3F0997-28, Responds to Restart Issue Identified in Integrated Performance Assessment Process Final Assessment Rept 50-302/96-201 Re Boron Precipitation Following Design Basis LOCA
| ML20210T936 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 09/12/1997 |
| From: | Holden J FLORIDA POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20210T939 | List: |
| References | |
| 3F0997-28, 3F997-28, NUDOCS 9709160184 | |
| Download: ML20210T936 (13) | |
Text
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=,% ' September 12, 1997 3F0997-28 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Post LOCA lloron Precipitation Mitigation Plan
Reference:
NRC to FPC letter dated August 23,1996, " Crystal River Unit 3 Integrated Perfonnance Assessment Process (IPAP) Final Assessment Report (NRC Inspection Report No. 50-302/96-201)" [3N0896-12] l
Dear Sir:
This letter responds to the restart issue identified in the referenced IPAP Report regarding baron precipitation following design basis loss of coolant accidents (LOCA). A description of the current methods for addressing post LOCA baron precipitation at Crystal River Unit 3 (CR 3) is provided in Attachment A. Florida Power Corporation (FPC) considers that the current methods, as previously approved by the Nuclear Regulatory Commission (NRC), are adequate for the restart of CR-3. The information included in this letter is provided to support closure of the NRC restart issue. In addition to the current methods of post LOCA boron dikition, FPC is developing an additional active method that will provide defense in depth for post LOCA boron precipitation. This method, which provides hot leg injection via reverse flow through portions of the low pressure injection (LPI) system, will require NRC approval prior to implementation. Reliance on this method of boron dilution is not required prior to restart of CR 3. FPC will submit a request for approval of this method and will implement this method following NRC approval. The following attachments are provided v 9h this submittal to support closure of the IPAP restart gg'. issue regarding boron precipitation following design basis LOCAs. A summary of these gp. attachments follow: WE-S. A11adiment A - Post LOCA Boron Predpitation Mitigation Plan S. E,.2. This attachment describes the methods used for post LOCA boron precipitation control for gs!. CR-3. The licensing basis and boron dilution methods available are discussed in this ~ attachment as wcil as providing an evaluation of these methods. The current methods used for CR-3 have been previously approved by the NRC and are adequate for the restart of CR-3. g 9709160104 970912 $DR ADOCK050003]2 j {(-{ /1 CRYSTAL Rn/ER ENERGY COMPLEX: 157so W. Power Line street + crystal River, Florida 344284708 e (352) 795 4486 ) A Florwa Progress Company
U.S. Nuclear Regulatory Commission 3F0997 28 Page 2 of 2 Also included in this attachment is a description of an additional active boron dilution method (hot leg injection via reverse flow through portions of the LPI system). This additional l method of boron dilution will be fonnally submittea by a separate letter to the NRC for l review and approval. Attachment II FTl Document 51-5000519-00 This attachment provides the Framatome Technologies incorporated (FTI) evaluation of l boron dilution methods at CR-3. This document provides supponing information for Attachment A. Attachment C - Sypnortine Information This attachment provides tables and figures associated with this submittal. Attachment D - List of Commitments This attachment provides the list of commitments made in this submittal. Attachment li-Acronyms and Abbreviations This attachment provides a listing of the acronyms and abbreviations used in this submittal. The current methods of post LOCA boron dilution for CR-3 have been previously approved by the NRC and, as such, FPC is not requesting any additional approval for these methods. The information provided in this letter supports closure of the NRC restan issue from the IPAP report. The use of hot leg injection via reverse flow through ponions of the LPI system as an additional defense in depth method for post LOCA boron dilution will be formally submitted for NRC review and approval by September 30,1997, if you have any questions regarding this submittal, please contact Mr. David Kunsemiller, Manager, Nuclear Licensing at (352) 563-4566. Sincerely, thw J hn J. Ilolden Director Site Nuclear Operations JJil/dah Attachments ec: Regional Administrator, Region 11 NRR Project Manager Senior Resident inspector
L FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3 DOCKET NUMBER 50 302/ LICENSE NUMllER DPR-72 i 3F0997-28 l l l ATTACIIMENT A POST LOCA BORON PRECIPITATION MITIGATION PLAN
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 1 of 10 ATTACHMENT A POST LOCA HORON PRECIPITATION MITIGATION PLAN Introduction 10 CFR 50.46, " Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors," requires that provisions be established to maintain low core temperatures and to remove core decay heat following successful emergency core cooling system (ECCS) actuation to mitigate the consequences of a loss of coolant accident (LOCA). Control of boron concentration in the reactor in post LOCA conditions is required to prevent boron precipitation that could potentially reduce core now and challenge long term core cooling. l - Boric acid, which is added to the reactor coolant system (RCS) to provide core reactivity control during steady state operation and during accident conditions, is dissolved in, and freely circulates with, the RCS liquid. The core Good tank (CFT) and borated water storage tank (BWST) also contain boric acid for additional reactivity control during accidents. During LOCA transients, conditions may arise which result in this boron becoming concentrated in the core region. The potential for boron precipitation in this situation is determined by the break size, break location, core region temperature, hot leg nozzle gap 110w, and the boron solubility limit. LOCA Break Location and Size To evaluate core boron concentration control, LOCAs are divided into hot leg and cold leg breaks. For hot leg breaks, a continuous flow of liquid through the core equivalent to the ECCS injection How rate will be readily established. This flow will be adequate to prevent excessive core boron concentration and no additional actions are necessary to prevent boric acid precipitation. For small cold leg breaks, the RCS will refill and flow through the core will be re-established, thus precluding boron precipitation. Larger cold leg breaks, however, can result in extended time periods without any direct flow through the core. Adequate decay heat removal is provided by pool boiling in the core region. This boiling continuously concentrates the boric acid in the core and upper plenum region. Cold leg breaks must, for the most part, be on the bottom of the cold leg. Cold leg breaks on the top of the cold leg will result in reactor vessel vent valve (RVVV) overnow, which is an effective means of mitigating boron concentration in the vessel. Post LOCA boron precipitation is also only a concern when the RCS remains saturated even at low RCS pressures. This further limits break sizes of concern, since the core region will become subcooled following smaller LOCAs once the ECCS injection flow exceeds the Dow out of the RCS through the break. Boron Solubility The possibility of boron precipitation is exclusively a function of the solubility of boron in the RCS, At high reactor vessel temperatures, the solubility of boric acid is sufficiently high so that
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 2 of 10 boron precipitation cannot occur. Doron solubility decreases as RCS temperature decreases. At saturation temperatures below 305
- F (corresponding to 72 psia), the core boron concentration could approach the solubility limit if given adequate time to concentrate in the core. Tids temperature was conservatively determined assuming that all the bomn initially in the RCS, plus the boron in the CITs and the injected volume of the BWST,is concentrated in the core region.
During the cooldown following a small break LOCA (SDLOCA), if the core remains saturated, with core pressures above 72 psia, boron precipitation cannot occur even if all the available baron is placed within the core mixing volume. Prevention of boron precipitation at lower temperatures with these conservative assumptions must rely upon boron dilution methods. For large break LOCAs (LBLOCA), the RCS depressurizes quickly to the containment pressure, which results in reduced boron solubility limits. For these cases, the time required for the core boron concentration to increase to the solubility limit is in excess of 5 hours. Prevention of boron precipitation beyond 5 homs after a LDLOCA must rely upon an active boron dilution method or in the event of a failure of the active method, the passive method must be relied upon. linkeround During the Integrated Performance Assessment Process (IPAP) inspection (Reference 1), the Nuclear Regulatory Commission (NRC) team identified concerns that the methods described in the Crystal River Unit 3 (CR-3) Final Safety Analysis Report (FSAR) for post LOCA boron dilution were different from those approved by the NRC. Original Licensing Basis The original licensing basis for CR-3, as provided by Babcock and Wilcox (B&W) in BAW-10103 (Reference 2), credited one short tenn passive method and two long term active methods for preventing boron precipitation in the reactor core following a LOCA. The short term method assumeu that froth spill in the outlet plenum would flow through the RVVVs to the reactor vessel downcomer. The two active methods assumed recirculation through the decay heat drop line to the reactor building (RB) sump and injection of water from the pressurizer through the auxiliary pressurizer spray line. A 1991 Framatome Technologies Incorporated (FTI) analysis found that the passive method involving froth spill through the RVVVs was ineffective unless sufncient renooding of the reactor vessel occurred post LOCA. This resulted from a determination that the water level in the reactor vessel following certain LOCAs would not reach the level of the RVVVs as previously predicted. Without the long term RVVV overflow (froth spill), the operator-initiated active dilution paths needed to be established much sooner than the times reported in the original calculations supporting the plant design bases. At the same time, FTl concluded that one of the active methods, auxiliary pressurizer spray, would not be effective at low flews (40 gpm). Due to such relatively low flow rates, the auxiliary pressurizer spray method would be ineffective for more than 46 days after the accident. Auxiliary pressurizer spray provides flow into the core region which must exceed core boil off in order to initiate a reverse flow (i.e., core region to downcomer). After approximately 46 days
U S. Nuclear Regulatory Commission Attachment A 3F0997-28 page 3 of 10 (based on conservative Appendix K decay heat levels), the auxiliary pressurizer spray flow rate would exceed the boil off rate. As core decay heat decreases beyond 46 days, the auxil:ary pressurizer spray flow in excess of boil off would provide boron dilution. Subsequent analysis for the B&W Owners Group (B&WOG) identified a previously uncredited passive method for post LOCA baron dilution. This passive method, involving gaps in the reactor internals, was accepted as a backup to active boron dilution methods in an NRC letter dated March 9,1993 to the B&WOG (Reference 3); however, a plant specific evaluation was never submitted for NRC review regarding the acceptability of the gaps at preventing boron precipitation. Addition:dly, limitations exist for the decay heat drop line method of boron dilution in that the drop line is not single failure proof and may not be opened under conditions in which the RB pressure is less than RCS pressure. In order to ensure the integrity of the RB sump screens, reverse flow to the sump from the drop line must consider effects of water hammer or two-phase flow. Thus the initiation of this method must be limited to conditions where the RCS and RB pressures are approximately equal. DiAll The current FSAR (Revision 23) describes the drop line to the RB sump as an active method and the hot leg nozzle gap flow as a passive (backup) method consistent with NRC approval of the gap flow method. Until the drop line to sump method is achieved, the FSAR recognizes a condition in which certain accidents require very long times for RCS and RB pressure to equalize. Under these very low probability events, boron dilution is accomplished via gap flow within the reactor vessel which is considered the backup (alternate, passive) method. A change to the FSAR to add the auxiliary pressurizer spray method will be initiated prior to plant restart. Description of Heron Dilution Metheds Currently approved post LOCA boron dilution methods available at CR-3 consist of gravity drain through the decay heat drop line to the RB sump, hot leg injection with the auxiliary pressurizer spray system, and hot leg nozzle gap flow. These methods have been previously approved by the NRC. Active methods of boron precipitation control do not need to be initiated until sump concentration has been determined to be inadequate (as a function of RCS temperature). The hot leg nozzle gaps are not relied upon to ensure adequate core cooling; however, if operating acceptably, no active method will be initiated. In addition to these methods, FPC is developing an active method that will provide defense in depth for post LOCA boron precipitation. This method consists of hot leg injection via reverse flow through portions of the low pressure injection (LPI) system. This method will require NRC l approval prior to implementation. Each of these methods is discussed below. See Attachment C for referenced figures. Drop 1 ine to Reactor Building Sump (Figures 2 & 3) In this method, aligning the decay heat drop line to the RB sump will allow gravity feed of RCS from the har leg to the RB sump which would then be recirculated back to the reactor vessel with
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 4 of 10 i the ECCS system. This will pull injection now through the core at a rate equal to the drop line now rate. This method can only be used when RCS and RB pressures are approximately equal to ensure that an excessive differential pressure (dP) does not adversely affect the integrity of the RB sump screens. In order to detennine the time at which the drop line should be aligned to the RB surnp, analyses were performed that did not credit RVVV entrainn.ent or hot leg nozzle gap flow. Based on these conditions, the decay heat drop line should be opened within 5 hours following a LDLOCA initiated from 2772 MWt. Additional time would be available for CR 3 due to the lower rated thermal power. In the case of a LBLOCA, RCS pressure and RB pressure reach equilibrium in a short time period after the initiation of the break. In these cases, use of the drop line method can be accomplished within 5 hours withoutjeopardizmg the integrity of the RB sump screens. For SBLOCAs that do not result in RCS refill, preventing boron precipitation using the drop line method would require alignment of the drop line to the RB sump prior to the RCS pressure decreasing below 72 psia, llowever, this would result in a dP across the RB sump screens that could compromise their integrity, in this situation, reliance must be placed upon other methods of boron dilution to prevent boron precipitation un'il the RCS and RB pressures can be equalized. The ability of the drop line to the RB sump method to function with a pas *ve or active failure was questioned by the NRC in Reference 4. CR 3 provided the response in Reference 5, stating that only active failures are considered in the CR-3 mechanical system design basis. From that perspective, a failure of any one of the five valves in the decay heat drep line now path to open would prevent the establishment of this method to control post LOCa boron precipitation. Following a failure, the reactor vessel internal gap now would be relied upon to prevent boron precipitation until a recovery P n and subsequent opening of the affected valve occueed. S jlot Leg Injection with Auxiliary Pressurizer Sprav (Figure 4) In this n ethod, dilute injection How is added to the reactor with the auxiliary pressurizer spray. This routes dilute injection to the core via the hot leg. The now path is through the auxiliary pressurizer spray line into the pressurizer, out of the pressurizer through the surge line into the hot leg, and then into the reactor vessel. At least 40 gpm is available from this mode of operation. As discussed above, the auxiliary pressurizer spray method would be ineffective for the first 46 days after the accident. After approximately 46 days (based on conservative Appendix K decay heat levels), the auxiliary pressurizer spray flow rate would exceed the boil off rate and the excess now would provide boron dilution. The flow from auxiliary pressurizer spray must pass over the hot leg nozzle gap before it enters the upper plenum and reaches the core. This How could disturb the boron dilution now path that exists from the hot leg nozzle gap method. Therefore, auxiliary pressurizer spray could hinder the effectiveness of the gap flow and would only be used upon indication that the hot leg nozzle gap method (passive) is not effective.
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 5 of 10 if the RB sump concentrations and/or other measurements indicate thct the reactor vessel nozzle gap dilution now is not working and the auxiliary spray now is equal to or greater than the decay heat boil off of all of the auxiliary pressurizer spray, then the auxiliary pressurizer spray method may be effective in controlling the core boron concentration. Although this active method is not currently discussed in the FSAR, the auxiliary pressurizer spray injection method is still available for use. After core decay heat decreases sufficiently, auxiliary pressurizer spray could be used as an active method for boron dilution in the reactor vessel on indication that the core boton dilution methods are not diluting the core borcn concentration. Ilot Leg Nonle Gap Flow (rigures 5 & 6) This is the only passive method identined for boron dilution following LOCAs. This methe:1 utilizes natural circulation via the gaps between the hot leg outlet nozzles and core support shield. The Dow path for the hot leg nozzle gap now is as follows. The steam being produced by the cote Dows through the RVVVs, through the broken cold leg, and out of the break. ECCS Dow replaces the boil off from the vessel with the excess flow above the boll off rate being discharged out the break. The flow of water through the hot leg nozzle gaps recirculates through the downcomer and mixing occurs. The volume of water passed by the gaps is replaced with water of reduced boron concentration resulting in a reduction in core boron concentration. The size of the hot leg nozzle gaps at CR 3 has been verified using as built measurement data which indicate that the gaps at CR 3 are the largest of the D&W plants. These measurements are included in References 5 and 6. Based on NRC concerns regarding post SDLOCA boron dilution, new generic analyses were performed to support the conclusion that hot leg nozzle gap flow will prevent boron precipitation. The analyses were presented to the NRC by the B&WOG in Reference 6 (March 1997). These analyses evaluated variations in the gap size and now, and their effect on boron dilution. The analyses demonstrated that hot leg nozzle gap flow would successfully control the core boron concentration during LOCA transients. These analyses also demonstrated that there is not a signincant safety concern related to post LOCA boron concentration control. The gaps provide a reliable, passive boron dilution mechanism that provides time to establish an active boron dilution method, without compromising the integrity of the RB sump screens. In addition, the analyses demonstrmed that a reduction in smallest as built gap flow area of up to ninety percent during the long term cooling phase does not preclude gap now from providing adequate dilution of the boron concentration in the core. Ilot Leg Iqlection via Reverse Flow through LPI(Figures 4 & 7) FPC is developing an additional active method that will provide defense in depth for the current methods of post LOCA boron dilution. This method, which provides hot leg injection via reverse Dow through a non-operating LPI pump, will require NRC approval prior to implementation. Reliance on this method of boron dilution is not required prior to restart of
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 6 of 10 CR 3. FPC will submit a request for approval of this method and will implement this method following NRC approval, in this method, one operating LPI pump is aligned to provide flow through the CIT nozzle and to the suction of one liigh Pressure injection (llPI) pump which is providing ECCS injection flow. The LPI cross connect line is opened and a portion of the ECCS flow is provided backwards through the idle LPI pump, through the decay heat drop line, and into the hot leg. This alignment reverses the typical flow direction in the decay heat drop line. Since the LPI fluid that is injected into the hot leg has passed through both decay heat coolers, the fluid will be below the upper design temperature of the decay heat drop line. This method of bomn dilution will be available post LOCA and would provide adequate flow to preclude boron concentrations that would lead to boron precipitation. FTl has determined conservative ECCS and hot leg injection flow rates that will ensure adequate core boron dilution and core decay heat ternoval. This evaluation is provided in FTl Document 51 5000519-00 (Attachment B). Flow division of the one operating LPI pump is required to provide for both boron dilution and decay heat removal. Fri recommends that the hot leg injection alignment provides for one llPI pump, with a minimum icverse flow of at least 500 gpm through the decay heat drop line for boron dilutk.a. and approximately 1000 ppm of LPI flow into one CFT nozzle. 1 This method willinvolve an abnormal lineup of the ECCS flow path that has not been previously approved by the NRC for CR 3. This lineup includes securing one train of ECCS (if nmning), providing reverse flow through an idle LPI pump and the decay heat drop line, and providing reverse flow through the reactor core. This method of post LOCA boron precipitation control was discussed in the topical repmt (B AW 10103) which forms the part of the basis for the LOCA analysis methods applied to CR 3. In the NRC evaluation of the topical repon (Reference 7), the NRC acknowledged the conceptutd feasibility of this method of boron dilution, indicating that its application would be reviewed on a case by case basis for individual plants. FPC is currently evaluating this method and plans on providing a submittal containing a description of change in system operation and safety analysis by September 30,1997. At that time, CR-3 will request NRC review and approval of the hot leg injection method for post LOCA boron dilution. SHLOCA Detection of Horon Concentntilen Boron concentration in the RB sump, which will be sampled post LOCA, will be used as an indication of baron concentration in the core region. The post LOCA boron concentration in the RB sump will be tracked as an indication of the effectiveness of boron dilution in the core region. Testing of the sampling method using the post accident sampling system (PASS) has been successfully performed. A flow path from the RB sump to the PASS boronometer and gamma spectroscopy was established to ensure that RB t. ump boron concentration could be determined. As the core boron concentration increases due to boiling of the water recirculated from the RB sump, the boron concentration in the sump will decrease. FTI document 51-50000519-00 (Attachment B) includes an evaluation of the expected change in the RB sump boron concentration as the core approaches the boron solubility limit, where boron precipitation may occur. Several SBLOCA cases were analyzed assuming the limiting 0.05 ft break with different initial BWST, CFT, and RCS boron concentrations. Plots of boron solubility limit versus __a
U. S. Nuclear Regulatory Conunission Attachment A 3F0997 28 Page 7 of 10 temperature, with the core region baron concentration translated into an equivalent BWST/ sump concentration difference,is included in Attachment B as figures 4 and 5. As the BWST/ sump concentration difference increases (indicating a reduction in the boron concentration in the RB sump), the core region boron concentration also increases. For a given BWST/ sump concentration difference, the core temperature must remain below the curve to ensure that boron precipitation does not occur. Conversely, for a given temperature, the difference between the initial BWST boron concentration and the sampled RB sump concentration (which is associated with the core boron concentration) must remain below the curve to preclude boron precipitation without initiating boron dilution. As conditions approach the curve, boror % must be initiated to prevent precipitation in the core. l Evaluation of Llunin Precipitation Control As stated above, the current post LOCA boron dilution methods for CR 3 consist of aligning the decay heat drop line to the RB sump, hot leg injection with auxiliary pressurizer spray, and hot leg nozzle gap flow. Ilot leg nozzle gap flow was analyzed in FTl Document 51-1266113-00 (Reference 6) as adequate to manage post LOCA boron concentration in the reactor vessel and comply with the requirements of 10 CFR 50.46. This method has been previously approved by the NRC in Reference 3. Aligning the drop line to the RB sump and hot leg injection via auxiliary pressurizer spray were previously analyzed by B&W document BAW-10103A (Reference 2) and subsequently approved by the NRC in Reference 8. Additionally, FTl document 515000519-00 (Attachment B) concludes that these methods are adequate for post LOCA baron precipitation control. FPC considers that the methods in place, as previously approved by the NRC, are adequate for the restart of CR-3. The active methods at CR 3 will also be tilized as appropriate for the control of post LOCA boron concentration. A decision matrix wm be used to ensure that proper boron concentration control methods will be utilized in post LOCA situations. The decision matrix is discussed mrther below, in addition to the current methods, FPC plans to request approval of an additional active method of post LOCA boron dilution. This method, which provides hot leg injection via reverse Bow through portions of the LPI system, will be formally submitted to the NRC for review and approval. Additionally, as stated in the response to a Notice of Violation (Reference 9), the B&WOG is moving forward on long term plans for this issue. FPC considers that the currently approved methods for post LOCA boron precipitation control along with the proposed additional active method are adequate to resolve the NRC restart issue with post LOCA boron precipitation for CR-3. Decision Matrix Utilization of post LOCA boron dilution methods at CR-3 will be coordinated in the Technical Support Center (TSC) using a decision matrix (Figure 1). This decision matrix will focus on identifying adverse trends in boron concentration in the reactor vessel that would lead to boron precipitation. Prior to initiating an active method of boron dilution, the TSC personnel will
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 Page 8 of 10 evaluate the available indications and equipment and will make a fact based decision on the best methods to control boron concentration, in initiating the drop line to RB sump method, evaluation of the RB to RCS pressure differential must be performed prior to opening the drop line valves to ensure the integrity of the RB sump screens. Appropriate guidelines will be provided to the TSC personnel to use in determining if this method is appropriate. i CR-3 has produced guidance on the use of the hot leg injection via reverse flow through LPI method. This method will only be implemented at the direction of the TSC. Although not approved for use at this time, this method could ba implemented as an emergency action in post LOCA conditions if other available methods of twron dilution are not adequately controlling boron concentration in the reactor vessel and approval by the emergency assessment team assembled in the TSC is given. Providing this guidance prior to plant restart based on the safety analysis will ensure that all options are readily available post accident. The decision matrix and guidance on the implementation of the hot leg injection via reverse now through LPI method will be proceduralized in Emergency Plan Implementing Procedure EM 225," Duties of the Technical Support Center Accident Assessment Team." The Emergency Operating Procedures (EOP) will provide guidance on the use of the drop line to the RB sump and hot leg injection with auxiliary pressurizer spray methods and require TSC approval prior to implementation of an active boron dilution method. Since a minimum of 5 hours will be available for implementing an active boron dilution method, this guidance will be sufficient to ensure proper control of post LOCA activities. The changes to EM 225 and the EOPs will be completed prior to plant restart. The affected procedures will be appropriately validated to ensure that the actions are reasonable and can be perfonned adequately in the control room and TSC. This will ensure that operator actions required for boron dilution can be performed and can be completed within the required time frame under expected post LOCA conditions. Instrumentalimi The current methods of post LOCA boron dilution at CR-3 will rely upon utilizing the drop line to the RB sump, the auxiliary pressurizer spray, and the hot leg nozzle gap Dow as dictated by the decision matrix. This decision matrix will require the use of instrumentation that was not previously identined as being required for post LOCA boron dilution, instrumentation requirements will include RB sump boron concentration as well as indications needed to compare RCS and RB pressures. The instmmentation required for post LOCA boron precipitation control will be determined and evaluated as necessary against Regulatory Guide 1.97 (Reference 10) requirements for post accident instrumentation. If a change to the instrumentation listed in Technical Specification 3.3.17, " Post Accident Monitoring (PAM) Instrumentation," is identified, a Technical Specification Change Request will be submitted prior to plant restart.
U. S. Nuclear Regulatory Commission Attachment A 3F0997 28 page 9 of 10 License Condition Requiring Installation and Testing of Flow Indicaton FPC has requested a change to the operating license for license condition 2.C.(5) by letter dated June 26,1997 (Reference 1l) and as supplemented on August 4,1997 (Reference 12). The amendment request removes the portion of Operating License Condition 2.C.(5) which requires the installation and testing of flow indicators in the emergency core cooling system to provide l indication of 40 gallons per minute flow for boron dilution. Approval of the amendment would allow removal of flow indicators Dil-45 Fi and Dil 46 Fi as shown on FSAR Figure 9-6 (sheet 3 of 3). This request was based on the boron dilution methods as described in the FSAR and did not consider the use of additional active methods as provided in this submittal (auxiliary pressurizer spray and hot leg injection via reverse flow through LPI). As a result, the basis of the amendment request will require revision to tellect the boron dilution methodologies reflected in this submittal. The conclusion of the proposed change will not be affected (removal of license condition); however, the amendment request will be revised to incorporate additional information. Originally, the flow indications were provided to aid in the decision making process in implementing post LOCA boron dilution methods, in the decision matrix for post LOCA boron precigdtation, flow indications in the drop line and auxiliary pressurize: 6 pray line are not relied upon. The effectiveness of boron dilution methods will be confinned through the sampling of RU sump boron concentrations. If baron dilution cannot be confinned to be sufficient, active methods as described previously will be initiated. Flow through the decay heat drop line or auxiliary pressurizer spray line will be initiated by opening the associated valves in the flow path. For both of these methods, the associated valves will be opened fully. Flow through these lines will be demonstrated by the position indications of the valves in the associated flow paths. These valves and position indications are safety related except for one valve in the auxiliary pressurizer spray flow path (RCV 53). These valves are also powered via class lE, emergency diesel genemtor backed power sources. Adequate boron dilution will be confirmed by RB sump sampling for boron concentration. Neither method requires the use of the flow indicators since actions will continue to be taken, regardless of flow indication as long as RB sump concentration is unacceptable. RCV 53 in the auxiliary pressurizer spray flow path is safety related, but the operator, limit switch, and poson indication are not safety related. The non safety related components are Environmentally Qualified and part of the Maintenance Rule Program. With no flow indication on the auxiliary pressurizer spray flow path, maximum LPI flow will be limited to less than allowable for net positive suction head concerns based upon throttling LPI flow to less than the expected auxiliary pressurizer spray flow rate prior to initiating this method. FPC will provide a revised amendment request for Operating License Condition 2.C.(5) that reflects the post LOCA boron dilution methods discussed in this submittal. The revised amendment request will be submitted by October 3,1997. J
U. S Nuclear Regulatory Conunission Attachment A 3F0997 28 Page 10 of 10 References i 1. NRC to FPC letter, " Crystal River Unit 3 Integrated Performance Assessment Process (IPAP) Final Assessment Report (NRC Inspection Report No. 50-302/96 201)," dated August 23,1996 [3N0896-12] 2. 13AW-10103A, Rev 3. Topical Report, July 1977, "ECCS Analysis of B&W's 177 FA Lowered Loop NSS," Babcock & Wilcox 3. NRC (A. C. Thadani) to B& WOO letter, " Post LOCA Reactor Vessel Recirculation to Avoid Boron Precipitation," dated March 9,1993 [3NO393 18] 4. NRC to FPC letter, " Crystal River Nuclear Generating Plant Unit 3 - Boron Precipitation Following Design Basis Accident - Request for Information Pursuant to 10 CFR 50.54(f)," dated June 26,1996 [3N069617] i 5. FPC to NRC letter, " Response to Boron Precipitation Issue," dated July-26, 1996 [3F079619] 6. B& WOO to NRC letter, '" Post LOCA Boron Concentration Management,' FTl Document No. 51 1266113-00 (Proprietary), March 1997," dated March 27,1997 [O0 1644] 7. NRC to B&W letter, Topical Report Evaluation, dated February 4,1976 8. NRC to B&W letter, " Evaluation of BAW-10103 " dated February 18,1977 9. FPC to NRC letter, "NRC Notice of Violation, Integrated Inspection Report No. 50-302/96-19, NRC to FPC letter,3N059713. dated May 16,1997," dated June 16,1997 [3F069712]
- 10. Regulatory Guide 1.97, Revision 3 " Instrumentation for Light Water-Cooled Nuclear Power Plants to Assess Plant and Environs Conditions During and Following an Accident,"
May 1983
- 11. FPC to NRC letter, " License Condition 2,C. (5) Requiring Installation and Testing of Flow Indicators," dated June 26,1997 [3F0697-08] [ TAC No. 99128]
- 12. FPC to NRC letter, " Drop Line Valve Position ladication," dated August 4,1997 (3F0897 24] [ TAC No. 99128]
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