ML20211J237

Rev 2 to Thermal-Hydraulic Evaluation of DAEC SFP W/Rhr Intertie

ML20211J237
Person / Time
Site:	Duane Arnold
Issue date:	09/18/1997
From:	Gupta V, Rampall I, Rosenbaum E HOLTEC INTERNATIONAL
To:
Shared Package
ML20211J229	List: ML20211J233 ML20211J237 NG-97-1578, Application for Amend 195 to License DPR-49,supplementing thermal-hydraulic Analysis Included as License Rept in
References
HI-971746, HI-971746-R02, HI-971746-R2, NUDOCS 9710080041
Download: ML20211J237 (37)

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Holtec Center,555 Uncoln Drke West, Martton, NJ 08053 l

HOLTEC M@hm @H) 797. M@

Fax (609)797 0909 iNTERHATloNAL Thermal-Hydraulic Evaluation of the DAEC Spent Fuel Pool with RHR Intertie 1

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FOR IES Utilities i

Holtec Report No: Hl.971746 Holtec Project No: 60884 Report Category: A Report Class : SAFETY RELATED W e l,5,17.s q.' h'.

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Fax (609)797 0909 INTERNATIONAL REVIEW AND CERTIFICATION LOG DOCUMENT NAME :

ThermaLHydtmulic Evaluation of the OAEC Spent Fuel Pool mth RHR Inteme HOLTEC DOCUMENT l.D. NUMBER :

971740 HOLTEC PROJECT NUMBER :

60884 CUSTOMER / CLIENT:

IES Uthes REVISION BLOCK REVisl0N AUTHOR &

REVIEWER &

QA & DATE APPROVED & '

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REVISION 3 REVISION 4 REVISION 5 REVISION S This document conforms to the requirements of the design specification and tae applicable sections of the governing codes.

Note : Signatures and printed names required in the review block, A revision of this document will be ordered by the Project Manager and carried out if any of its contents is materially affected during evolution of this project, The determination as to the need for revision will be made by the Project Manager with input from others, as deemed necessary by him, 1

Must be Project Manager or his designee.

x Distribution : C:

Client M:

Designated Manufacturer F:

Florida Office

• " Report category on the cover page indicates the contractual status of this document as "*

A = to be submitted to client for approval I = for client's information N

• not submitted externally THE REVISION CONTROL OF THIS DOCUMENT IS BY A"

SUMMARY

OF REVISIONS LOG" PLACED BEFORE THE TEXT OF THE REPORT

4

SUMMARY

OF REVISIONS REVISION 2: Revision 2 is issued to incorporate several clie nt editorial comments. The following items are affected:

Textual additions and modifications throughou'. the body of the report, e

Additional labels, referenced in expanded resula descriptions, added to Figures I through 3.

All revisions to the text appendices are marked by vertical bars in the margins. Revisio.,2 contains the following sections and pages.

Title Page 1

Review and Certification Log i

Nmmary of Revisions 1

Table ofContents 1

Section 1.0 2

Section 2.0 5

Section 3.0 1

Section 4.0 2

Section 5.0 2

Section 6.0 2

Section 7.0 2

Section 8.0 1

Tables 1

[

Figures 10 Appendix A 5

Appendix B' 23 Appendix C' 3

r Appendix D*

18

• Note:- Appendices B, C and D contain Holtec proprietary material. These appendkes are not provided to the client, but are available for review at Holtec's corporate offices.

i lloltec Report 111971746 11oltec Project 60884

4 TABLE OF CONTENTS SE Iills Page #

1.0 Introduction 1

2.0 Methodology 3

l 3.0 Acceptance Criteria 8

l 4.0 Assumptions 9

l 5,0 Input Data 11 l

6.0 Calculations 13 l

7,0 Results and Conclusions 15 l

8.0 References t?

l Tables Figures Appendix A Appendix B' Appendix C*

Appendix D'

• Note: Appendices B, C and D contain Holtec proprietary material These appendices are not provided to the client, but are available for review at Holtec's corporate offices.

Ilottec Report HI 971740 Holtec Project 60884

e d

1.0 INTRODUCTION

The Duane Arnold Energy Center is a boiling water reactor (BWR) style nuclear electric generating station owned and operated by IES Utilities. The plant has the ability to provide cooling to the spent fbel pool (SFP) by diverting a portion of the flow discharged from the Residual Heat Removal (RHR) system heat exchangers to the SFP. It must be demonstrated that the RHR system is capable of cooling both the reactor vessel cavity and the SFP simultaneously during both planned and unplanned fbil core discharge scenarios.

l The primary purpose of the RHR system is to reject heat from the reactor vessel cavity during a plant shutdown. The RHR heat exchangers are TEMA type CEU shell and tube heat exchangers l

with reactor water on the shell side and river water on the tube side, if the RHR system is to be 1

used to provide cooling to the SFP, the system must be capable of rejecting the decay heat of the core plus the residual decay heat in the previously discharged fbel assemblies in the SFP.

If RHR Supplemental Fuel Pool Cooling is operational, then the water which is discharged from the RHR system to the SFP must be returned to the reactor cavity tu prevent the SFP or skimmer surge tanks from overflowing. Two available options (others may exist) include:

1.

Opening the transfer canal gates and allowing water to flow from the SFP to the flooded reactor cavity.

2.

Operating the FPCCU system with suction from the skimmer surge tanks and discharge to the reactor cavity.

Operating the FPCCU system will result in a larger total cooling capacity for the combined SFP-reactor cavity system, which could only serve to reduce the imik temperatures. Therefore, all analyses presented in this report are assumed to have the transfer canal gates open and the FPCCU system off.

The total decay heat generation rate in the SFP and the reactor will vary based on the fuel power history, actual SFP inventory, etc, The design basis heat rejection capability of the RHR is defined l by the design basis RHR service water temperature and flow rate. Boiling must be prevented from occurring while forced cooling la available. Local water and fuel clad temperatures must be sufficiently low to preclude nucleate boiling on the fuel rod surfaces.

In order to demonstrate the sufficiency of the RHR to remove total SFP/ reactor decay heat load, a series of thermal evaluations are performed.

These evaluations examine the following parameters; 1,

. Maximum Spent Fuel Pool Temperatures 2.

Minimum Time-to Boil After a Loss 6f Forced Cooling 3.

Local Water and Fuel Cladding Temperatures lloltec Report 111971746 lioltec Project 60884

.l-pagei

5 The maximum SFP temperatures are calculated to determine if the bulk SFP temperature will exceed safe temperature limits. The time to boil calculations are performed with the initial temperatures set to the maximum calculated SFP bulk temperatures coincident with a cask pit isolation gate failure. The local water and fuel cladding temperature analyses are perforrned with the net SFP heat generation set at the maximum calculated values.

It should be noted that the analyses presented in this report are performed, in part, to update the licensing basis analyses originally performed for Holtoc Project 20170 and documented in Holtec Report HI 93972, Revision 3 (1). The current analyses will draw on this previously performed l

work for much of the required input data.

l lloltec Repod 111971746 Holtec Project 60884 page 2 l

.___J

2,0 METHODOLOGY j

2.1 Maximum Spent Fuel Pool Temperatures The transient thermal response of the SFP, reactor and RHR system to decay heat load transients is governed by the following equations:

i C, x

• = 0,(r)+ W x Cp x (T, - T,)- G,(Tu,)

t UT C, x j" = Q,(r)- W x Cp x (T, - T.)- Q,(T,)

where:

Caxw = Reactor vessel cavity thermal capacity, Btu /*F Ce = Spent fbel pool thermal capacity, Btu /'F Taxw = Bulk reactor vessel cavity temperature, 'F e

Te a Bulk spent fbel pool temperature, 'F t = Time after reactor shutdown, hr Qaxw(t) = Transient decay heat generation rate in reactor, Btu /hr Qspy(t) = Transient decay heat generation rate in SFP, Blu/hr l

W = RHR Supplemental Fuel Pool Cooling mass flow rate, Ib/hr Cp = Specific heat capacity of water, Btu /(Ibx'F)

Qann(Taxw) = RHR heat exchangers heat rejection rate, Btu /hr Tana = RHR heat exchangers exit temperature, 'F l

Qawv(Tw) = SFP Heat losses to the environment, Blu/hr The total transient decay heat in the SFP (Qw) consists of both an invariant contribution and a time varying contribution. The invariar.t contribution is due to the heat generation from previously discharged fb,,1 assemblies. Due to the nature of exponential decay, the decay heat for "old" fuel assemblies is relatively constant over short periods of time. Fuel transfer from the reactor to the SFP willincrease Qw nd correspondingly decrease Quxw.

a The invariant decay heat generation rates of both the previously and freshly discharged fuel assemblies is. determined using the Holtec QA validated computer program DECOR [2]. This program can perform decay heat calculations using either Branch Technical Position ASB 9 2 [3]

or the ORIGEN2 [4] computer code from the Radiation Shielding Information Center (RSIC) at the Oak Ridge National Laboratory (ORNL), For this analysis, the ORIGEN2 option is used. The fuel discharge schedule for this analysis, provided by lES [5), is included in Table 1; All fuel assemblies are assumed to have been irradiated to the maximum bumup level.

f

-The transient solution of the above differeniial equations, including the transient decay heat contribution and the temperature response,is performed using the Holtec QA validated computer i

Holtec Report Hi 971746 Hollec Project 60884 l

page 3

4 i

program MULPOOLD [6). This evaluation is performed for a number of different discharge scenarios, which are described later in this report, 2.2 Minimum Time-to-Boil After a Loss of Forced Cooling The second of the two differential equations presented in Section 2.1 is used to determine the time-to-boil. The RHR Supplemental Fuel Pool Cooling mass flow rate is set to zero and the l in'tial temperature is set as the maximum calculated bulk SFP temperature.

This reduced differential equation is:

C, x UT = G,(r)- G,(T,)

dr where t is now the time after loss of forced cooling and the ini'lal condition is given as:

O" en. men In addition, this scenario is assumed to occur coincident with a failure of the seals on the gate which separates the SFP from the cask pit. Thus, the value of C, is reduced to consider this considerable loss of water. The boiloff rate once 212*F has been reached can be calculated by dividing the net decay heat by the latent heat of vaporization of water.

This evaluation is performed iteratively, to determine the maximum time available, after loss of cooling, to provide makeup water to prevent the water level from dropping to the active fuel height. This evaluation la performed using the Holtec QA Validated computer program TBOIL

[7), which incorporates the decay heat calculation methodology of USNRC Branch Technical Position ASB 9 2. This evaluation is performed for each discharge scenario as described later in this report. -

2.3 Local Water and Fuel Cladding Temperatures The decay heat generated by the fuel assemblies stored in the SFP induces a buoyancy driven flow field upward through the fuel rack cells Cooler water is supplied to the bottom of the racks cells

- through the rack-to wall gaps and rack to-floor plenum. The presence of strong buoyancy forces results in a coupling of the SFP flow and temperature fields. As with any buoyancy dominated flow field, local effects can effect the global flow field. Quantification of the coupled flow and temperature fields can only be accomplished through the use of a computational fluid dynamics (CFD) analysis.

Other local temperature analysis techniques do exist, and have been used previously for evaluating the DAEC SFP and FPCCU for reracking [1]. The inherent simplifications in these other methods render them extremely overconservative. These oversimplified methods can be replaced by state of the art techniques, which yic!d more realisth.esults while remaining conservative. The CFD analysis methodology is outlined in the following paragraphs.

L Holtec Report HI 971746 Holtec Project 60884 Page 4 l

From a fluid flow modeling standpoint, there are two regions to be cor fdered. One region is the bulk SFP region where the classical Navier Stokes equations are solved with turbulence effects included. The other region is the heat generating fuel assemblies located in the spent fbel racks sitting near the bottom of the SFP. This second region is modeled as a porous solid region in which fluid flow is governed by Darcy's Law:

x V, -C x p x p1 x

=-

where OP/0X is the pressure gradient, K(i), Vi and C are the corresponding pai,d,ility, velocity i

and inenial resistance parameters and p is the fluid viscosity.

The CFD analysis will be performed on an industry standard FLUENT [8] fluid flow and heat transfer modeling program. The FLUENT code enables buoyancy flow and turbulence effects to be included in the CFD analysis. Turbulence effects are modeled by relating time-varying "Reynolds's Stresses" to the mean bulk flow quantities with the following turbulence modeling options:

1.

k c Model 11.

RNO k-c Model iii.

Reynolds Stress Model The k c model is a time-tested, general purpose turbulence model. The RNG and Reynolds Stress models are newer models developed for applications where the k c model gives unacceptable results, such a high speed flows and flows of highly viscous fluids. The k-c modeling option is -

_ used for the DAEC local water temperature analysis.

Rigorous modeling of fluid flow problems requires a solution to the classical Navier-Stokes equations of fluid motion (9). The equations (in modified form for turbulent flows with buoyancy eE:ts included) are provided below:

1 4 u,

@.u,u a ' ' n, h'

w

&.(ulul) v" i

M, M, f M, Mu_

M, M,

~ #*

~

where ui are the three time-averaged velocity components. p (u'i u'3) are time-averaged Reynolds stresses derived from the turbulence induced fluctuating velocity components u'i, P is the static pressure head, p is the fluid density at temperature T., E is the coefficient of thermal expansion, p is the fluid viscosity, gi are the components of gravitational acceleration and x; are the Canesian coordinate directions. The Reynolds stress tensor is expressed in terms of the mean flow quantities by defining a turbulent viscosity, and a turbulent velocity scale k as shown below h

[10):

f"I"]h = JPk0 ~ Ps A, * &,

2 e

g-liohec Report HI 971746 Holtec Project 60884 j

page5

The procedure to obtain the turbulent viscosity and velocity length scales involves a solution of two additional transport equations for kinetic energy (k) and rate of energy dissipation (c). This methodology, known as the k c model for turbulent flows, is described by Launder and Spalding

[11).

Once the spatial temperature distribution in the SFP is obtained, a set of temperature differences can be calculated. These temperature differences are:

Tta = Local water to bulk water temperature difference, 'F Ta. = Fuel clad to local water temperature difference, 'F These temperature differences will be very slightly temperature dependent, due to minor variations in the hydraulic properties of water with temperature. The calculations are performed such that bounding temperature differences are obtained. These bounding temperature differences can then be added to any known or calculated bulk temperature to obtain bounding local water-and fuel cladding temperatures.

The first difference (T a) is obtained ' irectly from the CFD results. In a well-mixed SFP the t

d temperature of the water exiting the SFP to the FPCCU system will be at the bulk temperature.

Therefore, this temperature difference is calculated using the following equation:

Tu = Tounst - Tua c

Tounrr = Temperature at SFP exit, 'F imx = Maximum in-cell temperature, 'F The second difference (Tei.), also called the clad superheat, is calculated from principles of laminar flow heat transfer. The Nusselt number for laminar flow with a constant heat rate can be obtained from various heat transfer handbooks. The following correlation for Nusselt number can then be solved for the convective hest transfer coefficient (h).

x D, Nu =

k where:

2 h = Convective heat transfer coefficient, Btu /(hrxft 7.p)

Dn = Hydraulic diameter of fuel assembly, ft k = Thermal conductivity of water, Btu /( hrxfix'F)

Ons: a heat transfer coefficient is known, the overall heat transfer coefficient (U), which includes the resistance of any crud on the rod surfaces cr be calculated as:

'^

U=l rh + R,,a >

Holtec Report HI-971746 Holtec Project 60884 Page 6 l

A

where Ra is the cmd heat transfer resistance, (hrxAx'F)/ Btu. The clad superheat car, now be

- calculated using the relationship:

T" = b*

U where qm is the maximum heat flux (including peaking), Btu /(hrxR ),

2 f

i 5

i l,-

1 e

I J

1

.~

Holtec Report HI-971746 Holtec Project 60884 l

page 7

3.0 ACCEPTANCE CRITERIA The following acceptance criteria are applied to the analyt.cs performed in this report.

1.

~ The bulk SFP temperature must not exceed the following maxi num temperature limits:

Discharge Type

1. of FPCCU Trains Prior to Temperature Limit RHR Supplemental Fuel Pool Cooling Plarind Full Core 2

180'F Planned Full Core 1

180*F Unplanned Full Core 2

180*F i

The 180 F temperature limit is consistent with the previously performed thermal nydraulic analyses performed to support the DAEC reracking license amendment request (1).

This temperature limit is selected primarily to provide a large margin against bulk SFP boiling.

2 Localized boiling is not permitted for any scenario where forced cooling is available.

l Holtec Report HI-971746 Holte ; Prewet 60884 page 8 l

- 4.0 ASSUMPTIONS Several conservative assumptions are required to perform the analyses documented in this report.

e In addition to those assumptions set forth in the previously performed work [1] the following

[

assumptions are used:

i-The minimum in-core hold time is the time between the loss of criticality in the reactor and the transfer of the first fuel assembly from the reactor into the SFP.

A single RHR system cooling train is in operation throughout the entire transient thermal l-analysis. The RHR Supplemental Fuel Pool Cooling diverts flow from this RHR train

only, Prior to aligning RHR Supplemental Fuel Pool Cooling, the SFP is cooled by either one or two FPCCU trains. Subsequent to aligning RHR Supplemental Fuel Pooi Cooling, the FPCCU ls not operating.

The transfer canal gates are open and water is able to flow through the canal to the I

flooded reactor cavity. This allows the water level in the SFP, the reactor cavity and the skimmer surge tanks to be maintained.

- The RHR Supplemental Fuel Pool Cooling is not performed until the bulk SFP l

temperature approaches 120 F. This allows sufficient time for operator action (RHR Supplemental Fuel Pool Cooling is aligned manually) before the operational temperature-limit of 150'F is exceeded.

_ In the unplanned full core discharge scenario, the recently loaded fresh fuel is assumed to have undergone 18 months of exposure even though it has been in the reactor for only 45 days.- This conservatively maximizes the decay heat generation rate of this fuel.

The thermal capacity of the reactor cavity conservatively neglects the volume of the water in the reactor vessel itself. This conservatively minimizes the reactor cavity thermal capacity, thereby minimizing the time-to-boil and maximizing the bulk temperatures.

The loss of forced cooling of the SFP occurs at the maximum' calculated bulk SFP temperatures and coincident with a cask pit gate seal failure.

This conservatively minimizes the times-to-boil.

i All fuel assemblies in the SFP have the maximum burnup of 41,400 mwd /MTU This conservatively maximizes the decay heat load associated with these assemblies.

Radial and axial peaking factors are included in the local water and fuel cladding temperature analysis. This conservatively increases the decay heat generation rates used to perform these calculations.

Holtec Report HI 971746 Holtec Project 60884 I

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i:

The local water and fuel cladding temperatures analysis uses the geometry of a GE 8x8 fuel assembly... Of all the fuel assembly types stored in the DAEC pool, the GE 8x8 fuel assembly is expected to have the limiting hydraulic resistance. This will conservatively maximize the rack cells hydraulic resistance and resulting local temperatures.

F The local water temperature (CFD) analysis incorporates the effects of blocking the east and west rack tc,-wall' downcomers.

This blocks approximately 2/3 of the total' downcomer area. As the total upcomer flow area through the assemblies in the rack cells is much greater than the total downcomer flow area, blockage of the downcomers is much more severe than an equivalent percentage blockage of cell outlet regions. This results in a local water temperature evaluation that bounds any realistic blockage scenario.

A fuel rod crud layer with a heat transfer resistance of 0.0005 (hrx"F)/ Btu is applied to all rod surfaces in the fuel cladding temperature analysis. This conservatively maximizes the fuel clad surface temperature.

i Holtec Report HI-971746 Holtec Project 60884 page 10 l

5,0 INPUT DATA l 5.1 Maximum SFP Temperatures The input data and corresponding references for the calculations required to determine the maximum bulk SFP temperatures and in-core hold time requirements are:

PARAMETER VALUE SOURCE

__SFP Storage Capacity (# of assemblies) 3152 Reference 1 Fuel Assembly Discharge Schedule see Table 1 Reference 5 Fuel Maximum Average Exposure 41,400 mwd /MTU Reference 5 Coolant Flow Rate per FPCCU Heat Exchanger 397,000 lb/hr Reference 1 Coolant Temperature tc FPCCU Heat Exchangers 95'F Reference 1 Coolant Flow Rate per RHR Heat Exchanger 2,400,000 lb/hr Rcf.rence 12 Coolant Temperature to RHR Heat Exchangers 85'F Reference 12 Number of Assemblies in Reactor Core 368 assemblies Reference 5 Reactor Thermal Power (102% of actual) 1691 MWt Reference 5 Minimum In Core Hold Time 60 hr Reference 13 Fuel Assembly Transfer Rate 6 per hr Reference 1 SFP Thermal Capacity 1,320,000 Btu / F Reference 1 Reactor Cavity Water Volume 157,000 gallons Reference 5 Flow Rate

• rough RHR Supplemental Fuel Pool 1,300 gpm Reference 14 Cooling to brr Flow Rate from Reactor Cavity to RHR.

4,800 gpm Reference 12 SFP Surface Area 800R Reference 1 2

Maximum SFP Building Ambient Temperature 100 'F Reference 1 5.2 -

Minimum Time-to-Boil ARer a Loss of Forced Cooling The input data and corresponding references (in addition to any listed in Section 5.1) for the calculations required to determine the time-to buil without forced cooling are:

PARAMETER VALUE SOURCE Maximum Makeup Water Flow Rate 75 gpm Reference 5 Makeup Water Temperature 90 F Reference 1 Specific Volume of Water at 212 F 0.01672 R /lb Reference 15 3

Holtec Report HI-971746 Holtec Project 60884 l

page11 l

l Specific Heat Capacity of Water at 212'F 1.0 Btu /(lbx'F)

Reference 15 Fuel Storage Rack Height 14.67 R Reference 1 SFP Water Volume aRer Gate Seal Failure.

6,955 n' Reference 1 Top of Active Fuel Elevation 13.52 R Reference 1 5.3 Local Water and Fuel Cladding Temperatures The input data and corresponding references (in addition to any listed in Sections 5.1 and 5.2) for the calculations required to determine the local water and fuel cladding temperatures are:

PARAMETER VALUE SOURCE SFP Water Inlet Temperature 100 'F assumed' Radial Peaking Factor 1.5 Reference 1 Total Peaking Factor 3.0 Reference 1 Fuel Rod Outer Diameter (GE 8x8) 0.484 in References 1, 5 Fuel Rod Inner Diameter (GE 8x8) 0.414 in References 1,5 Rack Cell Inner Dimension 5.90 in Reference 1 Fuel Assembly Active Fuel Length 150 in Reference 5 Number of Fuel Rods per Assembly 62 Reference 5 Rack Cell-to-Cell Pitch 6.06 in Reference 1 Fuel Rack Cell Length 169 in Reference 16 Minimum Bottom Plenum Height 4.5 in Reference 17 Minimum Rack-to-North Wall Gap 3.0 in Reference 18 Minimum Rack-to-South Wall Gap 2.0 in Reference 18 This value is an input to the CFD model, but since the pool local and fuci clad temperatures are actually calculated as temocrature differences, this assumed value does not substantially affect the results of the calculations.

Holtec Report HI-971746 Holtec Project 60884 page 12 l

6.0 CALCULATIONS 6.1-Maximum Spent Fuel Pool Temperatures Three separate discharge and cooling scenarios are evaluated in these calculations. These three scenarios are:

Case A: Planned Full Core Discharge, One FPCCU Train Before Aligning RHR Supplemental Fuel Pool Cooling Case B: Planned Full Core Discharge, Two FPCCU Trains Before Aligning RHR Supplemental Fuel Pool Cooling Case C: Unplanned Core Discharge, Two FPCCU Trains Before Aligning RHR Supplemental Fuel Pool Cooling l-The unplanned full core discharge (Case C) scenario consists of a normal refueling outage with a length of 36 days followed by 45 days of full power operation and a subsequent unplanned transfer of the entire core to the SFP.

The three cases analyzed evaluate the control and removal of decay heat generated by full core discharges. During a core shuffle discharge, the rate of heat transfer to the SFP as well as the total decay heat transferred to the SFP would be less than would be expected for a full core discharge. It is not anticipated, therefore, that initiating the RHR Supplemental Fuel Pool Cooling would be required. However, the RHR Supplemental Fuel Pool Cooling could be initiated ifit was determined that the FPCCU system was not adequately removing decay heat or if the FPCCU system was removed from service (i.e. maintenance). The decay heat removal capacity of RHR Supplemental Fuel Pool Cooling is larger than that of the FPCCU system, an i wou!d therefore be more than adequate the remove the SFP heat generated during a core shuffle.

As stated in the assumptions for the ' analysis (Section 4.0), the FPCCU is used to cool the SFP until the bulk SFP temperature reaches 120*F. Once RHR Supplemental Fuel Pool Cooling is aligned, FPCCU operation is discontinued.

These calculations are performed, using the analysis methodologies described in Section 2.1 of this report, in Appendix B. A listing of the computer files for these calculations is included on page B-2. All input and output files are included on an attached floppy disk, which is labeled

" Computer Data Files for HI-971746, Revision 1 "

l The STER output reports for the FPCCU and RHR heat exchanger models are included on pages B-3 through B-9 and B-10 through B-16, respectively.

The temperature effectiveness calculations for these units are included on pages B-r7 through B-20. The DECOR input files are included on pages B-21 and B-22. The MULPOOLD input files are included on page B-23.

Holtec Report HI-971746 Holtec Project 60884

-l' page 13

6.2 i Minimum' Time to-Boil After a Loss of Forced Cooling The minimum time between the loss of forced cooling and the onset of bulk SFP boiling is calculated for the limiting case of each of the scenarios evaluated in Section 6.1. The initial bulk SFP _ temperature for each time-to-boil scenario is the maximum temperature for each discharge / cooling scenario. Cases A' and-B are practically identical from the time-to boil l standpoint since their maximum bulk SFP temperature diff'er by only 0.0l*F, and a single evaluation is performed for both of these cases These calculations we performed, using the analysis methodology described in Section 2.2 of this report, in Appendix C. A listing of the computer files for these calculations is included on page C-2. The TBOIL input files are included on page C-3. All output files are included on the attached floppy disk, which is labeled " Computer Data Files for HI 971746, Revision 1."

6.3 Local Water and Fuel Cladding Temperatures -

The maximum local water and fuel cladding temperatures are calculated for a limiting (i.e. highest

' decay heat and Sulk temperatures) scenario, evaluated in Section 6.1.

The net decay heat

- generation for this bounding scenario must therefore bound the calculated net SFP heat load coincident with the maximum ienperature for the appropri*.a discharge / cooling scenario.

These calculations are performed, using the analysis methodology described in Section 2.3 of this report, in Appendix D. A listing of the computer files for these calculations is included on page D-2, The effective porous media properties calculation is included on pages D-3 through D-5. A hardcopy listing file for the FLUENT CFD model is included on pages D-6 through D-15. The calculated outlet temperature profile is included on page D-16. The fuel cladding superheat calculation is included on pages D-17 and D-18.

Holtec Report HI-971746 Holtec Project 60884 page 14 l

7,0 -

RESULTS AND CONCLUSIONS 7.1

- Maximum Spent Fuel Pool Temperatures These evaluations were performed as described in Section 6.1. The results of these calculation are summarized in the following table.

Scenario ID -

Maximum Bulk SFP Coincident Net SFP Coincident SFP Temperature @ Time Heat Load Environmental Losses l

Case A 154.31 'F @ 124 hrs 20.87x10' Btohr 9.451x10 Btu /hr 5

Case B 154.30 'F @ 124 hrs 20.87x10' Btu /hr 9.450x10 Btu /hr 5

Case C 159.87 'F @ 124 hrs 22.54x10' Btu /hr 1.116x10' Btu /hr Note that the results of Caw A and Case B are virtually identical. This demonstrates that the effects of a limited amount of FPCCU cooling available before RHR Supplemental Fuel Pool Cooling is rapidly overcome by the large cooling capacity of the RHR system. Figures I through 3 contain temperature versw time profiles for these three cases Figures 4 through 6 contain the corresponding net decay heat and environmental loss versus time profiles.

The temperature at time zero for each of the temperature profiles (Figures I through 3) is an initial guess expected to be at or near the steady-state temperature. The slight rise seen on each figure is the result of the initial guess being somewhat lower than the actual steady-state temperature value. This had no effect on the results of the analyses, as the temperature converges to the steady-state temperature.

The fuel transfer from the reactor to the SFP begins after 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> ofin-core hold time. This point is designated as "A" on each of the three temperature profile figures. The temperature begins to rise rapidly as the fuel transfer starts, due to the large thermal power of the freshly discharged assemblies. As the bulk SFP temperature approaches 120'F (point "B" on the three temperaturt profile figures), the FPCCU system is shut off and RHR Supplemental Fuel Pool Cooling is aligned.

The bulk SFP temperature continues to rise as fuel is transferred from the reactor to the SFP.

The maximum decay heat load in the SFP is obtained at 121.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after shutdown, designated as "C" on each of the three temperature profile figures. The peak bulk SFP temperature oecurs slightly after the peak decay heat load is reached, due to the finite thermal capacity of the water in the SFP. The magnitude of this temperature lag is approximately three hours for all cases.

Examining Figures I through 3, it is observed that the mir.imum time required for the SFP temperature to increase from 140'F to 150*F is appcoximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />. This corresponds to an average temperature rise of approximately 0.77'F per hour. This observation leads to the conclusion that sufficient time exists for supplemental cooling to be provided, if necessary, to meet plant procedurallimits.

l Holtec Report HI-971746 Holtec Project 60884 page 15

7.2 Minimum Time-to-Boil After a Loss of Forced Cooling The minimum time-to-boil following a loss of forced cooling were calculated for the limiting cases for the three scenarios described in Section 6.2. The results of these calculations are summarized in the following table.

l Scenario ID Initial Temp.

Time-to-Boil Max. Boiling Time to Provide Water Loss Makeup Water Cases A & B 154.31 'F 1.15 hrs 48.82 gpm 5.0 hrs Case C 159.87 'F 0.96 hrs 52.78 gpm 4.5 hrs 7.3 Local Water and Fuel Cladding Temperatures The maximum local water and fuel cladding temperatures were calculated for the scenario described in Section 6.2. The results of these calculations are summarized in the following table.

Item ID Parameter Value A

FLUENT SFP Water Outlet Temperature 136.21 'F B

FLUENT Maximum Local Water Temperature 148.08 'F C

Maximum Local Water Temperature Superheat (B-A) 11,87 'F D

Calculated Maximum SFP Bulk Temperature 159.87 F B

Maximum Local Water Temperature (D+C)

!?!.74 'F F

Calculated Fuel Clad Superheat 58.72 *F G

Maalmum Fuel Clad Temperature (F+E) 230,46 'F The top of the fuel storage racks are more than 23 feet below the norma' water level. The local saturation temperature at this depth is approxim::tely 239.29 *F, Thus, a substantial margin against nucleate boiling exists on the fuel rod surfaces and in the fuel rack cells. As stated in Section 4.0, the CFD model used to compute the local water temperature assumes that both the east and west downcomer regions are completely blocked. Because of this extreme water supply pathway blockage, the calculated local water temperature superheat (Item C) bounds that for any realistic cell or plenum blockage scenario.

Figure 7 presents a physical grid plot of the two-dimensional FLUENT model. Figure 8 presents a computational grid plot of the FLUENT model. Figures 9 and 10, respectively, present converged temperature contours and flow vectors from the FLUENT model.

Holtec Report HI-971746 Holtec Project 60884 page 16 l

8.0 REFERENCES

[1]

" Thermal Hydraulic Analysis of Duane Arnold Energy Center Spent Fuel Pool with Maximum Density Storage", Holtec Report HI 93972, Revision 3.

[2]

"QA Documentation for DECOR v1.0", Haltec Report HI 971734, Revision 0.

[3]

USNRC Branch Technical Position ASB 9-2, " Residual Decay Energy for Light Water Reactors for Long Term Cooling", Revision 2, July 1981.

[4]

A.G. Croff, "ORIGEN2 - A Revised and Updated Version of the Oak Ridge Isotope Generation and Depletion Code," ORNL-5621, Oak Ridge National Laboratory,1980.

[5]

Facsimile Transmission from M. Teply (IES) to E. Rosenbaum (Holtec) dated 6/18/1997.

[6]

"QA Documentation for MULPOOLIs v2.0", Holtec Report HI-92834, Revision 2.

[7]

"QA Documentation for TBOIL v1.4", Holtec Report HI-92832, Revision 0.

[8]

"QA Documentation and Validation of the FLUENT Version 4.3 CFD Analysis Program",

Holtec Report HI-961444.

[9]

Batchelor, G.K., "An Introduction to Fluid Dynamics", Cambridge Univ. Press,1967,

[10]

Hinze, J.O., " Turbulence", McGraw Hill Publishing Co., New York, NY,1975.

[11]

Launder, B.E., and Spalding, D.B., " Lectures in Mathematical Models of Turbulence",

Academic Press, London,1972.

[12]

Heat Exchanger Specification Sheet, Perfex Corporation, Revision 2.

[13]

Proposal letter from K.P. Singh (Holtec) to B. Willkomm (IES), Document ID: 608841, dated 4/28/1997.

[14]

Per verbal instruction from M. Teply (IES) to E. Rosenbaum (Holtec) on 7/21/1997.

[15]

Swain and Arrott, " Power Handbook - Basic Power Facts Made Easy", POWER, McGraw-Hill, March 1951.

_[16]

" Rack Construction - Spent Fuel Storage Racks", Holtec Drawing 1045, Revision 3.

[17]

" Support Detail for Spent Fuel Storage Racks", Holtec Drawing 1046, Revision 6.

[18]

"As Built Rack Gaps - Spent Fuel Storage Racks". Holtec Drawing 1429, Revision 0.

Holtec Report HI 971746 Holtec Project 60884 i

l page 17

Table 1 DAEC OPERATING DATA Cycle No.

Discharge Date

1. of Assemblies Total Stored Assemblies 1A-6/1975 4

4 iB 2/1976 84 88 2

3/1977 100 188 3

3/1978 88 276 4

2/1980 88 364 5

3/1981 84 448 6

2/1983 128 576 7

2/1985 120 6%

8 3/1987 128 824 9

9/1988 120 944 10 6/1990 104 1,048 11 2/1992 104 1,152 12 7/1993 128 1,280 13 2/1995 128 1,408 14 9/1996 120 1,528 15 3/1998 128 1,656 16 9/1999 128 1,784 17 3/2001 128 1,912 18 9/2002 128 2,040 19 3/2004 128 2,168 20 9/2005 128 2,296 21 3/2007 128 2,424 22 9/2008 128 2,552 23 3/2010 128 2,680 24 9/2011 128 2,808 25 3/2013 128 2,936 26 9/2014 368 3,304 Holtec Report HI-971746 Holtec Project 60884 page 18 l

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105-0 50 100 150 200 250 300 350 400 450 Twww# After Second Reedor Shutdown (hrs) 11oltec Report HI-971746 Hohec Project 60884

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Hohec Propect 60884 Holtec Report HI-971746

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IIoltec Report HI-971746 Holtec Protect 60884

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FIGURE 6: SFP NET DECAY HEAT LOAD AND HEAT LOSS PROFILES - CASE C 25.t.'+6 c

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Holtec Report HI-971746 hostec Project 60884

.i FIGURE 10: LOCAL TEMPERATURE CFD MODEL - CONVERGED VELOCITY VECTORS 2

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3

APPENDLX A Holtec QA Approved Computer Program Listing Holtec Report HI-971746 Holtec Project 60884 page A-1

6 REVISION 4: JULY 24,19*7 IlOLTEC APPt'OVED COMPUTER PROGRAM LIST CODE Computer PROGRAM VERSION USED Environment ANSYS 5.0, 5.0A, 5.1, 5.2, 5.3 AC-XPERT 1.12 AIRCOOL 5.01 E, 5.01 F, 5.02G, 5.11H, 5.21, 6.1 AIRSYS 1.03 ANYSHEET 1.3 AVESPC 1.0 AXISOL 1.0 BOUND.FOR 1.0 BOXEQ l.0 BULKTEM 2.0, 3.0 CANISTER 1.0 CASMO-3 4.4,4.7 CELLDAN 4.3, 4.4 CHANBP6.TRU l.0 CONPRO 1.0 CORRE.FOR 1.3 CROSSTIE.FOR 1.0 CYPOOL 1.0 DCPP-SFP 1.0

~

DECAY 1.4 DECOR 1.0 1.0 MS-DOS

=

DYNARACK (also known 1.5 thn 1.13 inclusive as DYNAMO XXXX)

Holtec Report HI-971746 Holtec Project 60884 page A-2 I

o!

DYNA 2D Hi 95 DYNAPOST l.0 FIMPACT 1.0 FLANGE 2.0 FLUENT 4.3, 4.32 4.32 Windows NT GENEQ.FOR 1.3 HEATER 1.0 HEXTEM 1.0 HEXTRAN 1.2 HYSYST 1.01 IBP.DAT 1.0 INSYST 2.01 KENO-5A ONCLUDES

'!.3 WORKER AND NITAWL)

LONGOR 1.0 LNSMTH2.FOR 1.0 LS DYNA 3D 936 LUINVS.F 1.0.

MAXDIS16 1.0 MAXDISP.FOR 1.2 MCNP 4A MASSINV.FOR 1.5 MR2,FOR 1.4 THROUGH 1.9 MR216.FOV 1.0, 2.0 MRPLOT.FOR 1.2 MR2 POST PROCESSORS 2.0 MSREFINE.FOR I.3 Holtec Report HI-971746 Holtec Project 60884 page A-3

?

s?

MULPOOLD 1.4, 1.3, 2.0 2.0 MS DOS MULTil.FOR 1.3,1.4,1.5 ONEPOOL 1.4,1.4.1,1.5 ORIGEN 2 (2.1), S PDl6 1.1,1.0 PIPE PLUS 5.04 3H PREDYNAl 1.5,1.4 PREMULT2.FOR I.0 PREMULT8.FOR 1.0 PRESPRG8.FOR 1.0 SACS 1.0, 1.01 SCALE (SAS2H AND 4.3 GRIGEN S MODULES)

SCANS lA SFMR2A.FOR 1.0 SFMR2 1.1 flFATIG 1.0 ST-XPERT 2,01 SPG16 1.0,2.0 STATICD.FOR I.0 STER 3.12B, 3.22 A, 3.22C, 3.24D, 5.04 Windows 3.11 3.3E, 4.12, 5.04 STORM 1.0 TBOIL 1.7,1.6,1.4,1.8 1.6 MS-DOS THERPOOL 1.2, 1.2 A TRIEL 2.0 TUBVIB 2,0 UBAX 1.0 Holtec Report HI-971746 Holtec Project 60884 page A-4

.?

UFLOW.FOR 1,0 VIBIDOF 1.0 VMCHANGE.FOR I.4,1.3 WORKING MODEL

3.0 NOTES

1, XXXX = ALPHANUMERIC COMBINATION GENERAL PURPOSES UTILITY CODES (MATHCAD, EXCEL, ETC.)

2.

MAYBE USED ANYTIME, n

i.

1 1

1 T

E i

4 Holtec Report HI-971746 Holtec Project 60884 page A-5 j