L-PI-11-099, Response to Requests for Additional Information Regarding Regulatory Guide 1.97 Instrumentation Associated with Adoption of the Alternative Source Term (AST) Methodology
| ML113430091 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/08/2011 |
| From: | Schimmel M Northern States Power Co, Xcel Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-PI-11-099, RG 1.097, TAC ME2609, TAC ME2610 | |
| Download: ML113430091 (14) | |
Text
L-PI-11-099 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 Response to Requests for Additional Information Reaardina Renulatorv Guide 1.97 InstrumentationAssociated with Adoption of the Alternative Source Term (AST)
Methodoloav (TAC Nos. ME2609 and ME26101 In a letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27, 2009 (Agencywide Documents and Management System (ADAMS) Accession No. ML093160583), the Northern States Power Company, a Minnesota corporation doing business as Xcel Energy (hereafter "NSPM"), requested an amendment to the Technical Specifications (TS) for Prairie Island Nuclear Generating Plant (PINGP). The proposed amendment requested adoption of the Alternative Source Term (AST) methodology, in addition to TS changes supported by AST design basis accident radiological consequence analyses.
The NRC Staff sent Requests for Additional lnformation (RAI) in a letter dated May 12, 201 1 (ADAMS Accession No. ML103540433) regarding the steam generator tube rupture (SGTR) event radiological consequence analysis. In a letter dated June 22, 2011 (ADAMS Accession No. MLI 11740145), NSPM provided a response to these RAls. On July 20, 201 1 (ADAMS Accession No. MLI 12081967), the NRC Staff sent a consolidated request for clarification of the June 22, 201 1 RAI response. In a letter dated August 9, 2011 (ADAMS Accession No. MLI 12220098), NSPM provided a response to the request for clarification of the June 22, 201 1 RAI response. On September 1, 201 I , the NRC Staff sent a draft request for further clarification of the August 9, 201 1 RAI response via electronic mail, regarding the classification of instruments as they relate to the criteria of Regulatory Guide 1.97, Revision 2. In a conference call held on November 14, 201 1, the NRC modified the request for clarification and provided a final request for additional information on November 22, 201 1 (ADAMS Accession No. MLI 13250575).
1717 Wakonade Drive East e Welch, Minnesota 55089-9642 Telephone: 651.388.1121
Document Desk Page 2 The enclosure to this letter provides the response to the November 22, 201 1 request for additional information. NSPM submits this supplement in accordance with the provisions of 10 CFR 50.90.
The supplemental information provided in this letter does not impact the conclusions of the Determination of No Significant Hazards Consideration and Environmental Assessment presented in the October 27, 2009 submittal.
In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this license amendment request supplement by transmitting a copy of this letter to the designated State Official.
If there are any questions or if additional information is needed, please contact Mr. John Fields at 763-271-6707.
Summarv of Commitments This letter makes the following new commitment:
NSPM will revise the Prairie Island Nuclear Generating Plant design and licensing bases to indicate that the Steam Generator Water Level - Narrow Range instruments are required to meet Regulatory Guide 1.97, Revision 2 requirements. This commitment will be completed prior to implementation of the Alternative Source Term license amendment.
See the enclosure for details concerning this new commitment. No revisions to existing commitments are being made.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on DEC 8 9 2011 Mark A. Schimmel Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region Ill, USNRC NRR Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC State of Minnesota
L-PI-I 1-099 NSPM Response to Clarification Questions ENCLOSURE In a letter to the U.S. Nuclear Regulatory Commission (NRC) dated October 27, 2009 (Agencywide Documents and Management System (ADAMS) Accession No. ML093160583), the Northern States Power Company, a Minnesota corporation doing business as Xcel Energy (hereafter "NSPM"), requested an amendment to the Technical Specifications (TS) for Prairie Island Nuclear Generating Plant (PINGP). The proposed amendment requested adoption of the Alternative Source Term (AST) methodology, in addition to TS changes supported by AST design basis accident radiological consequence analyses.
In a letter dated November 22, 201 1, the NRC provided the following request for additional information (RAI) related to the PINGP AST proposed license amendment.
For clarity, the NRC RAI information is provided below in italics font and the NSPM response is provided in plain font.
Background
By letters dated June 22, 201 1, and August 9, 201 1, in response to Nuclear Regulatory Commission (NRC) staff requests for additional information, the licensee provided a tabulation of instrumentation required to cope with a Steam Generator Tube Rupture (SGTR) event, The NRC staff has reviewed these responses and requests further clarification regarding the appropriate qualification levels for this instrumenfation.
Request for Additional Information
( I ) Identify which instrumentation on the table discussed above are the "Principal" Instrumentation and Controls (I&C) needed for the identification and mitigation of the SGTR event, and which equipment are considered "available" as a back-up or secondary instrument function, if needed. Principal and backup instrumentation are as described in Westinghouse topical report WCAP-10698-P-A (proprietary).
(2) For each of the items identified as Principal I&C equipment used, state whether this equipment is safety-related or not, and describe the qualification levels to which this equipment meets PINGP1scurrent licensing basis for identifying safety related equipment. Provide justification for the use of any equipment on this list that is not qualified to meet safety related standards appropriate to your licensing basis. Include a description of that equipment which is not fully-qualified to meet requirements for safety-related instrumentation per your licensing basis, but has been upgraded to have augmented quality, and describe how this augmented quality has been achieved.
NSPM Response By letters dated June 22, 201 1, and August 9, 201 1, NSPM provided a tabulation of instrumentation required to cope with a Steam Generator Tube Rupture. Table I Page 1 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions (provided below) tabulates the principal instrumentation from the June 22 and August 9 letters. For each principal instrument, Table 1 provides the following information:
o Function of each instrument used in mitigation of a Steam Generator Tube Rupture.
e Safety classification of the process loop associated with the instrument.
e Safety classification of the indication associated with the instrument.
o For those principal instruments or indications that are not safety related, the backup indication is identified.
o Additional details regarding power supply and other pertinent considerations.
As used in Tables 1 and 2, augmented quality (AQ) describes a subset of non-safety related items for which one or more of the governing Quality Assurance Topical Report (QATR) requirements apply. This includes items for which specific licensing commitments or additional controls over quality are deemed necessary by NSPM management, but are not explicitly defined in the QATR. Quality requirements for the instrumentation are established to satisfy the applicable requirements in the licensing basis as established through commitments to meet Regulatory Guide (RG) 1.97, Revision 2, "Instrumentation for Light-Water-cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following an Accident," as described in the PlNGP Updated Safety Analysis Report (USAR) Section 7.10. In lieu of classifying RG 1.97 instrumentation as safety related, the RG 1.97 instruments are classified as Augmented Quality; although the requirements are very similar. Qualifications regarding quality assurance, environmental qualification and seismic qualification are described in USAR Section 7.10.2, and are consistent with Regulatory Positions 1.3.1 (Category 1) and 1.3.2 (Category 2) in RG 1.97, Revision 2.
As demonstrated by Table 1, all of the instruments utilized for SGTR mitigation in the PINGP-specific Emergency Operating Procedures (EOPs) are currently classified as RG 1.97, Revision 2, instrumentation in the PlNGP USAR, except for Steam Generator (SG) Water Level - Narrow Range (NR). Based on a review of the specific mitigation function that the instrument provides, the SG-NR level instrumentation should be reclassified in accordance with RG 1.97, Revision 2. This mis-classification is being tracked as a corrective action in the PlNGP Corrective Action Program. Based on the failure to properly classify the SG Water Level Narrow Range Indication as RG 1.97 instrumentation, the corrective action also includes an extent of condition review to ensure that other instrumentation used in EOPs are correctly classified consistent with the PlNGP licensing basis.
Page 2 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions The function and classification of each of the instruments included in Table 1 is provided below.
Core Exit Thermocouples The core exit thermocouples (CETs) are used by operators to terminate the Reactor Coolant System (RCS) cooldown during SGTR recovery. Additionally, the CETs are used by the operators to demonstrate that SI flow termination criteria are met. As shown in Table 1, the CETs are currently classified design and qualification Category 1; therefore, they meet the qualification requirements prescribed by RG 1.97, Regulatory Position 1.3.1. Additionally, the CETs are listed in TS Table 3.3.3-1 as event monitoring instrumentation.
RCS Subcoolinq Monitor RCS Subcooling monitor indication provides information for operator action termination of RCS depressurization. Specifically, RCS subcooling is used for terminating RCS depressurization and SI termination. Pressurizer level, RCS pressure and SG pressure can also be used to terminate RCS depressurization.
The RCS Subcooling monitors are currently classified design and qualification Category 2; therefore, they meet the qualification requirements prescribed by RG 1.97, Regulatory Position 1.3.2.
Steam Generator Water Level - Narrow Range The SG Water Level - NR (SG-NR) instruments provide the primary means of identification of a ruptured steam generator by indication of a.n unexpected increase in any SG-NR channel level. Immediately following identification of the ruptured SG, operators manually isolate the ruptured SG. As such, SG-NR level provides the primary information required to permit the control room operators to take the specified manually controlled actions.
The SG-NR instrumentation is not identified in the PlNGP USAR as compliant with RG 1.97. This deficiency has been entered into the PlNGP Corrective Action Program. The Corrective Action Program condition evaluation determined that the SG-NR instrumentation should be classified as a RG 1.97 Type A instrument.
However, further evaluation is necessary to fully demonstrate and document the correct RG 1.97 type classification of the instruments and ensure the RG 1.97 design and qualification criteria requirements are implemented.
Based on this, NSPM is making the following commitment regarding the SG-NR instrumentation:
NSPM will revise the Prairie Island Nuclear Generating Plant design and licensing bases to indicate that the Steam Generator Water Level - Narrow Range instruments are required to meet Regulatory Guide 1.97, Revision 2 requirements. This commitment will be completed prior to implementation of the Alternative Source Term license amendment.
Page 3 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions This commitment will ensure:
Implementation of the correct design and qualification criteria for these instruments in accordance with RG 1.97, Revision 2, The PlNGP USAR is updated to document the correct RG 1.97 classification based on the results of the evaluation of the PlNGP EOPs in relation to the technical basis for the SG-NR instrumentation, and The Technical Specifications will be revised in accordance with 10 CFR 50.36(c)(ii), to change the licensing bases associated with the SG-NR instruments, if required.
Pressurizer Water Level Pressurizer water level indication is used by operators to provide Reactor Coolant System (RCS) depressurization and Safety Injection (SI) flow termination criteria for a SGTR event. The pressurizer water level indicators are currently classified design and qualification Category 1; therefore, they meet the qualification requirements prescribed by RG 1.97, Regulatory Position I.3.1. Additionally, the pressurizer water level indicators are listed in TS Table 3.3.3-1 as event monitoring instrumentation.
Reactor Coolant Svstem Pressure RCS pressure indication is used by operators to provide RCS depressurization and SI flow termination criteria for a SGTR event. The RCS pressure indicators are currently classified design and qualification Category 1; therefore, they meet the qualification requirements prescribed by RG 1.97, Regulatory Position 1.3.1.
Additionally, the RCS pressure indicators are listed in TS Table 3.3.3-1 as event monitoring instrumentation.
Steam Generator Pressure SG pressure indication provides information for operator action for determining the target cooldown temperature and for termination of RCS depressurization.
Specifically, RCS depressurization is terminated by the operator when the RCS pressure is lower than the ruptured SG pressure. As allowed by the EOP, depressurization of the ruptured SG can also be terminated based on either pressurizer water level or RCS subcooling. The SG pressure indicators are currently classified design and qualification Category 2; therefore, they meet the qualification requirements prescribed by RG 1.97, Regulatory Position 1.3.2 as described in the PlNGP USAR Section 7.10.2. As described above, pressurizer water level indication is classified as a RG 1.97 Category 1 variable and, accordingly meets the qualification requirements prescribed by RG 1.97, Regulatory Position 1.3.I .
Page 4 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions Table I Principal and Backup lnstrumentation Utilized for Steam Generator Tube Rupture Mitigation I
Principal Safety Safety Safety lnstrument Classification Backup Classification of Function Classification Remarks Name (Process lnstrumentation Backup (Indicator)
Loop) lnstrumentation Core Exit Monitor RCS SR SR Indication is safety Thermo- temperature for (RG 1.97, related. Several CETs couples securing Category 1) are provided. The CET (CETs) cooldown. power supply is safety related and will be available durina a LOOP.
RCS Monitor RCS AQ Redundant Same as Principal Subcooling is calculated Subcooling Subcooling for (RG 1.97 monitors lnstrument from an average of Monitor securing RCS Category 2) Core Exit depressurization Thermocouples and and SI RCS Pressure. CETs termination. are SR. The RCS Pressure input provides Class 1E inputs to the display systems.
Page 5 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions Safety Principal Safety Backup Classification of Remarks Instrument Function Instrumentation Backup Name (Indicator) lnstrumentation SG Water Identify Ruptured NSR Three separate Same as Principal The instrument loops Level SG. indication Instrument due to from the sensing line Indication - (Note that, channels for each redundancy. through the transmitter Narrow currently, this steam generator are safety related. The Range (NR) indication is not are displayed in indication is on the non-classified per the control room. safety related side of RG 1.97 in the the loop. The indicator PlNGP licensing Emergency power supply is safety basis. The Response related and will be indication will be Computer System available during a classified as (ERCS) provides LOOP.
described in the backup indications response to RAI for SG narrow Questions 1 and range water level.
2.) ERCS is supplied by an Uninterruptible Power Supply (UPS) and redundant power sources to network switches and remote multiplexing units.
Page 6 of 12
L-PI-11-099 Enclosure NSPM Response to Clarification Questions Safety Safety Principal Safety Classification Backup Classification of Instrument Function Classification Remarks (Process Instrumentation Backup Name (Indicator)
Loop) lnstrumentation Pressurizer Provides SR AQ Three separate Same as Principal The instrument loops Water Level indication to the (RG 1.97, indication Instrument due to from the sensing line Indication operators that Category 1) channels per Unit redundancy. through the transmitter supports securing are displayed in are safety related. The RCS the control room. indicators are depressurization augmented quality. The and termination ERCS provides indicator power supply of SI. backup indications is safety related and will for pressurizer be available during a water level. ERCS LOOP.
is supplied by a UPS and redundant power sources to network switches and remote multiplexing units.
Page 7 of 12
L-PI-11-099 Enclosure Response to Clarification Questions Principal Safety Safety Safety Classification Backup Classification of lnstrument Function Classification Remarks Name (Process lnstrumentation Backup (Indicator)
Loop) lnstrumentation RCS Provides AQ AQ Two separate Same as Principal The RCS pressure Pressure indication to the (RG1.97, indication lnstrument due to indicators and Indication operators that Category 1) channels per Unit redundancy. transmitters are supports securing are available in the augmented quality. The RCS control room. indicator power supply depressurization is safety related and will and termination ERCS provides be available during a of SI. backup indications LOOP.
for RCS pressure.
ERCS is supplied by a UPS and redundant power sources to network switches and remote multiplexing units.
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L-PI-11-099 Enclosure NSPM Response to Clarification Questions Safety Safety Principal Safety Classification Backup Classification of Instrument Function Classification Remarks (Process Instrumentation Backup Name (Indicator)
Loop) lnstrumentation SG Pressure Provides SR AQ Three separate Same as Principal The instrument loops Indication indication to the (RG 1.97, indication Instrument due to from the sensing line operators that Category 2) channels per redundancy. through the transmitter supports steam generator are safety related. The determination of are available in the indicators are non-target cooldown control room. safety related. The temperature. indication meets all ERCS provides requirements for a RG SG pressure backup indications 1.97, Category 2, indication is also for SG pressure. instrument. The used during RCS ERCS is supplied indicator power supply depressurization by a UPS and is safety related and will to secure the redundant power be available during a depressurization. sources to network LOOP.
switches and remote multiplexing units.
During RCS As shown above, depressurization, Pressurizer water pressurizer water level level and RCS instrumentation is subcooling monitor RG 1.97, Category can also be used 1. RCS as an indication to subcooling monitor stop RCS is RG 1.97, depressurization. Category 2.
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L-PI-11-099 Enclosure NSPM Response to Clarification Questions Table 2 identifies instrumentation used as secondary instrumentation in the SGTR event. The function and classification of each of the instruments included in Table 2 is provided below.
Radiation Monitors (Condenser Air Ejector, Steam Generator Blowdown. Main Steam Line)
The radiation monitors can be used to provide an early indication of a SGTR. In addition, the main steam line radiation monitors can provide indication to help determine which SG is ruptured. In the event that operators do not transition to the SGTR Emergency Operations Procedure (EOP) based on the radiation monitor signal, the operators would transition based on the SG-NR Water Level indication.
The SG-NR water level indication is the credited indication in the Margin to Overfill (MTO) analysis for identifying that a SGTR exists and for identifying the ruptured SG. Thus, the radiation monitors provide an early identification, but are not credited in the analysis. The condenser air ejector and main steam line radiation monitors are classified as RG 1.97 Category 2 instruments and meet the design and qualification criteria in RG 1.97, Revision 2, Regulatory Position 1.3.2 as described in the PlNGP USAR section 7.10.2. No changes to the design and licensing bases are required for this instrumentation.
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L-PI-11-099 Enclosure NSPM Response to Clarification Questions Table 2 Secondary lnstrumentation Utilized for Steam Generator Tube Rupture Mitigation Safety Secondary Safety Classification Instrument Function Classification Backup Instrumentation Remarks (Process Name (Indicator)
Loop)
Condenser Although the AQ AQ In the event that the operators The power supply to the Air Ejector radiation monitors (RG 1.97, do not transition to the SGTR condenser air ejector and steam Radiation are not credited Category 2) EOP based on the radiation generator blowdown radiation Monitor in the SGTR monitor signal, the operators monitor is safety related and will Steam analyses, they NSR NSR would transition to the SGTR be available during a LOOP. The Generator provide an early EOP based on SG-NR level power supply to the main steam Blowdown indication of a indication increasing in an line radiation monitor is non-Liquid SGTR event. In uncontrolled manner. safety related, but is backed up Radiation addition, the main by a non-safety related diesel Monitor steam line ERCS provides backup generator and expected to be Main Steam radiation monitors AQ AQ indications for these radiation available during a LOOP.
Line provide indication (RG 1.97, monitors. ERCS is supplied by Radiation of which steam Category 2) a UPS and redundant power Monitor generator is sources to network switches ruptured. and remote multiplexing units.
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L-PI-11-099 Enclosure NSPM Response to Clarification Questions Request for Additional Information (3) The PlNGP Updated Safety Analysis Repotf, Tables 7.10-1 and 7.10-2 enumerate the Regulatory Guide 1.97, Rev. 2 variables applicable to Units I and 2, respectively. These tables have been previously reviewed and approved by the NRC in various safety evaluations. Verify that appropriate accident monitoring instrumentation supporting Principal SG TR indication functions is included on these tables.
NSPM R e s ~ o n s e The PlNGP Updated Safety Analysis Report (USAR), Tables 7.10-1 and 7.10-2 enumerate the Regulatory Guide 1.97, Rev. 2 variables applicable to Units 1 and 2, respectively. The information in these tables has previously been reviewed and approved by the NRC in various safety evaluations. The Principal instrumentation supporting SGTR events described above is included in USAR tables 7.10-1 and 7.10-2 with the following exception:
Steam Generator Water Level - Narrow Range is not included in USAR Tables 7.10-1 and 7.10-2. This instrument will be added to USAR Tables 7.10-1 and 7.10-2. This mis-classification is being tracked as a corrective action in the PlNGP Corrective Action Program. Based on the failure to properly classify the SG Water Level Narrow Range Indication as RG 1.97 instrumentation, the corrective action also includes an extent of condition review to ensure that other instrumentation used in EOPs are correctly classified consistent with the PlNGP licensing basis.
For further details concerning the commitment which addresses this condition, see the discussion concerning the SG-NR instruments provided in the response to RAls 1 and 2.
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