Safety Injection with LOOP:
SI initiation causes immediate diesel start, load rejection, and load sequencing (sequencing will not occur until a source is The bus may or may not restored). The LOOP causes source tripping. .
sequence to the other offsite source (because of LOOP it may look l bad right away) and when it does not successfully repower the bus l (because of LOOP), the diesel closes onto the bus and load i sequencing occurs.
l page 1 l
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121 Cont Rm Chiller 30 see 121 Cent Rm Chiller i l
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I I
lI ATTACHMENT 4 i
NSP Internal Correspondence from Keith E Higar to Marcia Madson, dated December 31, 1992 2 Pages (excluding this cover page)
This attachment does not include the two attachments which are with the original letter since one attachment is included in ATTACHMENT 3 above and the other attachment is an earlier revision to that same document. ,
i i
I J
1
Internal Correspondence case December 31, 1992 .
Locadon Ren Sq 8 From Keith E. Higar NES To Marcia Madson Location PI NPD SB0 subject Station Blackout / Electrical Safeguards Upgrade Project (SB0/ESU)
SBO/ESU Project Design Review / Modification 89Y976 part B Rev.0 This letter is in response to your request on November 9, 1992 for Nuclear
+
Engineering Services (NES) formerly Nuclear Analysis Department (NAD) to: ,
1
- 1. Review Modification 89Y976 part B Rev. 0,,
- 2. Review DS/D6 Load Sequence Calculation No. M-375-EG-002, j and '
- 3. Evaluate the impact of the SB0/ESU's imposed time delays j upon NES's analyses and assumptions in the following-three areas: ,
I
- a. Probabilistic Risk Assessment (FRA),
- b. Transient Analysis, and
NES performed a review of PRA and Transient Analysis, and Westinghouse has 4' evaluated non-PRA and non-Transient conditions (LOCA) . Westinghouse has completed their analysis; however, I do not have an official copy of their ,
report yet. Westinghouse has informed NSF via a draft report (NSP-92-181) l and a Resolution of Comments memorandum (NSP-92-183) that all technical issues were addressed and there were no unreviewed safety issues pertaining to non-PRA and non-Transient conditions (see attachments 'l & ,
t
- 21 In regards to items #1 and '2, NES has reviewed the stated documents and i all issues have been resolved; therefore, this memorandum denotes that the ;
review by NES according to N1ACD 5.1 Rev. 6 Nuclear Plant Modification :
Process has been satisfactorily fulfilled.
In regards to item #3, NES has evaluated the impact of the SB0/ESU's imposed time delays upon NES's analyses and assumptions for PRA and Transient Analysis. The SB0/ESU imposed time delays affect the Steam Line areak (SLB) transient.
The five second source searching time delay and the additional two second sequencing time delay do not adversely impact NES's analysis of the SLB accident. Even with the additional time delays, the SLB with LOOP does not become more limiting than our current most limiting SLB with Offsite Power analysis. Both the primary and' secondary responses for the SLB with LOOP vere less severe than the SLB with Offsite Power case. Specifically, peak power and peak heat flux were lower, and mass and energy release
. - , . ~.- - .. .. - . . - . ... . . . . - . . - - . - . . _ _ . _ _ -
4 Marcia Madson December 31, 1992 to' containment was less. Therefore, there are no concerns regarding maximum peak clad temperature (PCT) or containment integrity.(mass and energy release) in regards to SLB with LOOP.
The PRA section has . determined that the SB0/ESU Project will have no -
adverse effects upon their analyses.
As stated earlier, Westinghouse has evaluated non-Transient events (the
_ Loss nf Coolant &ccident (LOCA), SG Tube Rupture, etc.). Westinghouse has informed NSP via a draft report that all technical issues were addressed and there were no unreviewed safety issues pertaining to non-Transient conditions. A final SB0/ESU report will be mailed to NSP pending Westinghouse document control requirements.
If you have any questions or concerns, please-feel free to give me a call at x2001(Transient), or Tom Asmus at x2058(PRA) - thank you.
Sincerely K th E. Higar Engineer I ATTACHMENTS: 1. NSP-92-181, Preliminary S20/ESU Report
- 2. NSP-92-183, Resolution of comments on Draft SB0/ESU Report ec: R O Anderson C A Bonneau T M Parker e
I
,