ML030910600

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Slides: Expansion Cooling Modeling Presented by Fenco at Public Meeting
ML030910600
Person / Time
Site: Davis Besse Cleveland Electric icon.png
Issue date: 05/22/2002
From:
- No Known Affiliation
To:
Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0018
Download: ML030910600 (19)
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Text

t s Expansion Cooling Modeling Overview I

' Approach is to determine extent of cooling along the leak path as a function of leak rate using

  • Heat required to vaporize all leaking liquid is the leak rate times the enthalpy increase (from primary water at 613 Btu/lb to saturated steam at atmospheric pressure at 1 150 Btu/lb)
  • FEA heat transfer model of conduction within head materials with convection boundary conditions from primary coolant and to space above
  • Correlations for two-phase and single-phase heat transfer coefficients along the leak path
  • ~Extent of cooling affects important parameters including
  • Location of concentrated liquid
  • pH
  • FAC susceptibility Technical Assessment of Davis-Besse Degradation - May 22, 2002 35

Expansion Cooling Modeling Magnitude of Heat Sink 1=

111 III 11111 jjjlwgmmm

 1"Mil A2=

O-1,000,000.

100,000. - _

I 10,000.-

1,000.-

100.1-

-0.

^

1. M-0.1 '

0.000001 0.00001 0.0001 0.001 0.01 0.1 Leak Rate (gpm) 1 Technical Assessment of Davis-Besse Degradation - May 22, 2002 36

IT Expansion Cooling Modeling

  • YF -32.286 A-ZS-6.591 PRECISE HIDfl FEyoe z

Terhnical A!ssessment of Davis-Besse Degradation - May 22, 2002 37

Expansion Cooling Modeling Finite Element Analysis of Head Heat Transfer r = 1: 11





 2111 11 72111 EEEEEEMMEMM=

ANSYS 5.7 APR 2 2002 12:00:37 LPLOT NO.

3 ELEMENTS

~

~~-~4

~

~.

OMINn--.5682-05 QMAX=0 YV -.700326

~

,..~.

~ ~ZV

--. 189006

  • DIST-16.541

,:Y~

  • XF -107.147
  • YF

-32.286

~

A-ZS-6.591 f

'~

rPRECISE HIDDEN

~-j~4 ~-

-1.5682-05

.4 *

.441E___

gm -. 3152-05 E

-.252E-05 1262-05

-.631E-06 0

Uniform Surface Heat Sink Along the Leak Path Assumed Technical Assessment of Davis-Besse Degradation - May 22, 2002 38

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Expansion Cooling Modeling Finite Element Analysis of Head Heat Transfer Y

Z_'L.V TEMP SMN -603.37 SMX -604.996 603.37 603.551 603.731 603.912 ME3.

604.093 604.273

-71 604.454 604.635 604.815 604.996 Example Calculation for Low Leak Rate (18.6 Btulh Heat Sink:

complete vaporization of 7x105 gpm leak)

Technical Assessment of Davis-Besse Degradation - May 22, 2002 39

6>

0 Expansion Cooling Modeling Finite Element Analysis of Head Heat Transfer Iz=_=

rI1 1-1 I,7"TMOI' III Y~ % -z TEMP SMN =514.122 SMX -604.939 514.122 524.212 534.303 544.394 Km 55448 564576

=-

574.667 EJ 584.758 594.849 604.939 Example Calculation for Moderate Leak Rate (1860 Btulh Heat Sink:

complete vaporization of 0.007 gpm leak)

Technical Assessment of Davis-lBcsse Degradation - May 22, 2002 40

Itl(T C)

. Expansion Cooling Modeling Finite Element Analysis of Head Heat Transfer 650 Average Metal Surface Temperature Along the Leak Path I-.

0

.40 0

.4 a-

'Ia.2 1,

04 1.4 V4, 600 550 500 450 400 350 300 250 200 A45 Deg alf Asre (h -600) 045 Deg HalrArc(h-110)

A 22 5 Deg Hair Arc (h -600)

  • 225 Deg Half Am (h-110)

T -.0 02537Q + 604.55678 Sink irposed on total 90° arc surface

,h on inside head - 600 Btu/h.fl 2-°F T - -0 02670Q + 604 55110 I

\\Sink imposed on total 90° arc surface h on inside head -

110 Btu/h-fl2-TF T = -0 03505Q + 604.54874 Sink imposed on total 45° arc surface h on inside head - 600 Btu/h-fl2-°F T - -003647Q + 604 39390 /

\\

\\\\

Sink imposed on total 45' arc surface on inside head - 110 Btu/h-f2°F 0 2,00 4,0\\,0\\,00 1,0 200 400 1,

0 2,000 4,0w0 6,0w0 8,000 lo,ooo 12,000 14,000 16,00o 5SDIO Magnitude of Heat Sink, Q (Btulhr) 1

¶'"?echnical Assessment of Davis-Besse Degradation - May 22, 2002 41

Volume of Boric Acid Deposits on the Vessel Head Methodology

>' Integrate the leaking boron mass over the fuel cycle

> Calculate the volume of leaked boron based on the density of boric acid (H3BO3) or boric oxide (B203) crystals, conservatively assuming no porosity

> The fraction of precipitated boron compounds that deposits on the head adjacent to the leaking nozzle may be affected by

  • Droplet entrainment into the steam flow

Technical Assessment of Davis-Besse Degradation - May 22, 2002 48

Volume of Boric Acid Deposits on the Vessel Head

. Example Integration of Boron Mass

.mm INUM-_

NWENNNM--

25,000

  • M x

U

._O cl 4._

rA t0 0

0 20,000 15,000 10,000 5,000 0

0 1

2 3

4 5

6 EFPYs After Start of First Cycle Technical Assessment of Davis-Besse Degradation - May 22, 2002 49

  • The end results depend upon the rate of concentration and drying If drying is fast, boric acid powder will result If drying is slow, a single irregularly shaped mass is likely

> Molten boric acid

/

  • When heated above 340-3650F, solid boric acid melts to form a highly viscous liquid that will fuse into a single mass and flow under the influence of gravity
  • Molten boric acid can contain 8-14% water by weight and is known to be corrosive

.> Solid boric oxide I

  • Above 302'F boric acid is subject to a dehydration reaction to form boric oxide
  • The resultant crystalline mass is an anhydrous, white, opaque, non-glasslike, stony solid

> Molten boric oxide >

  • Above 6170F boric oxide begins to soften and at about 8420F becomes a highly viscous liquid Technical Assessment of Davis-Besse Degradation - May 22, 2002 50

I )

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C)

Boric Acid Morphology and Properties Key Temperature Behavior 100%

0 0-. _

¢ Po 80%

60%

40%

20%

0%

0 100 200 300 400 Temperature (0F) 500 600 Technical Assessment of Davis-Besse Degradation - May 22, 2002 51

Boric Acid Morphology and Properties Partial Vapor Pressure 1.. r&UawISEm7_M11" 11 250 200 -

Calculated Using Raoult's Law u' 150 C 100 ALm 50 inn b

Ann 4A0n 5s0 600 700 800 900 Technical Assessment of Davis-Besse Degradation - May 22, 2002 52

e'.-

I Boric Acid Morphology and Properties General pH Effects without Large Local Cooling 0

NUMImm-

> For low concentration factors, the solution becomes slightly alkaline, having a small effect on crack growth rates

> For high concentration factors, the solution becomes acidic with a high-temperature pH of 4.5 according to MULTEQ calculations

> The initial high ratio of crevice surface area to volume may allow some buffering by the iron in the head material

> Precipitation of complex lithium and boron compounds occurs and tends to limit pH swings Technical Assessment of Davis-Besse Degradation - May 22, 2002 53

'-N MULTEQ Modeling Three Main Flow Models Available Step 1: Equilibrium Calculated Using Step 2: Vapor and/or Solids Removed Variable Volume Mass Equilibrium Vapor Constant Liquid Phase Flow Out Water Massl Solution

~

olid Phases, S~i;;/

US Rem ain Flow In Water Mass Flow In (Solution)

Equals Water Mass Flow Out (Vapor)

Flowing Static Static with Removal Technical Assessment of Davis-Besse Degradation - May 22, 2002 54

0, MULTEQ Modeling

^. Available Control Volumes IN__._

I a

Only Vapor Flow Out Control Volume with Constant Liquid Mass Only Solution Flow In 0

0 G

0o1s Only Vapor Flow Out Control Volume with Constant Liquid Mass Q

Control Mass at Higher Concentration Factor Control Mass at Lower Concentration Factor I

I IPI ZLP Only Solution Flow In

/V Technical Assessment of Davis-Besse Degradation - May 22, 2002 55

6Ž Example MULTEQ Calculation pH in a Flowing System at 10000 C)

MmJagaikjag 7

6 L

5 4

3 0.08 0.07 0.06 0.05 X I

004 :0 0.03 S 0.02 0.01 2

I 0

1.E+00

_4 0 I.E+06 I.E+0I I.E+02 I.E+03 I.E+04 I.E1+05 Concentration Factor Technical Assessment of Davis-Besse Degradation - May 22, 2002 56

(T)

I

Molten Boric Acid Orthoboric Acid-H3B03 Metaboric Acid-HBO2 Boric Oxide B203

> Corrosion in molten boric acid largely unstudied

> Degradation:

  • Melting point above the degradation point Orthoboric acid: melts at 170.90C (340TF); degrades to metaboric acid at 169.60C (337TF)

Metaboric acid: melts at 23600 (4570F); degrades to boric oxide at 23500 (4550F)

  • Degradation reaction is slow
  • Effect of degradation products on corrosion largely unknown (degradation probably lower in boric oxide, B203, than in either acid)
  • Degradation products highly hygroscopic Analysis of deposits not likely to indicate their at-temperature composition

' Solubility issues largely unstudied

  • Miscibility limits unknown
  • For pH calculations, molten boric acid could be an additional precipitate
  • Degradation products not included in MULTEQ Technical Assessment of Davis-Besse Degradation - May 22, 2002 57

O r

-N

(

I Molten Boric Acid Molten Salt Corrosion

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.Imfa

> Molten salt corrosion is electrochemically very similar to aqueous corrosion, depending on a reaction couple:

  • Fe 4 Fe2+ anodic reaction 02 -

OH-or H+ 4 H2 cathodic reaction

  • Additional cathodic reactions unlikely in molten boric acid
  • Typical molten salt corrosion occurs through de-passivation Not relevant since LAS and CS are not passive in acidic media

. > Acceleration possible due to high conductivity of molten salts

  • Unlikely to lead to a qualitative difference relative to highly concentrated solutions Technical Assessment of Davis-Besse Degradation - May 22, 2002 58

'(Th 0.

Molten Boric Acid Issues Molten Salt Corrosion (continued)

>- Solubility of corrosion products likely to be less in molten boric acid than in water

  • Leads to lower corrosion rates

>- Molten boric acid corrosion likely to be significantly slower than corrosion in aqueous solution

  • Lower 02 and He concentrations (slower cathodic reactions)
  • Possibly lower conductivity
  • Likely lower corrosion product solubility (slower anodic reactions)

>- Corrosion in molten boric acid is a particular case of corrosion in boric acid solutions, not a separate phenomenon Technical Assessment of Davis-Besse Degradation - May 22, 2002 59

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