ML101950505

MPS3 RAI 6

ML101950505
Person / Time
Site:	Millstone
Issue date:	07/13/2010
From:	Sanders C Plant Licensing Branch 1
To:
Sandeers, Carleen, NRR/DORL, 415-1603
References
GL-04-002, FOIA/PA-2011-0115
Download: ML101950505 (13)

Text

I Millstone Unit 3 (MPS3) , I RAI6 NRC GL 2004-02 POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED-WATER REACTORS July 13, 2010 1

MPS3 RAI 6 NRC Staff Concern:

The impact of the chemical precipitates could be significantly higher than was deduced from the Rig-89 test results. This is because Rig-89 head loss results were an order of magnitude lower than Rig-33 results} which .t he NRC staff considers to be more representative of the plant condition from the perspective of bed formation. Filtration of chemicals on a less porous bed generally leads to significantly higher head losses. As a result} NRC staff does not consider it appropriate to add Rig-89 chemical effects differential head I

loss to the Rig-33 nonchemical head loss result. Nor does the lNRC staff accept the licensee's arguments regarding why Rig-33 result is not representative of the plant.

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Dominion Position

• Rig 89 head loss is design basis head loss for MPS3 and is conservative.

• Rig 33 is not prototypical of the MPS3 containment.

• Head loss with chemical precipitants will not challenge the significant existing NPSH margins.

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• Significant Margins assure that strainer will provide long-term recirculation even if non prototypical Rig 33 results are considered.

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Rig 89

• Conservative debris preparation and addition methodology identical to that used for Rig 33.

• No continuous stirrer to artificially keep debris in suspension.

• Submergence of test header section was prototypical of MPS3 containment.

• Minimal surfaces other than strainer for debris settling ensured a conservatively high amount of debris attached to the strainer.

• Chemical additions of both calcium and aluminum were a conservative simulation of MPS3 containment.

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Rig 33

• Non-prototypical for MPS3 Containment

- Low submergence (6 inches) in test rig versus 5 ft submergence in containment-increasing the susceptibility to air evolution in the debris bed.

- Continuous stirring in test rig versus no significant turbulence near strainer (located in containment annulus) as shown by CFD analysis.

- River water used in test rig versus deionized water in containment which may have increased head loss somewhat by adding some bacteria or suspended solids.

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Related Conservatisms

• Debris Bed

- 10% margin on coatings particulate (2.1 ft 3 margin)

- Unqualified coating makes up 1/3 of total particulate load.

- Fibrous debris prepared as "single-fine".

- Debris transport assumes all debris arrives at strainer including chemical precipitants.

• Strainer Area

- Installed strainer area (5200 ft 2 ) exceeds tested area (4290 ft-),

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MPS3 Containment Velocity Contours Velocity [ft's] Velocity [ftls]

0.40+ 0.28+

0.36 0.26 0.32 0.24 0.28 0.22 0.24 0.20 0.20 0.18 0.16 0 .16 0.12 0 .14 0.08 0.11 0.04 0.10 0.00 0.08 0.06 0.04 0.02 0.00 a) Color Range 0.0 100.40 ftls b) Color Range 0.0 100.28 ftls I

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12. 2007 7

Factors for MPS3 Plant Margins

• Strainer Size is 20% larger than tested size.

• Large Refueling Water Storage Tank (RWST): 1.2 million gallons.  :

• Modification implemented in 2007 toI delay RSS pump start to provide additional strainer submergence. I

• Strainer submergence is 4.9 ft at 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

• Required NPSH for RSS pumps is 4 ft.

• Lowest available NPSH for RSS pumps is 22.9 ft.

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Margins

• Margins include Rig 33 non-chemical head loss (5.1 psi at 104°F) which bounds Rig 33 and Rig 89 chemical effects head loss test results after 30 days.

- NPSH margin (4 ft NPSH required)

• 3 h 0 urs: 17 ft

• 30 days: 27 ft

- Strainer Flashing margin

• 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />s: 4 ft

• 30 days: 14 ft

- Suction Line Flashing margin

• 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />s: 10 ft

• 30 days: 20 ft 9

Calcium in Containment

• Calcium concentration in the MPS3 containment is negligible.

• Without calcium, one of the two major components for chemical precipitant head loss is not present.

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Rig 33 Chemical Test Head Loss Millstone 3 Rig 33 Chemical Effects Test 150 i i i , , , i i 10 I I I - FIowrate (USGPM) I I I I I

.- 135 -----~-----~-----~----- - K:P ReBUts (ppm) --+ 9 1 I I 1 Ie I I I

- CalcUatedCa Concemtion (ppm) --+

I 120 -----~-----~-----~----- 8

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• 105 I i i i i 7

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O ~' I  : I *: I I  : '0 06I04I08 11~108 16104108 21~108 26104108 01105108 06J05I08 11105108 16.<l5J08 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 0:00 Time (standard)

Figure 26 Head Loss and Ca Concentration for the Whole Test 11

Rig 33 Chemical Head Loss Test

• One test was run in Rig 33 with chemicals (in Apr-May 2008)

Identical debris addition methodology to Rig 33 and Rig 89.

Non-chemical head loss was 5.3 psi as compared to 5.1 psi for strainer sizing test.

Deionized water was used instead of river water.

One aluminum addition was made prior to any calcium additions-no noticeable effect on head loss.

Immediate head loss peaks occurred during fiber additions and calcium additions.

Overall, head loss changed from a steady value of 5.3 psi prior to any chemical additions to a value of 5.5 psi after 10 calcium additions and 1 aluminum addition. The head loss then drifted down to 3.8 psi before the test was stopped ( > 30 days).

Head loss from the first to the last calcium addition decreased-possibly due to migration of air out of the debris bed offsetting any rise due to chemical precipitants.

Debris bed was intact at end of test (no bore holes or dislocations).

End of Rig 89 head loss was 2 psia and end of Rig 33 chemical test head loss was 3.8 psia only a factor of 2 different.

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Conclusion

• Rig 89 submergence is prototypical of MPS3 containment. Rig 33 submergence is too low and adversely affected head loss results.

• Head loss with chemical precipitants is conservatively bounded by Rig 89 results which showed a maximum of 2.2 psid at 104°F.

• Significant margins assure that strainer will provide long-term recirculation even if non prototypical Rig 33 results are considered.

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