ML14066A097
| ML14066A097 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 03/07/2014 |
| From: | Richard Ennis Plant Licensing Branch 1 |
| To: | Meena Khanna Plant Licensing Branch 1 |
| Ennis R, NRR/DORL, 415-1420 | |
| References | |
| TAC MF3085, TAC MF3086 | |
| Download: ML14066A097 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 7, 2014 MEMORANDUM TO:
Meena K. Khanna, Chief Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Richard B. Ennis, Senior Project Manager /RA/
Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
SUBJECT:
LIMERICK GENERATING STATION, UNITS 1 AND 2, DRAFT REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. MF3085 AND MF3086)
The enclosed draft request for additional information (RAI) was transmitted on March 6, 2014, to Mr. Frank Mascitelli of Exelon Generation Company, LLC (Exelon, the licensee). This information was transmitted to facilitate an upcoming conference call in order to clarify the licensees amendment request for Limerick Generating Station (LGS), Units 1 and 2 dated November 15, 2013. The proposed amendment would revise the Technical Specification requirements related to the response time for the main steam line flow-high isolation function.
The draft RAI was sent to Exelon to ensure that the questions are understandable, the regulatory basis for the questions is clear, and to determine if the information was previously docketed. This memorandum and the enclosure do not convey or represent an NRC staff position regarding the licensee's request.
Docket Nos. 50-352 and 50-353
Enclosure:
Draft RAI
March 7, 2014 MEMORANDUM TO:
Meena K. Khanna, Chief Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation FROM:
Richard B. Ennis, Senior Project Manager /RA/
Plant Licensing Branch I-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
SUBJECT:
LIMERICK GENERATING STATION, UNITS 1 AND 2, DRAFT REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. MF3085 AND MF3086)
The enclosed draft request for additional information (RAI) was transmitted on March 6, 2014, to Mr. Frank Mascitelli of Exelon Generation Company, LLC (Exelon, the licensee). This information was transmitted to facilitate an upcoming conference call in order to clarify the licensees amendment request for Limerick Generating Station (LGS), Units 1 and 2 dated November 15, 2013. The proposed amendment would revise the Technical Specification requirements related to the response time for the main steam line flow-high isolation function.
The draft RAI was sent to Exelon to ensure that the questions are understandable, the regulatory basis for the questions is clear, and to determine if the information was previously docketed. This memorandum and the enclosure do not convey or represent an NRC staff position regarding the licensee's request.
Docket Nos. 50-352 and 50-353
Enclosure:
Draft RAI DISTRIBUTION PUBLIC RAlvarado, NRR/DE/EICB LPL1-2 R/F SWyman, NRR/DE/EICB RidsNrrDorlLpl1-2 Resource RidsNrrDorlDpr Resource RidsNrrPMLimerick Resource ACCESSION NO.: ML14066A097 OFFICE LPL1-2/PM NAME REnnis DATE 03/07/14 OFFICIAL RECORD COPY
DRAFT REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED LICENSE AMENDMENT MAIN STEAM LINE FLOW-HIGH ISOLATION RESPONSE TIME EXELON GENERATION COMPANY, LLC LIMERICK GENERATING STATION, UNITS 1 AND 2 DOCKET NOS. 50-352 AND 50-353 By application dated November 15, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13322A448), Exelon Generation Company, LLC (Exelon, the licensee), submitted a license amendment request for Limerick Generating Station, Units 1 and 2. The proposed amendment would revise the Technical Specification (TS) requirements related to the response time for the main steam line flow-high isolation function.
The Nuclear Regulatory Commission (NRC) staff has reviewed the information the licensee provided that supports the proposed amendment and would like to discuss the following issues to clarify the submittal.
- 1. Please describe the reasons that have caused the instrument channel response time to drift, and thus reduce the margin in response time for the trip unit and relays to meet the TS response time limit.
- 2. Please describe testing or analysis performed to confirm that increasing the instrument channel response time to 1.0 seconds will be sufficient to rectify the problem of the instrument channels not meeting the TS-required response time limit. In addition, please describe the tolerance limit for the relays and how this will be taken into consideration for the increased channel response time.
- 3. As discussed on page 1 of Attachment 1 to the application dated November 15, 2013:
The total response time for a main steam line isolation on high steam flow is 5.5 seconds. The Main Steam Isolation Valves (MSIVs) start to close at 0.5 seconds on a high flow signal and are fully closed at 5.5 seconds. The TS-required instrument response time for the MSIV closure initiation instrument channel on high steam line flow is 500 milliseconds (0.5 seconds). The TS Table 3.3.2-3 had been previously amended, in license amendments 132 and 93 (Reference 2) in December 1998 to eliminate response time testing of the flow transmitter in each main steam line flow instrument channel. Prior to the license amendment, the allotted allowable response time limit for the trip unit and the output, isolation and
Enclosure implementation relays was 184 milliseconds (msec), allowing 316 msec for the transmitter response time. Per the amendment, 355 msec has been allotted for the transmitter and, as such, the remaining 145 msec has become the TS required limit for the trip unit and the three relays of the instrument channel. An administrative limit (allotted time) of 135 msec is used to proactively identify for drift, and hence alert if the TS limit is being approached.
Page 4 of Attachment 1 to the application dated November 15, 2013, states that the proposed amendment will change the assumptions and conditions for the main steam line break analysis with respect to the MSIV closure time. Specifically, following implementation of the proposed amendment, it will be assumed that the MSIVs start to close at 1.0 seconds on a high flow signal and are fully closed at 6.0 seconds.
The following table presents the current design basis versus the proposed design basis. Please provide the missing values in the table:
Parameter Current Design Basis Proposed Design Basis MSIVs start to close on high flow signal 0.5 seconds 1.0 seconds Response time allotted for transmitter 0.355 seconds
?
Response time allotted for trip unit and relays 0.145 seconds
?
Administrative limit for response time of trip unit and relays 0.135 seconds
?