ML20118D187

Forwards TVA Technical Rept on Hydrogen Control Measures & Effects of Hydrogen Burns on Safety Equipment, Re Addl Hydrogen Rule 10CRF50.44 Analyses Submitted Via 880129 & s for Resolution of USI A-48

ML20118D187
Person / Time
Site:	Sequoyah
Issue date:	09/28/1992
From:	Joshua Wilson TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20118D188	List: ML20118D187 ML20118D194
References
REF-GTECI-A-48, REF-GTECI-CO, TASK-A-48, TASK-OR TAC-R00356, TAC-R00357, TAC-R356, TAC-R357, NUDOCS 9210090383
Download: ML20118D187 (2)

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w- vn , o , n,I, $ os ,. n ,, f w u ,, , , m.w ym J. L Vhn VL s hir J t t\, n a W f Lv h u Y y a September 28, 1992 U.S. Nuclear Regulatory Commissian ATTNt Document Control Desk Washington, D.C. 20555 Gentlemens In the Matter of ) Docket Nos. 50-327 Tcnnessee Valley Authority ) 50-328

, SEQUOYAH NUCLEAR PLANT (SQN) - ADDITIONAL IIYl1ROGEN RULE (10 CFR 50.44)

ANALYSES (TA0 R00356 AND R00357)  :

Referencest 1. WA Ictter to NRC dated January 29, 1988, " Additional llydrogen Rule Analyses Submittal"

2. T'1A letter to NRC dated February 19, 1987, " Additional Hydrogen Rule Analyses Submittal" By Roterence 2. WA committed to obtain_ and review reports submitted by Duke Power Company to NRC on additional hydrogen analyses that were being-performed and determine their applicability.to SQN. By Reference 1 TVA ,

indicated that the commitment dates of Reference 2 could not be met  ;

because of the unavailability of the-Duke submittals, restated the l necessity for these reports to complete TVA's commitments, and that the commitment due dates would follow the Duke effort. The Duke effort for Catawba Nuclear Plant was described in detail-in Attachment 1 of a letter from Duke to NRC dated April 25,-1986, which is :ontained in Enclosure 1 to this submittal. Duke completed this effort and provided the results to TVA on March 10, 1992. Ilowever, thlh teport has not been submitted to-NRC'on tha Catawba docket.

Reference 2 committed WA to perform evaluations on applicability of this Duke effort for the hydrogen rule to SQN and to perform an analysis on issues not addressed by this effort. TVA has completed these evaluations, and the-results are provided in Enclosure 2. The'four-020 0 7ipgraded core sequences selected by Duke for the Catawba analysis are-acceptable es-the dominant sequences for hydrogen generation. The individual. plant evaluation (IPE) for SQN also identifies these same sequences as the dominant sequences for hydrogen generation during-l ' degraded core accidents._ The-SQN IPE was performed in accordance with Generic-Letter 88-20 and submitted.to NRC by letter dated '

September 1, 1992.

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P U.S. Nuclear Regulatory Commission ('

Page 2 September 28, 1992 IVA considers the analytical assumptions and parameters associated with 4

the Catawba Station to be applicable to SQN for equipment survivability after a degraded co.e accident and confirms acceptance of the Catawba i analysis for applicability to SQN.

The results of the Catawba analysis, in combination with the original SQN specific analyses, meet the re airements of the hydrogen rule (10 CFR 50.44), and 1VA considers all associated commitments to be complete based on this submittal.

I' lease direct questions concerning this issue to K. C. Weller at >

(615) 843-7527.

Sincerely, d h)t rW.

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' {/1.. Wilson Enclosures cc (Enclosures):

Mr D. E. LaBarge, Project Managrr U.S. Nuclear Regulatory Commission

- One White F11nt, North 11555 Rockville Pike Rockville, Maryland 20852 h NHC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry. Road Soddy Daisy, Tennessee 37379

'Mr.=B. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region Il 101 Marietta Street, NW, Suite 1900 Atlanta, Georgia'30323 4

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ENCLOSURE 1

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reru.a teamewream (?04) 373-saat April 25, 1986 Mr. Harold R. Danton, Directof Of fice of Nuelaar Reactor Regul.ation U. S. Nuclear Regulatory Commission Vashington, D. C. 20555 Attentioni Mr. 5. J. Toungblood, Project Director PWR Projaet Directorate No. 4 Ret 4 tawba Nuclear Station Docket / Nos. 50-413 and 50-414 McGuire Nuclear Station -

Docket Nos. 50-369 and 50-370

Dear Sir:

On April 8,1986, representatives from Duke Power Cotcpany and the NRC Staff met at the NRC's offices in Bethasda, Maryland to discuse hydrogen control measures at Catawba and McGuire. As a follovup to that meeting. Duka has prepared a plan for resolution of concerns on equipment survivability (Attachment 1) and on fana and domra (Attachment 2). A schedule for resolution of these outstanding issues is also included in the respective attachments.

Very truly yours, c.<f M Hal 3. Tucker ROS: sib Attachments xc Dr. J Nelson Grace. Regional A,hinistrator U. $. Nuclaar Regulatory Cot =tission Region II 101 Marietta-Street, NV, Suite 2900 Atlanta, Georgia 30323 Mr. W. T. Ordera NRC Resident Inspector McGuf.re Nuclear Station NRC Residant inspector Catawba Nuclear Station hi P $1[dh[ Jhd ~~ . .

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f ATTACHMENT 1 PLAN FCR RESOLUTION OF CONCERNS ON EQUIPMENT SURVIVABILITY Purpose and Summary Description The purpose of this document is to describe a proposed plan for a

the resolution of the issue of equipment survivability during deliberate ignition of hydrogen in the containment at Catawba.

The plan consists of three parts as follows:

1. Evaluation of the hydrogen and steam releases to containment for an appropriate selection of accident sequences which lead to large releases of hydrogen into containment. The selection of accident sequences and the method of analysis is described below.

2. Using the resulta of the first part of the plan as input, evaluation of the response of the containment and its associated systems to the accident cequences, and a determination of the pressure and temperature in containment as a function of time.

The specific method of performing this analysis, and the major assumptions and parameters to be used, are described below.

3. Using the results from the first two parts of the plan, determination of the response of equ Apment in containment to hydrogen burning and evaluation of its survivability. The steps in this part of the plan include selection of the equipment to be analyzed, determining the appropriate models for the analysis, comparison of results from the analysis with equipme?*

qualification test data and hydrogen burn survivability testa performed under the sponsorship of KRC and EPRI, and assessing the margin associated with the equipment response. ,

Detailed discussion of each part of the plan follows.

Analysis of Accident Sequences The first step in this parv et the plan is the selection of the specific accident sequences to be analyzed. A spectrum ut accidents wequences that envelope the range of hydrogen and steam release' rates will be studied. Since steam flow through the core is tho 1.imiting factor for cladding oxidation, primary system pressure is the parameter of importance dua to its effect on steam availability. There.iore the following sequences will be analyzed:

51D (1fv primary system pressure) 1-1

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S2D (itatermediate primary system pressure)

TMLU (high primary system pressure)

As a result of NRC staff concerno about sequences involving ECCS .

failure in the recirculation mode, S2H will also be investigated.

These accident s9quences envelope the possible primary system pressure conditions under which hydrogen could be developen in the primary system, the release rates of that hydrogen to -

containment, and conditions in containment at the time of hydrogen release. Each sequence of events will be terminated by resumption of ECCS prior to excessive core melting, consistent ,

with previous analyses of degraded core hydrogen generation.

1 Analysis of these accident sequences will be performed using MAAp 2.C. This code was developed by IDCCR and its contractors in order to assess the progrees of degraded core events. The specific assumptions to be used are to be based on the best estimate models in KAAP which meet with NRC staff approval as a

.resul t of their ongoing review. In addition, the total amount of_

hydrogen to be considered for each sequence will be that produced by 754 m/w reaction of the clad or the maximum amount which can be generated by adjusting the time of resumption of ECCS flow, without employing non-mechanistic assumptions or extrapolations in order to force the release rate to be equivalent to 75% m/w. s The S2D accident sequence will be extrapolated to 75% m/w, if necessary, in order to meet . tr.= requirement of the hydrogen rule that the effectiveneen of the system be shown for hydrogen releases up to 75% of the clad oxidized. .

The output of the MAAP analysis will be time histories of the mass and energy releases for hydregen an( aream into the containment. These time histories will be tempared to those reported in References 1 and 2 to ensure that they aza representative of calculations performed using MARCH.

Analysis of Containment Response to Hydrogen Burning Several possibilities have been consioered for performing the containment analysis portion of the plan. The long run times sssociated with CLASIX would make analysis using CLASIX varv expensive. In our containment code development work, we e

modified CONTEMPT 4-MCDS by adding better models for the ice condenser Ice bed and doors, but deficiencies in the hydrogen

' burn models would require more d1velopment. For these reasons at heu been determined that the HEC. ". code would represent the best choir.e for containment analysis. Action has been taken to obtain HECTR from the National Energy Software Center. Following receipt and installation of HECTR, it will be examined to ensure that the ice cendenser model is not excessively conservative our concern over the ice bed model is prcmpted by the work reported in Reference i wherein ice bed moltout appears to occur I

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prematurely when compared with LOTIC and CLASIX results. Any changes we make in HECTR as a result of our review will be documented. If HECTR cannot be made operational on our computer system, either CLASIX or CCNTEMPT4-MODS will be selected for the analyses.

Regardless of which containment analysis code we select, a number of parameters will have to be determined for input to the code.

These parameters affect the results of the code significantly and therefore need to be agreed to prior to starting the work. The following are the proposed containment analysis assumptions and parameters:

1. Spray and fan operation - based on best estimate analysis methods, it will be assumed that both trains or sprays and f ane are started automatically at the proper time and operate throughout the accident. The fan performance will be based on vendor supplied curves derived from test data. Spray performance will be based on FSAR values for injection and recirculation sources. As a sensitvity analysis, response of the containment will be calculated for the came of a single train of fans and sprays available.

2. Ignition and propagation criteria - following study of the various hydrogen combustion tests performed by NRC and EPRI contractors, the following ignition and propagation criteria have been selected for a base case analysis.

a. Lower compartment - Ignition and propagation at 6%

hydrogen by volume.

b. Ice condenser - no igniters are present in the bed or icwer plenum, therefore ignition cannot occur. Propagation upward from the lower compartment at St.. propagation downward from the upper plenum at 84. In the upper plenum, ignition at 8% hydrogen by volumo, propagation downward from the upper compartment at 8% hydrogen. The upper plenum ignition and propagation concentrations will be adjusted downward in those cases where substantial ice melting (greater than 80%) has occurred and little or no ice remains in the ice bed,

c. Upper compartment - ignition at 6% hydrogen, propagation from the upper plenum at 64 hydrogen.

d. Deadended compartments - ignition at 5% hydrogen, propagation ~ from the lower compartment at 6% hydrogon.

In all compartments, burning is suppressed if the steam concentration is greater than 554 by volume or if the. oxygen concentration is less than $4 by volume.

3. Combustion completeness - combustion will bv 604 complete at 6% hydregen or less, 100% complete at 8% hydrogen.

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4. Flame speed - a batter measure of this parameter would be burnout time, the time it takes for hydrogen burning to burn completely in a compartment. The following burnout times will be used for the containment compartments:

lower compartment - 10 seconds lower plenum and ice bed - 8 seconds upper plenum - 7 seconds (will be increased consistent with the previous discussion on ignition concent.?ntion for accident sequences with less than 20% ice in ice bed) upper ecmpartment - 10 seconds deadended compartments - 10 esconda

5. Heat transfer coeffAcients for containment heat sinks and equipment in conta'sment - as reported in Reference 3, with a ponelble modification to the ice heat transfer coefficient to reflect proprietary correlations used in LOTIC and CLASIX.

6. Ice *ondenser drain temperature - 150F, as used in early CLASIX analysis, based on Westinghouse test data, for the early part of the transient when ice melt rate is significant.

This temperature will be adjusted downward in the cases where the ice melt rate is very low at the time of the hydrogen burning.

7. Compartmentalization - as given in the extmple reported in Reference 3.

The results of the containment analyses will be time histories of compartment temperatures and indication of the number of hydrogen burns occurring in each compartmont.

Justification for the selection of hydrogen burning parameters for the base case:

The selectee nycrogen ourn parameterm are based on atudy of the various hydrogen burning experiments carried out under the sponsorship of NRC, the ice condenser owners, and EPRI. These are the test series at Factory Mutual, Acurex, Sandia (VGES), and Nevada Test Station (NTS). It is recognized that none of these experiments duplicates containment conditions during an accident exactly and that some judgment must be applied in order to establish parameters for analysis based on these experiments.

1However, it is the best data available and its use in this regard is consistent with the best estimate nature of the analysis to be performed.

Lower Compartment Parameters .he relevant data is obtained from experiments in which fan induced turbulence is present. The sources of turbulence in the lower compartment will be the flow of the air return fans coming from variour openings between the lower containment and the dead ended compartments and the continuing release of steam and gasses from the primary system.

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It is noted from experiment tha. e ignition occurs consistently at less than 64 hyJyogen by volume under these conditions. Of particular interest tre tests P-3, P-6', and P-7 from the NTS 2

series in wh,ch hydrogen at 64 concentration or less was ignited in the pewuence of steam quantitles representative of those found in the lower compartment during 1 trogen reisess. These tests also indicate flame speeds in tr/ ange of 5 e feet /second which translates based on compartaent geometry to a burn time in the

lower c>ntainment of 10 seconds. The actual burncut time in the

1. 1; lower cantainment will be Innger than this due to che congested y arrangement of equipment and the downward propagation of the y fInmec.

Upper Plenan - the various experiments show that dry mixtures, as would be expected at the outlet of the ice condenser :ce bed would be ignited at 5-64 hydrogen. The use of bW in the analysis reflects the uncertainty over the presence of a fog in the flow q eut of the ice h?d. Analysis performed by Westinghouse for McGuire (Referencs 6) and tests 3.3 and 3.4 from Acurex confirm l

i that nixtures of 83 hydrogen will ignite in the presence of fog. -

Flame speed is basod on NTS tests P-4, P-5, and P-13' Wherein (

upward propagation goes at 4-6 feet /second. This gives a qP compartment burn ~ + time of 7 seconds based on igniter era 'ng and compartment :otry. This is considered conserve, tis-because the NTS h cs were for upevc' gropagation and props; tion in the ice condenser is predce.Aaatriy downward and horizont Upp-r campartment - tha upper compt. w.snt parameters are based on tr ; ed cs of NTS experiments P-7 and 9-22 in which nixtures of lear an 5.5% hydrogen were casily ignitable and burned quick 2v in the presence of fans and spray. The burn timo was conservatively extrapolated from test P-22 to be 10 seconds, the gh this is considered to be much fanter than an actual hurn would take in the upper compartment due to the larger volut+ over m

the NTS vesse) (a factor greater then 30) and the (;edominatu downwerd propagation. Ten seconds is also consistent with the spray droplet fall time which has traditier. ally been used for upper compartment analyois.

Dead Ended Compa.~tments - conditions in ths dead ended compartments are much like those of the lower compartment, with fas induced turbulence due to the air return fans, but at Icerr concentrations of steam in the atmosphere. Ignl. tion concentpation is selected at 6% hydrogen, but the f]ame speed and burnout timus are longer due to the decreased turbulence (no blowdown edurcer in dead ended compartments) and the larner volume to igniter ratio (igniters are not as closely spaced).

These arsumptions are expected tc be of no consequence to the analysin because previous experience shows that hydrogen does not burn in the dead ended compartasnts.

Where the analysis appears to be particularly sensitive to the selection of parameters, and where there is justification from experiment of theory that alternative parsmeters are possible, 1-5

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'i; sensitivity studies will be performed. Guidance for such

, sensitivity studies will be based on that given in References 1 and 3. Of interest is the case of continuous hydrogen burning in the lower compartment because of results seen in certain of the NTS dynamic injection tests. The conditions under which such continuous burning might occur in containment will be evaluated j by comparison _to the parameters used in the NTS tests. If it

, appears appropriate for the ice condeneer ccatainment conditione, continuous burning will be considered in the evaluation of equipment survivability in lower containment.

l Certain additional models not previously employed in the CLASIX 1 analyste reported in Rsterence 4 will also be used this time.  !

Work by Westinghouse has confirmed the ability of the ica ,

l andenser drain flow to act as a lower compartment spray. l desurerheating the atmosphere and condensing steam. Because f d

the consequences of t.he condensation of ctema (increasing the ll hydrogen concentration) of lowering the temperature (less severa l y

environments for lower compartment equipment survivability),

this model will be included in the containment analysis done for hydrogen burning if NRC staff approval for that meiel has been j obtained. In addition, in order to minimize the-d2fferential i pressure developed between the upper and lower compartments if upper compartment burning is shown by analysis to occur, the containment analysis will include speciffe models for the bypase paths between upper and lower containment. These paths include the refueling canal drains and the ice condenser door bypass areas, including the ice condenser drains.

I I Establishment of Equipment Survivability The first step in the process of establishing equipment survivability is to determine the specific equipme.it required to survive hydrogen burn events. The basic requirement is that equipment to maintain the unit in safe shutdown, to mo*ator the prcgress of the event, and to maintain containment integrity must be operable fellowing hydrogen burning. This selection process has been performed for Catawba and the results reported in Reference 4. We plan to continue using thin list.

There are two possible approacnes to determine equipment survivabili3y analytically. The first approach is to model the ,

equipment ^f interest in the containment analysis code as heat 1

sinks and aetermine the temperature response of the equipment directly. Due to the unsophisticated nature of the heat sink models it. HECTR (one dimension slabs only). it would be necessary '

' to modify the code to im

1ude the proper modals. This approach

! will be investigated dusing the performance of the work contained i in this plan and will be used if it proves to be feasible, our. ,

l analysis would be similar to that tried by Sandia and reported in .

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Reference S, but with the elimination of excess conservatism and inappropriate avaumptions.

An alternative approach to the analysis of the equipment temperature response is to repeat the method used in Reference 4 in which the equipment la modeled as a series of coupled differential equations based on conductive, convective, and radiative heat transfer rslationahlpa. These equationa are solved using a general purpose differential equation solver. This approach will be used if the direct meched described above proves infeasible.

Following the detwrminntion of the tea r fature response of the equipment, a comparison will be made with the equipment qualification temperature in a manner similar to that reported in aeference 4. In addition, the results of the extensive amount of actual testing of equipment performed under EPRI and NRC aponsorship will be reviewed to determine its applicability and cited whera'rer it le relevant.

Conclusion Following completion of all analyses to be performed, appropriate revisions to Reference 4 will be prepared and submitted to I(RC.

It Cs expected that sections 4 5, and 6 of Reference 4 will be substantially rewritten as a rest.'.t of this work. The work will include parea.+ers specific to both Mc vilre and catawba and will be applicable to both s ta tions .

Schedule The work required to carry out the plan in extensive. There are uncertaintles in the proposal, such as the use of HECTR, which make determination of exact durations difficult. The following schedule is proposed:

September, 1986 - complete MAAP analysis of accident-sequeness. Complete installation and checkout of HECTR; or identify and make operational the alternative method of containment analysis. Submit the results of the MAAp analysis to NRC for approval.

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December, 1986 - following staff approval of the MAAP i analysis, begin containment response calculations.

i March, 1987 - complete containment response analysis.

l submit results to NRC for approval, i

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June, 1987 - following NMC approval of the containment response analysis, begin equipment survivability analysis.

September, 1987 - complete equipment survivability analysis and submit to NRC for approval.

December 31, 1967 - following resolution of all comments, prepare and faubmit appropriate revisions to Reference 4.

This schedule is consistent with the nature of the analysis (being associated with beyond design basis events) and the conflicting responsibilities of the principal analysts involved in performing the work.

Refersuces

1. Camp, A. L., et. al., "KARCH-HECTR Analysis of Selected Accidents in an Ice condenser tantainnent," NUREG/CR-3912, December, 1984

2. NRC letter (D. L. Wiggenton) dated December 16, 1985, reporting on a meeting held December 5, 19t$ between NRC and IMEC

3. Camp, A. L., et. al., "NECTR Version 1.0 User's Manual,"

NUREG/CR-3913, Feoruary, 1985

4. Duke Power Company, "An Analysis of Hydrogen Control Measures at McGuire Nuclear Statien," October, 1981, complete through Revision 14, April, 1986

a. Dandini, V. J., and W. H. McCollough, "HECTR Analysis of Equipment Temperature Responses to Selected Hydrogen Burns in an Ice condenser Containment," NUREG/CR-3954, February, 1985

6. Tsai. S. S., " Fog Inerting Analysis l'or PWR Ice Condenser Plants," Westinghouse Electric Corporation, October, 1982 k