ML20033C708

Forwards Hydrogen Control Section Request for Addl Info Re Hydrogen Ignition Sys

ML20033C708
Person / Time
Site:	Grand Gulf
Issue date:	11/06/1981
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Mcgaughy J MISSISSIPPI POWER & LIGHT CO.
References
NUDOCS 8112030705
Download: ML20033C708 (11)

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Docket File NRC PCR LB#2 Reading LOCAL PDR ASchwencer TERA Docket Nos: 416 MService NSiC and 50-417 DHouston TIC OELD ACRS'(16)

I&E (3)

Mr. J. P. McGaughy Jr.

CTinkler Assistant Vice. President Pltatthews tiuclear Production JKennedy NOV 6-19 81 tif ssissippi Power & Light Company SIsrael Post Office Box 1640 Jackson, Mississippi. 39205

Subject:

Request for Additional Infomation - Hydrogen Control Grand Gul f Nuclear Station, Units 1 a 2 U

-In the perfomance of the Grand Gulf licensing review,.the staff has identified concerns in regard to hydrogen control. The infomation that we renuire is identified in the enclosure.

We request that you provide the information in your submittal on this subject scheduled for December 15, 1981.

If you re' quire any clarification of this request, please contact H. D. Houston, Project Manager, at (301) 492-8430.

Sincerely, A. Schwencer, Chief Licensing Bisnch flo. 2 Division of Licensing

Enclosure:

Request for Additional Infomation O

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Docket File NRC PDR.

LB#7 Reading Local PDR ASchwencer TERA MService NSIC DHouston TIC Docket Nos: 50-416 OELD

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Mr. J. P. McGaughy Jr.

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Assistant Vice President Nuclear Production Mississippi Power & Light Company Post Office Box 1640 Jackson, Mississippi 39205 i

Subject:

Request for Additio'nal Infomation-liydrogen Control, Grand e

Gulf Nuclear Station, Units 1 & 2 In the perfomance of the Grand Gulf licensing review, the staff has identified concerns in regard to hydrogen control. The infomation that we require is identified in the enclosure.

We request that you provide the infomation in your subraittal on this subject scheduled for December 15, 1981.

If you require any clarification of this request, please contact M. D. Houston, Project flanager, at (301) 492-8430.

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Sincerely, A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing

Enclosure:

Request for Additional Infomation cc: w/ encl:

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OFFICIAL RECORD COPY usom im-mmo (unc ronu ais om uncu mo

Mr. J. P. McGaughy Assistant Vice President Nuclear Prbduction-Mississippi Power & Light Company P. O. Box 1640 Jackson,-Mississippi 39205

. cc: Robert B. 'McGehee, Esquire Wise, Carter, Child, Steen and Caraway P. O. Box 651' Jackson, Mississippi 39205 Troy B. Conner, Jr., Esquire Conner and Wetterhahn 4

1747 Pennsylvania Avenue, N. W.

Washington, D. C.: 20006

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f Dr. D. C. Gibbs, Vice President Middle South Energy..Inc..

225 Baronne Street P. O. Box 6100 New Orleans, Louisiana 70161 Mr. John Richardson ~

Mississippi Power & Light Company

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P. O. Box 1640 Jackson, Mississippi 39205 Mr. R. Trickovic, Project Engineer Grand Gulf Nuclear Station r-Bechtel Power Corporation Gaithersburg, Maryland 20760 Mr. Alan G. Wagner Resident Inspector Route 2, Box 150 Port Gibson, Mississippi 38150 4

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x ENCLOSUREFORGRAND'Gl[LFHYDROGENIGNITIONSYSTEM 1)

With regard to surveillance testing of the Hydrogen Ignition System (HIS):

a)

How will the system be tested? Specifically, what indicates that a particular igniter is or is not functioning properly.

b)

'Specify the frequency of testing.

c)

Are hydrogen detectors to be used as part of the HIS? If so. please specify the types of detectors, number, location of sampling ports, system response time, and testing format and frequency.

2)

Please provide construction drawings for several " typical" igniter mounts in the wetwell and containment regions. Also, provide a list of the ap-

. proximate elevation coordinates for each igniter in these regions and the corresponding elevation coordinates of the nearest ceiling.

3)

With regard to the CLASIX-3 calculations to determine the containment at-mosphere pressure and temperature response:

a)

Justify the values of the following parameters and/or coefficients used in the CLASIX-3 calculations:

1) beam lengths

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11) gas emissivity, absorptivity, heat capacity, heat conductivity, and viscosity iii) convective heat transfer rates and coefficients i

iv) wall thermal properties (emissivity, absorptivity, heat capacity, conductivity) v) flow coefficients (define and justify values) vi) spray droplet fall time.

vii) heat sink surface areas (identify location) viii) upper pool surface thermal properties s

l ix) painted surface thermal properties ENCLOSURE m

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b)

What is the form of the momentum equation used to link the control volumes?

c)

What model is used for heat transfer to and evaporation of the spray droplets?

d)

Why was the number-mean diameter (230 pm) used for th~e' spray. drop-lets instead of the mass-mean diameter (370-400 pm)?

e)

How are the various floor gratings treated thermally? Are they as-sumed to be a lumped mass? Are they assumed to be thermally iso-lated from the rest of the floor and/or wall's?

f)

Are the presence of liquid layers on walls and condensation heat i

j transfer treated consistently with radiative heat transfer to the walls?

g)

What fraction of the spray carryover (from containment to the wet-well) is assumed to remain as a spray and what fraction is assumed to be in liquid layers?

h)

What is the nominal elevation of the top of the suppression pool during an accident with and without sprays activated? What is the level of the upper pools under similar circumstances?

i)

-How and under what conditions are the upper pools drained into the suppression pool?

j)

What is meant by " satisfactory" convergence of the CLASIX-3 solu-tions?

k)

Where have the sensitivity studies for CLASIX, mentioned.in section C.3 of the June 19 final report, been published (list references)?

1)

Please provide an estimate of free volume and surface areas (with appropriate thermal property estimates) as a function of elevation

for the annular wetwell region for the following discrete eleva-tion ranges: 110 - 135 ft.,135 - 161 ft.,161 - 209 ft.

m)

During normal operation, does the equipment " hatchway" (at azimuth angle 225', radies 42 - 62 ft.) have gratings in it? If so, at what elevationt?

n)

How are the heat and mass transfer rates (due to condensation and evaporati-,.: from the compartment atmosphere to the suppression pool 4

and upper pools determined?

4)

Regarding the containment atmosphere mixing mechanisms:

a)

Describe the flow rates of the ventilation system in the containment /

wetwell regions.

b)

What are the elevations and radial positions df the spray rings?

c)

Which spray rings operate when a single RHR loop is operating and what is the flow rate under such conditions? Does the spray water 4

contain additives?

d)

Describe any sprays, fans, or other systems that could move air in the annular wetwell region and estimate the velocities in the region due to these sources.

5)

Considering the actuation criteria of safety systems:

a)

Under what conditions are the sprays activated?

b)

How long after the sprays are activated does the spray system attain full flow rate?

l l-c)

When during an energency situation would the'HIS Se activated?

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d)

. hhat role would hydrogen detectors play in actuating the HIS?

e) ' What role, if any, would the hydrogen recombiners play with respect -

to the HIS?

6)

Are there any accident sequences that might lead to the introduction of hydrogen and steam directly into containment without having passed through the suppression pool?

7)

Briefly explain the workings of the "drywell purge system" including

" purge compressors" and " vacuum breakers." Estimate flowrates from this system during an accide'nt. Briefly explain the workings of the "back up containment purge system."

8)

Verify that all enclosed regions of the containment are served by re-dundant igniters.

9)

Discuss the effect of submergence of igniters.

For those igniters which will continue to be' necessary describe the testing which will be perfonned to assure igniter performance. Such testing should be completed prior to conclusion of a staff interim evaluation.

1,0)

It is our position that the minimum igniter surface temperature be raised above your specified value of 1500*F. to a value of approximately 1700*F.

It is also our position that the voltages remain as close to 12V as possible.

Therefore discuss your plans for increasing the minimum temperature specifi-l cation of the igniter.

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. 11)

Discuss whether the power cables to the igniter are routed in conduit and describe the heat shrink used on the connection to the igniter as-sembly power leads.

12)

The analyses of a stuck-open ralief valve assumes a uniform release and distribution of hydrogen above the suppression pool. Consider the likeli-hood and consequences of localized injection of hydrogen into the pool (e.g., a single stuck-open safety relief valve).

Also, for the cases of a pipe break in the drywell, discuss the mixing of hydrogen in the various regions of the containment including the effects of interior structures.

13)

Provide an evaluation of the potential and consequences of flame acceler-ation in the various containment regions including consideration of cir-cumstances leading to a transition to detonation.

14)

Provide an analysis of the concomitant effects of the largest conceivable detonation which could occur. Demonstrate that the effects of such an event could be safely accommodated by structures and essential equipment.

Also, provide an estimate of the limiting size of a cloud of detonable gas with regard to the structural capability of the containment shell.

15)

Provide verification of the CLASIX-3 code.

It is our position that the limited verification documented for the CLASIX code is insufficient as a basis for relying on the results of CLASIX-3 calculations.

16)

Provide the results of sensitivity studies on flame speed increasing the assumed speed to 10 and 100 times the present value (6 ft/sec) utilized e

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, in the analyses. [In recent experiments at' McGill University, flame velocities exceeding 150 m/s were measured for a 10% concentration of hydrogen in air.] For the con.puter model it may be desirable to make i

~ the flime speed a function of hydrogen concentration and compartment -

geometry (i.e., t.'1e flame would be expected to-have a highea speed at higher concentration and in more cluttered compartments).

17)

Provide the results of sensitivity studies on the hydrogen concentration criteria for. ignition and propagatio'n. A suggested range of values 4

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would include ignition at concentrations up to 10 v/o H and propagation g

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at concentrations of 4-5 v/o H. Also, provide the results of calcula-2

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tions to determine the sensiti11ty to propagation delay time and justify i'

the value selected for your HIS evaluation.

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18)

Provide the results of studies to determine the sensitivity to assumed j

spray carryover fractions. Based on our estimates of blocked areas at elevation 209' it appears that spray carryover fractions from the dome i

region into the wetwell (i.e., from above 209' to below 209') in the f

range:

0.0 < droplets

<0.20 0.33 < sheet flow <0.53 19)

The current CLASIX-_3 model of the containment treats the volume above the wetwell up to elevation 209' as part of the upper containment.

In order to evaluate the adequacy of this simplified model provide the results of analyses perfonned using a more detailed representation of the region; the following nodalization is a possible alternative model (volumes listed are approximate):

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a.

t a)

Annular region from top of suppression nool to elevatior.135' 3

(150,000 ft ),

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' b)

Partial annular region from elevations 135' to 161' (130,000 ft ),3 This excludes the volume occupied by the steam tunnel and the sec-tion considered to be part of volume 5.

3 c)

Free region between elevations 161' and 209' (170,000 ft ).

This complex region excludes the volume of the various pools, internal concrete walls, and the sector ~ considered as volume 5.

3 d)

Region above elevation 209' (840,000 ft ).

This region is open and free of obstructions except for the polar crane.

3 e)

" Pie" shaped sector from elevations 135' to 209' (60,000 ft ).

This sector, near azimuth 225*F, is free from obstructions since it is used in the movement of equipment from the equipment hatch.

20)

Baseo on the description provided in the FSAR, the sprays are not a dedi-cated system but share pumps with other subsystems intended to cool the Core.

Since a basic postulate of degraded core accidents is that cooling water to the core is unavailable (e.g., cooling pumps unavailable) it appears in-i consistent to assume th1t components of a core cooling system would be used -

to provide containment spray flow. Therefore, provide justification for the assumption that sprays are available.

1 1.' i

s.

Enclosare 720.1 Identify and. substantiate the circumstances which provide the worst consequences attributable'to hydrogen explosion / burn and-or compromise.'

the effectiveness of the proposed hydrogen-igniter system.

You should consider the effects of non-uniform distribution of hydrogen, as appropriate.

720.2 Provide a list of accident sequences (initiators and equipment failure) which give rise to the circumstances identified in 720.1 Both degraded core (only) and core melt situations 'should be considered, to the extent that such differentiations can be made.

Rank the sequences in the order of probability of occurrence based on your best estimates, and include a description of uncertainties involved in your analysis.

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