RBG-47279, Response to Request for Additional Information on License Amendment Request 2011-05
| ML12255A169 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 09/05/2012 |
| From: | Roberts J Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBF1-12-0126, RBG-47279 | |
| Download: ML12255A169 (8) | |
Text
Entergy Operations, Inc.
River Bend Station 5485 U.S. Highway 61 IN St. Francisville, LA 70775 SEn tergy Tel 225 381 4149 Fax 225 635 5068 jrober3@entergy.com Jerr C. Roberts Director, Nuclear Safety Assurance RBG-47279 September 5, 2012 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Response to Request for Additional Information on License Amendment Request 2011-05 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47
REFERENCES:
- 1. Entergy letter to NRC, dated December 8, 2011, License Amendment Request 2011-05, Degraded Voltage Surveillance Frequency Extension and Allowable Value Changes (Letter No.
RBG-47193)
- 2. NRC letter to Entergy (via email), dated August 7, 2012, Request for Additional Information RBF1-12-0126
Dear Sir or Madam:
On December 8, 2011, Entergy Operations, Inc. (Entergy) submitted a request to extend the frequency of a surveillance requirement and revise the allowable value for degraded voltage relays (Reference 1). During their review, the NRC staff determined that additional information is needed to complete the processing and approval of Entergy's request. The request for that information was transmitted to Entergy per Reference 2.
The attachment to this letter contains the requested information.
This letter contains no commitments. If you have any questions on this matter, please contact Joey Clark, Manager - Licensing, at 225-381-4177.
I declare under penalty of perjury that the foregoing is true and correct. Executed on September 5, 2012.
Sincerely, XJCR/dw /1 /o
RBG-47279 September 5, 2012 Page 2 of 2 : Response to Request for Additional Information cc: Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 E. Lamar Blvd.
Arlington, TX 76011-4511 NRC Senior Resident Inspector River Bend Station U. S. Nuclear Regulatory Commission Attn: Mr. Alan Wang MS 8-G14 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Department of Environmental Quality Office of Environmental Compliance Radiological Emergency Planning and Response Section JiYoung Wiley P.O. Box 4312 Baton Rouge, LA 70821-4312 Ms. Tracie Lowery Public Utility Commission of Texas 1701 N. Congress Ave.
Austin, TX 78711-3326
Attachment 1 RBG-47279 Response to Request for Additional Information RBG-47279 September 5, 2012 Page 1 of 5
- 1. It is stated in RAI Responses 1, 3, 4 to RAI REQUEST No. 1, that outliers were rejected based on t-Test. Indicate what additional investigations, other than t-Test, were performed.
RESPONSE
No additional evaluations were performed for the outlier evaluation, the EOI drift analysis followed the River Bend Drift Analysis Design Guide, ECH-NE-08-0015, which the NRC evaluated as acceptable in ML 02350266, (SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 168 TO FACILITY OPERATING LICENSE NO. NPF-47 ENTERGY OPERATIONS, INC.
RIVER BEND STATION, UNIT 1 DOCKET NO. 50-458). The drift design guide specifically states in Section 3.6.1, Detection of Outliers, 'This design guide utilizes the Critical Values for t-Test (Extreme Studentized Deviate)."
Section 3.6.2 identifies the equations used and Section 3.6.3 defines the limits of outlier expulsion. The t-Test as identified is consistent with the drift evaluations performed for the River Bend 24 Month Fuel cycle license Amendment Request and also with the license amendment requests for several other 24-Month fuel cycle requests. The analysis never removes more than a single outlier as discussed with NRC.
- 2. It is stated in RAI Response 3 to RAI REQUEST No. 1, that the maximum recorded drift was 6.31 VAC and was not rejected as outlier while the drift permitted by setpoint calculations for 30 months has been selected to be + 5.823 VAC. Provide justifications why maximum drift of 6.31 VAC is considered acceptable.
RESPONSE
The 6.31 VAC was a historical change between an as-left condition and the next as-found condition. As explained in Section 3.2.1.2 of the above referenced drift design guide, while termed as drift, these changes in output value from one calibration to the next can also contain accuracy errors, Measurement and Test Equipment uncertainty, uncertainty due to minor temperature variations and other possible environmental related uncertainties. The statistics as identified in the drift design guide are used to generate an acceptable and conservative computation of the 30 month drift.
Section 4.6 of the drift design guide identifies the methods used to calculate the drift value. In summary, the random portion of the Analyzed Drift is calculated by multiplying the standard deviation of the Final Data Set by the Tolerance Interval Factor for the sample size and the Normality Adjustment Factor (if required from the Coverage Analysis) and then extrapolated as necessary. Since the drift value is determined based on 95/95 criteria, it is possible that single values within the analysis will exceed the limits computed. Research into the historical information did not reveal any problems with the data such as data transcription errors, calibration errors, RBG-47279 September 5, 2012 Page 2 of 5 Measurement & Test Equipment errors, scaling or setpoint changes, failed instruments or design / application deficiencies, as outlined in Section 3.6 of the drift design guide. In this case, the value is an unidentified anomaly, but is the second outlier identified (and as such, could not be removed by the drift design guide criteria).
- 3. RAI Response 3 to RAI REQUEST No. 1, Function 2.a, Division 3 - 4.16 kV Emergency Bus, indicates that more than 50 samples have been reviewed for Normality test. Provide similar minimum number of samples used for each of the functions listed in RAI Response to REQUEST No. 1.
RESPONSE
In accordance with the drift design guide discussed above, a minimum sample set of 30 samples was generally used to derive a 95/95 confidence drift value. The following table provides the final data set sample size, after removal of outliers, for each calculation addressed.
Calculation Title Sample Size G13.18.6.3-006 Drift Study for ABB Model ITE-27H 41 Undervoltage Relays G13.18.6.3-009 Drift Study for ABB ITE-62 Timers 42 G13.18.6.3-012 Drift Study for General Electric Model NGV13B 58 Undervoltage Relays G13.18.6.3-014 Drift Study for Agastat ETR Series Time Delay 48 Relays
- 4. It is stated in response to REQUEST No. 4, 'The setpoint calculation methodology allows for using the Loop Calibration Tolerance instead of Loop Reference Accuracy to determine Loop Uncertainty when the Loop Calibration Tolerance is greater than the Loop Reference Accuracy." Clarify what parameters are used in calculating these two tolerances and how the adequacy of those parameters have been established.
RESPONSE
The value of Loop Calibration Tolerance (LCT) used in setpoint and measurement uncertainty calculations is equal to the calibration tolerance specified in the associated Surveillance Test Procedure (STP) for the loop in question. The adequacy of this value is established by the fact that it is the actual tolerance used by the technician in performing the calibration. LCT may be equal to or greater than the Loop Reference Accuracy (LRA).
Where the LCT is greater than LRA, then the LCT replaces the LRA term in the Channel Uncertainty calculation. This ensures that the actual tolerance around the setpoint is accounted for in the Channel Uncertainty.
RBG-47279 September 5, 2012 Page 3 of 5 Loop Reference Accuracy is the combined vendor published accuracy for all Loop devices. Reference accuracy is a value that defines the limit that errors will not exceed when the device is used under the vendor specified operating conditions.
- 5. Response to REQUEST No. 4 states, "...the STP 'As-Found' and 'As-Left' calibration tolerance is the same..." Provide clarification how the As-Found and As-Left tolerances are calculated, especially if drift is included in them.
RESPONSE
STP 'As-Found' and 'As-Left' calibration tolerances are the same because neither 'As-Found' nor 'As-Left' calibration tolerances contain an allowance for drift. See the response to question 4 above for a discussion of how 'As-Found' and 'As-Left' calibration tolerances are determined. This represents a very conservative as-found value since some drift is expected between calibrations.
- 6. Section 9.0 in Setpoint Calculation G13.18.3.1-004 addresses Maximum Loop Setting Tolerance, CTLv and TRM. Explain what CTLv and TRM represent and what tolerances are included in them.
RESPONSE
The term TRM Trip Value in Calculation G13.18.3.1-004 Section 9.0 refers to the Technical Requirements Manual Nominal Trip Setpoint, which includes allowance for Total Loop Uncertainty. Section 10.1 of calculation G13.18.3.1-004 provides a TRM setpoint of TRM < 52.55 seconds and Section 10.2 provides a TRM setpoint of TRM > 51.23 VAC. CTLV represents Loop Calibration Tolerance. This value is obtained from uncertainty calculations G13.18.6.2-ENS*002 and G13.18.6.2-ENS*006 and is equivalent to the Loop Calibration Tolerance value used in the associated Surveillance Test Procedures (STP-302-1600, STP-302-1601, STP-302-1602 and STP-302-1603). The variable CTLv described in Section 9.0 of calculation G13.18.3.1-004 is identified as CTL in Section 10.1 of that calculation, where CTL = 3 seconds. It is also identified as CTL in Section 10.2 of the calculation, where CTL = 0.87 VAC.
- 7. Section 8.4 in Calculation G13.18.6.2-ENS*007, Rev. 1, refers to References 3.2, 3.3, and 3.11, which the staff has not received. Clause 8.4 addresses CTLT and procedural as-left band (PALB) parameters. Provide the relevant information on how the CTLT and PALB parameters are established, especially to ensure 95/95 confidence level.
RBG-47279 September 5, 2012 Page 4 of 5
RESPONSE
The CTLT parameter is set equal to PALB in Section 8.4 of Calculation G13.18.6.2-ENS*007. PALB is the Loop Calibration Tolerance used in the associated Surveillance Test Procedures (STP-302-1604 and STP-302-1605). Therefore, although treated as 95/95 confidence level values in calculation G13.18.6.2-ENS*007, since the tolerance value is verified 100%
of the time during the performance of the surveillance, the confidence level of PALB and CTLT are actually greater because they are the actual tolerance values used during calibration.
- 8. Assumption 7.1.2 in Calculation G13.18.6.2-ENS*007, Rev. 1, states, "For conservatism all uncertainties given in vendor data specifications are assumed to be 20 unless otherwise specified." Provide justifications for this assumption.
(a) Please be sure to identify any components NOT purchased as safety-related (i.e., commercially dedicated)
(b) Please be sure to include the exact statement that the vendor made regarding the uncertainties (e.g., Tolerance interval, distribution, and confidence level).
RESPONSE
Assumption 7.1.2 in calculation G13.18.6.2-ENS*007, Rev. 1, is based on vendor published specifications for normal operating conditions, including ambient temperature and power supply voltage variations. The vendor does not provide any information regarding the confidence level, tolerance interval or distribution for the specified accuracy values. However, the assumption that vendor data specifications are 2a is supported by the drift evaluation performed in Reference 3.16.3 (calculation G13.18.6.3-014). This calculation evaluated relay performance using 48 data points at various plant environmental and power supply conditions within the relay normal operating range and concluded that 30 month drift is within +/- 3.725% of setpoint with a 2a confidence level. Calculation G13.18.6.2-ENS*007, Rev.
1, utilizes a vendor supplied reference accuracy value of +/- 5% of setting.
Additionally, although the vendor specifies that this +/- 5% of setting accuracy value includes an allowance for normal environmental temperature and power supply voltage variations, calculation G13.18.6.2-ENS*007, Rev. 1, includes an additional +/- 5% of setting uncertainty for temperature effect and an additional +/- 5% of setting uncertainty for power supply effect. Since the +/-
5% of setting allowance for reference accuracy is significantly larger than the
+/- 3.725% of setpoint value resulting from the drift study and a large amount of conservatism was included in the calculation by combining additional allowances for temperature effect and power supply effect with reference accuracy, it was concluded that the vendor supplied accuracy value may be conservatively treated as having a 2o confidence level.
RBG-47279 September 5, 2012 Page 5 of 5 All components evaluated by calculation G13.18.6.2-ENS*007, Rev. 1, are purchased as safety related.
- 9. Sections 8.7.3.1 and 8.7.3.2 in Calculation G13.18.6.2-ENS*007 Rev. 1, state, "Relay Drift for Time Delay Setting (DRRT) (Assumption 7.1.14)
DRRT1 = + 3.725% Setpoint" Assumption 7.1.14 states Instrument Drift is deleted.
Provide clarification between the above two statements.
RESPONSE
The content of Sections 8.7.3.1 and 8.7.3.2 in Calculation G13.18.6.2-ENS*007 Rev. 1, is correct, with the exception of reference to Assumption 7.1.14. Section 7.1.14 contained an assumption regarding relay drift in a previous revision of the calculation which is no longer required with the inclusion of the results of the drift study performed in Reference 3.16.3.
- 10. Sections 8.3.1 and 8.3.2 in Calculation G13.18.6.2-ENS*007 Rev. 1, refer to Sections 8.2.3, 8.1.3, and 8.1.5 but there are no Sections 8.2.3 and 8.1.5 in this calculation. Section 8.1.3 refers to Reference 3.9.1, and Assumption 7.1.6.
Assumption 7.1.6 refers to Reference 3.9.6 which also the staff has not received.
Provide the necessary information.
RESPONSE
An error exists in the section numbers referenced by Sections 8.3.1 and 8.3.2 in Calculation G13.18.6.2-ENS*007 Rev. 1. Section 8.3.1 should reference Sections 8.2.1, 8.1.1 and 8.1.3. Section 8.3.2 should reference Sections 8.2.2, 8.1.2 and 8.1.4.