NL-12-059, Response to Request for Information Regarding Proposed Change to the Technical Specification Requirement for Containment Sump Level Indication
| ML12132A049 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 04/27/2012 |
| From: | Ventosa J Entergy Nuclear Operations, Entergy Nuclear Northeast |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-12-059 | |
| Download: ML12132A049 (11) | |
Text
Enterav Nuclear Northeast Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 SEntergy Buchanan, NY 10511-0249 Tel 914 254 6700 John A Ventosa Site Vice President Administration NL-12-059 April 27, 2012 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Response to Request for Information Regarding Proposed Change to the Technical Specification Requirement for Containment Sump Level Indication (TAC ME7367)
Indian Point Unit Number 2 Docket No. 50-247 License No. DPR-26
REFERENCES:
- 1. NRC Letter to Entergy, Request for Additional Information Regarding Amendment Application For Containment Water Level Monitoring (TAC No ME7367), dated March 29, 2012 2 Entergy Letter NL-1 1-119 to NRC Regarding Proposed Change to the Technical Specification Requirement for Containment Sump Level Indication, dated October 18, 2011
Dear Sir or Madam:
Entergy Nuclear Operations, Inc (Entergy) is hereby providing a response, Attachment 1, to the NRC request for additional information, Reference 1, associated with the proposed change to the Indian Point 2 Technical Specification requirement for containment sump level indication in Reference 2.
A copy of this response and the associated attachment is being submitted to the designated New York State official in accordance with 10 CFR 50.91.
There are no new commitments being made in this submittal. If you have any questions or require additional information, please contact Mr. Robert Walpole, Manager, Licensing at (914) 254-6710.
NL-12-059 Docket 50-247 Page 2 of 2 I declare under penalty of perjury that the foregoing is true and correct. Executed on April 27, 2012.
Sincerely, JAV/sp Attachments: 1. Response to Request for Information Regarding Proposed Change to the Technical Specification Requirement for Containment Sump Level Indication cc: Mr. Douglas Pickett, Senior Project Manager, NRC NRR DORL Mr. William Dean, Regional Administrator, NRC Region 1 NRC Resident Inspectors Mr. Francis J. Murray, Jr., President and CEO, NYSERDA Ms. Bridget Frymire, New York State Dept. of Public Service
ATTACHMENT 1 TO NL-12-059 RESPONSE TO REQUEST FOR INFORMATION REGARDING PROPOSED CHANGE TO THE TECHNICAL SPECIFICATION REQUIREMENT FOR CONTAINMENT SUMP LEVEL INDICATION ENTERGY NUCLEAR OPERATIONS, INC.
INDIAN POINT NUCLEAR GENERATING UNIT NO. 2 DOCKET NO. 50-247
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 1 of 8 In a letter dated October 18, 2011, Entergy Nuclear Operations, Inc. (Entergy), submitted an application for a proposed amendment to the Technical Specifications (TSs) for Indian Point Nuclear Generating Unit No. 2 (IP2) which would revise the TSs on post-accident monitoring for the containment building water level. By letter of March 29, 2012 the Nuclear Regulatory Commission Staff requested additional information on that request. Those requests and the responses are addressed below.
Question 1 Please provide a description of the containment and recirculation sumps including approximate volume and relative location in containment and confirm that the recirculation sump and the containment sump are independent sumps not connected below the containment floor at 46 feet.
Response
The Emergency Core Cooling System (ECCS) contains two post-LOCA sumps, the Internal Recirculation (IR) Sump and the Vapor Containment (VC) Sump that provide a long-term source of cooling water to the fuel/core following a Loss of Coolant Accident (LOCA) Event. Following initial SI (Safety Injection) System operation, outflow from the ruptured pipe and Containment Spray (CS), is collected in the IR Sump, where it is returned to the Reactor Pressure Vessel (RPV) Core, and if required, to the CS (Containment Spray) System headers via the Internal Recirculation Pumps situated within the IR Sump. The Residual Heat Removal (RHR) System Pumps provide a redundant recirculation flow path by means of the independent VC Sump.
The IR Sump has an approximate overall volume of 1742 ft 3 (
Reference:
Calculation IP-CALC 00306 Rev. 0) and is located within the Crane Wall on EL 46'-0", west of the Reactor vessel. A concrete shield wall protects the IR Sump, pumps, piping, and other necessary components from the effects of an RCS pipe break. The IR Sump is the suction source for the two, vertical type IR Pumps that are located within the Sump.
The VC Sump has an approximate overall volume of 496 ft3 (
Reference:
Drawing 501241 Rev. 0).
It is located inside, and adjacent to, the Crane Wall on EL 46'-0" approximately 90 degrees away from the IR Sump, south of the Reactor vessel. The Containment Sump is the suction source to the two Residual Heat Removal Pumps. The RHR Pumps are located in the Primary Auxiliary Building (PAB) and are supplied through a line connecting the Containment sump to the pump suction.
The IR and VC Sumps are operated independently and there is no piping that connects the sumps.
The original plant design intended the Containment Sump essentially as a full backup to the Recirculation Sump. It is also needed, based on the existing license, as the alternate flow path for certain single active or passive failures. As part of the resolution to GSI-191, the Indian Point 2 license was clarified / modified regarding failures and the required backup capability of the Containment Sump if the Recirculation Sump flow path is disabled.
In response to Generic Letter 2004-02 barriers were installed in the Vapor Containment, EL 46'-0" to force the recirculation flow into the Reactor Cavity Sump area, up and out the Incore Instrumentation Tunnel, through the Crane Wall via the three nominal 20 inch square openings and into the annulus area outside the Crane Wall. The recirculation flow will migrate towards the
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 2 of 8 Recirculation Sump Strainer or the Containment Sump Strainer depending on which pump(s) are operating. Flow channeling barriers are installed on the reactor Cavity Platform, EL 29'-4", around the Incore Instrumentation Tunnel, on the Recirculation Sump Trenches, at the Containment Sump, and on Crane Wall penetrations up to the flood level. Flow channeling barrier doors are installed in the Northeast and Northwest quadrant openings of the Crane Wall. In addition, flow channeling barrier doors are installed in the North and South entrances to the Recirculation Sump area. Perforated plate is installed on the RHR Heat Exchanger Platform, EL 66'-0" to preclude debris from washing through the existing grating and into the Recirculation Sump area. Forcing the recirculation flow path into the Reactor Cavity Sump area (a low velocity zone) allows the larger debris an opportunity to settle.
Question 2 IP2's current configuration has redundant credited detectors co-located in the respective sumps.
The proposed configuration credits one detector in each sump. Your licensing commitments with respect to Regulatory Guide 1.97 requires continuous and redundant indication for Category 1 variables. The proposed configuration is only redundant for detecting levels above the top of the respective sumps at the 46 foot elevation. Please list all required operator actions based on indicated containment level (wide range) and/or containment sump level (narrow range) and the corresponding water level(s).
Response
The IP2 letter of August 30, 1985 proposed compliance with Regulatory Guide 1.97 using wide range and narrow range level indicators. This was clarified by letter dated October 27, 1989 which indicated that the wide range and narrow range functions would be performed by a single level indicator since these are monitored, continuously, from the bottom of the sumps to the design flood level. The redundancy requirement was met by one instrument in the recirculation sump and one in the containment sump.
At the time the IP2 Technical Specifications (TS) were converted to the standard TS, the older TS contained requirements for discrete level indication in the containment sump and the recirculation sump as well as a continuous monitor in each sump. When the conversion process took place, the TS for PAM type A instruments was added as a more restrictive change. The inclusion of the discrete and continuous monitors was viewed as an administrative change since the existing TS were required to be operable for input to the RCS Leakage Monitoring Instrumentation.
Therefore, our Licensing commitment is for two continuous monitors to meet RG 1.97 and, as of approval of the revised TS, two discrete monitors to also provide post accident level indication.
The Licensing basis for redundancy is one continuous monitor in each sump, and, as of approval of the revised TS, implies additional redundancy using discrete monitors.
A listing of all required operator actions using the narrow range or wide range capabilities follows:
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 3 of 8 IP2 tPt IP2 1P2 ERG Setpoint Setpoint Analytical 1P2 Definitions for Containment Setpoint Term -e Water Level Procedure Value Value Tert Term SP1-T.07 - Containment water level just below Status 4915" 50 5" design flood level, minus allowances T.06 Tree for normal channel accuracy, as 2-F-05 indicated on LI-939.
SP1 -T.09 - Containment water level just below Status 48' 19 50' 15 design flood level, minus allowances T.06 Tree for normal channel accuracy, as 2-F-05 indicated on LI-941.
NONE -
2-ES-1.3 NONE NONE Containment Level - Trending NONE step 1 Upwards (LR-3300/LR-3301)
SP1 -T.08 - Minimum VC level to provide 2-ES-1.3 46'8-1/2 46' 8-1/2" adequate NPSH for the NONE step 1 step 1on Recirculation LI-941 pumps, as indicated Maximum sump level to ensure SP1-T.16 - 42' 10-1/2" 46' 3" MCC 28 cable/splices are not under NONE Various water for postulated VC flooding events, as indicated on LI-941.
SP1-U.04 - Table of RWST level vs. Recirculation sump 2-ECA-3.1 Values volume [based upon ECA-3.1 NONE background documentation]
NONE - NONE NONE Abnormal Sump Level indication NONE Various Containment Sump Level - Normal NONE - NONE NONE Recirculation Sump Level - Normal NONE Various Reactor Cavity Sump Level -
Normal The Type A variables associated with water level in the TS 3.3.3 are the confirmation that the break is inside containment and the decision to transfer to recirculation.
" LT-3300, LT-3301 are used in Step 1 of 2-ES-1.3, Transfer to Cold Leg Recirculation, as part of recirculation switchover criteria. They are checked just to confirm that water has entered the Containment and is trending upward when the RWST Low Low Level alarms actuate. This also confirms the break is inside containment,
- LT-941 is also used in ES-1.3 as the contingency check of sump level when RWST alarms or LT-3300, LT-3301 fail.
- LT-939 was not identified in ES-1.3 that procedure but will be added as a redundant instrument that would be used for contingency check.
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 4 of 8 The Type B variable is for maintaining RCS integrity safety function per RG 1.97, Rev. 3, with the purpose being detection, accomplishment of mitigation, and verification. The Type C variable is for determining the breach or potential breach of the RCS pressure boundary per RG 1.97 with the purpose being detection of breach, accomplishment of mitigation, verification and long term surveillance. LT-3300 and LT3301 were licensed to perform these functions and there are no specific procedural actions associated with this.
LT-939 and LT-941 are used as part of the logic for Status Tree 2-F-0.5, Containment, to diagnose higher than expected water level (approaching flood level) in Containment which can be considered in accomplishment of long term surveillance.
Question 3 Provide an analysis describing how the proposed change appropriately fulfills the requirements for maintaining accident monitoring instrumentation in the plant technical specifications. List which detectors are credited for A7, B131 wide range, B1 1 narrow range, and C6 variables. These are the plant-specific designators which can be found in the IP2 Regulatory Guide 1.97 submittals, such as the letter dated August 30, 1985 (ADAMS Accession Nos. ML100322029 and ML100322031).
Response
Refueling Water Storage Tank level indicators [LI-920 and LI-5751] provide diverse means to control the manual action for switchover to internal recirculation.
The continuous Containment Water Level indicators LT-3300 and LT-3301 are independently powered (Instrument Bus 22 associated with power train 2A/3A for LT-3300 and Instrument Bus 21 associated with power train 5A for LT-3301), and both are qualified in accordance with RG 1.97 Category 1 requirements (Engineering Change 3714 replaced the Barton transmitters with Weed transmitters qualified per Weed Qualification Reports QAOAAC10, QAOAAC1 1, and QAOAAC12).
LT-3300 and LT-3301 provide both narrow range and wide range functions for A7, B131 wide range, B1 1 narrow range, and C6 RG-1.97 variables. Instrument accuracy was judged acceptable based on information provided in an Indian Point letter to the NRC dated April 29, 1983. Therefore, they provide the instrumentation functions to satisfy RG 1.97 requirements for Type A, Type B and Type C instruments.
The non-continuous level indicators LT-939 and LT-941 provide both narrow range and wide range Containment Water Level functions for A7, B131 wide range, B1 1 narrow range, and C6 RG-1.97 variables. They were never specifically reviewed by NRC as RG 1.97 monitors. They are independently powered (Instrument Bus 22 associated with power train 2A/3A for LT-939 and Instrument Bus 21A associated with power train 5A for LT-941), and both are qualified in accordance with RG 1.97 Category 1 requirements (FCI Qualification Test Reports 708093 dated June 28,1982 and 7087009 dated March 14, 1978 and FIX-00033 Rev 2). The LT-939 and LT-941 transmitters indicate containment level using 5 indicator lights located on Central Control Room (CCR) Panel SB-i. The level indicator LT 941 consists of thermal type detectors that energize the lights as a preset level is reached. The level indicator LT 939 consists of magnetic float / switch type sensors that energize the lights as a preset level is reached. The current setting has lights go on in series as the sump and containment water levels rise. LT 939 lights currently go on at elevations 35', 46' 7", 47' 5", 49' 5" (flood level), and 51' 9' and have an 6" loop error. LT 941 lights currently go on at elevations 40' 5.125", 42' 10.5", 46' 8.5", 48' 9', and 51' 7.5" (flood level), and have a 0.5" loop error. The transmitters do not meet the requirements of RG 1.97
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 5 of 8 Revision 2 with respect to the Category 1 requirement for continuous monitoring but they were discussed as used for non-continuous sump level monitors when a third similar instrument was removed from the PAM TS (NRC Letter to Indian Point regarding "Issuance of Emergency Amendment Re: Containment Sump Level Indication" (TAC MD2655), dated July 28, 2006). The display is continuous in the sense that the lights associated with each level stay on as long as the level remains above the setpoint and goes off when it falls below the setpoint. They do provide clear indication when a specific set point has been reached and this provides level indication sufficient for operator action considering the required levels and the instrument loop error. LT-939 does provide continuous indication to the plant computer over its entire range. LT-941 provides indication to the plant computer using 9 discrete step inputs which provides increased trending capability. Therefore, they provide adequate instrumentation functions to satisfy RG 1.97 requirements for Type A instruments as discussed in the July 27, 2006 amendment.
This change involves no significant reduction in the margin of safety because the TS requirements are being changed from four to two detectors to reflect the Standard Technical Specifications and two level transmitters (i.e., LT-3300 and LT-3301) will have a backup set of post accident level detectors (i.e., LT-939 and LT-941) that are currently identified as post accident monitors and can be used to meet the LCO when subject to the required surveillance testing to assure operability.
Note LT-939 (recirculation sump) and LT-3300 (containment sump) are powered from instrument buses supplied by 2A/3A and LT-941 (containment sump) and LT-3301 recirculation sump) are powered from instrument buses supplied by 5A. Redundancy requires the credited instruments to be in different sumps and have different power supplies.
Question 4 Entergy states in the second paragraph of Section 3.0, Technical Analysis, that 'The minimum water level for the Recirculation pump to have adequate NPSH [Net Positive Suction Head] is a function of the specific type of LOCA [Loss of Coolant Accident] and the peak water level to keep equipment from flooding is elevation 50' 5"." Please identify the minimum water levels associated with adequate NPSH for each type of LOCA.
Response
As referenced in NL-09-138 [ML093290316] the minimum water levels for various accident scenarios were determined in the Indian Point Unit 2 Water Level Calculation [IP-CALC-05-00805].
The following Table (Table 3g. 1-3) from this calculation summarizes the results:
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 6 of 8 Break Location Case Water Level (feet EL.)
Large Break Loss-of-Coolant At Start of SI Recirculation 48.04 Accident At Start of Recirculation 48.87 Double-Ended Pump Suction Break Spray After Recirculation Spray is 48.23 Secured End-of-Event 48.35 Alternate Break Loss-of-Coolant At Start of SI Recirculation 47.87 Accident At Start of Recirculation 48.69 Double Ended Pressurizer Surge Spray Line Break After Recirculation Spray is 48.40 Secured Small Break Loss-of-Coolant At Start of SI Recirculation 47.78 Accident - No Sprays End-of-Event - No Sprays 47.69 At Start of SI Recirculation 47.54
- Sprays At Start of Recirculation 48.37 Spray NRC Question 3g in NL-09-138 provides additional information which was used to determine the NPSH margin for the ECCS and CSS pumps that would exist during a loss-of-coolant accident (LOCA) considering a spectrum of break sizes.
Question 5 The no-significant-hazards analysis takes credit for the detectors that are proposed to be removed from the plant technical specifications. Please provide justification for crediting the detectors that are being removed from plant TSs or provide analysis based on the detectors remaining in the TSs.
Response
The no significant hazards analysis does not take credit for the detectors proposed to be removed from the plant TS. The no significant hazards analysis revises the detectors from 4 to 2 (one in each sump). The no significant hazards analysis and the technical justification clarifications are discussed below:
- 1. "Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No. The proposed change will revise the requirements for water level monitors from 4 to 2. These level indicators are provided for monitoring the post-accident water level in the bottom of the containment to aid operator action to initiate recirculation and to assess the potential for excessive level. The presence or absence of these instruments has no bearing on accident precursor conditions or events. The proposed requirement will maintain redundancy and, utilizing the RWST level indication, diversity to continue to provide information to the plant operators to monitor
Attachment 1 NL-12-059 Docket Nos. 50-247 Page 7 of 8 and manage accident conditions. Therefore, the proposed change does not involve a significant increase in the probability or consequences of previously evaluated accidents."
This significant hazards analysis is correct but the technical justification submitted requires clarification. The October 18, 2011 letter said:
This change involves no significant reduction in the margin of safety because the TS requirements are being changed from four to two detectors to reflect the Standard Technical Specifications and two level transmitters (i.e., LT 3300 and LT 3301) will each have a backup post accident level detector (i.e., LT 939 for LT 3300 and LT 941 for LT 3301) that are currently identified as post accident monitors and will continue to be subject to the required surveillance testing to assure operability. Note LT 939 and LT 3300 are powered from instrument buses supplied by 2A/3A and LT 941 and LT 3301 are powered from instrument buses supplied by 5A.
The Recirculation Sump contains LT-3301 associated with bus 5A and LT-939 associated with bus 2/3A and the Containment Sump contains LT-3300 associated with bus 2/3A and LT-941 associated with bus 5A. The use of the above described backup detectors would leave the remaining credited detectors on different power supplies but they would be in the same sump.
Redundancy requires that they be in different sumps. Therefore, only the redundant sets of level detectors can be used to meet the LCO. This assures that the redundancy requirement of one detector in each sump and redundant power supplies for the detectors is met. That paragraph is revised to say:
This change involves no significant reduction in the margin of safety because the TS requirements are being changed from four to two detectors to reflect the Standard Technical Specifications and two level transmitters (i.e., LT-3300 and LT-3301) will have backup post accident level detectors (i.e., LT-939 and LT-941) that are currently identified as post accident monitors and will continue to be subject to the required surveillance testing to assure operability. If either one or two of the detectors being credited is out of service then the other two detectors could be used to meet the TS PAM LCO. Each set of detectors has different power supplies for the two detectors and each set of detectors meets the redundancy requirements of one in each sump. The discrete detectors do not meet the continuous monitoring requirements.
The Bases is revised in the same respect:
- 5. Containment ,uime-Water Level (Containmentand Recirculation Sump)
RGcFircuatin Sump ContainmentWater Level is a Type A, category I Function that is provided for verification and long term surveillance of RCS integrity.
Reoir.*Uation Sump Containment Water Level is used to determine that water has been delivered to the containment following a LOCA, and subsequently show that sufficient water has been collected by the sump to permit recirculation to the reactor and/or to the spray headers. Rc~irc'ulatin sump Containmentwater level also provides a diverse indication for RWST level regarding when to begin the recirculation procedure.
Attachment 1 NL-1 2-059 Docket Nos. 50-247 Page 8 of 8 This LCO is satisfied by the OPERABILITY of two channels of containment sump water level instruments(Reirculati+n Sump). LT- 3300 and LT-3301, differentialpressure transmitters,located in the Containmentand RecirculationSumps, respectively, are used to meet LCO requirementsfor the two channels. These provide a calibratedsump level span that is continuously indicated. LT-939 (recirculationsump), a magnetic switch/float type detector, and LT-941 (containmentsump, a thermal type detector are additionalqualified detectors and may be is used to meet LCO requirements fe0-eoe-ef-th twe in place of the LT-3300 and LT-3301 channels (i.e., the instrumentbuses for L T-3300 and L T-939 are powered by bus 2A/3A and the instrument buses for LT-3301 and LT-941 are powered by bus 5A). This The LT-939 and LT-941 channels provides a series of five lights each energized from the associated instrument as a preset level is exceeded. LT-3301, a diffe*rntial prossuro transmitter, is used to mooet COQ roquiromonet6 for the second channel.
This channel provides a calibrated sumsp level span that is continuously indicated The TS has boon dteirmnod to bo non...ns..'ativ" and TRM' 3.3.L pr.vides guidance per Administrative Lottor 89 10.
- 2. "Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No. The proposed change will revise the requirements for water level monitors from four to two. The change reduces the number of channels required but retains redundancy and, coupled with the RWST level indication, diversity of indication.
The Technical Specification does not require the instruments for normal plant operations and does not affect how the plant is operated. The removal of the two indicators does not create the possibility of any equipment failure or effect on other equipment. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.
This significant hazards analysis is correct based on the prior discussion.
- 3. Does the proposed change involve a significant reduction in a margin of safety?
Response: No. The proposed change will revise the required number of water level monitors. The revised requirement will remain consistent with the requirements found in the Standard Technical Specification for level monitors provided for monitoring the post-accident water level. The level monitors no longer required by the TS will continue to serve as backup instrumentation feF4he irntruments on the same power supply as long as they continue to meet surveillance requirements. Other instrument channels will remain in service and provide diverse indication for operator response and to support existing accident mitigation strategies. The proposed change does not involve changes to existing setpoints for automatic or operator actions. Therefore, the proposed change does not involve a significant reduction in a margin of safety.
This significant hazards analysis is correct but has been revised (see the lined out words) so that using individual instruments (e.g., LT-939 or LT-941) as alternates would not appear to be allowed.