ML050610273
| ML050610273 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/17/2005 |
| From: | Robertshaw A Entergy Nuclear Northeast, Entergy Nuclear Operations |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| BVY 05-017 VY-RPT-05-00003, Rev 0 | |
| Download: ML050610273 (19) | |
Text
BVY 05-017 Docket No. 50-271 Vermont Yankee Nuclear Power Station Proposed Technical Specification Change No. 263 - Supplement No. 23 Extended Power Uprate Response to Request for Additional Information Exhibits
BVY 05-017 Docket No. 50-271 Exhibit I Vermont Yankee Nuclear Power Station Proposed Technical Specification Change No. 263 - Supplement No. 23 Extended Power Uprate Response to Request for Additional Information Suppression Pool Cooling Study l Total number of pages in Exhibit 1 l (excludina this cover sheet) is 17
Engineering Report No.
VY-RPT-05-00003 Page 1
Rev.
0 Of 17 ENTERGY NUCLEAR NORTHEAST Entergy Engineering Report Cover Sheet Engineering Report
Title:
VYNPS Suppression Pool Cooling Study Performed With 2 RHR Pumps Engineering Report Type:
New l
Revision El Cancelled El Superceded Applicable Site(s)
IP2 C
IP3 0D JAF aI PNPS El VY El1 IPI E Quality-Related: Z Yes a No Prepared by:
Verified/
Reviewed by:
- Reviewed by:
Approved by:
Alan L. Robertshaw (X K Q,6V7-Z7 Responsible Eng~ineer (Print Name/Sign)
Pedro B. P6rez H
i Z Design Verifier/Reviewer (Print Name7ign)
N/A Authorized Nuclear In-service Inspector (ANII)
James G. Rogers Su sor (Prin ame/!gn)
Date:
10 February 2005 Date:
10 February 2005 Date:
Date: Z//7/4-Multiple Site Review Site Design Verifier/Reviewer (Print Name/Sign)
Supervisor (Print Name/Sign)
Date
- For ASME Section XI Code Program plans per ENN-DC-120, if required.
ENN-DC-147 Rev. 3.1
- Entergy Engineering Report REPORT No. VY-RPT-05-00003 I
Revision 0 IPageI 2 ]of'j7 RECORD OF REVISIONS Page 2 of 17 Engineering Report No: VY-RPT-05-00003 VYNPS Suppression Pool Cooling Studv Performed With 2 RHR Pumps Revision No.
Description of Change Reason For Change 0
Original report NA
.I
TABLE OF CONTENTS Description Paqe Cover Sheet....................................................
Record of Revisions...................................................
2 Table of Contents....................................................
3 EXECUTIVE
SUMMARY
4 Nomenclature...........................................................................................................................................5 SECTION 1 INTRODUCTION...................................................
6 1.1.
P urpose.........................................................................................................................................
6 1.2.
Background.................................................................................................................................
.6 SECTION 2 EVALUATION...................................................
7 2.1.
Method of Analysis
.7 2.1.1.
General
.7 2.2.
Assumptions................................................................................................................................
7 2.2.1.
EPU Conditions
.7 2.2.2.
RHR Availability for Suppression Pool Cooling
.7 SECTION 3
SUMMARY
OF RESULTS..................................................
10 3.1.
GOTHIC and SHEX Comparison..................................................
10 3.2.
GOTHIC RHR Study Results...................................................
10 SECTION 4 CONCLUSIONS...................................................
13 4.1.
Suppression Pool Temperature...................................................
13 SECTION 5 REFERENCES..................................................
14 LIST OF ATTACHMENTS AT TACHMENT A-RAI Responses................................................
15 Attachment B - CD VY-RPT-05-00003 Contents................................................ 16 Attachment C - Technical Review Comments And Resolution Form................................................ 17
Engineering Report Entergy REPORT No. VY-Rff'05-00003 Revision 0 Page 4
of 17 EXECUTIVE
SUMMARY
The suppression pool cooling study summarized in this report supports the responses to a Nuclear Regulatory Commission Request for Additional Information. The study was originally performed when a question was asked by the State of Vermont regarding the worst single failure assumption in the DBA LOCA suppression pool temperature calculation with respect to containment overpressure. The State of Vermont was interested in the results if the single failure compromised containment overpressure.
Design basis analyses are performed with a single failure assumption. The single failure assumption that compromises containment overpressure is independent of Residual Heat Removal (RHR) system performance. Only one single failure needs to be assumed and in the case of containment overpressure unavailability, the coincident unavailability of an RHR heat exchanger does not have to be assumed.
The suppression pool cooling study was performed to demonstrate the use of two RHR pump trains in suppression pool cooling mode results in a suppression pool temperature that would not require containment overpressure to meet net positive suction head requirements.
Ent-A Entergy Engineering Report REPORT No. VY-RPT-05-00003 Revision 01 Page 5 1BofIl71 I-.
DBA DBD ENO EOP GENE LOCA NPSH NRC RAI RHR RHRSW TS VYNPS WW Nomenclature Design Basis Accident Design Basis Document Entergy Nuclear Operations, Inc.
Emergency Operating Procedure General Electric - Nuclear Energy Loss of Coolant Accident Net Positive Suction Head United States Nuclear Regulatory Commission Request for Additional Information Residual Heat Removal Residual Heat Removal Service Water Technical Specifications Vermont Yankee Nuclear Power Station Wet well (same as Suppression Pool)
I Engineering Report Entergy REPORT No. VY.-.PT-05-00003 Revision 0 l Page 6
of l 17 SECTION 1 INTRODUCTION 1.1.
Purpose The scope of this study is limited to supporting the NRC RAI related to suppression pool cooling with two trains of RHR in suppression pool cooling mode.
Specifically, RAI SPSB-C40 requests the following [Reference 1]:
"The response to SPSB-C-10, dated July 2, 2004, contains a calculation which shows that with two heat exchangers operating but all other conservative assumptions of the licensing basis calculation unchanged, the suppression pool temperature is reduced from 194 F to 169 F. Is the flow through each heat exchanger due to just one residual heat removal (RHR) pump and one service water pump? Under what conditions would the operator actually use both trains of RHR to cool the suppression pool as opposed to using one train to cool the suppression pool and one train to inject water into the reactor vessel? The RAI response states that the calculation was not performed to QA program requirements. The staff requests that this calculation be verified according to the VYNPS Appendix B program."
1.2.
Background
The VYNPS DBA LOCA suppression pool temperature analysis assumes conditions that maximize the energy addition to the suppression pool [Reference 2]. The analysis assumes that all ECCS pumps are available and introduce pump heat to the fluid systems that is ultimately added to the suppression pool.
This assumption is different from the 10CFR50.46 evaluation that assumes a loss of an electrical division.
The worst single failure in the DBA LOCA suppression pool temperature analysis is the unavailability of a RHR heat exchanger. The RHR pump would continue to deliver flow to the suppression pool without the RHRSW system removing energy. This single failure assumption, along with other conservatisms in the analysis results in a suppression pool temperature that requires containment overpressure to meet ECCS pump NPSH requirements.
The State of Vermont in April 2004 informally questioned the worst single failure assumption in the DBA LOCA suppression pool temperature calculation with respect to containment overpressure. The State of Vermont was interested in the results if the single failure compromised containment overpressure. The single failure assumption that compromises containment overpressure is independent of the RHR system performance. Only one single failure needs to be assumed and in the case of containment overpressure unavailability, the coincident unavailability of an RHR heat exchanger does not have to be assumed.
The VYNPS GOTHIC model for the DBA LOCA containment response was modified to perform the suppression pool cooling study for EPU. The study results demonstrate the use of two trains of RHR in suppression pool cooling mode results in a suppression pool temperature that would not require containment overpressure to meet ECCS net positive suction head requirements.
The study was not formally documented at that time, but the suppression pool temperature results were used in an earlier RAI discussion.
E Engineering Report
~Entergy f REPORT No. VY-RPT-05-00003 Revision l Page l
of 17 SECTION 2 EVALUATION 2.1.
Method of Analysis 2.1.1. General The Vermont Yankee GOTHIC DBA LOCA containment model [Reference 3] was used in this study. The model was updated for EPU conditions in order to reproduce the SHEX DBA LOCA EPU results [Reference 4]. The GOTHIC model was then modified to add a second RHR train in suppression pool cooling mode with the same characteristics as the DBA model. The DBA LOCA model with 1 RHR train and the modified model for this study with 2 RHR trains are shown ion Figures 2-1 and 2-2, respectively. The GOTHIC code is designated Level A software and is documented in Reference 7.
2.2.
Assumptions 2.2.1. EPU Conditions The DBA LOCA initial conditions and assumptions that were used in the SHEX analysis were also applied in this study. The only difference is the RHR trains available.
2.2.2. RHR Availability for Suppression Pool Cooling The RHR system is described in the RHR DBD [Reference 6]. The study assumes there are two RHR trains available for maximizing suppression pool cooling as called in EOP-3 [Reference 5] to improve the cooling function (see below).
torus Bemperature cannot be maintained below 90 IF Operate asi available torus cooling using only those RHR pumps not required for adequate core cooling The study assumes that the core spray system is also available to maintain adequate core cooling.
!Enfergy Engineering Report REPORT No. VY-PPT-05-00003 I Revision 0 l Page I 8 1 or j 17 I
I Figure 2-1 GOTHIC DBA LOCA Model LONGTMW - Long Teri Contaimeat Response to LB LOCA E
Break t=
Lp i
(< 80 sea)
Peed Flow P113-() 80 see)
Core Spray (' 80 sac)
& LVCZ XnjtctioA (80-600 Sc(
-s 1
I~I.
I 1
I I
Vessel I
1)1 I
I.
I I.-.
4K
~ -a +]
I>
q t
IBreak(
QO see',
I
_I I
I Vent I
.3--
I ZCCS Suotlon (4 80 sce) ix UR in Torus cooling
(
600 see)
Al Engineering Report Entergy REPORT No. VY-RPT.05-00003 Revision 0 Page 9
of 17 Figure 2-2 GOTHIC Study Model LO1NEPMA Long TenA Contaifrent Rtspoymse to LB LOCA 1
D ryvetl Break M&6E ffJ-U (< 00 sec)
Feed Flw o
(80 se¢)
1 a
I iVessel II 4
L........
3reak (
0 seeic) core 5pray ()
80 see)
I 4 LPWC injection (80-600 seol a
-iI
'I I J 12
-I J I
I vet
.J-Vtte I -
_M in Torus ZCCS suotln cooling
(< 0 stc)
)
600 sec)
SECTION 3
SUMMARY
OF RESULTS 3.1.
GOTHIC and SHEX Comparison The GOTHIC and SHEX models for the comparison case used the same inputs to the extent of the computer code requirements. The GOTHIC and SHEX suppression pool temperature profiles are provided in Figure 3-1.
The times corresponding to peak suppression pool temperature are approximately equal. The peak temperature comparison is presented in Table 3-1. The difference of 2.10F is most likely due to the differences between SHEX and GOTHIC codes. For example, SHEX applies a constant heat exchanger "K" value whereas GOTHIC calculates the time variant heat exchanger performance based on the calculated conditions. The difference in peak temperature is not considered significant and the GOTHIC model is used in this sensitivity.
Table 3-1 GOTHIC and SHEX Comparison Suppression Pool Peak Temperature GOTHIC SHEX 192.60F 194.70F 3.2.
GOTHIC RHR Study Results The GOTHIC RHR sensitivity results are summarized in Figure 3-2 and Table 3-2.
The suppression pool temperature with 2 RHR pump trains is 169.60F and is below the containment overpressure threshold temperature of approximately 1830F.
Table 3-2 GOTHIC RHR Study Results Suppression Pool Peak Temperature 1 RHR 2 RHR 192.60F 169.60F
Figure 3-1 Suppression Pool Temperature Comparison GOTHIC and SHEX Results 24 SP (roTus) TeMyrature TL2 DC15 N
'.4 CY
-CD on Time (Scc) 6TE!
?.6jt2jfA) May17/2I?1$
7a,4S_
Entergy Engineering Report REPORT No. VY-RPTO05-00003 Revision 0 Page 12 j of 17 Figure 3-2 Suppression Pool Temperature Comparison DBA 1 RHR and Study 2 RHR 24 SP (TORUS) Temyerature TL2 DCIS i~d 75 0%
01 D
54 w
CZ
'-4
-0to CD1 Tint (SeC)
GOTM 7.4,2(0A) fW2412S85 14:4C.22
- Entergy Engineering Report REPORT No. VY.RPT05-00003 l sReon Page
-13 ofl 17 SECTION 4 CONCLUSIONS 4.1.
Suppression Pool Temperature The suppression pool temperature following a DBA LOCA, assuming two trains of RHR in suppression pool cooling mode, is approximately 170'F. This temperature is well below the threshold for requiring containment over pressure to meet NPSH requirements.
Entergy Engineering Report REPORT No. VY-RPT-05-00003 Revision 0 Page 14 of 17 SECTION 5 REFERENCES (1)
Letter, R. Ennis, USNRC to M. Kansler, ENO, Inc., "Request for Additional Information -
Extended Power Uprate, Vermont Yankee Nuclear Power Station (TAC No. MC0761),"
dated 31 December 2004.
(2)
GE-NE-0000-0029-7076-RI, "VYNPS LOCA-DBA Long Term NPSH Information Transmittal -
15% per Day Leakage and 100% Containment Spray Thermal Mixing Efficiency," dated July 2004.
(3)
ENVY Calculation VYC-1628, Revision 0, CCN-03, "Torus Temperature and Pressure.
Response to Large Break LOCA and MSLB Accident Scenarios."
(4)
ENVY Technical Evaluation TE-2003-038,"GOTHIC Benchmark of GE LOCA Model for Power Uprate," dated July 2003.
(5)
ENVY Emergency Operating Procedure, EOP-3, Revision 3, "Primary Containment Control."
(6)
VYNPS Design Basis Document for Residual Heat Removal (RHR) System, Revision 2.
(7)
VYC-2208, Revision 0, GOTHIC 7.0 Code Installation, Validation and Verification at Vermont Yankee.
l Engineering Report
= Entergy REPORT No. VY-RPT-05-00003 Revision 0 l Page 1 15 of 17 ATTACHMENT A-RAI Responses Is the flow through each heat exchanger due to just one residual heat removal (RHR) pump and one service water pump?
Yes, the flow through each of the two heat exchangers is from one RHR pump and one RHR service water pump.
Under what conditions would the operator actually use both trains of RHR to cool the suppression pool as opposed to using one train to cool the suppression pool and one train to inject water into the reactor vessel?
The conditions would be best estimate where the ECCS is fully available and core spray adequately maintains the core cooling.
The RAI response states that the calculation was not performed to QA program requirements.
Tihe staff requests that this calculation be verified according to the VYNPS Appendix B program.
The initial calculation was performed to address a question from the State of Vermont. The calculation has been subsequently performed to QA requirements and documented in Engineering Report VY-RPT-05-00003.
Engineering Report Entergy REPORT No. VY-RPT-05-00003 Revision 0 Page l 16 of l 17 Attachment B - CD VY-RPT-05-00003 Contents FHe Edt Vie. Favktes To*
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~Enfergy Engineering Report REPORT No. VY-RPT-05-00003 I Revision 0j Page l 1
o 17 I Attachment C - Technical Review Comments And Resolution Form ENN Site Applicability: El IPi
[ IP2 J IP3 L JAF LI PNPS l VY t' En teg Engineering Report Technical Review Comments and Resolutions Form Engineering Report VY-RPT-Rev. 0 Title VYNPS Suppression Pool Cooling Study Number:
05-0003 Performed With 2 RHR Pumps Quality Related:
3 Yes D No Special Notes or Instructions: None Comment Section/
Review Comment Response/Resolution Responsible Number Page No.
Engineer's Accept Initials I
Various Minor editorial changes.
Completed 6-S 2
References Please add RHR DBD as a Completed 6 44 reference.
3 Section 3.2 Indicate/label data curves Completed 6 4 for graphs.
Reviewed/ Verified By:
Date:
2/60S Pedro B. P6rez Site/Department:
VYNPS/Design Engineering, Phone: 802-451-3118 Fluid Systems ENN-DC-147 Rev. 3.3