ML16258A208

(External_Sender) South Texas Project Generic Safety Issue 191 Resolution RAI 34 Clarification for September 14, 2016 Public Meeting

ML16258A208
Person / Time
Site:	South Texas, Perkins
Issue date:	09/14/2016
From:	Harrison A South Texas
To:	Regner L M Plant Licensing Branch IV
References
MF2400, MF2401
Download: ML16258A208 (7)

Text

1 NRR-PMDAPEm Resource From:Harrison Albon <awharrison@STPEGS.COM>

Sent: Wednesday, September 14, 2016 10:17 AM To: Regner, Lisa; Klos, John

Subject:

[External_Sender] DRAFT Supplemental Re sponse to SSIB Follow up to RAI 34 Attachments:

Supplement F2009 RAI-34 (002).pdf Lisa, John, Here is draft supplemental response to Follow up SSIB 34 for Steve Smith and our public call today.

Wayne Harrison STP Licensing (979)292-6413 Hearing Identifier: NRR_PMDA Email Number: 3061 Mail Envelope Properties (526e43adcf214610b6f14e934678d060)

Subject:

[External_Sender] DRAFT Supplemental Response to SSIB Follow up to RAI 34 Sent Date: 9/14/2016 10:16:57 AM Received Date: 9/14/2016 10:17:03 AM From: Harrison Albon Created By: awharrison@STPEGS.COM Recipients: "Regner, Lisa" <Lisa.Regner@nrc.gov>

Tracking Status: None "Klos, John" <John.Klos@nrc.gov>

Tracking Status: None Post Office: CMBXEXCH03.CORP.STPEGS.NET

Files Size Date & Time MESSAGE 168 9/14/2016 10:17:03 AM Supplement F2009 RAI-34 (002).pdf 360524 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: Recipients Received:

DRAFT Supplemental Response to SSIB Follow up to RAI 34 This supplemental response was written to provide further clarification and analysis to support follow up to RAI-34 response (2016). Follow-up to RAI-34 provided analysis of degasification for bounding temperature conditions from STP

's design basis accident analysis [1]. For all analyzed temperatures above 212 F overpressure was credited to prevent boiling in the pool or a calculated void fraction of less than 2%. This overpressure credit was intended to be applied in accordance with RG 1.82 [2], which states that additional pressure credit should not be taken above what is needed to prevent a failing NPSH value; where boiling conditions and a void fraction >2% were treated as NPSH failure. This previous degasification analysis in the follow-up RAI-34 response, however, did not directly analyze the effect of the calculated void fraction on net positive suction head required (NPSHR) and calculated net positive suction head margin (NPSHM). This supplemental response provides NPSHM, as well as comparison to head loss, analysis to support the follow-up RAI-34 analysis. Additionally this supplement provides results for a best estimate LBLOCA temperature case. Results from the follow-up to RAI-34 analysis are provided below for convenience in Table 1; including an additional Case "1N" representing a best estimate LBLOCA evaluation with cool water conditions. Table 1: Results from 2016 Follow-Up to RAI-34 Analysis Case # Temperature at Sump [°F]

Head Loss (ft)

Accident Analysis Containment Pressure (psia) PContainment Analyzed Pressure (psia)

Pressure value used to yield non-boiling pool conditions / unchallenged conditions Pressure value used to yield passing void fraction (<=0.02) PContainment (psia) Void Fraction PContainment (psia) Void Fraction **1 269.8 0.497 43.3 *41.9 0.000 **2 273.6 0.488 44.9 *44.5 0.000 3 266.9 3.757 45.6 *41.3 0.020 4 213.6 4.946 29.0 *17.5 0.019 5 144.0 7.994 18.3 14.7 0.004 6 144.0 1.071 18.3 14.7 0.000 7 121.0 9.8780 16.9 14.7 0.006 1N 190 5.716 ~16 14.7 0.007 *Smallest pressure above saturation pressure credited to achieve passing degasification scenarios **No debris bed head loss is used for these cases

- only clean strainer head loss is considered. These cases occur less than 5 minutes after the start of recirculation so there will be less than a third of a full sump pool volume turnover. Chemical debris is not expected at this early time post-LOCA. Thus there will not be sufficient debris accumulated on thestrainer to have an impact on head loss at the time of this case. The best estimate case (Case 1N) utilized temperature and pressure from MELCOR-RELAP 5 sump temperature sensitivity analysis [3] modelling a DEGB break on a 27.5" CL. The highest temperature achieved after the initiation of recirculation was found to be 190F, and this single case is evaluated as bounding of the nominal temperature analysis. Results for this case will be provided along with the Follow-up to RAI-34 cases throughout this supplement.

DRAFT Supplemental Response to SSIB Follow up to RAI 34 NPSHM for a given pump can be calculated by taking the difference between the available head of water (NPSHA), adjusted by major and minor flow losses in system piping, and the NPSHR; defined by the pump manufacturer with testing corresponding to the centerline of the pump impeller or calculated with flow rate and geometry at the pump inlet nozzle depending on which case is limiting. The vertical pumps installed at STP, are limited by NPSHM calculated at the pump inlet nozzle in the design basis NPSH calculation [3], however adjustments of NPSHR for air ingestion, following RG 1.82, are made to the impeller centerline test defined NPSHR value. Therefore calculation of adjusted NPSHR, and resultant NPSHM in this supplemental evaluation will be based on the test specified NPSHR value at the pump impeller centerline. The use of NPSHR found from the empirical examination of pump performance at the impeller centerline should not be confused with the calculation vertical datum. Because design basis analysis used a vertical datum at the pump inlet nozzles, all hydraulic head values in this supplemental evaluation will also be referenced from the elevation at the pump inlet nozzle. The equation for NPSHM is provided below for reference. Equation 1 Values of NPSHA and NPSHR from the NPSHm design basis [3] evaluation were used as inputs for this evaluation and are provided below in Table 2 below. Table 2: NPSHR and NPSHA Values from Design Basis Calculation Pump NPSHR Pump Impeller (ft). NPSHA 2015 Calc (ft) T>212 F NPSHA 2015 Calc (ft) T=190 F NPSHA 2015 Calc (ft) T<171 F LHSI 13 7.5 20.1 27.9 HHSI 11 7.4 20.2 28 CS 12 7.2 19.8 27.6 To perform the NPSHM and head loss difference evaluation, first NPSHR from Table 2 was adjusted by the calculated void fraction (Table 1above) from the follow-up to RAI-34 response utilizing the adjustment provided in RG 1.82 Rev. 4 [2] shown in the equation below; where is the void fraction applied as the percentage value and not as a fraction. Equation 2 Adjusted (RG 1.82) NPSHR values utilizing the void fractions calculated in Follow-Up RAI-34 are given in Table 3 below. .

DRAFT Supplemental Response to SSIB Follow up to RAI 34 Table 3: Void Fraction Adjusted NPSH Values Case # Void Fraction LHSI NPSHR Pump CL (ft) HHSI NPSHR Pump CL (ft) CS NPSHR Pump CL (ft) LHSI NPSHRAdj @ Pump CL (ft)

HHSI NPSHRAdj @ Pump CL (ft)

CS NPSHRAdj @ Pump CL(ft) 1 0.000 13 11 12 13.00 11.00 12.00 2 0.000 13 11 12 13.00 11.00 12.00 3 0.020 13 11 12 26.00 22.00 24.00 4 0.019 13 11 12 25.35 21.45 23.40 5 0.004 13 11 12 15.89 13.45 14.67 *6 0.000 13 11 12 13.00 11.00 12.00 7 0.006 13 11 12 16.68 14.11 15.40 1N 0.007 13 11 12 17.55 14.85 16.20

• Case 6 is a half full flow condition however full flow NPHSR values were used in this evaluation.

Next void adjusted NPSHR values, representing adjustment to tested values at the center line of the pump impeller, were related to the datum at the vertical pump inlet datum; which is 15-feet above the centerline of the pump impeller. This relation subtracts 15-feet from the adjusted NPSHR value to account for the 15-feet of water head gained by relating values to the pump inlet datum. Results of this NPSHR relation as well as NPSHM calculated using Equation 1 are provided below in Table 4; noting that NPSHA is related to case temperatures using the rules in Table 2. Table 4: Follow-Up to RAI-34 Void Adjusted NPSHM Case

1. Void Fraction LHSI NPSHRAdj @ Pump Inlet (ft) HHSI NPSHRAdj @ Pump Inlet (ft) CS NPSHRAdj @ Pump Inlet (ft) Void Adjusted NPSHM LHSI (ft)

Void Adjusted NPSHM HHSI (ft)

Void Adjusted NPSHM CS (ft) 1 0.000 -2.00 -4.00 -3.00 9.5 11.4 10.2 2 0.000 -2.00 -4.00 -3.00 9.5 11.4 10.2 3 0.020 11.00 7.00 9.00 -3.5 0.4 -1.8 4 0.019 10.35 6.45 8.40 -2.9 1.0 -1.2 5 0.004 0.60 -1.80 -0.60 27.3 29.8 28.2 6 0.000 -2.00 -4.00 -3.00 29.9 32.0 30.6 7 0.006 1.90 -0.70 0.60 26.0 28.7 27.0 1N 0.007 2.55 -0.15 1.20 17.6 20.4 18.6 Utilizing the void adjusted NPSHM (Table 4) values the difference between adjusted NPSHM and head loss (Table 1) is now evaluated.

DRAFT Supplemental Response to SSIB Follow up to RAI 34 Table 5: Head Loss Differences for Follow-up tor RAI-34 Cases Case # Temp (F) Head Loss (ft)

Void Adjusted NPSHM LHSI (ft)

Void Adjusted NPSHM HHSI (ft)

Void Adjusted NPSHM CS (ft) LHSI Difference [NPSHM-HL] (ft) HHSI Difference [NPSHM-HL] (ft) CS Difference [NPSHM-HL] (ft) 1 269.8 0.497 9.5 11.4 10.2 9.0 10.9 9.7 2 273.6 0.488 9.5 11.4 10.2 9.0 10.9 9.7 3 266.9 3.757 -3.5 0.4 -1.8 -7.3 -3.4 -5.6 4 213.6 4.946 -2.9 1.0 -1.2 -7.8 -4.0 -6.1 5 144 7.994 27.3 29.8 28.2 19.3 21.8 20.2 6 144 1.071 29.9 32.0 30.6 28.8 30.9 29.5 7 121 9.878 26.0 28.7 27.0 16.1 18.8 17.1 1N 190 5.716 17.6 18.6 13.9 11.8 14.6 12.9 Of the head loss difference [NPSHM-HL] values calculated above further analysis is only needed for cases 3 and 4 (highlighted yellow) which yielded negative head loss differences when considering the void fractions calculated in follow-up RAI-34. For these cases (3 and 4) the void fraction was decreased in (0.001) increments, while updating NPSHR adjustments as performed in Table 3 and Table 4, until positive head loss difference was realized. This iteration yielded void fraction 0.008 and 0.006 for Case3 and 4 respectively, which were the first void fraction values found by decreasing in 0.001 increments to yield a positive head loss difference value. Results of this iteration are shown in Table 6 which follow the same calculation methodology used for Table 3 through Table 5. Table 6: Results of Incremental Void Fraction Iteration for Positive HLoss Difference Case # Temp (F) Head Loss (ft) Analyzed Pressure (psia) Void Fraction LHSI Difference [NPSHM-HL] (ft) HHSI Difference [NPSHM-HL] (ft) CS Difference [NPSHM-HL] (ft) 3 266.9 3.757 *?? 0.0080 0.5 3.2 1.6 4 213.6 4.946 *?? 0.0060 0.7 3.2 1.7 * ?? denotes that this iteration was performed to find a void fraction that would yield a positive head loss difference. Analyzed pressure is found the next step. In Table 6 the calculated head loss differences including NPSHR adjustment are shown in Columns 6 through 8, increasing the void fraction in Column 5 by 0.001 and redoing calculations would yield a negative number for the head loss difference; ie this is the first positive head loss difference value found with the void fraction incremental iteration. To complete the evaluation the void fraction values for Case 3 and 4 in Table 6 were used as targets, and the CASA Grande degasification model was run by incrementally increasing containment pressure by 0.1 psia until void fraction values equal to or smaller than the respective fractions in Table 6 were found; doing this finds the lowest containment pressure needed to guarantee positive head loss DRAFT Supplemental Response to SSIB Follow up to RAI 34 difference utilizing RG 1.82 adjustments for voiding. Note that all degasification inputs except for the containment pressure and the void fraction found in Table 6 were held constant to their assignments defined in the follow-up to RAI-34 response. Results of this incremental pressure iteration analysis are provided below in Table 7. Table 7: Results for Lowest Containment Pressure to Satisfy Positive HLoss Difference Case # Temp (F) Head Loss (ft) Analyzed Pressure (psia)

Void Fraction LHSI Difference [NPSHM-HL] (ft) HHSI Difference [NPSHM-HL] (ft) CS Difference [NPSHM-HL] (ft) 3 266.9 3.757 42.4 0.0077 0.7 3.4 1.8 4 213.6 4.946 19.8 0.0059 0.7 3.2 1.7 The results of Table 7 were substituted for the original Follow-up to RAI-34 results in Table 5 to form the updated final results (Table 8). Table 8: Updated Final Results - Degasification Implications on Head Loss Difference The results in Table 8 show that positive head loss difference has been achieved for all cases while analyzed pressure remained below DBA accident analysis pressures. In accordance with RG 1.82 only over pressure needed in excess of vapor pressure was credited, and the difference between DBA calculated pressure and analyzed pressure has been tabulated. Case #Temp (F)Head Loss (ft)Design Basis Calc Pressure (psia)Analyzed Pressure (psia)Pressure Difference [DBA-Analyzed] (psia)Void FractionLHSI Difference [NPSHM-HL] (ft)HHSI Difference [NPSHM-HL] (ft)CS Difference [NPSHM-HL] (ft)1269.80.49743.341.91.40.00009.010.99.7 2273.60.48844.944.50.40.00009.010.99.7 3266.93.75745.6242.43.220.00770.73.41.8 4213.64.9462919.89.20.00590.73.21.7 51447.99418.314.73.60.004019.321.820.2 61441.07118.314.73.60.000028.830.929.5 71219.87816.914.72.20.006016.118.817.1 1N1905.716~1614.71.30.00711.814.612.9