View source for CPSES-200700147, Response to Request for Additional Information Regarding Resolution of Generic Letter 2006-02, Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power

{{Adams
| number = ML070370349
| issue date = 01/29/2007
| title = Response to Request for Additional Information Regarding Resolution of Generic Letter 2006-02, Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power
| author name = Blevins M, Madden F
| author affiliation = TXU Power
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000445, 05000446
| license number = 
| contact person = 
| case reference number = CPSES-200700147, GL-06-002, TXX-07014
| document type = Letter type:CPSES
| page count = 11
| project = 
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:TXU Power WI Power                Mike Blteviins Comanche Peak Stearn    Se =er ice. Presidenit &
Elactriic Stateiant     Chiel Nthdear Officer P. G. Box: 1002' (EGT})
Glen, Rose, TX 76043                                                                                          Ref: I OCFR50.54 Tel" 254 897 5209, Fax- 254 897 6652                                                                                                     GL 2006-02 mike: blevins@txu.com CPSES-200700147 Log # TXX-07014 January 29, 2007 U. S. Nuclear Regulatory Commission Attn: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852

==SUBJECT:==
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RESOLUTION OF GENERIC LETTER 2006-02, "GRID RELIABILITY AND THE IMPACT ON PLANT RISK AND THE OPERABILITY OF OFFSITE POWER" REF:         1. NRC Generic Letter 2006-02, "Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power," dated February 1, 2006.
: 2. TXU Power Letter, logged TXX-06056, from Mike Blevins to the U.S. Nuclear Regulatory Commission, dated April 3, 2006.
: 3. TXU Power Letter, Logged TXX-06096, from Mike Blevins to the U.S. Nuclear Regulatory Commission, dated June 29, 2006.
: 4. NRC Letter from Catherine Haney to Holders of Operating Licenses for Nuclear Power Reactors, dated December 5, 2006.

==Dear Sir or Madam:==

In Reference I above, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2006-02 to determine if licensees are maintaining compliance with NRC regulatory requirements governing electric power sources and associated personnel A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
* Comanche Peak
* Diablo Canyon  *. Palo Verde
* South Texas Project &deg; Wolf Creek A(23

TXX-07014 Page 2 of 2 training. As required in Reference 2, TXU Power provided a response to the GL. In Reference 3, TXU Power revised the GL response to provide greater clarity and more detail. After reviewing the GL responses, the NRC issued the request of additional information to the GL in Reference 4.
By means of the Attachment to this letter, TXU Generation Company LP (TXU Power) submits its response to the Nuclear Regulatory Commission's request for information pursuant to Generic Letter 2006-02, "Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power."
Some of the questions in GL 2006-02, however, seek information about analyses, procedures, and activities concerning grid reliability for which CPSES does not have first-hand knowledge, are beyond the control of CPSES, and cannot be verified or validated by CPSES. In providing information responsive to such questions, CPSES makes no representation as to its accuracy or completeness.
Should you have any questions, please contact Ms. Tamera Ervin at (254) 897-6902.
This colnmunication contains no new or revised licensing basis commitments.
I state under penalty of perjury that the foregoing is true and correct.
Executed on January 29, 2007.
Sincerely, TXU Generation Company LP By:      TXU Generation Management Company LLC Its General Partner Mike Blevins By:
reW. Madden Director, Oversight and Regulatory Affairs TJE Attachment c -      B. S. Mallett, Region IV M. C. Thadani, NRR Resident Inspectors, CPSES

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template Offsite Power Operability                                                                                         >~(t RAI Topic            RAI Question                       CPSES Response 2 Loss of Real-Time  Your response to question 2(f) did Contingency Analysis not identify the actions that (RTCA) Capability    would be taken if the online grid analysis tool (software program) that you rely upon as an input for offsite power operability became unavailable.
2a                   If the online grid analysis tool   Per the regulatory guidance of NRC Regulatory that you use to determine if the   Information Summary (RIS) 2005-20, the term offsite power is inoperable        "Operable/Operability" is defined in the Technical becomes unavailable, what          Specifications (TS) and applied only to TS Systems, actions would you take to          Structures, and Components (SSCs). Thus, the nuclear determine if post-trip voltages    power plant (NPP) offsite power system is not referred will be acceptable, including any  to as "operable" or "inoperable," because the grid is not other compensatory actions, until  a TS SSC. SSCs that are not included in the TS (e.g.,
the post-trip voltage is confirmed NPP offsite power system (OPS)) are referred to as to be adequate?                    Functional or non-Functional.
As an example, the actions may include reliance on a backup       Comanche Peak Steam Electric Station (CPSES) does (third party's) real-time          not use online grid analysis tools to determine the contingency analysis or similar    functionality of the OPS. The OPS is considered program, or relying on a grid      functional as long as it provides adequate voltage at the planning study to confirm that     safety related buses. The safety related buses are the original assumptions bound     automatically isolated from the OPS and connected to the existing grid conditions.      the onsite emergency diesel generator (EDG), if the OPS can not maintain safety related bus technical specification voltages.

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template CD W CPSES has a formal agreement in place for notification        o if the transmission service provider's (TSP's) (TXU Electric Delivery) online analysis tools are unavailable.
Electric Reliability Council of Texas (ERCOT) (CPSES' transmission service provider (TSO)) also runs online analysis tools. Due to redundancy of TSP and ERCOT online analytical tools, CPSES does not expect to be without the ability to determine if offsite voltage and capacity are adequate.
In the remote likelihood that both analysis tools are unavailable and absent information that a grid instability condition exists, CPSES OPS is not considered non-functional. Use of conservative margins in the grid planning analysis for compliance to CPSES OPS requirements, and Grid Operation to maintain the CPSES switchyard voltages at a level such that a single grid system contingency will not cause the switchyard voltages to be outside the CPSES requirements, assure that a loss of online analysis tool by itself will not result in non-functionality of CPSES OPS.
Per CPSES Abnormal Conditions Procedures Manual ABN-601 "Response to a 138/345 kV System Malfunction," if notified by the TSP that grid conditions exist such that inadequate voltage may exist on loss of a unit or grid conditions are degraded and a "grid estimator" is not available to predict grid conditions following a unit trip, CPSES would enter a Limiting Condition for Operation Action Requirement (LCOAR)

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template for potential loss of offsite source and would make an offsite power functionality determination. In addition,  0 CPSES' TSP would initiate evaluation of grid activities, \O =
specifically on lines feeding CPSES and adjacent switchyards, and those activities may require termination to ensure a reliable source of offsite power to CPSES if the plant were to trip or require down power.

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template                                                 &#xfd;Z C
RAI Topic         RAI Question                        CPSES Response 3 Verification of Your response to question 2(g)                                                                   C RTCA Predicted    indicates that you have not Post-Trip Voltage verified by procedure the voltages                                                               H predicted by the online grid analysis tool (software program) with actual real plant trip voltage values. It is important that the programs used for predicting post-trip voltage be verified to be reasonably accurate and conservative.
3a                What is the range of accuracy for   The grid planning analyses to determine the post-trip your GO's contingency analysis      voltages at CPSES switchyards are performed with program?                            conservative contingencies. The contingencies considered, in addition to the tripping of CPSES units, are tripping of a grid system generator or loss of a line critical to CPSES. These analyses result in conservative and bounding voltage conditions for CPSES switchyards. CPSES has not experienced switchyard voltages outside the analyzed values after an unscheduled inadvertent trip of a CPSES unit.
Consideration of conservative contingencies to provide bounding analyses eliminates the need for validation of post trip voltages. Due to consideration of conservative contingencies for compliance to CPSES OPS requirements, a validation by procedure for post event analysis to check accuracy of the TSO Real Time Contingency Analysis (RTCA) tool is not required.

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template The TSP uses a commercial grade RTCA tool that has           0 reasonable accuracy. TSP's planning department has          0 0
experience and confidence in the tools predictions and has not revealed any deficiencies in the tool. Thus, the H
results of the tool are representative of the grid system.
4                                  3b   Why are you confident that the       Per the guidance of NRC RIS 2005-20, the term post-trip voltages calculated by     "Operable/Operability" is defined in the TS and applied the GO's contingency analysis        only to TS SSCs. Thus, the NPP offsite power system is program (that you are using to       not referred to as "operable" or "inoperable," because the determine operability of the         grid is not a TS SSC. SSCs that are not included in the offsite power system) are            TS (e.g., NPP OPS) are referred to as Functional or non-reasonably accurate and              Functional.
conservative?
CPSES does not use online grid analysis tools to determine the functionality of the OPS. The OPS is considered functional as long as it provides adequate voltage at the safety related buses. The safety related buses are automatically isolated from the OPS and connected to the onsite EDG if the OPS can not maintain safety related bus technical specification voltages.
In addition to the TSO studies, CPSES' TSP performs yearly, seasonal, and daily studies and the grid is operated within these bounding studies. Specifically, the CPSES switchyard voltages are maintained at a level such that a single grid system contingency will not cause the switchyard voltages to be outside the CPSES requirements. Furthermore, the tools used by the TSP meet the analysis reauirements of ERCOT and North

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template                                              -p >
American Electric Reliability Council (NERC).
The grid planning analyses to determine the post-trip       CD voltages at CPSES switchyards are performed with conservative contingencies. CPSES and the TSP have confidence in the analysis tool to provide post trip voltages which are reasonably accurate and conservative.
3c What is your standard of       The State Estimator meets the ERCOT acceptance acceptance?                    criteria for accuracy. The contingency analysis tool is a commercial grade tool that is accepted throughout industry. Application of the State Estimator will identify and resolve discrepancies in modeling Supervisor Control And Data Acquisition (SCADA) data accuracy. This application follows good utility practices and meets transmission grid safety and reliability requirements.

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template RAI Topic           RAI Question                       CPSES Response                                              CD 4 Identification of In response to question 3(a) you   In this question, the loss of other critical transmission Applicable Single   did not identify the loss of other elements is outside the current licensing basis. There is Contingencies       critical transmission elements     no credible postulated off-site scenario that will actuate that may cause the offsite power   the low-voltage relays, thus, there is no compliance issue.
system (OSP) to degrade, other than the loss of the nuclear unit. Note that response 2(e) to GL 2006-02 identified a list of analyzed contingencies that are considered against the CPSES switchyard voltage requirements.
4a                  If it is possible for specific     See response 3(a) to GL 2006-02.
critical transmission elements (such as other generators, critical transmission line, transformers, capacitor banks, voltage regulators, etc.) to degrade the OSP such that inadequate post-trip voltage could result, have these elements been included in your N -1 contingency analysis?
4b                  When these elements are            See response 3(a) to GL 2006-02.
included in your GO's contingency analysis model and failure of one of these transmission elements could result in actuation of your degraded voltage grid relay, is the offsite power declared inoperable?

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template 4c If not, what is your basis for not See response 3(a) to GL 2006-02.
cc-declaring the offsite power inoperable?
0 H

Requests for Additional Information (RAIs)
Generic Letter 2006-02 Industry Response Template                                              rr*
RAI Topic           RAI Question                   CPSES Response                                             2 6 Interface With                                                                                               _
Transmission System Operator During Extended Plant Maintenance                                                                                                      C:
6a                  How do you interface with your Per station procedure STA-629, "Switchyard Control,"
GO when on-going               Attachment 8.f, "Communication Protocol," CPSES would maintenance at the nuclear     notify the TSO for:
power plant, that has been previously coordinated with    1. Planned unit shut downs.
your GO for a definite time    2. Degraded safety equipment that may cause CPSES a frame, gets extended past that    future down power due to regulatory requirements.
planned time frame?            3. Modifications to the CPSES generator, controls or main power transformer operating specifications.
Notifications to and from CPSES for confirmed emergent grid or plant conditions should be made as soon as possible, typically within 30 minutes Furthermore, on-going maintenance activities are communicated routinely until the activity is complete.}}