ML20236L278

Rev 0 to Calculation ENG-ME-170, Flooding of Unit 2 Loop a Msn Actuation Equipment

ML20236L278
Person / Time
Site:	Prairie Island
Issue date:	07/06/1998
From:	Agan C, Matthew Meyer NORTHERN STATES POWER CO.
To:
Shared Package
ML20236L244	List: ML20236L242 ML20236L278
References
ENG-ME-370, ENG-ME-370-R, ENG-ME-370-R00, NUDOCS 9807100296
Download: ML20236L278 (8)

Text

i PINGP 1083, Rav. 2 Pcg71 of 1 (FRONT)

Retention: Life NORTHERN STATES POWER COMPANY g*,

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PRAIRIE ISLAND NUCLEAR GENERATING PLANT

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CALCULATION COVER SHEET Calculation Number:

E5NG-t#-370 Calculation Rev. No.: 0 Addenda No.: O Calculation

Title:

F(Dadina of Und 1 L. cap A MSN Achafran toyijsmerd Safety Related7:

Y Calculation Verification Method (Check One):

M Design Review 0 Alternate Calculation O

Qualification Testing Scope of Revision:

L h d tss a Documentation of Reviews and Approvals:

Originated By:

lkk1 MartJ.Meme 07/05/98 Date:

Checked By:

C 6-Date: 76/fT v

v Na e 0 6.kM Date:

N6[TT Verified By:

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Approved By:

Date:

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ENERAL COMPUTATION SHEET Northern States Power Company Calc. No. ENG-ME-370 REV.

0_,

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' PROJECT PINGP 2 HELB Verification SHEET No.

2 oF 8.

DATE 07/06/98

,A SUBJECT Rooding of Unit 2 Loop A MslV Actuation Equipment COMP BY M. Meyer C'K'O BY C Y)t 1.0 Purpose and Summary Result As discussed in LER 1-98-05 (Reference 1), a postulated break, at Elev. 735' of the Auxiliary Building in Unit 2 Loop A Feedwater piping, could potentially spray water through an open doorway into a concrete masonry enclosure in southeast comer of the Building. Water entering this enclosure would spill down an uncovered manway where it would enter and potentially flood a concrete masonry enclosure at Elev. 723'-4. The Unit 2 Loop A MSIV actuation equipment loccted in this enclosure is not qualified for submergence.

The purpose of this calculation is to establish the maximum credible flow rate down the manway and compare this to the drain capacity of the masonry enclosure at Elev. 723'-4 with both of its doors closed. Based on the resuits of this calculation, the enclosure at Elev. 723'-4 will not flood.

2.0 Methodology The first step will be to review the Feedwater piping break scenarios described in Appendix I of the USAR (Reference 2) for high-energy line breaks. Based on this review, potential breaks that could cause flooding will be identified.

The second step will be to evaluate the potential breaks to determine which break is controlling, that is, deposits the most water in the enclosure at Elev. 735'.

The last step will to determine the flow rate into the masonry enclosure at Elev. 723'-4 and compare this to its drain capacity.

3.0 Acceptance Criteria The flow rate into the enclosure at Elev. 723'-4 is considered acceptable if it is determined to be less than its drain capacity. According to Calc. ENG-ME-364 (Reference 15), the drain capacity of the enclosure, with both of its doors closed, is approximately 4196 gpm.

4.0 Assumptions There are no generic assumptions. Refer to Section 6.0 for specific assumptions.

5.0 Design inputs Drawing NF-38300-4 (Reference 3) identifies the configuration of key structural elements in the vicinity of Feedwater piping at Elev. 735' including the concrete masonry structure. Drawings NF-39223, NF-39274-1 & 2, and XH-1106-246 (References 4, 5, 6 & 7) depict the Unit 2 Loop A Feedwater piping system. This includes line sizes and materials (Reference 7).

Section 1.2 of USAR Appendix ! (Reference 2) discusses high-energy line break criteria. And, USAR Figures 11.2-1 & 5 (Reference 8 & 9)identifyfeedwater system conditions at 100% power (935 psia,427.3 F) and 25% power (1169 psia,318.3 F).

(

CENERAL COMPUTATION SHEET Northern States Power Company CALC. No. ENG-ME-370 REV. O, j

PROJECT PINGP 2 HELB Verification SHEET No.

3 oF 8

oATE 07/06/98 i

4 SUBJECT Floodino of unit 2 Loop A MslV Actuation Equipment COMP BY M. Meyer c'K'D BY /L'Jt#

---5.0 Design input (Cont'd)

These and all other design inputs are identified in the text of Section 6.0 at the location used.

l 6.0 Calculations 6.1 Identify Potential Feedwater Line Breaks 6.1.1 General Section 1.4 of USAR Appendix I discusses breaks in Unit i Feedwater piping, but not Unit 2. For Unit 2, breaks locations are similar to Unit 1 with some minor variations. Refer to Attachment A for l

postulated Unit 2 Loop A Feedwater break locations.

Attachment A identifies five breaks, a break at Node 325 in a 16" line and breaks at Nodes 275, 370,1605, and 1620 in a 4" line. These will be called "Large Breaks" because USAR Section 1.2 (Reference 2) requires assuming they have an area equal to the cross section of the pipe. For the l

2 l

16" line, which is Schedule 100 material, this would be 152.6 in. And, for the 4" line, which is z

l Schedule 80 material, this would be 11.5 in (References 7 & 10).

USAR Section 1.2 also requires postulating a design basis crack in each line at the most adverse location. The size of the cracks, which this calculation will call"Small Breaks,"is one-half the pipe l

diameter times one-half its wall thickness. For the 16" line, this would be %(13.938) x %(1.031) or 2

2 3.59 in. And, for the 4' line, this would be %(3.826) x %(0.337) or 0.322 in (References 7 & 10).

l 6.1.2 Large Break in 16-Inch Line Based on USAR Section 1.2, a Large Break can be circumferential or longitudinal. In the case of Node 325, a circumferential break would represent the worst case. Refer to Attachment B.

l Whereas a longitudinal break would spray water on walls a dozen or more feet north of the enclosure, a circumferential break would spray water in the general direction of the enclosure.

Subsection 6.2 will investigate whether this break can spray enough water into the enclosure to make it a controlling line break.

6.1.3 Large Break in 4-Inch Line The four Large Breaks postulated in this line are depicted in Attachment B. A break at Node 370 would be the furthest from the enclosure and manway. A break at Node 1605 is not a viable candi-date because spray toward the enclosure would be blocked by piping at Node 1620. A break at i

Node 275 would be worse than one at Node 1620 because it is easier to conceive a longitudinal break at Node 1620 that would place a stream of water at the center of the enclosure opening.

Subsection 6.2 will determine which of the two Large Breaks, the break at Node 275 or Node 325, represents the worse case. Though Node 275 is much closer to the enclosure than Node 325, it is also a much smaller line.

GENERAL COMPUTATION SHEET Northern States Powe-Company CALC. No. ENG-ME-370 REV.,0_

PROJECT PINGP 2 HELB Verification SHEET No.

4 oF 8

DATE 07/06/98 i

SUBJECT Flooding of Unit 2 Loop A MslV Actuation Equipment COMP BY M. Meyer C'K'D BY F 'thr

- --- 6.1.4 Small Break in 4-Inch and 16-Inch Lines A worst case Small Break in the 16"line would be near Node 275. While a break three feet further north would be nearer the enclosure, a large concrete pipe restraint block at this location would deflect any spray in the direction of the enclosure. The most worst case Small Break in the 4" line l

would be about three feet north of Node 1620, between Valves 2FW-6-1 and 2FCV-408.

However, neither of these breaks need to be considered because, compared to a Big Break at Node 275, they cannot compete. A break at Node 275 would be over three times larger and about the same distance from the enclosure.

l 6.2 Determine the Controlling Feedwater Line Break 6.2.1 Large Break in 16-Inch Line i

Attachment B identifies the location of Node 325 with respect to key structural elements in the l

Auxiliary Building. The distance from Node 325 to the center of the enclosure door is 24 feet. A l

straight line from Node 325 to the door would pass over the corner of a large section of grating.

The distance from Node 325 to the comer of the grating is 17 feet.

Node 325 is at the elbow between Valves 2FCV-466 & 2FW-5-2. A worst case circumferential break would: a) spray water toward the southwest over a large section grating, andb) have a rela-tively wide spray cone. A spray pattem aimed more to the southeast would be result in an angle I

too steep for spray to enter the enclosure opening, and one directed more toward the Shield Building would require an unrealistically wide spray cone.

l l

Even in the worst case scenario, virtually no water from the break will enter the enclosure. As can l

be seen from Attachment B, the opening in the enclosure is too far from Node 325 and too narrow a target. And, to reach the opening, water has to cross a large expanse of grating.

6.2.2 Large Break in 4-Inch Line i

The maximum flow of steam and water from a Feedwater break will occur at its maximum operating pressure (Reference 11). Based on References 8 & 9, this would occur at 25% power when Feed-water pressure is 1169 psia.

According to Figure 3 in Reference 11, the maximum mass flow rate of water for 1169 psia in a saturated condition is 8575 lbs/sec per square foot of break area. This must be adjusted forcondi-l tions in the pipe which are not at saturation temperature,563.9 F, but at 318.3 F (Reference 12).

According to References 13 & 14 flow rate is proportional to the square root of density. Thus, the 8575 needs to be increased to account for the specific volume (inverse of density) of saturated 8

water at 318.3*F vs. 563.9 F which is, respectively,0.01763 ft /lb vs. 0.02221 ft /lb (Reference 12):

Adjusted mass flow rate = 8575 x (0.02221/0.01763)'d = 9,625 lbs/sec/ft 2

l

l GENERAL COMPUTATION SHEET Northern States Power Company I

CALC. No. ENG-ME-370 REV. 0-PROJECT PINGP 2 HELB Venfication SHEET No.

5 oF 8

oATE 07/06/98 a

SUBJECT Flooding of Unit 2 Loop A MslV Actuation Equipment COMP BY M. Meyer C'K'D BY (' tRr" L

- To allow a margin for other factors such as viscosity differences and compressibility, the above 2

number is increased by five percent; 9625 x 1.05 = 10,106 lbs/sec/ft.

l 2

Based on an 11.5 in break, flow would be:

2 2 2 8

3 l

[11.5 in /144 in /ft ) x [(10,106 lbs/sec/ft x 0.01763 ft /lb) x 7.48 gal /ft x 60 sec/ min]

= 6386 gpm.

1 O.01763 ft*/lb is the specific volumeof saturated water at 318.3*F (Reference 12). The other con-versions are self-explanatory.

Some of the 318.3 F water in the Feedwater pipe would convert to steam as soon as it leaves the break and encounters room temperatures and pressures, probably about 10 percent. However, this calculation conservatively assumes all of the 6386 gpm of water flowing from the break is avail-able to be directed at the enclosure opening.

The last consideration that needs to be addressed is the fraction of the 6386 gpm that could reasonably be expected to enter the enclosure opening. While it could safely be assumed that some water will fall short of the opening or hit masonry to the left or right of the opening, thiscalcu-lation conservatively assumes all of it enters the enclosure.

6.3 Establish Flow Rate into Enclosure at Elev. 723-4 in addition to spilling back out the 6'-0 long door opening, water entering the enclosure would spill over a 5'-6 long perimeter around the manway. Though the manway's perimeter is actually 8'-6, the northern 3'-0 of the opening is inaccessible due to a 3%" high tceolate.

Water would also drain through cracks around ductwork on the south end of the enclosure. The effective perimeter of these cracks is 2'-0. And, the " wetted" perimeter of all openings that drain out of the enclosure totals 13.5 feet. Of this,7.5 feet empty into the enclosure at Elev. 723'-4. As such, the flow rate into the lower enclosure would be 7.5/13.5-x 6386 or 3548gpm. Since this is considerably less than the 4196 gpm drain capacity of the enclosure, it will not flood.

7.0 Conclusions The worst case Feedwater piping break is in a 4"line that bypasses regulator valve 2FCV-466. A large break in this line could spray as much of 6386 gpm through the opening in the west wall of the concrete masonry enclosure at Elev. 735'. However, almost half of this would run back out the opening and only 3548 gpm would spill into the enclosure below, at Elev. 723'-4. Since the drain capacity of this enclosure is 4196 gpm, Loop A MSIV actuation equipment in this enclosure will not be damaged by flooding.

l t

CENERAL COMPUTATION SHEET Northern States Power Company l

CALC. No. ENCrME-370 REV. 0 j

i PROJECT PINGP 2 HELB Venneadon SHEET No.

6 oF 8

i DATE 07/06/98 A

SUBJECT Flooding of Unit 2 Loop A MSIV Actuadon Equipment COMP BY M. Meyer C'K'o BY /' 'O'T j

i 8.0. References

1. ER 1-98-05, Inoperability of Actuation Logic for Main Steam Isolation Valves in Certain Flooding Conditions from a Feedwater Une Break, Supplement 1, May 22,1998

2. USAR Appendix I, Section 1.2, Criteria forPictection Against Pipe Rupture I

i

3. PINGP Drawing NF-38300-4, Auxiliary Building Concrete - Operating Floor Outline Plan, Revision l-l

4. PINGP Drawing NF-39223, Flow Diagram Feedwater System, Revision AV f

1

5. PINGP Drawing NF-39274-1, Feedwater Piping Unit 2, Revision N l

6. PINGP Drawing NF-39274-2, FeedwaterPiping Unit 2, Revision K

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7. PINGP lsometric XH-1106-246, FeedwaterPiping, Revision B

8. USAR Figure 11.2-5,139905 KW Gross load Heat Balance (25% Power)

9. USAR Figure 11.2-1,559592 KW Gross Load Heat Balance (100% Power)

10. Marks' Standard Handbook for Mechanical Engineers, McGraw Hill,10* Edition

11. F. D. Moody, " Maximum Flow Rate of a Single Component, Two-Phase Mixture," Transactions of the ASME Jaumalof Heat Transfer, pp.134-142, February 1965

12. ASME Steam Tables, American Society of Mechanical Engineers,1967

13. Technical Paper No. 410, Flow of Fluids through Valves, Fittings and Pipe, Crane Company,

p. 2-9,1973

14. M. M. El Wakil, Nuclear Heat Transport, Intemational Text Book Company, pp. 344-353,1971 15.PINGP Calculation ENG-ME-364, Unit 2 Loop A MSIV Junction Box Area Water Outflow, Revision i

16. FINGP Calculation ENG-ME-357, HELB Break Location Section, draft.

9.0 Attachments A. Node Diagram B. Plan View of FeedwaterPiping Area 1

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