ML20127B055

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Requests Addl Info Re Ice Condenser Containment Bldg Capabilities to Withstand Reverse Pressure Differentials Developing After Combustion of Large Quantities of Hydrogen
ML20127B055
Person / Time
Site: Catawba  Duke Energy icon.png
Issue date: 11/21/1983
From: Butler W
Office of Nuclear Reactor Regulation
To: Adensam E
Office of Nuclear Reactor Regulation
Shared Package
ML20125C450 List:
References
FOIA-84-927 NUDOCS 8312060236
Download: ML20127B055 (13)
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NOV 2 : 1933 MEMORANDUM FOR: E. Adensam, Chief, Licensing Branch #1, DL FROM: W. R. Butler, Chief, Containment Systems Branch, DSI

SUBJECT:

REQUEST FOR lilFOR1ATION REGARDING HYDROGEN CONTROL FOR CATAWBA, UNITS 1 & 2 As part of the Containment Systems Branch (CSB) review of hydrogen control measures for ice condenser plants, we have identified the need for additional information regarding the capability of the Duke Power Company's ice conden-ser containment buildings to withstand reverse pressure differentials which may develop following combustion of large quantities of hydrogen.

Specifical19., . the combustion of hydrogen removes oxygen from the containment atmosphere and in the long tenn may result in containment pressures lower than design, i..e, a reverse pressure differential greater than the 1.5 psid design value may develop. The Duke plants, to our knowledge, have no vacuum breaker system or other automatic means for relieving this reverse differential pres-sure. Therefore, we request that the licensee provide details and analyses, on the Catawba application, to show that reverse pressure differentials resulting from combustion of large quantities of hydrogen will not unduly threaten cen-tainment integrity. The licensee's submittal should include:

1) calculations of the reverse pressure differentials which would result from complete combustion of an amount of hydrogen cor-responding to a 75% metal-water ' reaction, and the subsequent cooling of the containment atmosphere.
2) calculations of the ultimate external pressure capacity of the containment shell, including discussions of (a) the calcula-tional method and material properties used; and b) the pressure retention capabilities of the penetrations for reverse pressure loads.
3) a description of the design provisions regarding automatic and manualmeans for relieving reverse pressure differentials.

. 4) a discussion of the operating procedures concerning monitoring of containment pressure, and operator actions to relieve reverse pressure differentials following onset of an accident.

We request that the above. detailed concerns be transmitted to the Duke Power Company. Duke should also address the applicability of the responses to these concerns, to the McGuire plants.

K N W. R. Butler, Chief g 37 ,g , Containment Systems Branch Division of Systems Integration cc: See'page 2 [

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E. Adensam fly,r a gg cc: R. Mattson R. Houston B. Clayton K. Jabbour C. Tinkler 9

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1) calculations of the reverse pressure differentials which would result from complete combustion of an amount of hydrogen cor-responding to a 75% metal-water reaction, and the subsequent cooling of the containment atmosphere.

2) calculations of the ultimate external pressure _ capacity of the containment shell, including discussions of (a) the calcula-tional method and material properties used; and b) the pressure retention capabilities of the penetrations for reverse pressure loads.

3) a description of the design provisions regarding automatic and manualmeans for relieving reverse pressure differentials.
4) a discussion of the operating procedures concerning monitoring of containment pressure, and operator actions to relieve reverse pressure differentials following onset of an accident.

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-January 26,,1984 ,

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H.- B. Tucker, Vice President Nuclear Production Department Attn: G. A. Copp

Subject:

McGuire Nuclear Station Containment Hydrogen Mitigation Responses to NRC Questions Attached are responses to several recent NRC questions and requests for addi-tional.Information for inclusion in the Red Book. These responses completc Design Engineering action on containment hydrogen mitigation.

In ' order .to complete the Red Book, the following figures marked "Later" should be replaced by the indicated Duke drawing-

- Figure 31A delete this figure and Indicate that the Information has been incorporated ,Into Figure 3.1 A-6 Figure 3.lA CNEE 0165-02.01 and CNEE 0165-02.02 Figure 3.1A CN 1735-02.01 The following figures should be updated as Indicated:

Figure 3.4 delete and Indicate that the Information is now incorporated i-

  • Into Figure 3.4-7 Figure 3.4 replace with MCEE 0162-02.01 and MCEE 0162-02.02 Figure 3.4 delete

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Figure 3.4 replace with MC 1735-02.01 These new McGuire drawings are on limited distribution in the NSM flies. Please call me if you need further assistance in preparation of the appropriate revision to the Red Book.

5. K. Blackley, Jr., Chief Engineer Mechanical & Nuclear Division
b. N . Ltddo6 A. L. Sudduth, Design Engineer 11 AL5/kh

Attachment:

! cc w/atta: C. L. Sansbury, R. E. Miller,/ R. O. Sharpe cc w/o atta: F. G. Hudson ,

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1. With regard to the CLASIX code, the staff has previously requested ~clarlfl-cation of the structural heat sink heat transfer models. The following pertinent points have been derived from the responses:
1) Heat transfer is based on a temperature difference determined by ( bulk - wall).
11) Heat transfer. coefficients for degraded core accident analysis are determined from a natural convection (stagnant) correlation applicable to condensation heat transfer.

111) CLASlX does not explicitly model mass removal due to condensation heat transfer.

Based on the description of the CLASIX structural heat sink model, it appears that the CLASIX model differs dramatically from generally accepted approaches and is not, as is claimed, consistent with standard methods such as those used in CONTEMPT. The differences are related to the treat-ment of the three items cited above. By comparison, previously accepted approaches are characterized by the following:

f 1) Heat transfer is based on (T -T w ), when the surface temperature oftheheatsinkislessthagay,, ; p.e., T g) < Tsat'

) II) Heat transfer coefficients are based on condensation only when Tg ,j; < Tsat*

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Condensed mass removal is based on condensation heat transfer with a 0

  • sf provisions for revaporizing a small fraction of the condensate.

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A more detailed description of accepted practice is contained in NUREG-0588 --

t'\ and NU'"G/CR-0255.

The effect of the CLASIX models would appear to be the de-superheating of the atnosphere too rapidly thus ' reducing gas temperatures and possibly altering the combustion characteristics.

Based on the above discussion, provide Justification for the models In-corporated in CLASIX or provide the results of analyses with acceptable models as outilned above. The analyses should encompass selected senst-tivity studies to assure that the effects of the changes are determined for both containment integrity and equipment survivability considerations.

Respnse:

The following additional Information is provided concerning the method by which CLASIX models heat transfer to the passive heat sinks.

1. A close examination of the CLASIX code reveals that all heat transfer for the cases reported in our analysis used heat transfer coefficients based on the stagnant portion of the Tagami correlation:

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F 2 + 50 (Mass of .noncondensables) -

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Table 1 compares this value of heat transfer coefficient with the Uchida. correlation used in CONTEMPT 4, Reference (2). It can be seen that, for 'the small break LOCA case analyzed by Duke Power, CLASIX consistently selected conservative convective heat transfer coefficients.

At no time did CLASIX use the correlations for natural convection of the form Nu = f (Pr, Re) due to the program logic associated with the particular heat transfer option selected for our analysis.

2.

The use of Tbulk' rather than T , to compute the temperature diff'rence e '

appropriate to passive heat sink heat transfer is supported by experi-mental and analytical work. This type of heat transfer is dominated by a boundary layer containing "noncondensables, particularly in an Ice containment where operation of the air return fans assures that a continuous source of noncondensables is available in all compartments.

An examination of CLASIX output reveals that typical values of the mass ratio of noncondensables to steam is greater than 1.5, even immediately following a hydrogen burn. As discussed in reference (1), use of T sat rather than T bd t calculate heat transfer in the presence of non-condensables is " inappropriate."

3. CLASIX does not remove mass from the atmosphere by condensation at the walls. There is therefore no credit taken for condensing heat transfer and no atmospheric temperature decrease due to energy removal by conden-

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sate revaporization. This does not affect the period of most interest in and > sis of hydrogen burning in containment - the ' period during and '

immediately following a hydrogen burn during which the passive heat sinks function to desuperheat the atmosphere. Energy deposition in the heat sinks of coinpartments where hydrogen burning occurs causes T,g g to rise to temperatures above T,, . These wall temperatures remain above satura-tion for the duration of the period during which hydrogen burning occurs.

Therefore no condensing heat transfer can take place on heat sinks in compartmentsw ' here hydrogen burning occurs, and the fact that CLASIX cannot model wall condensation is irrelevant. The principal cooling mechanism for the lower compartment atmosphere is the flow from the upper compartment due ' to operation of the air return fan. ,

in summary, it is apparent that CLASIX handles convective heat transfer in a conservative manner consistent with the physical processes occurring in the containment atmosphere. As noted in Table 1, the heat transfer coefficients are lower than those used in the Uchida correlation of CONTEMPT 4. The use of the temperature difference between the wall and 9 +

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'present during the period of hydrogen burning. We conc t no further CLASIX analysis is required. *

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Re fe rences :

(1) Lamkin, D., A Koestel, R. Gido, and P. Baranowsky, Containment Main Steam Line Break Analysis for Eauf pment Qualification, NUREG/CR-1511, June, 1980.

(2) Cheng, T. C. , L. Metcalfe, J. Hartman, W. Mings, and A. Crall, CONTEMPT 4/ MOD 3, A Multicompartment Containment System Analysis Program, NUREG/CR-2555, December, 1982.-

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Table i Heat Transfer Coefficients Mass of steam H (CONTEMPT 4)

Mass of-noncondensables (BTUH /ft2 (CLASIX{F) hr (BTU /ft2 hr U)

F 0.02 3 2 2- 0.05; 4.5 8 0.10 7 14 0.20 12 21 0 33 18.7 29

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1. 2 5. 64.5 98

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  • According ' to data f rom CLASIX results, the mass ratio before, durings and after hydrogen burning Ile in this range. The CLASIX heat transfer coef ficients are about 35% less then.those used In CONTEMPT 4 in this range.

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- Questlon:

2. Provide a complete evaluation of fan (both air return and hydrogen skimmer as applicable) operability and survivability for degraded core accidents.

In this regard discuss the following items:

a. The identification of conditions which will cause fan overspeed, in terms of differential pressure and duration, and hydrogen combustion events.
b. The consequences of fan operation at overspeed conditions. The response should include a discussion of thermal and overcurrent breakers in the power supply to the fans, the setpoints and physical locations of these devices, and the fan loading conditions required to trip the breakers.
c. Indications to the operator of fan inoperability, corrective actions which may be possible, and the times required for operators to complete these actions,
d. The capability of fan system components to withstand differential pressure transients (e.g., ducts, blades, thrust bearings, housing),

in terms of limiting conditions and components.

, Response:

This question was addressed previously by Duke Power. Refer to pages 7.0-123 and 7.0-124 of the Red Book.

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Questlon:

3 Provide an evaluation of the ultimate capability of Ice condenser doors to withstand reverse differential pressures.

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Res ponse : '

The top deck blankets rest on grating. In a reverse differential pressure situation, the grating would be the primary struct .ral component if the closed blankets were pressed down on the grating. Calculations performed by TVA show a nominal static failure loading of 4 psi. The limiting component for the intermediate deck is the door which is conservatively estimated to fall at a static loading of 6 psi.

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Any reverse differential pressure across either the top or intermediate decks 3 would be mitigated by the existing bypass area and any additional bypass area created by flow through the Ice condenser which displaces the top deck blankets laterally. However, our previous analysis has demonstrated that for all reason-able assumptions on the course of events associated with a recoverable degraded core,, hydrogen burning is precluded in t!Le_ upper _._compar-tment. Therefore, we

/ do not consider the case of reverse differential pressure on the ice condenser

/ doors to represent a realistle loading conditlon.

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Additional Information concerning contalment conditions following the hydrogen burn period:

It has been postulated that when the containment had been cooled down to ambient temperature following hydrogen burning that the pressure in containment would become subatmospheric. In order to check this postulation, the following calculations were made:

Taking the' Initial conditions in the containment at the start of the small break LOCA from CLASIX input, we note the following atmospheric constituents mass of oxygen - 22265 lbm  % :- 6 % )

mass of nitrogen - 73627 lbm Ng s x,jtg j y / f;, f M mass of hydrogen -

0 lbm i /

mass of water vapor - 658.1 lbm %c= ?7

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If we assume that 1500 lbm of hydrogen is added to the containment and burned, then we consume 12000 lbm of oxygen in burning. Also, at the end of the hydrogen burn period, the air return fans and containment sprays'have served to mix the atmosphere and create 1,00% relat'Ive humidity" throughout containment.

Assuming that there is no net reduction in available free space in containment (a conservative assumption which assumes no flow from the engineered safeguards systems outside containment into either the high pressure injection or contain-ment spray systems), we can calculate the atmospheric constituents in containmer't when the containment is cooled to ?OO T. T $ 44. - [

partial pressure of H 2O at 100 F = .9503 psia MA O"

-r corresponding amount of water vapor In air = 3650.4 lbm y '7< 3 '

mass of oxygen = 22265 - 12000 = 10265 lbm nW mass or nitrogen is unchanged mass of hydrogen = 0 on a nolar basis:

n (water) = 202 9 n (nitrogen) = 2629.5 n (oxygen) = 320.8 g' rp

. final pressure at 100 F =

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p , (202.8 + 2629.5 + 320.8)(10.73)(560) -

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P = 14.8 psia ,

4 I. therefore only a slight vacuum is drawn in containment /upon containment cooldown, well within the containment reverse pressure capability.

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S It is not difficult to see why this is true. In the preaccident containment, most volumes contain little water vapor: cost accident conditions will have a saturated atmosphere in all contain .ent compartments due to the action of the containment spray and the primary coolant release from the break, if one makes the more realistic assumption that the containment sump water level will rise due to injection of water from the Refueling Water Storage Tank via the high and low pressure injection systems and the containment spray, then the final pressure upon containment cooldown will be higher. Finally, the assumption that all 1500 lbm of hydrogen released to corealnment will burn is unrealistically conservative. Once the hydrogen concentration falls below 4% by volume, further burning will be impossible, and the remainirg hydrogen will be removed by the electric hydrogen recombiners over a period of several days.

A system to control containment pressure is available to the operator, if containment pressure falls below -0.25.psig, an alarm sounds in the control r The operator can then _ manually add _ air f rom the Auxiliary Building to e containment to restore pressure to atmospheric. This alarm provides substantial margin to the containment design reverse pressure of 1.5 psig.

Information concerning the reverse pressure capability of containment is con-i tained in the Catawba FSAR, Section 6.2.1.1.1. -The system which the operator

\ uses to control containment pressure and mitigate a vacuum condition in contain-ment is described in the Catawba FSAR, Section 9.5.10.

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