ML091190256

Summary of Category 1 Meeting with the Donald C. Cook Nuclear Plant to Discuss Draft Requests for Additional Information Associated with GL 2004-02

ML091190256
Person / Time
Site:	Cook
Issue date:	05/13/2009
From:	Beltz T Plant Licensing Branch III
To:	Office of Nuclear Reactor Regulation
beltz T, NRR/DORL/LPL3-1, 301-415-3049
References
GL-04-002, TAC MC4679, TAC MC4680
Download: ML091190256 (62)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 May 13, 2009 LICENSEE:

INDIANA MICHIGAN POWER COMPANY FACILITY:

DONALD C. COOK NUCLEAR PLANT (CNP)

SUMMARY

OF APRIL 16, 2009, CATEGORY 1 PUBLIC MEETING WITH INDIANA MICHIGAN POWER COMPANY TO DISCUSS DRAFT REQUESTS FOR ADDITIONAL INFORMATION (RAls) ASSOCIATED WITH THE SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 (TAC NOS. MC4679 AND MC4680)

On April 16, 2009, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of Indiana Michigan Power Company (the licensee) at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was to discuss the NRC-issued draft RAls associated with the licensee's supplemental response to Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized Water Reactors," and for the licensee to present to the staff information to support its proposed RAI response.

The licensee's presentation included three handouts, which are provided in Enclosure 2. The handouts included simplified plant drawings to assist in discussing the design features of the Cook Nuclear Plant (CNP) recirculation sump and containment; a draft "Margins and Conservatisms Evaluation;" and preliminary responses to the NRC staff's draft RAls.

The public meeting provided an open forum to discuss the CNP sump design, conservatisms in the licensee's evaluations, and the draft RAls. The discussion allowed the NRC staff to identify to the licensee, at an early stage, any significant misinterpretation or deficiency in its proposed RAI response. The staff noted that certain aspects of the licensee's presentation provided a clearer understanding of the characteristics associated with the CNP recirculation sump and containment, and supported the reasoning behind some of the proposed RAI responses. The staff concluded that some of the original draft RAls would likely be reworded to provide enhancement or clarification, and that another set of draft RAls would be submitted to the licensee in the immediate future.

- 2 A list of attendees is provided in Enclosure 1. Members of the public were in attendance, including industry and vendor representatives. Public Meeting Feedback forms were available, but comments were not received.

Please direct any inquiries to me at 301-415-3049, or Terry.Beltz@nrc.gov.

~

Terry A. Beltz, Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-315 and 50-316

Enclosures:

1. List of Attendees

2. Licensee Handouts cc w/encls: Distribution via Listserv

LIST OF ATTENDEES APRIL 16, 2009, MEETING WITH INDIANA MICHIGAN POWER COMPANY (I&M)

TO DISCUSS DRAFT REQUESTS FOR ADDITIONAL INFORMATION ASSOCIATED WITH SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Members of the Public Sher Bahadur Paul Leonard John Butler (Nuclear Energy Institute)

Donnie Harrison Paul Schoepf Mark Manoleras (First Energy)

Stewart Bailey Mike Testa (First Energy)

John Lehning Dave Midlik (Southern Nuclear)

Paul Klein Wendy Croft (Exelon Nuclear - TMI)

Joanne Savoy Ed Carmack (Southern Nuclear - Farley)

• Matt Yoder Timothy S. Andreychek (Westinghouse)

• Ervin Geiger John Marushak (Westinghouse)

• Ralph Architzel Tim Croyle (Westinghouse)

• Bruce Lin Chuck Feist (Comanche Peak)

• Steve Smith William Knous (Alion Science & Technology)

• Terry Beltz Gilbert Zigler (Alion Science & Technology)

• Steven Unikewicz (Alion Science & Technology)

• Timothy D. Sande (Alion Science & Technology)

• Ken Petersen * (STARS / Wolf Creek)

Mark Harriman (Ginna)

• Ron Holloway (Wolf Creek)

• Kip Walker (Enercon Services)

• Iver Jacobson (Entergy - Arkansas Nuclear One)

• Dan Brosnan (PG&E - Diablo Canyon) *

• Participated via Telecon

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Vectors Showing Pool Flow Direction Wlodty (ftM 0.250 0.188 0,'25 0,053 0.000 2007-11-21 DC Cook Task 1 Loop 4 go'll. SlockEld uniCVElelors_annulus_aCfioor.bmp

DRAFT Margins and Conservatisms Evaluation 1

Introduction The purpose of this evaluation is to demonstrate how the Cook Nuclear Plant ECCS is conseNatively designed and operated with respect to the requirements of 10 CFR 50.46 following completion of the corrective actions associated with the resolution of GL 2004-02 (GSI-191).

rovided to offset the aken by the licensee.

. wed by the NRC forward to the 2

Design Basis Event Scenarios 2.1 tie CNP ice condenser containment consists of four uniquely defined and seRarated vo u es: 1) upper containment, 2) ice condenser, 3) lower containment, and reaCto. cavity. Refer to the February 29, 2008 Supplemental Response, Attachm nt~, Figures A4-2 through A4-10 for illustrations of various views of lower containment and a plan view of upper containment.

The upper containment area (Figure A4-2), which does not contain any high energy piping, is physically separated from the lower compartment by the divider barrier and the ice cqndenser.

The ice condenser forms an approximate 300 0 arc around containment between the containment wall and the crane wall. The ice condenser has 24 paired doors in the lower containment area that will open following a pipe break allowing for

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suppression of the initial pressure surge in containment. There are also doors just above the ice bed and at the top of the ice condenser section to allow steam and non-condensable gases to vent to the upper containment volume.

The lower containment volume contains both the loop compartment inside the crane wall and the annulus area between the crane wall and the containment wall.

The crane wall that separates these two regions is three feet thick. There are ventilation openings in the crane wall which are above the maximum flood elevation of containment. These ventilation openings provide for the supply of cooled air to the loop compartment from the contain ent lower ventilation units, and also provide a relief path for the mass and en~,

release from a HELB for short term containment subcompartment pressuri ti n considerations. Within the loop compartment above nominal elevatio

. 8 are the SG and PZR enclosures. These enclosures utilize the crane all a.0 e part of the enclosure with cylindrical concrete walls forming the' s of the en as res. Each of these enclosures has a concrete roof, the to ot which is at no inal elevation 695 ft.

The cylindrical wall sections and th

,0.0' comprise a portion I be divider barrier separating the lower containmeo rom the u per containm to The loop compartment is surrounded on i s outside pe eter by the cr wall.

The primary shield wall and refueling cavit

~alls.

on the inside perimeter of the loop compartment. The nominal distanc ft. fie primary shield wall to the crane wall varies from 22 to

'ft.

The nomina i tance from the crane wall to the containment wall is 13 ft.

All pos U,latea pipe break LOCAs for which sump recirculation would be required would ta ~~ place within the loop compartment, which is the area inside the crane wall, or in the reactor cavity.

For an LBLOCA, once water level in the loop compartment exceeds approximately 4 in. during the injection phase, debris laden water would begin to flow through the main strainer into the recirculation sump.

When the level in the recirculation sump reaches slightly above floor level (598 ft 9318 in. elevation), strained water from the recirculation sump would begin to flow through the waterway toward the remote strainer. Initially, this would only fill the waterway until the water level reaches approximately 8 1/2 in. above the floor, the height of the lowest set of strainer elements in the remote strainer. When the loop compartment water level exceeds this height, strained water would begin

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back-flowing out of the remote strainer. A significant quantity of debris laden fllJid would be transported to the main strainer, partially loading it with debris. During this pool fill (injection) phase, the calculated maximum reverse flow rate is approximately 6400 gpm.

Debris laden water would also flow from inside the loop compartment to the debris interceptor installed to protect the 10 in. diameter flow holes through the overflow wall. This flow into the area between the overflow wall and the curb at the annulus side of the crane wall opening would continue until the level reached approximately 12 in. above the floor. This is the heig of the curb on the annulus side of the overflow wall area. By the time this leve s. reached, water flow out of the remote strainer would have been established.

With recirculation flow established, the reverse flow through the remote strainer will cease. Water will then flow into the sump through both the main strainer and through the remote strainer and waterway.

Since a pipe break requiring recirculation would not occur in the annulus, the debris that would be available to the remote strainer would be the debris that was transported from the loop compartment to the annulus region from the initial blowdown, the debris that was transported to the annulus region through the overflow wall flow holes during pool fill, and latent debris resident in the annulus prior to the event. As a result, the

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remote strainer would be essentially debris free at the beginning of recirculation.

Due to the waterway head loss, the preferential flow path would be through the main strainer until the main strainer became substantially blocked by debris. The division of flow between the main and remote strainers would therefore be a function of the head loss through the associated strainer and the waterway.

For the DEGB, water level in lower containment would decrease from the level that existed at the beginning of recirculation flow (7.7 ft) until the minimum water level of 5.9 ft above the floor (604 ft 7 in.) is reached. For the DGBS, a minimum water level of approximately 5.6 ft above the floor (604. 6 in.) is reached. These decreases in water level are the result of a conserva h7 Iy assumed minimum ice melt and the flow into the lower reactor ca' via the ex-core nuclear instrumentation position device sleeves in the en a, shield wall. For the 2 in.

line break, a minimum water level of approxi ately 5.1' fabove the floor (603 ft 11 in.) is reached.

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DRAFT Figure 1 General Arrangement of Recirculation Sump

'1IlIO Vent

.'111 IIlIO Elev. 814 fl *29/16 in.

Contelment wall Elev. 60311.

• 11 318 in.

• JlNJ I" 'I Level Switch Sel Poin~

Elev.601 fl.* 9 fn. }Main Strainer:

Containment Floor 000 sq. ft Elevation 598 It *9318 in~

4 in. Curb JI From Lower

~;;~

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3 Debris Generation I Zone of Influence 3.1 Methodology

a.

The insulation debris sources were determined through extensive walkdowns to be different between CNP Unit 1 and Unit 2. The insulation debris sources for Unit 2 were determined to be bounding for both units and were used as the input for analysis and testing. The total quantity of Cal-Sil insulation in Unit 2 that could be subjected to a LOCA jet is about 60% greater than that in Unit 1.

3.2 Key Conservatisms I Margins

b.

c.

d.

e.

For tn s all amQunt of Min-K installed at CNP, no credit was taken for the stainless teel flash'n installed around the Min-K.

In summary, the debris generation analysis conservatively maximized the quantity of debris tha could be generated following a LOCA.

This resulted in conservatively increasing tfle strainet ~head loss and increasing the potential for wear and blockage of downstream' ents.

ompo Latent Debris 4.1 Methodology

a.

The quantity of latent debris to be considered for contributing to strainer head loss was conservatively established at 200 Ibs in containment, with 15%

assumed to be fibrous.

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b.

The contribution of latent debris on vertical surfaces was conservatively assumed to be 30 Ibs.

c.

104 latent debris samples were taken in Unit 1 during separate outages and 80 samples were taken in Unit 2 during separate outages. The samples were all taken in areas that are not routinely cleaned as part of containment closeout activities or had some accumulation of oily residue (below RCPs, on polar crane rails).

4.2 Key Conservatisms I Margins

a.

The calculated quantity of latent debris was Unit 1 and 117.26 Ibs for Unit 2. This repres'~e'~~'argin of 38.28 Ibs for Unit 1 and 82.74 Ibs for Unit 2.

The assum

'uan*,'* f 200 Ibs represents a 23.7% increase for Unit 1 and a 70.6o/! "hcrease for n

b.

c.

5 5.1

a.

h mo tl~>b"rs transport methodology utilized as-built containment information to e. ow paths and significant obstructions to flow within lower containment.

b.

The debris transport methodology modeled the main and remote strainers and determined the flow split between the two strainers as a function of head loss through the system. The methodology also modeled the flow path through the flood-up overflow wall holes and the surrounding structural features.

c.

Additional information regarding the debris transport methodology is contained within the February 29, 2008 and August 29, 2008 Supplemental Responses to GL 2004-02.

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5.2 Key Conservatisms I Margins

a.

Debris in the sump pool would not transport to the reactor cavity, an inactive volume, while it was filling through the nuclear instrumentation detector positioning device penetrations.

b.

The debris transport methodology established transport fractions that resulted in greater than 100% of the debris source available for transport to the uipment or structural elements, condenser, as a result of the

c.

d.

strainers. These were the values that were used fa ainer head loss testing.

The materials and quantities are provided below.

e.

Debris Source

g.

The debris transport analysis conservatively did not consider the debris interceptor installed at the flood-up overflow wall flow openings as a debris limiting device for those fines and other debris sources that would be capable of being transported to the remote strainer. In other words, no credit was taken for the filtering capability of the debris interceptor (01) and the RMI bed that would exist at the DI.

h.

The debris transport analysis conservatively modeled the vertical face of the 01 as being fully blocked during recirculation transport. The effect of this was to

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maximize the velocity of the pool water passing through the design 6 inch opening at the top of the DI increasing the transportability of the debris sources in the pool.

i.

The debris transport analysis conservatively maximized the effects of water sources entering the containment pool to increase the turbulence of the pool which led to greater transport fractions for the debris sources.

j.

The debris transport analysis conservatively neglected the capture of fibrous and particulate debris by the significant quantity of Q onents that exist in the annulus including the debris. gates that exist 0 ei ner side of the approach 6

area to the remote strainer.

k.

he potential for settling rain Tank pit.

The second was to perform more extensive walkdowns of containment to catalog the unqualified coatings that exist in containment. This effort completed following the strainer testing that was performed.

b.

For qualified coatings that would be subjected to a LOCA jet, an extensive CAD model of containment was developed that included the structural elements that exist. The debris generation analysis overlaid the ZOI sphere

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onto the model which then calculated the affected areas of concrete and steel surfaces.

c.

All OEM unqualified coatings outside of the coatings lOI were assumed to fail initially as paint chips with a thickness equivalent to the original coating thickness. The EPRI report for OEM coating failures documented autoclave DBA tests of non-irradiated and irradiated unqualified OEM coatings that demonstrated that the majority of the failures were as chips.

The debris generation analysis assumed that OEM coatings failed as 83 micron particles.

6.2 Key Conservatisms I Margins

a.

b.

c.

d.

The non-OEM unqualified coatings outside the lOI have the same failure rate as the OEM coatings outside the lOI (100%). Since the non-OEM unqualified coatings are not applied to a correctly prepared substrate, it is expected that these coatings would fail as chips of various sizes. Therefore, the non-OEM unqualified epoxy and alkyd coatings outside the lOI were assumed to fail with chip sizes of 10% (250 - 500 microns), 80% (500 - 1000 microns), and 10%

(1000 - 4000 microns). Autoclave testing (Keeler & Long Report 06-0413, DBA Testing of Coatings Samples for Comanche Peak) indicates that paint

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chips would be generated in sizes larger than 4000 microns which shows that the distribution used in this calculation is conservative.

e.

The cold galvanizing coating used at CNP is an organic zinc material. For determination of debris transport and ultimately strainer head loss testing, the cold galvanizing compound was conservatively assumed to fail as 10 micron particles.

f.

The conservatively calculated unqualified coatings quantities within containment are as follows:

g.

Based on detailed w

h.

e cold galvanizing compound. This testing In su l:Qa, the cpJ'}servatively determined quantities of unqualified coatings that were assumed* 0 fail nd* e available for transport at time zero of recirculation is significantly greater than t e guantities that exist. This represents a significant conservatism in that the increase q antity of particulate increases strainer head loss and increases the potential for wear and blockage of downstream components. Additional conservatism exists through the use of a ZOI of 5D for qualified coatings in lieu of the 4D recommended by the test report, and the assumption that unqualified coatings will principally fail as small particulate.

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7 Head Loss and Vortexing 7.1 Methodology

a.

Head loss testing was performed by the strainer vendor, CCI, at their facilities in Winterthur, Switzerland. All testing was witnessed by a CNP representative.

b.

Due to the unique installed strainer configuration for CNP, the debris only strainer head loss testing was performed using a dual sided strainer assembly with the test pool configured to provide equivalent dace areas for the main and remote strainer and locations to introduce t e propriate debris quantities to each strainer section.

c.

CNP performed multiple tests to determin debris only head loss for both the DEGB and DGBS, inclu i durations to ensure head loss had reached a stable valU!

d.

Since the strainer head los aterway that connects the remote strainer to ump, addition nalysis was performed to establish an overa 1 loss for the installed strainer configuration.

e. Testing was perform near field settling of de

f.

g.

d to ensure that air would not be drawn into One of the significant margins established during strainer head loss testing as the inclusion of a 50% increase in strainer system head loss to address uncertainties that could exist as a result of debris distribution, test mettlo 01 y, or other factors.

b.

Margin is also available in the strainer system head loss values as a result of normalizing the results to 68°F (20°C). The margin exists in that at the initiation of recirculation, the containment pool water temperature is at a maximum of 190°F with temperature ultimately decreasing to approximately 100°F. With containment pool temperature at 100°F, the strainer system head loss would be about 30% less than it would be at the normalized value of 68°F.

c.

Significant margin is also available as a result of the conservative total debris quantities that were used for testing as compared to the quantities that would

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Debris Type be available for transport to the strainers. Considering the margins discussed in Sections 3, 4, 5, and 6 of this evaluation, the expected head loss through the strainer system would be significantly reduced due to the reduction in fibrous and particulate debris that would be at the strainers. The table below provides a comparison of the as-tested values (conservative) and the as-expected (realistic) values for debris quantities.

Debris Quantities Mar in Determination Table Actual DEGB Quantity Units Test Available Margin Quantity at Both Strainers 307.665 Ibs 298.82 Ibs 0.188 0.1894 Ibs 1.5228 1.534 Ibs 1.52 Ibs 203.585 Ibs 0.57 Ibs 19.712 Ibs 78.4:16 8.'

Ibs 0.00022 0.002 7.41582 0.00022 0.0021 0.002 13.2116 7.40382 As oan De seen from the information in the preceding table, there is significant margi between the debris quantities that were used for strainer head loss testing and the actual quantity of debris in containment that would be expected to be available to the strainers during an actual LOCA event. This margin could be further increased by considering the relative absence of fibers within the latent debris inside containment, as discussed in Section 4 of this evaluation.

d.

As discussed in Section 8 of this evaluation, the flow rate assumed for testing was approximately 1000 gpm greater than the conservatively determined maximum flow rates for both trains of ECCS and CTS taking suction from the

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recirculation sump. This 7% reduction in flow represents an approximate 20%

reduction in head loss across the strainer.

e.

The strainer system head loss analysis conservatively assumed the water level in containment was at its minimum water level at the time of maximum head loss. For the bounding DEGB case, the containment water level at the time of maximum head loss (16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />) would be approximately 6.1 ft. This provides an additional allowable head loss of 0.1 ft. For the bounding DGBS case, the containment water level at the time of maximum head loss (23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />) would be approximately 6 ft. This provides an additional allowable head loss of approximately 0.18 ft.

f.

g.

NPSH 8.1 Methodology

a.

In the 1998 to 1999 time frame, CNP performed a complete reanalysis of containment water level. The analysis performed considered all parameters that would minimize the quantity of water available in the containment pool.

including those that would minimize ice melt and minimize displacement.

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8.2 Key Conservatisms I Margins

a.

The containment minimum water level analysis did not consider the increase in water level that would occur if the equipment that occupies the lower containment volume was considered. This would increase the water level at the initiation of recirculation and during recirculation by at least 2.2 in.

b.

For the small break analysis, the assumed maximum RCS cooldown rate of 100°F/hr was used. This minimized the energy discharged into containment thus decreasing ice melt.

d.

c.

The lake water temperature was as U '

The RWST temperature was assumed to a

(70°F) thus increasing the effectiveness of eo energy from the containment atmosphere, S Itin its minimum temperature ment sprays at removing

,educed ice melt.

e.

Initial containment temperature wa pressure to be condensed.

"l.J:"~;.'

f.

The assumed mass contribution of water from the RCS summed the

g.

k.

The b

rate assumed for recirculation flow was approximately 1000 gpm v

greater than the conservatively modeled maximum flow rate for two train ECGS and CTS operation.

This represents an approximate 7% reduction in flow through the strainer system.

I.

For the SBLOCA, conservative values were established for the quantity of water remaining within the RCS and not available for sump water inventory.

m. The NPSH analysis assumed a minimum water level of 601.5 ft in the recirculation sump, which provides a minimum NPSH margin of 9.2 ft.

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9 In summary, these conservatisms minimized the driving head for flow through the recirculation sump strainers by minimizing the containment water level, maximized the demand on strainer head loss through establishment of How rates in excess of those calculated for worst case system operation, and minimized the NPSH available to the ECCS and CTS pumps.

Downstream Effects - Ex-Vessel 9.1 Methodology

a.

per the guidance provided in WCAP limitations of the NRC SER considered 9.2 Key Conservatisms I Margins

a.

b.

c.

The downstream effects wear evaluation considered that approximately 28.5%

o total cold-galvanizing compound would pass through the recirculation sump trainers. This is significantly greater than the less than 2% failure of the cold galv. nizi g compound that was identified through DBA testing.

f.

As described in Section 7 of this evaluation, the use of more realistic values for the debris quantities in containment demonstrate' additional conservatism for the methodology that was used for the ex-vessel downstream effects analysis.

In summary, these conservatisms maximized the potential for blockage and wear of components downstream of the recirculation sump strainers, including consideration of the pumps being at their MOL and at the end of plant life wear point.

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11 10 Downstream Effects - In-Vessel 10.1 Methodology

a. The methodology that was used for performing the in-vessel downstream effects analysis was per WCAP-16793 with consideration of staff comments on that document, including the letter from the NRC to NEI. Additionally, as more questions were raised about the adequacy of the proposed methodology, the PWROG undertook additional testing to determin uel assembly blockage could occur.

Earlier this year, the PWROG pr IdeC! informal results to the NRC and licensees.

The PWROG also pr e the threshold criteria for fibrous and particulate debris below which tiel.(

age was demonstrated by testing to not be problematic.

10.2 Key Conservatisms I Margins

a. The debris quantities usedr interaction with the reactor vessel described in Section 7 of this eva 11.1 using the 11.2

a.

The CCI chemical effects testing determined a maximum increase in head loss across an established debris bed of 53%. CNP increased this to 70% for the entire recirculation sump strainer system for both the DEGB and DGBS to provide additional margin for uncertainty.

b.

The chemical effects testing performed at CCI established a debris bed for the main strainer only which is expected to be the most heavily laden with debris.

This provides conservatism in that for this strainer, the head loss will be greater

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than that for the remote strainer since a higher head loss is indicative of less available flow area through the strainer and a more highly compacted debris bed.

With less available flow area, chemical precipitates will more readily block flow through the strainer bed, resulting in a higher head loss increase as a result of the chemical effects.

c.

Additional conservatism exists with chemical effects as a result of the debris source term margins and conservatisms discussed in Section 7 of this evaluation.

If testing were to be performed with the more realistic debris quantities, the impact of the chemical precipitate would be significantly redured.

d.

to 68°F. This is below the expected low containment pool.

e.

Conservatism exists within the that would be formed as a res higher than would be expected

f.

g.

In summary, th~~liemical effects testing that was performed has demonstrated that CNP will be able to mitigate the consequences of a LOCA considering the inputs and methodologies that were used to establish bounding conditions for determination of the impacts.

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12 Upstream Effects 12.1 Methodology

a.

The methodology that was used for performing the upstream effects analysis was to consider all required flow paths that will either return water from upper containment to the containment pool, or will provide the necessary flow path to the main and remote strainers in lower containment.

12.2 Key Conservatisms I Margins

a.

13 13.1 for establishing the strainer system for

c.

The strainer structural analysis also considered the different phases of the event including temperature and pulse pressure from the failure of the pressurizer surge line, as well as the flow effects on the strainer system, and seismic effects.

13.2 Key Conservatisms I Margins

a.

Use of the code of record provides conservatism within the code itself.

- 19

b.

The values of the margins for structural analysis were provided in the February 29, 2008 and August 29, 2008 Supplemental Responses to GL 2004-02.

In summary, the strainer structural analysis provides margin to design allowable stresses which ensures that the strainer system will perform its function as long as is necessary following an event which requires its use.

14 Debris Source Term 15 14.1 Methodology

a.

14.2 Key Actions Taken

a.

b.

was to establish an engineering Additionally, were revised to include the As discussed in this eval ation, CNP has demonstrated that significant quantifiable margins and conservati$lJ)s,Dave been established as part of the success path for resolving GL 2004-02 and GSI-

~. CNP has also performed extensive analysis and testing, along with significant changes to the plant, to ensure that the ECCS system will meet the requirements of 10 CFR 50.46 following a LOCA. The same testing and analysis also ensures the CTS system will function to remove containment heat and radioactive iodine from the containment atmosphere for the necessary period following an accident.

- 20

DRAFT REQUESTS FOR ADDITIONAL INFORMATION DONALD C. COOK NUCLEAR PLANT, UNITS 1 AND 2 SUPPLEMENTAL RESPONSES TO GENERIC LETTER (GL) 2004-02 Debris GenerationlZone of Influence

1.

a) Identify what zone of influence (pipe diameters)

Cook RubatexlArmaflex configuration and how it was Labs test report data.

Response: The new CNP RubatexlArmaflex conti without failure. Due to limitations of l/'te" the jet that could be achieved.

If so, how

Response

2.

As describe I

the ijebruary 29, 2008 Supplemental Response, the jet I pingement testimg determined the effects of a direct jet impinging on the target aterial. As in ta led in the plant, due to the small size of the CNP containments, there is sign"flca t congestion surrounding the target materials with very few exceptia s.

is will result in deflected jets at the targets. For the Marinite board

testing, stated in the Supplemental Response, the failure mode was the deformati' of the simply supported cable tray section on which the board was mounted. For the label testing the jet size was very closely matched to the size of the labels. For the ArmaflexlRubatex tests the jet was intentionally directed toward the openings of the jacketing to maximize the forces acting on the material to determine if failure would occur. The single jacket tests demonstrated that failure would occur. For the tape tests the jet was again directed in the direction of the laps of tape to induce the greatest impact on the material. Since these tests were not attempting to determine the destruction of large quantities of materials, the use of a 2.45 in. diameter jet is jUdged to be reasonable and acceptable.

- 21

Debris Characteristics

3.

a) Describe the scaling process used to apply the results of the debris generation testing of the Marinite, Armaflex, fire barrier tape, and other materials to the plant condition. In particular, the staff noted that the size of the nozzle (2.45 inches) used for the testing resulted in a significantly smallerjet than would be created by a large-break LOCA. As a result, large test targets may only have been exposed to the peak pressure at the jet centerline over a limited area due to the radial decay of the jet pressure.

Thus, a significant area of the target material could have been ext! sed to much lower jet pressures than this peak pressure. This effect could be si ifiJ ant, not only with respect to ablation of base material by the impinging jet, but

'So to applying the total force necessary to rip off insulation jacketing or break insulation ding.

Response: See the response to RAI 2 above.

b) Please describe how the radial decay analysis of the test results to demonstr. e" conservatively scaled to the plant conditio

Response

4.

Response: Tests 9, Section 3.b, Table _",","""-T

5.

Response: The m t~ri!31 ed for erosion testing was the specific material that is installed in the CNP cont~ments within potential ZOls (Thermo Gold 12). The OPG testing that is referenced was performed with Thermo Gold 12. This was confirmed through discussion with one of the individuals from OPG that was involved with the testing.

Debris Transport

6.

In the D. C. Cook debris transport analysis, both the total quantity of transported debris and the distribution of this transported debris to the main and remote strainers have an impact on the final system head loss.

- 22

Please describe the basis for considering the Loop 4 break to be bounding, not only from the standpoint of transporting the greatest total amount of debris, but also from the standpoint of the degree of uniformity in the debris distribution between the main and remote strainers.

Response: The Loop 4 break does not transport the greatest quantity of debris. It provides the greatest quantity of problematic debris. Since the remote strainer is significantly removed and separated from the breaks that could occur within the loop compartment, there will not be a uniform distribution of debris between the main and remote strainer.

As described in the Februa 9, 2008 Supplemental Response, Section 3.e, following the break, during th n ction phase, there will be two distinct flow directions for the water and deb is hin the loop compartment.

One will be toward the main strainer and th 0

r ill be toward the debris interceptor at the flood-up overflow wall 0 "ngs.

th of these flows are transporting water to the annulus. Wit t e water flo 0 the annulus, the transportable fines will be accumulating' eas away from e emote strainer. At the end of the injection phase, the e cted distribution 0 e ris in the loop compartment will be at the 01 a

.e main str: iner.

Also, stated in the discussion on debris transport in Se n 3.e, t e' sumption was de that the debris inside the loop compartment u*. y distributed to maximize the quantity that could be trans orted to the m I r mer and the annulus.

7.

The debris transport analysis deriving the flow and debris distributions between the main a appear to lack adequate basis, including the following:

a.

- 23

100 90

.,~-

SO

~.5 70 u;

c 6{)

~

~

50

I e 4()

30 C.

u;

~

20 c

ti::

10 0

0 Main Sa-diner Open Area Ratio (-k)

b.

To determl an ex split of debris between the main and remote strainers would have require~ a substantial number of iterative tests followed by analysis followed by tests followe. by analysis, etc. The debris transport analysis factored in this l-!pcertainty when.(:letermining the debris distribution between the main and remote strainers. This IS }nost evident when looking at the total debris transport factor for th e t at resulted in a value greater than 1 with 1 being the total quantity of debris availatsle; or tRose debris sources that had a total debris transport factor less than 1, the saQ1~~ proach was applied resulting in debris transport factors greater than would exist for a single strainer approach design.

Refer also to the discussion provided in Sections 5 and 7 of the Margins and Conservatisms Evaluation.

c. Water draining into the containment pool during the fill-up phase is clean. Such a condition is not realistic, and the time dependence of blowdown, washdown, and pool-fill-Up transport modes is not well known and can vary significantly from one accident scenario to the next.

For this reason, conservatively estimating time dependent debris transport is very challenging.

- 24

As a result of these observations, the staff does not consider the flow and debris distributions to the main and remote strainers (including the time-dependent transport modeling used to determine these distributions) to be adequately justified.

The measured flow rates to the main and remote strainers in the large scale tank tests performed at Control Components Inc. (CCI) further provide support to the staffs view that the fraction of flow and debris transport to the main strainer were overestimated by the transport analysis.

Since non-uniformity of the flow and debris loading tends to reduce the overall system head loss, this overestimate of flow and debris transport to the main strainer appears non-conservative.

Please provide adequate justification to support the above the determination of flow and debris transport to the main _

Response

8.

a.

b.

Response

c. The bas~~ Q using a velocity of 0.4 ftls, since calcium silicate pieces larger than those tesf(i~)I.e., in the large piece category) would not transport at this velocity.

Response: A higher velocity will result in a greater probability for erosion to occur.

d. The basis for considering the turbulence conditions prototypical or conservative, since defining a limiting condition for turbulence is difficult given that a variety of conditions may exist throughout the containment pool at different times following a LOCA.

- 25

9.

Please identify the basis for the assumed calcium silicate tumbling transport velocity metrics for small pieces (0.33 ft/s) and large pieces (0.52 ft/s).

NUREG/CR-6772 identifies the incipient tumbling velocity of 0.25 ftis for small pieces of calcium silicate.

Response: Specific testing was performed by ALION to establish both incipient tumbling and tumbling velocities. The test report that documents the results of this test is ALlON REP-LAB-2532-81, Testing to evaluate the Settling and Tumbling velocities of Cal Sil Insulation Debris. This is an ALiON proprietary document. The following has been excerpted from the test report:

The Cal-Sil insulation samples were tested in the T, a. sport Flume under uniform flow conditions. The assembly shown in Figure 2..68S used. An intemal channel was inserted in the Transport Flume to reduce ross sectional area from 21.5X24 in2 to 12.25X24 in2 to achieve a highe ve ocity; at a particular flow rate. A flow distributor and flow straightener were used a achieve' a inar and unidirectional flow.

e excerpt is Small Debris Samples <<1 in.

petween 1 in. and 3 in. diameter), and Large

10.

Please pro'{ide justi ica ion that the debris introduction methods used during head loss testing resulted in prototypical or conservative head loss results.

Response: The introctyction of the debris directly in front of the strainer prevented settling of any debris before it could reach the strainer. Additionally, following testing and drain down of the test loop, there appeared to be a fairly even distribution of fine debris in the strainer pockets.

A prototypical debris loading would have had significantly greater debris loading in the lower pockets. It is judged that the results obtained during the testing were conservative.

Refer also to the information provided in Sections 5 and 7 of the Margins and Conservatisms Evaluation.

11.

The submittal stated that the fibrous debris was shredded, and then blasted with a water jet to render it into fine debris. The submittal stated that the fibrous debris was verified to

- 26

be less than 10 mm in size. It is not clear that the debris was easily suspendable which is the primary consideration for fine fibrous debris. In addition, the submittal did not state the extent to which the fibrous debris was diluted.

Therefore, agglomeration of debris could have occurred resulting in non-prototypical debris bed formation and non conservative head losses.

Please provide information that shows that the debris preparation and introduction methods used during head loss testing were conducive to prototypical debris arrival at the strainer and resulted in prototypical or conservative head loss results, or evaluate the effects of the non-prototypical debris on the head loss results.

Response: The overall methodology for determination of strai r bead loss was conservative in that debris quantities significantly in excess of me h t exist in the plant were used for the testing.

The debris preparatio ct dervef\\Y was performed as a homogeneous mixture that was well prep' f 0 preven 9910meration, which is not prototypical, but is conservative.

efe also to the in ation provided in Sections 5 and 7 of the Margins and Ccmservatisms Evaluation.

12.

he QiCttl es ~'9 referred to are those of the chemical effects testing that modelea fie main s riner only to determine a chemical effects bump-up factor.

During the ~FrL tesfngi there was no "pool-fill" sequence for debris*addition. The inclusion of RML in a -tr iner test is prototypical as there will be a signi'ficant quantity of R I debris' generated during an event which will transport and

~ccumulate at a'1d in the main strainer. Due to the very low fiber that exists at ON?, the testin that was performed conservatively determined the head loss that would be developed. If testing had been performed with the debris quantities that actua Iy exist in containment, the resulting head loss would have been significantly lower. AgC;1jn, refer to the information provided in Sections 5 and 7 of the Margins and Conservatisms Evaluation.

13.

During head loss testing the flow rate was started at 60% of the maximum flow. The flow rate was then increased to 80%, then to 100% along with debris additions to the same percentages. It is not clear why flow was not maintained at 100% for the entire test.

Please provide the basis for increasing the flow rate during the beginning of the test and provide information that verifies that this practice did not result in non-conservative head loss results. Adding debris with the flow rate below 100% is likely non-conservative due to lower bed compression, and therefore, head loss.

The following provides additional

- 27

details on the staff concerns. Forming the bed at reduced flow (60% of debris added at 60% flow), as was done in the large scale extended duration head loss tests, does not appearjustified unless a reduced water level is also simulated that could help model the building of the bed from the base of the strainer to its top at a higher approach velocity.

The staff also questions whether the addition of 60% of the debris during fill up can be justified, and notes that this overestimates the licensee's calculations.

For the large scale event sequence testing, the concern is even more substantial, with 100% of the debris being added at flows representing between 38 and 50% of the scaled plant flow rates. The staff is concerned that the time-dependence of the debris arrival sequence in the plant is not known with confidence, and adding all of the ebris at less than 100% of the design flow is non-conservative, unrealistic, and ultimately leads to lower bed compression and lower debris bed head loss than a mo e conservative methodology that is better aligned with the expected plant behavior. The s aft questions whether the time based addition of debris for the main strainer (io' dding.the "pool-fill" transported Of material first) has an adequate technical basis, It appears 0 based on arbitrary transport assumptions. Debris addition in this ina ner may lead to ratified bed that is non-representative of the expected plant onCJitlOn.

Since the wate 'height in the test tank during the pool-fill debris addition WB-S,'fat prototypical, the local proach velocity during bed formation was not represente'.a curately n J the actual p7a' water level

14.

Response

n addition, the conservatisms reached the water level modeled in the test.

Please address these concerns.

The tes Please p.rovide the re~u/ts of the similar tests run for each flow scenario and provide an evaluationlComparison of the results.

Response

$sults requested in. this RAI were provided in the February 29, 2008 Supplemental Response, Section 3.f.

15.

During the chemical effects testing, non-chemical head losses were significantly greater than large scale non-chemical head loss testing with a similar debris mixture.

a)

Please provide an explanation for this behavior and evaluate how a higher non chemical debris head loss could affect the calculated bump-up factor.

- 28

Response: The MFTL chemical effects test was performed with the main strainer only with the debris load for that strainer. The head loss for the main strainer is greater than the remote strainer which is indicative of a dense and compacted debris bed. Applying chemical precipitates to this condition will result in a more significant increase in strainer head loss since there are less available flow paths through the debris bed than there would be with a strainer with less debris.

b) Provide a justification that the chemical test head loss should not be applied directly to the net positive suction head evaluation.

Response

16.

ious debris as predicted by he transport much debris will arrive at each

17.

loss would be considered to be

'1'oC,j;,""'~at the clean strainer head loss the clean strainer portion or confirm that this

18.

Response: The non-prototypical addition of debris to the test loop (significant quantities in a relatively short period of time) initially results in a head loss from the near term blockage of the strainer assembly.

As the debris circulates, the debris bed transforms from a film effect to a compacted bed. Due to the debris constituents used during CNP testing, there is insufficient fiber to maintain a tightly interlaced debris bed. Holes will open up in the bed allowing flow through the bed.

- 29

b) Provide justification that the chemical precipitates were added at a time such that a prototypical or conseNative bump-up factor would be calculated. The staff considers that adding chemicals when baseline head loss is continuing to decrease could result in a non-conseNative bump-up factor.

Response: The primary driver for the decreasing head loss was the increasing temperature within the test loop. Refer to the February 29, 2008 Supplemental Response to GL 2004-02, Section 3.0.13, Figures 3013a-1 and 3013a-2 on pages 303 and 304.

Additionally, the values for head loss were normalized to 68°F for both debris only head loss and chemical effects head loss.

19.

Response

20.

Add"" s.s in your respof} e whether the scaling back of this head loss result based on the reducea flo rate ca. be justified because flow rate determination in the large scale tank was base','Q!timately, on arbitrary assumptions made during the transport analysis. In actuality, the. CJistJj'tpancy in flow rate for this test indicates that too little debris was assumed to tralJ§port to the remote strainer (versus the main strainer) and that a higher flow rate would occur at the main strainer, presumably with slightly less debris. In other words, it is a non-converged solution.

Response: Please refer to the responses previously provided regarding flow splits, debris transport, and conservatisms and margins that exist.

Also, the flow rate determination for the large scale testing was not based on debris transport assumptions. The basis for the statement was intended to show that the debris loading for the main strainer in the large scale test was similar to the debris loading for the main strainer in the MFTL. It was not intended to provide justification for

- 30

debris quantities, but that there was minor difference in the calculated main strainer head loss from the large scale test and the directly measured main strainer head loss from the MFTL test.

Coatings Evaluation

21.

In the submittal, non-original equipment manufacturer alkyds and epoxies fail as chips in accordance with Keeler and Long Report No. 06-0413. The Keeler and Long report is only applicable to degraded qualified epoxies and not unqualified epoxies or alkyds.

Please provide additional justification for the unquar J non-original equipment manufacturer alkyd and epoxy coatings assumption to fa*

chips.

Response: The coatings that were considered as chips -a

22.

Response

was Rustoleum with an b)

23.

Based upon the information provided in the response, it appears that the potential exists for a break location to be submerged by the water in the containment pool, potentially resulting in a flow path for unfiltered pool water to enter the reactor vessel.

The centerline for the reactor inlet nozzle is at 614 ft elevation. The maximum containment pool water level is also 614 ft elevation.

a) Please address whether the potential for debris bypass into the reactor vessel through this pathway has been analyzed.

- 31

Response: The maximum, conservatively predicted water level for containment is just below the 614 ft elevation. The analysis that determines this water level is biased in the opposite direction of the analysis that determines the minimum water level in containment.

One of the most significant conservatisms in the maximum water level analysis is the quantity of ice assumed to be in the ice condenser. Several additional conservatisms are included within this analysis which further increases the water level in containment, such as containment pool temperature, available volume from the RWST, RCS, and Accumulators, and the quantity of items that can displace water.

Considering just the difference i lee mass results in an approximate decrease in water level between 6 ill; rnit 2) and 1 ft (Unit 1).

Additionally, by the time the maximum water leve s reached, there will be little to no debris remaining in the containment pool du 0tHe dtration of the recirculation sump strainers.

o time is core

Response

NPSH

24.

ater level calculation included ~ of the ReS It is not clear that these volumes should be small-break LOCA could result in the eriod and the RCS maintaining more than Response: The s.. R lemen al response statement was strictly referring to the large break scenari s.

OF small breaks, the analysis considered the effects of cooldown, refill, and dela td accumulator volume additions as a function of RCS pressure. Refer to the following description of the water level analysis.

The current licensing basis containment sump inventory analysis was performed using the MAAP4 code version 4.0.4.1 (FAI, 1999).

The MAAP4 code calculates the behavior of and interactions between the ECCS, RCS and containment following a postulated accident. Consequently, the predicted containment sump inventory reflects time-dependent mass and energy inputs from ECCS/containment spray injection and recirculation, ice melt, RCS holdup, accumulator injection, and water flow between containment compartments. The Cook Nuclear Plant reactor

- 32

coolant system is represented as a typical Westinghouse 4-loop design available in MAAP4. Two RCS loops are included in the standard MAAP4 model, with one loop including a single steam generator and associated piping, and the other loop including the composite behavior of the remaining three steam generators and associated piping. The spectrum of RCS break sizes evaluated include a Double Ended Cold Leg (DECL) and a variety of smaller breaks. The MAAP4 primary system break flow model determines mass and energy releases for steam and water flows leaving the reactor coolant system by assuming they are in thermodynamic equilibrium. This characterization of the break flows maximizes water enthalpy, and minimizes steam release to cont ii1 ent atmosphere that is available to melt ice.

The modeling assumptions for the containment minimum water level analysis considered those conditions that would result in the least amount of water being available for the containment sump.

These included use of a maximum procedurally driven cooldown rate of the RCS along with maximum refill of the RCS for those breaks where inventory in the RCS could be restored. The analysis also considered the accumulators at their minimum pressure and temperature with water addition from the accumulators being controlled by RCS pressure and pressure

- 33

head driven flow from the accumulators. The water levels provided for the DEGB, the DGBS, and 2 in. line break in the February 29, 2008 Supplemental Response to GL 2004-02 represent these conservatisms, where applicable.

Refer also to Section 8 of the Margins and Conservatisms Evaluation.

b) Please provide the basis for concluding that there are no small breaks near the top of the pressurizer that should be analyzed for sump performance.

Response: When this was first evaluated four years ago, the ability of the Operators to recognize, mitigate, and establish recovery determined ftat for the maximum 6 in.

break, the plant would not be in a condition wher:e r ' irculation was required.

Discussions with members of the Licensed Opera or raining staff confirmed the original conclusion. Unfortunately, we are curren y.. u be to revalidate this on the simulator since both of the CNP units are in a 0 age either the training staff or the operators are available to perform t e arios.

c) Verify that operators have th preventswftchove~

Response

25.

D. C. Cook US$S both sodium tetraborate in the ice and sodium hydroxide in the containment spray.

Tables 301-1 and 301-2 indicate that only sodium tetraborate is added to the multi-functional test loop for in-situ chemical precipitate formation in the chemical effects head loss testing.

Please provide a justification for not including sodium hydroxide in these tests.

Response: The addition of NaOH was unnecessary for this test. Ample quantities of Na and OH existed in the test solution as a result of the sodium aluminate and Sodium

- 34

Tetraborate additions to the test loop. The sodium aluminate is a strong alkaline which maintains the pH at the specified level of 8.9.

26.

Please explain why the later batches of chemicals have no apparent impact on the measured head loss. The staff is concerned that the addition of extra chemicals may not provide a significant degree of conservative if the phenomena behind why later batches of chemicals in the testing don't seem to have a noticeable impact on head loss is not understood and known to be present in the plant condition also.

Response: The chemical additions in excess of the quantities speci Ie did not have the other necessary chemicals to react with to form addition Q cipitate. The conditions expected for 140% chemical addition were met for H

• est.

.um flowrate of 1 Umin to preclude stagnant

a.

VUEZ Testing

27.

C. Please s ate whether agitation or manual stirring of the tank was performed during the testing, and please describe the direction that the recirculation discharge flow entered the large tank relative to the opening of the pocket strainer.

d. Please state whether photographs were taken of the tank floor at the completion of the test and whether the quantity of debris that settled on the tank floor was estimated. What is the estimated quantity of the debris that settled? Was any of the settled debris manually pushed into the strainer pockets?

- 35

e. Please discuss how the reduced velocities used during debris bed formation affected the settling of debris in the test tank. For instance, the response (e.g., page 74 of 100) indicates that debris settled in tank, particularly prior to the initiation of full recirculation flow.

What is the basis for allowing debris settlement at strainer approach velocities that are significantly less than the prototypical value?

28.

Please explain how the containment spray flow for the first 25 minutes of the experiment was scaled, and the basis for the flow rate that was chosen.

29.

Debris does not appear to be prepared as fines in the PhotOgf;~h provided in the Alion test report (pg. 66). Fiber is conservatively expected to be 0

. mdividual fibers because it is all latent debris. Calcium silicate insulation at the s r. I er is analytically expected to be 86% fines and 14% small pieces. Similar observat~b t<..~n also be made for Marinite

30.

debris. These important debris sources do not app.e to nave been prepared per the plant-specific debris transport results.

r*t e ebris accumulation on the strainer to clarify

31.

Simi! r10 the eel teslifJ.,q, all of the debris for the VUEZ test appeared to be added during the POQ -til phase.

V!.e staff is concerned that this approach is non-conservative because 'f the lower velocities during the fill-up phase (2/3rds of the value during recirculation)

];ii~ower flow rate through the strainer would lead to reduced debris bed compression.

itFrhermore, it is not clear whether a representative water level modeling was used. The use of a non-representative water level would further reduce the velocity during bed formation and further contribute to reduced bed compression. Additionally, due to pump cavitation, the flow in the VUEZ loop had to be substantially reduced during the debris bed formation process, which resulted in a bed being formed at velocities substantially lower than even the reduced velocities during pool fill.

a) Please address the potential for a resultant non-uniform debris distribution on the 2x2 pocket strainer module, with more debris going toward the bottom pockets as well as some piling of debris at the pocket openings rather than the formation of a thin bed.

- 36

b) Please also address the potential for reduced debris bed compression due to non representative test conditions that had the potential to underestimate the potential limiting head loss for the plant condition.

32.

Similar to a staff observation for the small-scale VUEZ test loops, when taken in aggregate, uncertainties are not negligible on the VUEZ large scale test apparatus:

a. Approximately 1% of volume is discarded due to sampling

b. Approximately a 3% reduction in head loss because Ie s calcium silicate debris was added to test than revised calculations showed.

c. Temperature uncertainty is +/-5°F

d. Flow measurement uncertainty is 5%

e. Pump flow uncertainty is 5%

33.

34.

- 37

REQUESTS FOR ADDITIONAL INFORMATION DONALD C. COOK NUCLEAR PLANT. UNITS 1 AND 2 SUPPLEMENTAL RESPONSES TO GENERIC LETTER (GL) 2004-02 Debris Generation/Zone of Influence

1.

a) Identify what zone of influence (pipe diameters) was determined for the new D. C.

Cook RubatexiArmaflex configuration and how it was arrived at from the referenced Wyle Labs test report data.

b) Were there any potential break locations within this zone of influence? If so, how much debris would be generated from this source, how much would be expected to arrive at the strainers, and what would its contribution be to strainer blockage and head loss?

2.

Describe the basis for determining that the results of jet testing with the 2.45 inch diameter jet were prototypical of that which could be expected from the much larger jets potentially experienced during a loss of coolant accident (LOCA)?

Debris Characteristics

3.

a) Describe the scaling process used to apply the results of the debris generation testing of the Marinite, Armaflex, fire barrier tape, and other materials to the plant condition. In particular, the staff noted that the size of the nozzle (2A5 inches) used for the testing resulted in a significantly smaller jet than would be created by a large-break LOCA. As a result, large test targets may only have been exposed to the peak pressure at the jet centerline over a limited area due to the radial decay of the jet pressure. Thus, a significant area of the target material could have been exposed to much lower jet pressures than this peak pressure. This effect could be significant, not only with respect to ablation of base material by the impinging jet, but also to applying the total force necessary to rip off insulation jacketing or break insulation banding.

.b) Please describe how the radial decay of the jet pressure was accounted for in the analysis of the test results to demonstrate that the results have been prototypically or conservatively scaled to the plant condition.

4.

Please' identify which,destruction test or tests were used as the basis for the Marinite size distribution given inTable 3c1-2 of the supplemental response.

5.

Based upon discussions with manufacturers of calcium silicate, the staff understands that there were several different manufacturing processes used to make calcium silicate insulation in the U.S., and that the calcium silicate produced by the different processes may have significantly different characteristics with respect to exposure to jet impingement and erosion.

What verification or analysis was done to ensure similarity between the calcium silicate at D. C. Cook and the material tested for both erosion and for the jet destruction testing performed by Ontario Power Generation?

- 2 Debris Transport

6.

In the D. C. Cook debris transport analysis, both the total quantity of transported debris and the distribution of this transported debris to the main and remote strainers have an impact on the final system head loss.

Please describe the basis for considering the Loop 4 break to be bounding, not only from the standpoint of transporting the greatest total amount of debris, but also from the standpoint of the degree of uniformity in the debris distribution between the main and remote strainers.

7.

The debris transport analysis makes assumptions in deriving the flow and debris distributions between the main and remote strainers that appear to lack adequate basis, including the following:

a. During pool fill up, the flow resistance on the main strainer is assumed to be negligible, even though a substantive amount of debris is assumed to accumulate there during fill up. Given the reduced water levels along with the fact that static head is the only driving force to move water through the main strainer at this time, the neglect of this flow resistance could have a non-negligible impact on the flow distribution during fill up, resulting in increased flow to the remote strainer.

b. Ten percent of the area of the main strainer is assumed to remain clean during recirculation, even though large scale test results for D. C. Cook suggest a greater degree of flow resistance. Furthermore, a significant number of head loss tests with a variety of different strainer geometries have demonstrated the potential for debris to form a continuous bed over the entire strainer surface area rather than leaving part of the strainer area open (presuming a sufficient quantity is available).

Therefore, a more representative analytical model of head loss at the main strainer during recirculation would likely result in a significantly larger flow and debris fractions arriving at the remote strainer.

c.,'\\Water dr~ining into the containment pool during the fill-up phase is clean. Such a

. condition is not realistic, and the time dependence of blowdown, washdown, and pool-fill-up transport modes is not well known and can vary significantly from one accident scenario to the next. For this reason, conservatively estimating time dependent debris transport is very challenging.

As a result of these observations, the staff does not consider the flow and debris distributions to the main and remote strainers (including the time-dependent transport modeling used to determine these distributions) to be adequately justified. The measured flow rates to the main and remote strainers in the large scale tank tests performed at Control Components Inc. (CCI) further provide support to the staff's view that the fraction of flow and debris transport to the main strainer were overestimated by the transport analysis. Since non-uniformity of the flow and debris loading tends to reduce the overall system head loss, this overestimate of flow and debris transport to the main strainer appears non-conservative.

Please provide adequate justification to support the above assumptions used to support the determination of flow and debris transport to the main and remote strainers.

8.

Please provide additional information concerning the erosion testing of calcium silicate insulation and Marinite board, including the following items:

a. The basis for not accounting for erosion and dissolution effects in combination. The presence of chemicals in the test fluid may enhance the erosion rate, and, conversely, a high erosion rate may lead to increased dissolution.

b. The basis for not including the plant buffer materials in the test fluid.

c. The basis for using a velocity of 0.4 ftls, since calcium silicate pieces larger than those tested (i.e., in the large piece category) would not transport at this velocity.

d. The basis for considering the turbulence conditions prototypical or conservative, since defining a limiting condition for turbulence is difficult given that a variety of conditions may exist throughout the containment pool at different times following a LOCA.

9.

Please identify the basis for the assumed calcium silicate tumbling transport velocity metrics for small pieces (0.33 ftls) and large pieces (0.52 ftls). NUREG/CR-6772 identifies the incipient tumbling velocity of 0.25 ftls for small pieces of calcium silicate.

Head Loss and Vortexing

10.

According to the submittal, the debris was added directly in front of the strainer to reduce near-field settling. The staff has foun9 that this. debris introduction method can result in non-prototypical bed formation and non-conservative head loss values during testing.

Please provide justification that the debris introduction methods used during head loss testing resulted in prototypical or conservative head loss results.

11.

The submittal stated that the fibrous debris was shredded, and then blasted with a water jet to render it into fine debris. The submittal stated that the fibrous debris was verified to be less than 1Omm in size. It is not clear that the debris was easily suspendable which is the primary consideration for fine fibrous debris. In addition, the submittal did not state the extent to which the fibrous debris was diluted. Therefore, agglomeration of debris could have occurred resulting in non-prototypical debris bed formation and non conservative head losses.

Please provide information that shows that the debris preparation and introduction methods used during head loss testing were conducive to prototypical debris arrival at the strainer and resulted in prototypical or conservative head loss results, or evaluate the effects of the non-prototypical debris on the head loss results.

12.

Reflective metallic insulation (RMI) debris was added to the head loss tests. In pictures of the chemical testing in the multi-functional test loop (MFTL), the RMI was piled up in front of the strainer and transported into the bottom several rows of the strainer. The staff considers this non-prototypical and it could result in non-conservative head loss values. Pictures of the non-prototypical RMI debris bed can be seen in photos on pages 288-293. With the RMI present, a prototypical fiber and particulate bed could not have been created. In particular, some of the RMI was part of the earlier-transported "pool-fill" transported debris. This resulted in an RMI layer being formed between the fibers and

- 4 particulate that was added early representing pool-fill transport and that which was added later representing recirculation transport.

Please address this testing approach wherein the RMI was apparently responsible for reducing head loss but was added to the tank in a non-prototypical way.

13.

During head loss testing the flow rate was started at 60% of the maximum flow. The flow rate was then increased to 80%, then to 100% along with debris additions to the same percentages. It is not clear why flow was not maintained at 100% for the entire test.

Please provide the basis for increasing the flow rate during the beginning of the test and provide information that verifies that this practice did not resl:'h'i'h~non-conservative head loss results. Adding debris with the flow rate below 100o/d i5;I~ikely non-conservative due to lower bed compression, and therefore, head loss. TQ~,fo!t0~lng provides additional details on the staff concerns. Forming the bed at redllced flow'(~O% of debris added at 60% flow), as was done in the large scale extendeCl duration headJoss tests, does not appear justified unless a reduced water level is, 'alsb simulated thaf'bbuld help model the building of the bed from the base of the straine~htb its top at a higher afiipro.ach velocity.

The staff also questions whether the additlRn of 60% of t~e debris during ~II up can be justified, and notes that this overestimates,t!1ejicense~:s'~alculations. For'tti.e large scale event sequence testing, the concern is even more'substantial, with 10()% of the debris being added at flows representing between., 38~hd 50% of the scaled plant flow rates. The staff is concerned thCilt the time-dependebce of the debris arrival sequence in the plant is not known with confrdence;'and adding ail of,the debris at less than 100% of

/.;';

• 14'::1-.

the design flow is non-conservative, unrealistic,: and ultill)~t~ly leads to lower bed compression and lower debris bed head loss*~h~n a more'c~mservative methodology that is better aligned wittt~.~e e~pected plant be.~~VJor: The ~taff questions whether the time based addition of ebris-for.the main strairilk(1.e., adding the "pool-fill" transported material first) has::a'n adequ~te..technicaL't)asis. It appears to be based on arbitrary transport assumptions. Debris',addition in tbis manner may lead to a stratified bed that is non-representative of the expected plant condition. Since the water height in the test tank during the P6~bfill deJ:j~s~a(@tionwas -~ol prototypical, the local approach velocity during b~Jormati0n~~s not representee accurately until the actual plant water level reached the water level-modeled in the test.

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" Please address th'"ese con&'rhs.

14.

The test sequencesttlat result~:d"in the maximum tested head losses for the double endef;!.9 illotine break~nd debris generation break size scenarios were different. The double-e. ded guillotine break limiting head loss was attained by adding a homogeneous debris ml~u.~e.in ~te'ps of 60%,80%, and 100% while increasing flow in the same steps.

The debris gerieralipii break size limiting head loss was attained during a sequence intended to mimic the flows that would occur through the strainer following a LOCA.

There is no apparent reason that different test sequences for would result in the limiting head loss for these breaks.

Please provide the results of the similar tests run for each flow scenario and provide an evaluation/comparison of the results.

- 5

15.

During the chemical effects testing, non-chemical head losses were significantly greater than large scale non-chemical head loss testing with a similar debris mixture.

a) Please provide an explanation for this behavior and evaluate how a higher non chemical debris head loss could affect the calculated bump-up factor.

b) Provide a justification that the chemical test head loss should not be applied directly to the net positive suction head evaluation.

16.

Provide an evaluation of the sensitivity of overall system head loss to various debris loads split between the main and remote strainers as predicted by the transport evaluation. Because it is difficult to determine how much debris will arrive at each strainer, this is an important issue.

17.

The submittal (pg 227) stated that the debris-only head loss would be considered to be 1.57 ft after being increased by 50%. It was not' clear that the clean strainer head loss was included in this value.

I Please provide the total head loss including the clean strainer portion or confirm that this value includes the clean strainer head loss.

18.

The head loss charts for the chemical effects testing>show a large rapid increase in head loss immediately following non-chemical debris addition.. The increase is followed by an immediate decrease in head loss to a'slgnificantly lower value, then a slower decrease until chemical precipitates are added (see pages 303 and -304). This behavior is unexpected.

a) Please provide an explanation for the rapid increase and decrease in head loss that occurred during this testing.

b) Provide justification that the chemical precipitates were added at a time such that a prototypical or conservative bump-up factor would be calculated. The staff considers that adding chemicals when baseline head loss is continuing to decrease could result in a non-conservative bump-up factor.

19.

The submittal stated that the d~sign maximum head loss is 2.8 ft for a large-break LOCA based on the available driving head of water at the recirculation sump. This limit was based on NUREG-CR,;.6808 guidance that head loss should not exceed 1;'2 of the strainer height (or in this case submergence above the bottom of the strainer). A slightly lower limit for the debris generation break size was also listed. There was no limit provided for the small-break LOCA and no calculation of potential head losses associated with a small break.

Provide justification that the strainer will maintain its function under all required scenarios including a small-break LOCA.

20.

The basis for the comparison being made on page 306, that the resulting head loss for the large scale head loss on the main strainer only is 3 ft, which compares favorably to the MFTL debris only head loss of 2.67 ft is not clear.

Please clarify this statement, which helps to undergird the bump-up factor approach.

- 6 Address in your response whether the scaling back of this head loss result based on the reduced flow rate can be justified because flow rate determination in the large scale tank was based ultimately on arbitrary assumptions made during the transport analysis. In actuality, the discrepancy in flow rate for this test indicates that too little debris was assumed to transport to the remote strainer (versus the main strainer) and that a higher flow rate would occur at the main strainer, presumably with slightly less debris. In other words, it is a non-converged solution.

Coatings Evaluation

21.

In the submittal, non-original equipment manufacturer alkyds and epoxies fail as chips in accordance with Keeler and Long Report No. 06-0413. The Keeler and Long report is only applicable to degraded qualified epoxies and not unqualified epoxies or alkyds.

Please provide additional justification for the u(lqualified non-origirial equipment manufacturer alkyd and epoxy coatings assumption to fail as chips.

22.

a) Please provide the characteristics of the paint chip surrogate including the density and type of paint used.

b) Please clarify how the paint chip surrogate simulates the expected coating debris.

Downstream - in vessel

23.

Based upon the information provided in the response, it appears that the potential exists for a break location to be submerged by the water in the containment pool, potentially resulting in a flow path for unfiltered pool water to enter the reactor vessel. The centerline for the reactor inlet nozzle is at 614 ft elevation. The maximum containment pool water level is also 614 ft elevation.

a) Please address whether the potential for debris bypass into the reactor vessel through this pathway has been analyzed.

b) Are there any adverse debris effects from submerging other RCS break locations?

24.

The submittal stated that the minimum water level calculation included Y:z of the RCS volume and the vQI.~me of the accumulators. It is not clear that these volumes should be credited for all breaks. For example a small-break LOCA could result in the accumulators remaining full for an extended period and the RCS maintaining more than Y:z of its volume. In addition, the RCS would tend to refill as it cooled off. Based on these observations it is not clear that the levels used in the vortexing evaluation are conservative. It was not clear that the increasing density of RCS inventory as it cooled was considered in the sump level calculations.

a) Please provide information that justifies that the sump pool level calculations resulted in realistic or conservative levels for the large-and small-break LOCAs.

- 7 b) Please provide the basis for concluding that there are no small hre(1ks ne(1r the top of the pressurizer that should be analyzed for sump performance.

c) Verify that operators have the ability to cooldown and depressurize in sufficient time to prevent switchover.

d) How is a single failure accounted for in this analysis?

e) If the currently calculated minimum water levels require revision, please provide updated vortexing and air entrainment evaluations using conservative submergence values.

Chemical Effects

25.

D. C. Cook uses both sodium tetraborate in the ice and sodium hydroxide in the containment spray. Tables 301-1 and 301-2 indicate that only sodium tetraborate is added to the multi-functional test loop for in~situ chemical precipitate formation in the chemical effects head loss testing.

Please provide a justification for not including sodium hydroxide in these tests.

26.

Please explain why the later batches of chemicals have no apparent impact on the measured head loss. The staff is concerned that the addition of extra chemicals may not provide a significant degree of conservative if the phenomena behind why later batches of chemicals in the testing don't seem to have a noticeable impact on head loss is not understood and known to be present in the plant condition also.

VUEZ Testing The NRC staff performed a detailed review of the test procedures used by Alion at the small loops at the VUEZ test facility in Slovakia. The staff concluded that it was unlikely that the plants relying on this testing could use it as a basis for demonstrating strainer design adequacy to resolve Generic Letter 2004~02. The staff's review did not specifically address testing performed in the larger loop at VUEZ that was used for the D. C. Cook testing. Although some similarities existed in the small-scale and larger-loop test programs, there were also some significant differences. If VUEZ testingis being used as part of the basis to demonstrate the adequacy Of the D. C. Cook strainers, then please address the following requests for additional information on this testing bel()w:

27.

Please provide the fohowing additional information concerning the modeling of debris transport for" the, VUEZ testing:

a. Please explain the basis for the minimum flowrate of 1 Umin to preclude stagnant regions in the test tank.

b. Please provide a basis for the statement on pages 56 and 64 of 100 of the VUEZ appendix that states that the water volume was much smaller than the actual plant condition, and therefore the turbulence and velocity in the (test) pool is higher. The relative size of the fluid volumes does not appear to the staff to be directly related to the velocity and turbulence.

- 8 Please compare the test tank flow characteristir.s to the velocity and turbulence contour plots for the plant condition provided in the February 2008 supplemental response.

c. Please state whether agitation or manual stirring of the tank was performed during the testing, and please describe the direction that the recirculation discharge flow entered the large tank relative to the opening of the pocket strainer.

d. Please state whether photographs were taken of the tank floor at the completion of the test and whether the quantity of debris that settled on the tank floor was estimated. What is the estimated quantity of the debris that settled? Was any of the settled debris manually pushed into the strainer pockets?

e. Please discuss how the reduced velocities used during debris bed formation affected the settling of debris in the test tank. For instance, the response (e.g., page 74 of 100) indicates that debris settled in tank, particularly prior to the initiation of full recirculation flow. What is the basis for allowing debris settlement at strainer approach velocities that are significantly less than the prototypical value?

28.

Please explain how the containment spray flow for the first 25 minutes of the experiment was scaled, and the basis for the flow rate that was chosen.

29.

Debris does not appear to be prepared as fines in the photograph provided in the Alion test report (pg. 66). Fiber is conservatively expected to be only individual fibers because it is all latent debris. Calcium silicate insulation at the strainer is analytically expected to be 86% fines and 14% small pieces. Similar observations can also be made for Marinite debris. These important debris sources do not appear to have been prepared per the plant-specific debris transport results.

Are there photos of the as-prepared debris, slurries or close-ups of the debris during the addition process that show' the form of this debris immediately prior to the addition to the tank, which would demonstrate that these debris sources were eventually prepared into a representative.form?

30.

'Debris predominately entered the bottom row of pockets as evidenced in the photo on Page 67 of the Alion test report. The debris used for this testing should have been very nearly 100% fines (although some calcium silicate is small pieces). Although there may be some bias toward the bottom pockets during a LOCA even for fines, based on the photo, the biasing toward the bottom pockets seems much more pronounced than expected by the staff. Such significant non-uniformity can be attributed to either non representative debris preparation or the introduction of the debris so close to the bottom strainer pockets that it approached the strainer on a non-representative flowstream into the bottom pockets nearest the debris addition line.

a) Please provide additional photos of the debris accumulation on the strainer to clarify the situation.

b) Please identify the level the water was when the debris was being added, and identify whether the water level was representative of the plant condition at that time.

- 9

31.

Similar to the CCI testing, all of the debris for the VUEZ test appeared to be added during the pool-fill phase. The staff is concerned that this approach is non-conservative because of the lower velocities during the fill-up phase (2/3rds of the value during recirculation). This lower flow rate through the strainer would lead to reduced debris bed compression. Furthermore, it is not clear whether a representative water level modeling was used. The use of a non-representative water level would further reduce the velocity during bed formation and further contribute to reduced bed compression. Additionally, due to pump cavitation, the flow in the VUEZ loop had to be substantially reduced during the debris bed formation process, which resulted in a bed being formed at velocities substantially lower than even the reduced velocities during pooLfiII.

a) Please address the potential for a resultant non-uniform debris distribution on the 2x2 pocket strainer module, with more debris going toward*th~ bcjttqm pockets as well as some piling of debris at the pocket openings rather than the foonation of a thin bed.

b) Please also address the potential for reducedvdebris bed compt~\\sion due to non representative test conditions that had the pol~ntial to underestimateth~;potentiallimiting head loss for the plant condition.

~

32.

Similar to a staff observation for the smail-scaleVUEZtest loops, when taken in aggregate, uncertainties are not negligible on tJ1eVUEZ large scale test apparatus:

a. Approximately 1% of volume,isdiscarded due tdsampling

b. Approximately a 3% reduction in head lossoec9use tess, calcium silicate debris was added to test than"r,~yjsed calculati.ons showed~.

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c. Temperatute,lincertairityis +/-soF' "'.

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d. Flow measurement uncertainty is S%'.~',

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e. I?ump,flow uncertainty i's soio '::"1" !t':'. '

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..HoW'have uncer1.aintiesbe~[l accounted for in the application of the head loss results

,i'ffom the VUEZ testihg?

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33.

~Y'WhY did the head~loss increase early in the head loss test to a fraction of a kPa (see figute 7.2-14) before the official start of the test?

b) Wha(iNas the re,ason the head loss subsequently increased fairly rapidly to 11 kPa?

'. i 'L..u,;

34.

Please identifY theconcentration of the debris slurry used for the VUEZ tests and the degree to which agglomeration of the debris in the slurry affected the prototypicality of the test debris.

May 13, 2009

- 2 A list of attendees is provided in Enclosure 1. Members of the public were in attendance, including industry and vendor representatives. Public Meeting Feedback forms were available, but comments were not received.

Please direct any inquiries to me at 301-415-3049, or Terry.Beltz@nrc.gov.

IRA!

Terry A. Beltz, Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-315 and 50-316

Enclosures:

1. List of Attendees

2. Licensee Handouts cc w/encls: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsOgcRp Resource RArchitzel, NRRlDSS/SSIB LPL3-1 r/f RidsRgn3MailCenter Resource EGeiger, NRRlDSS/SSIB RidsAcrsAcnw_MailCTR Resource CTucci, NRR PKlein, NRRlDCI/CGSB RidsNrrDorlLpl3-1 Resource DHarrison, NRRlAPLA SSmith, NRRlDSS/SSIB RidsNrrPMTBeltz Resource SBailey, NRR/DSS/SSIB WJessup, NRRlDE/EMCB RidsNrrLABTuily Resource JLehning, NRR/DSS/SSIB SCampbell, EDO Region 3 SBahadur, NRRlDSS JSavoy, NRRlDSS MYoder, NRRlDCI BLin, RES Agencywide Documents Access and Management System (ADAMS) Accession Nos.:

Package: ML091200377 Meeting Notice: ML090860742 Meeting Summary: ML091190256 Licensee Handouts* ML091200364 OFFICE DORLlLPL3-1/PM DORLlLPL3~1/LA DSS/SSIBIBC DORLlLPL3-1/Be DORLlLPL3-1/PM NAME TBeitz THarris SBailey LJames TBeitz DATE 04/29/09 05/01/09 05/08/09

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