ML20126E134

Responds to FOIA Request for Records Re 850212 Meeting Between NRC & Hydrogen Control Owmers Group.Forwards First Two Documents Listed in App A.Updated Draft Summary of Subj Meeting by C Stahle Withheld (Ref FOIA Exemption 5)

ML20126E134
Person / Time
Issue date:	03/27/1985
From:	Felton J NRC OFFICE OF ADMINISTRATION (ADM)
To:	Hiatt S OHIO CITIZENS FOR RESPONSIBLE ENERGY
References
FOIA-85-113 NUDOCS 8506150303
Download: ML20126E134 (3)

Text

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ug[og UNITED STATES Y o NUCLEAR REGULATORY COMMISSION -

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r. j WASHINGTON, D. C. 20555

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MAR 27 886 Ms. Susan L. Hiatt OCRE Representative 8275 Munson Road IN RESPONSE REFER Mentor, OH 44060 TO F01A-85-113

Dear Ms. Hiatt:

This is in response to your letter dated February 12, 1985, in which you requested, pursuant to the Freedom of Information Act (F0IA), all records concerning the February 12, 1985, meeting between the Nuclear Regulatory Comission and the Hydrogen Control Owners Group.

The three documents listed on the enclosed appendix are responsive to your request and are enclosed. You will be billed separately by our Division of Accounting and Finance in the amount of $1.37 for enclosed documents one and two.

Document three is a 13-page handwritten draft summary of the meetings held on January 30 and 31, February 1, February 6, February 12 and February 20, 1985.

This document is being withheld in its entirety. This draft document was written by an NRC staff person. The document contains predecisional information and contains no reasonably segregable factual portions. Release of this document would tend to inhibit the open and frank exchange of ideas and other information essential to the deliberative process. The document reflects the predecisional process, and, therefore, is exempt from mandatory disclosure pursuant to Exemption (5) of the F0IA (5 U.S.C. 552(b)(5)) and 10 CFR 9.5(a)(5) of the Commission's regulations. The final meeting sumary will be available upon request within the next few months and will be provided to parties on the Perry service list.

Pursuant to 10 CFR 9.9 of the NRC's regulations, it has been determined that the information withheld is exempt from production or disclosure and that its t production or disclosure is contrary to the public interest. - The persons responsible for this denial are the undersigned and Mr. Harold R. Denton, Director, Office of Nuclear Reactor Regulation.

8506150303 850327 PDR FOIA HIATT85-113 PDR

This denial may be appealed to the NRC's Executive Director for Operations within 30 days from the receipt of this letter. As provided in 10 CFR 9.11, any such appeal must be in writing, addressed to the Executive Director for Operations, U.S. Nuclear Regulatory Commission, Washington, DC 20555, and should clearly state on the envelope and in the letter that it is an " Appeal from an Initial FOIA Decision."

Sinc rely, ish cs ,,: ;

J. M. Felton, Director Division of Rules and Records Office of Administration

Enclosures:

As stated 5

APPENDIX FOIA 85-113

1. . February 14, 1985 - Letter to Mr. Robert Bernero from S. H. Hobbs with attachment: Acceptance Criteria for Task 1 - Establish Most Probable Hydrogen Generation Event (36 pages)

2. February 19. 1985 - Letter to Robert Bernero from S. H. Hobbs, subject:

Hydrogen Control Owners Group Submittal of Revised Acceptance Criteria for Hydrogen Control Program Plan with attachments: Acceptance Criteria for Tasks 1 through 14. (39pages)

3. Undated - Draft Handwritten Summary of February 12, 1985, meeting by C. Stahle. (13pages) 2

MARK 111 CONTAINMENT HYDROGEN CONTROL OWNERS GROUP so m a.wotes.csoirm on c/o Mssissippi Power and ught e P.O. Box 1640 e Jackson. Mssissippi M205 601 969 2458 February 19, 1985 HGN-029 U. S. Nuclear Regulatory Omnission Office of Nuclear Reactor Regulaticn Washington, D.C. 20555 Attention: Mr. Robert Bernero

Subject:

Hydtma Ccntrol Owners Group Subnittal of Revised Acceptance Criteria For Hydrogen C%ntrol Fr4s Plan I

Reference:

Istter IEN-028 frtzn S.H. Hobbs to Mr. Robert Bernero t

The reference letter t m amitted the Hyi @ i Control owners Group's (HCDG) Hyivge.n Control Program Plan acceptance criteria to the NRC. staff. "bese acceptance criteria had been revised to reflect changes p.w-M by your staff and additional changes irs.u. W ated by HCOG to c.u.M typographical errors, gramatical errors or l canissions.

Enclosed with this letter are 24 copies of identical revisions to the acceptance criteria for all fourteen tasks identified in the s. ,s plan. These revisions have been generated in the same word processing format as currently in the Hyimi Cbntrol Pr@s Plan. Major changes are noted by a change bar "]" in the right hand margin. In addition, each changed page has a revision

, date in the lower right hand corner. Please note that the page numbering of the acceptance criteria is A M and that any apparent discrepancies with other text page nirnbers will be cw.im.ted in the next general revision of the IT@mu Plan. These copies should be used as page l replacements for acceptance criteria in the twenty-four i copies of the g es plan currently in the NRC's

! possession. Please dispose of the old acceptance criteria l pages accordingly.

HCDG plans to subnit a revised program plan to iru.u. gate the results of the recent meetings with the NRC by March l

1, 1985. As indicated in the reference letter, HOOG requests that the NRC provide a safety Evaluaticn Report hwanting acceptance of the conplete prograrr. plan by April 9,1985. -

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l Page 2 of 2 3 24-027 This suhaittal was otsipiled by 3DG from the best infonnation available for submittal to the Nuclear W1= tory Ozunission. The subnittal is believed to be oczuplete and accurate, but it is not subnitted crt any plant specific docket. The infonnation contained in this letter and its attachments should not be used for evaluation of any specific plant unless the information ,

has been endorsed by the appropriate ==mhar utility. IEDG

==mhers may individually referunae this letter in whole or in part as being applicable to their specific plants.

, HCDG w ciatas the NRC staff's support to date in

. reviewing the program plan. Please contact me if you have any questions m_ -:- eing this subnittal.

Sincerely,

) ,,,. k S. H. Hones Cb=4 ==n, Hylvyma Cbntrol Owners Group SHH/jlw Attachments oc: Mr. Carl R. Stahle Hyl uwwa Control Fiv.f. u W U. S. Nuclear Regulatory Ozanission Office of Nuclear Reactor Regulation i Washington, D.C. 20555 Mr. Charles G. Tinkler Containment Systems Branch U. S. Nuclear Regulatcry Ozunission Office of Nuclear Reactor Regulation W =hington, D.C. 20555 Mr. John om=irgs

, Project Manager Hyivy-a Studies Divisiat 4441 Sandia National Tahnratory Albuquerque, M 87185 S

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+S ACCEPTANCE CRITERIA FOR TASK 1 ESTABLISH MOST PROBABLE HYDROGEN GENERATION EVENT

]

1. Hydrogen generation events which involve amounts of hydrogen production up to the equivalent of oxidizing 75% of active fuel cladding shall be defined. Probabilistic considerations shall be used to determine the most probable initiating event. Plant systems available to mitigate the event will be consistent with O

assumptions regarding event progression and recovery of lost vessel inventory makeup systems. The frequency of occurrence ]

for a variety of postulated initiating events shall be based on existing BWR/6 probabilistic data and considered in conjunction with loss of all core makeup to determine the probability of core melt. The consolidated events with the highest probability of leading'to hydrogen generation without gross core melting shall be established.

i ,

2. Station blackout events and Anticipated Transients Without ]

Scram (ATWS) shall be demonstrated to be low probability events ]

which need not be considered as probable precursors to ]

recoverable degraded core accidents. The probability of these ]

! events leading to a recoverable degraded core accident shall be ]

shown to be less than 1x10-6 events per reactor year'.- )

f. 3. Operator actions to recover various ECCS systems and respond to plant conditions will be consistent with symptom based emergency operating procedures or guidelines. The ]

consequences of reasonable variations in the timing for operator ]

actions to depressurize the vessel and to recover core ]

j makeup shall be considered. ]

l 4. A recoverable core geometry shall be maintained by assuring i that adequate core make-up is provided prior to the onset of i

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~h gross core melting. Melt shall be defined as the percentage of the core for which the metal cladding temperature exceeds the ]

melting point of zircaloy (2170 0K). Gross core melting shall be ]

that amount of core melt which would cause the core to be

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unrecoverable.

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1 4-10 2/14/E5

j ACCEPTANCE CRITERIA FOR TASK 2 SELECT MITIGATION SYSTEM

]

1. The mitigation system shall not create conditions which impose unacceptable loads on the containment structure.

2. Recognizing the Mark III containment is a " working containment", the hydrogen mitigation system shall not present a safety hazard to operating personnel in containment during periods of normal plant operation. Inadvertent actuation shall not present a hazard to plant personnel working in the containment.

3. Mitigation system actuation shall not produce unacceptable environmental effects on equipment required to:

A. protect the containment integrity B. recover the reactor core, C. mitigate the consequences of the accident D. evaluate and follow the course of the accident and ]

provide guidance to the operator for initiating actions ]

in accordance with the Emergency Procedures Guidelines ]

E. function in order to prevent failure of components ]

required to function ]

l This can be accomplished by showing that the results of mitigation system actuation does not exceed the environmental l qualification envelope of essential equipment. Inadvertent actuation of the mitigation system during normal plant l 4-16 2/14/35

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operations shall not adversely affect systems and components needed for safe operation of the plant.

4. The mitigation system shall prevent accumulation of hydrogen ]

to detonable mixtures under conditions conducive to combustion ]

following a hydrogen generation event.

5. The hydrogen mitigation system shall not endanger the health and safety of the public due to planned or inadvertent actuation and shall meet the requirements of 10CFR100 as applicable.

6. The hydrogen mitigation system shall be capable of demonstrating its operability by periodic surveillance tests.

7. The hydrogen mitigation system shall be capable of maintaining the containment integrity in the environment present in the Mark III containment after a hydrogen generation event.

The mitigation system shall be environmentally and seismically qualified or capable of being qualified in accordance with the requirements of IEEE-323 and IEEE-344 as applicable.

8. The hydrogen mitigation system equipment and components shall be readily available and shall not require substantial efforts to procure or fabricate the equipment.

.)

4-17 2/14/55

. . . . ~ .

1 Q ACCEPTANCE' CRITERIA FOR TASK 3 DESIGN HYDROGEN IGNITION SYSTEM

]

1. In order to protect the containment integrity, the spacing of ignitors throughout the containment and drywell volume should I -

assure'that hydrogen ignition occurs at low concentration and that pocketing of hydrogen does not occur. Separation of ignitors by a distance of 30 ft. with all igniters operable

, shall be acceptable. The igniter spacing of 30 ft. need not be

. maintained in the large, open area between the refueling floor i and the containment dome or in the lower regions of the drywell

[ which are subject to submersion following a loss of coolant ]

. accident. The separation distance between operable igniters may ]

be 60 ft. if one division of engineered safeguard feature AC power is inoperable. The separation criterion may be modified ]

to 35 feet with all igniters operable or 70 feet if one division ]

of engineered safeguard feature power supply is inoperable in ]

,, order to account for construction interferences and support ]

availability. ]

j 2. Igniter 1,ocations shall not present a hazard to personnel

working in containment during testing or inadvertent operation.

3. The hydrogen igniter device used in distributed ignition systems must be capable of functioning in the environment

! present in a Mark III containment following a degraded core accident. In order to assure that the igniter will be functional following the accident, the igniter and associated support components located inside the containment should be environmentally qualified in accordance with the requirements of j IEEE-323. Supports for the igniter assembly should be designed ]

to withstand the appropriate design load combinations. The igniter device should be sealed to assure that the presence of containment sprays or 3n all steam environment does not i

. 4-25 2/14/S5 l

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must be, submerged or subject to pool swell, the component must

,j be designed to withstand the anticipated submergence or pool ] l

swell impact loads. The effects of high energy pipe whip and jet ] '

impingement shall be considered. ]

4. The operating temperature for the igniter device must assure reliable ignition of hydrogen at low concentrations. A minimum )

, surface temperature of 1700 0F at an applied voltage of 12.0v for the igniter glow plug shall be acceptable to meet this A minimum surf ace temperature of 15000 F will be requirement.

maintained at a minimum voltage of 10.8v.

5. The hydrogen ignition system shall be sufficiently redundant to assure that no single active or passive failure will prevent

the system from performing its intended function. The ignition system shall be divided into divisional subsystems powered from redundant onsite and offsite emergency safeguard feature power supplies. In enclosed regions of the containment which may be susceptible to pocketing of hydrogen, separate igniters powered from redundant power supplies shall be installed.

4

6. The hydrogen ignition system shall have the capability to be initiated prior to onset of hydrogen production. Manual initiation of the system shall be acceptable provided that guidance is available to the operator on system initiation i procedures. A minimum of 10 minutes shall be available between ]

l the time when the vessel level reaches the top of the active ]

fuel and the time when siginificant hydrogen production begins ]

for the most probable hydrogen generation event identified in ]

Task 1. ]

7. The hydrogen mitigation system shall be designed as seismic Category I system and in accordance with IEEE-344 and shall be 4-26 2/14/85

_ . - - . _ - - - - - - . . . . - - . - _ _ . --__.___.D-

(3; designed to withstand the effects of the SSE and remain functional.

8. The hydrogen ignition system shall be designed and procured as Safety Class 2, Quality Group B equipment.

9. The use of A.C. power for the igniter system is acceptable provided that criterion 2 in Task 1 is satisfied with respect to )

station blackout being demonstrated to be sufficiently )

improbable. ]

10. Technical specification limi,ts shall be established to assure that the hydrogen ignition system will be operable when required. This will include requirements that igniters in enclosed regions are operable and that sufficient igniters are operable in other regions of the containment to assure ignition of hydrogen at low hydrogen concentrations. Surveillance

'3 requirements shall be specified to assure that the system is operable during normal plant operation. Surveillance requirements shall also be established to assure that the igniters are capable of achieving the required surface temperature.

i 4-27 2/14/55

[ ACCEPTANCE CRITERIA FOR TASK 4 CONTAINMENT ULTIMATE CAPACITY ANALYSIS

]

1. The containment structural integrity shall be established by ]

analyzing the ultimate internal pressure capacity. The ultimate )

internal pressure capacity shall be defined as that pressure ]

where a general state of yield is reached by the limiting ]

structural section or component. Local components such as ]

containment air lock and hatch seals, and penetration's shall be ]

shown to maintain their structural integrity at pressures which ]

equal or exceed the ultimate internal pressure capacity. ]

2. The calculational method for determining ultimate internal ]

pressure capability may include the use of actual material ]

properties with suitable margins to account fo'r uncertainties in modeling, in material properties, in construction tolerances, and so on. Another method which can be used is to demonstrate the following specific criteria of the ASME Boiler and Pressure Code are met:

A. Steel containments shall meet the requirements of the ASME Boiler and Pressure Vessel Code Section III, Division 1, Subsubarticle N-3220, Service Level C Limits, considering pressure and dead load alone. The evaluation of instability is not required.

B. Concrete containments shall meet the requirements of the ASME Boiler and Pressure Vessel Code,Section III, Division 2, subarticle CC-3720, Factored Load Category, I considering pressure and dead load alone.

3. For containments which do not have vacuum breakers to admit additional air mass into the containment volume, the containment structure shall be demonstrated to withstand an external J

4-33 2/14/85

^ pressure dif ferential due to a hydrogen combustion event which depletes oxygen or. reduces the partial pressure contribution of steam due to the operation of sprays or coolers, or loss of containment inventory due to leakage. For containments which do not have vacuum breakers, the external pressure is acceptable if the containment will withstand a 4 psid pressure.

4. The ultimate pressure capability of the drywell structure ]

shall be established or the structure will be shown to have a ]

pressure capability in excess of the maximum pressure which ]

l could result from hydrogen combustion in the drywell. This ]

maximum pressure may be estimated with a containment response ]

analysis which meets the acceptance criteria for Task 8. The ]

ability of the drywell to withstand external pressurization - ]

shall be evaluated. ]

5. The containment ultimate internal capacity shall be demonstrated to be greater than the peak internal pressure loading resulting from hydrogen combustion as calculated with a ]

containment response analysis which meets the acceptance ]

criteria of Task 8. ]

6. The potential for accumulation of hydrogen above detonable limits in enclosed regions of the containment shall be evaluated. Postulated detonations which could occur in these enclosed areas shall be evaluated or it shall be shown that hydrogen concentrations are' controlled by the selected mitigation system such that the probability of detonations

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occurring is sufficiently small to assure that the consideration ]

of detonations is not warranted. ]

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ACCEPTANCE CRITERIA FOR TASK 5 J. -SELECTION OF CONTAINMENT RESPONSE ANALYSIS CODE

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1. The containment response analysis code used for evaluating

. hydrogen combustion effects shall model Mark III containment features important to hydrogen generation events. Specific features which shall be modeled by the code include:

A. Mark III compartments consisting of at least the i drywell, wetwell and upper containment. The code shall

!* have the capability to nodalize additional components.

. B. Suppression pool behavior and the effect of upper pool I

dump.

C. Flows paths between compartments such as vacuum breakers, combustible gas control compressors, or the

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LOCA vent system.

' D. Flows into or out of compartments from hydrogen / steam inj ection , containment sprays, spray carry over, or break flows.

j E. Hydrogen combustion in each compartment F. Energy loss due to containment heat removal systems or heat sinks.

2. The containment response code shall be able to predict pressure, temperature, and concentration of constituent gases in each compartment modeled.

3. The analysis code shall model energy addition to various f ..~,

compartments due to hydrogen , combustion. Hydrogen combustion i

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4-41 2/14/35 1

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_ energy addition rates shall be controlled by external input parameters such as ignition criteria, burn time, and completeness of burn. Control volumes may be assumed to be perfectly mixed. ]

4. The containment response analysis code used to evaluate effects of hydrogen control system operation shall be coropared with other accepted containment response analysis codes. This comparison' shall show that the selected containment response analysis code predicts containment response in agreement with predictions of accepted codes. The suppression pool modeling shall be shown to represent the behavior of the Mark III suppression pool.

5. The containment response analysis code used to evaluate ]

effects of hydrogen control system operation shall be compared ]

with large scale test data relevant to the Mark III containment. ]

4 c.d This comparison shall be completed in accordance with the ]

acceptance criteria identified for Task 12. ]

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ACCEPTANCE CRITERIA FOR TASK 6 HYDROGEN COMBUSTION TESTING

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1. A program to evaluate completed and on-going industry )

efforts concerning hydrogen generation events, combustion testing, and equipment testing shall be conducted. Data which

', affects the analysis of hydrogen combustion phenomena or the design and use of a distributed igniter mitigation system sha.ll

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be reviewed for applicability to Mark III hydrogen control programs.

2. Information required to support burn parameter input and selection for containment response analysis shall be identified.

This will include data to support selection of:

A. minimum concentrations of hydrogen for ignition l

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1 C. flame propagation velocity l

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D. steam effects on ignition

. 3. Mark III unique hydrogen combustion phenomena shall be evaluated. Phenomena which shall be evaluated include potential inverted diffusion flames in the drywell, potential standing diffusion flames above the suppression pool, and combustion of hydrogen rich / oxygen limited combustion conditions in the drywel'l.

4. The combustion phenomena in the Mark III containment shall be evaluated to determine if adequate oxygen can be recirculated to the suppression pool surface in order to support steady diffusion flames. .

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5. 'The ability.to ignite hydrogen rich mixtures in steam rich and oxygen lean atmospheres shall be evaluated. Ability to ignite these mixtures in a condensing environment shall also be evaluated. Testing shall verify the values for combustion initiation assumed in analyses.

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p ACCEPTANCE CRITERIA FOR TASK 7 GENERATION OF HYDROGEN RELEASE HISTORIES

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1. Codes used to calculate hydrogen generation release ]

histories shall model BWR/6 cores. The code shall physically model BWR/6 fuel assemblies, fuel channels, control' rod blades and include representations of upper vessel components. The code shall have the ability to predict hydrogen produced by oxidation of the zircaloy cladding, the zircaloy fuel channels, and the stainless steel control blade housing. The code shall j' account for energy produced by decay of fission products in the fuel and energy produced by oxidation reactions. The code shall

. have the capability to analyze heat transfer by conduction out of the fuel and cladding, convective heat transfer between steam and and affected components, and radiant heat transfer. The

, code shall provide the capability to predict level in individual power bundles including two phase level and simultaneously 4 balance water level in the bypass region. The code shall provide an accurate mass and energy balance throughout the

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control volumes.

Correlations used to predict hydrogen production shall be

. conservative. The Cathcart-Pawel correlation for hydrogen production as a function of temperature shall.be acceptable for

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! temperatures below the zircaloy phase transition temperature.

The Baker-Just correlation shall be extrapolated linearly to

. provide conservative predictions of hydrogen production at temperatures above the Baker-Just data.

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2. Operator actions assumed in calculating hydrogen generation I histories shall be consistent with guidance-provided to the operator in symptom based emergency procedures. The operator shall be assumed to have depressurized the reactor pressure vessel prior.to the start of core heatup. The vessel shall be 4-71 2/14/55 i

l assumed to remain depressurized throughout the subsequent core heatup,- hydrogen production, recovery of vessel inj ection, and quenching of the core. The operator will be assumed to devote all of.his efforts to recovering vessel makeup once he has recognized that inadequate core cooling conditions exist. ]

Variations in the time for completion of operator efforts to ]

depressurize the vessel and to recover core makeup flow shall be ]

analyzed to determine the effect on hydrogen production.

3. _The code utilized to predict hydrogen generation shall ]

provide a reasonable representation of degraded core behavior.

The code shall model the oxidation rate as a function of zircaloy temperature and provide for oxidation termination at high temperatures. A conservatively high value of 2400 0 K as a ]

maximum shall be used for this irreversible oxidation cutoff.

Justification for use of the irreversible oxidation cutoff shall ]

. be provided by evaluating the accumulation of an oxide layer on

] ,

5 the cladding surface. If a small oxidation layer is formed on

, ]

, the cladding surface, the 24000 K oxidation cutoff shall be ]

valid. The code shall not be required to accurately model' core ]

. geometry deformations which occur,during core heatup including ]

molten zircaloy relocation. ]

4. Hydrogen generation histories evaluated for input to the 1/4 ]

scale test program shall be limited to hydrogen generation -

histories produced by recoverable degraded core accidents. In order for an accident to be recoverable, the core must be maintained in a coolable geometry. Once 30% of the total zircaloy inventory in the active fuel region exceeds the melting temperature of zircaloy, i.e., 21700 K, a coolable core geometry can no longer be assured.

5.- The sensitivity of code predictions of hydrogen generation ]

' histories for variations in significant code input parameters

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shall be evaluated. Variations in the following significant parameters shall be assessed:

A. Core nodalization, i.e., number of unit cells B. Zircaloy oxidation cutoff temperatures C. Core reflood flow rates D. Reflood recovery timing E. Assumed initial core water level F. Timing for initial core uncovering f

G. Timing for assumed reactor vessel depressurization ]

H._ Total amount of active core zircaloy inventory allowed ]

to melt and still consider the accident recoverable ]

shall be varied to 50% )

6. Hydrogen release histories.which are selected for input to ]

the 1/4 scale test facility shall correspond to degraded coreaccidents which can evolve based on symptom based emergency 4 procedu,re guidelines. The reflood flow rates for hydrogen release histeries which are selected for input to the 1/4 scale test program shall correspond to the. flow rates from systems installed in the plant and capable of providing injection to the vessel within the required time frame. The flow rates shall be based upon system flow rates to an essentially depressurized vessel. Only systems which are available with all supporting components and systems which can operate during a loss of offsite power event shall be considered in defining available reflood flow rates. Reflood flow rates considered shall be f

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m further limited to those flow rates which can be placed in service in time to prevent the accident from becoming non-recoverable. The time required to place a system in service shall be based on the amount of time required to realign the system for injection to the vessel, the time required to make any physical modifications to system configuration, and the time 4

required for the system to be pressurized and begin providing

- flow to the vessel. The timing for initiating the vessel reflood shall assure that the accident remains recoverable ir.

accordance with criteria 4 at the end of hydrogen generation.

7. A hydrogen release history which produces a total amount of )

hydrogen equivalent to oxidizing 75% of the active fuel cladding }

shall be calculated. This hydrogen release history shall be }

calculated in a manner which accounts for mechanistic degraded ]

core phenomena to the maximum extent possible.

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-[ 4-74 2/14/85

i m ACCEPTANCE CRITERIA FOR TASK 8 CONTAINMENT RESPONSE ANALYSIS

1. Analyses to evaluate the consequences of hydrogen release to ]

the containment, from a metal-water reaction of up to 75% of the fuel cladding surrounding the active fuel region, shall be conducted. -The analysis shall specifically address effects produced by operation of the hydrogen control system.

2. Accidents involving hydrogen release to the drywell and to the suppression pool shall be evaluated. Assumptions regarding containment and drywell initial conditions shall be based upon ]

, realistic assumptions. This analysis shall include the period ]

from the time of occurrence of the initiating event until recovery from the degraded condition. -

3. A containment response code and meeting the acceptance

, criteria for Task 5 shall be used to analyze the containment

,' pressure and temperature response.

4. Hydrogen combustion parameters used for containment analysis shall have sufficient supporting information to justify their use. The following parameter values are acceptable for containment analysis:

!- A. Minimum hydrogen volume fraction required 0.06 L for ignition.

B. Minimum hydrogen volume fraction to support 0.06 i

flame propagation.

C. Hydrogen fraction burned 0.65 (Burn completeness) l lJ 4-83 2/14/85 i -

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1 D. Minimum oxygen volume fraction to support 0.05 ignition.

E. Minimum oxygen volume fraction to support 0.00 combustion.

. F. Speed of propagation (flame speeds) 6 ft/sec

< 5., Initial pressure conditions for oxygen, nitrogen and steam partial presures shall be calculated from initial compartment temperatures, pressures and relative humidities.

j - 6. Hydrogen release histories used in containment response

- analysis shall meet acceptance criterion 7 under Task 7.

7. Operator actions during the time period of the hydrogen g'eneration event shall be consistent with actions required by plant symptom based emergency procedures. These actions shall determine when vessel depressurization occurs, containment ]

. sprays are actuated and when hydrogen mixing systems are ]

4 activated.

1

8. Sensitivity studies shall be conducted to determine the change in predicted containment response due to changes i n input parameters. Analysis of the following cases shall be sufficient to assure that uncertainties in containment response ]

analysis have been adequately characterized based upon the J i - ' expected range of input parameters and assumptions. ]

I A) Steam and hydrogen release rates one half of the base

, case value for a 75% metal water reaction.

B) Steam and hydrogen release rates twice the base case value for a 75% metal water reaction.

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4-84 2/14/85

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e-C. Steam and hydrogen release rates four. times the base case value for a 75% metal water reaction.

D. Hydrogen ignition-criterion changed.to 10 v/o and burnup to 100% from the values stated in Acceptance

-Criteria 5.

E. Flame propagation criterion changed to 7.5 v/o and burnup to 75% from the values stated in Acceptance Criterion 5.

F. Flame speed increased to 12 f t/sec from 6 ft/sec.

G. Containment spray flow increased to flow from two trains..

H. Containment spray flow reduced to zero.

I. Containment spray carry-over reduced to zero.

J. Convective heat transfer coefficient to heat sinks reduced to zero.

K. Radiant heat transfer beam lengths reduced by 1/2.

. The results of the sensitivity studies on predicted compartment ]

temperatures and pressures shall'be evaluated. ]

9. A representative case for containment' response analysis shall use specific geometric and system parameters _for a typical Mark III design such as the Grand Gulf Nuclear Station (GGNS).

Th'is case shall be demonstrated to conservatively predict the response of containment arrangements other than GGNS or plant specific containment response analysis shall be conducted.

I 9

r 4-85 , 2/14/35

.j

. . .~

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() ACCEPTANCE CRITERIA FOR TASK 9 DIFFUSION FLAME THERMAL ENVIRONMENT

] (1/4 SCALE TEST PROGRAM) 1

1. The containment thermal environment resulting from ]

diffusion flames anchored at the suppression pool surface during recoverable degraded core accidents shall be defined using

, experimental data. The thermal environment shall consist of convective heat loading front hot gases, radiation from the ]

diffusion flame, and radiation from hot gases and hot

, gratings or other components. Data shall allow definition of the thermal environment in areas of the containment where equipment required to survive these accidents is located.

2. The scaling basis for the test facility shall assure that ]

the ratio of inertial and buoyant forces is preserved ]

between the scaled test facility and full scale.

)

3. The scaled test facility used to define the diffusion flame

[ thermal environment, shall represent the Mark III containment j- plants. The containment geometry for each Mark III plant shall be simulated or it shall be shown that differences between plant geometries do not affect the thermal environment. The major blockages to flow such as the steam tunnel or concrete portions I of individual floors shall be simulated. Grating shall be simulated to preserve the ratio between open areas and blocked areas.

Containment cooling systems such as containment sprays or safety related unit coolers shall be simulated in the scaled tes+

l

-facility. The scaled lowest containment spray flow rate from any member Mark III containment plant with containment sprays or the scaled actual flow rate from a specific plant shall be used

in the test facility in order to model the effect of heat

.I 4-104

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l .

. - .. ~. .. _ . _ _ . _ . _ . _ _ _ _ _ _ _ - . _ _ _ - . _ _ _ . , ~.-_ _ ____._______._, __ _ _ _ _ _ _ . - -. _ __.

transfer to the containment sprays. The sprays shall be demonstrated to produce bulk atmosphere mixing patterns which are representative of the bulk atmosphere mixing patterns expected at full scale.

The total heat transfer characteristics of the scaled test ]

facility shall be conservative with respect to the heat transfer characteristics of all full scale Mark III containment or representative of the actual heat transfer characteristics. It shall be demonstrated that the heat losses to the gratings, ]

walls and other heat sinks in the scaled test facility shall not ]

exceed the heat losses to gratings, walls, equipment and other ]

heat sinks in the full scale facility. Alternately, it may be ]

demonstrated that heat losses in the scaled test facility are ]

compensated for by other factors. A typical compensating factor ]

which could be considered is a comparison of heat sink capacity ]

included in the scaled test facility versus heat sink capacity )

, in the full scale plants. ]

The scaled test facility must. nave the capability to simulate variable hydrogen and steam flow into the facility. The hydrogen flow rate into the facility must be variable over the the range of expected hydrogen production rates. The hydrogen shall be injected into t.he facility at locations which correspond to the points of hydrogen release in the full scale plant.

4. The repeatability of the test data shall be evaluated. A ]

set of tests with comparable initial conditions and identical -)

geometry shall be completed. Acceptable repeatability for ]

the test data will be determined by comparing the gas ]

temperatures, velocities, and radiant heat fluxes. ]

4-105 2/14/95 o

- - - , - - - - _ , . ~ - - + -- . _ _ . _

l 1

l A Specifically, the following parameters.will be compared for the ]

repeatability tests: )

,' . ]

O F measured along a A. Peak gas temperatures i n )

circumference with the simulated SRV spargers at an ]

i. elevation just above the simulated HCU floor. Peak ]

temperatures shall be compared in the four chimneys and ]

in the region between azimuth 172.5 0 and 2100 . ]

]

. B. Peak radiant heat flux as ressured by instrument R-184 ]

I in the 315 0 chimney ]

]

C. Peak gas velocity measured by instrument W-184 in the ]

315 0 chimney Test repeatability shall be acceptable if the range of each of ]

these parameters is less than or equal to 154. If these ]

criteria are not met factors of conservatism shall be applied in

[

- defining the local thermal environment for asessing survivability of equipment.

5. The testing conducted in scaled facilities shall be ]

consistent with the course of events in a full scale plant based upon emergency procedure guidelines. The ignition system shall be energized prior to injection of hydrogen. The simulated sprays shall be actuated when the bulk average containment temperature reaches the temperature limit identified in the emergency procedure guidelines. The same number of spargers 4

shall be open during testing as the number of spargers used to

,depressurize the reactor pressure vessel plus one additonal spargerasfppropriatetosimulateastuckopenreliefvalve.

4 4

6. The parameters which could affect definition of the thermal }

environment in a Mark III containment shall be evaluated in the 1 4-106 2/14/95

,-my.-- ,* - t--rv-+*-g-T'-t e=*-vew- --N * -'*"7" ---~w' -

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'S scaled test facility. For each parameter which is evaluated, the test including that parameter shall be completed identically

. with tests which are conducted to assess repeatability. Each parameter may be judged to have no effect on the combustion  ;

transient. If the temperatures, gas velocities and radiant heat flux measured in.the test facility for all instruments at the HCU floor level are within the data scatter defined during ]

the repeatability tests, or these parameters are within 15% of ]

the mean value established during repeatability testing, the ]

parameter will be assumed to have no effect. If the parameters are shown to have a significant effect, these parameters shall be addressed in the testing.

7. The thermal environment including gas temperature convective ]

heat flux and radiative heat flux shall be defined for all areas

, in the wetwell and containment where equipment required to sarvive hydrogen combustion is located. A limiting thermal environment in each area of the containment shal'1 be established. The possible release points for hydrogen through stuck open safety relief valves, open ADS values, and release through LOCA vents shall be considered in establishing the limiting thermal environment. The effect of having two open relief valves under a hot chimney, the effect of a single open relief valve below HCU floor grating, and the effect of -

i simultaneous hydrogen release through the SRV spargers and LOCA vents shall be evaluated in establishing the limiting thermal l

environment.

l 8. Sufficient data on gas distribution throughout the wetwell ]

! and containment shall be obtained from tests with and without ]

operation of containment sprays to evaluate the effectiveness of

( hydrogen mixing with the containment atmosphere. A gas sampling system shall be included in the facility which is capable of l measuring hydrogen, oxygen and water vapor concentrations at a B

-> 4-107 -

2/14/85 l

i

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i 1

number of different locations in the wetwell and containment. ~

The mixing data will be evaluated to demonstrate that mixing of l the containment gases prevents significant accumulation of hydrogen. Hydrogen concentrations shall be shown to not exceed l 8 v/o at elevations above the first row of igniters and that )

detonatable mixtures do not exist. ) i

9. Data shall be obtained from the test facility to validate )

analytical methods which are used by HCOG. An instrumented calorimeter with complex geometry shall be included in the facility. This calorimeter shall be used to validate the heat transfer methods used in calculating the temperature response of the component.

4 I

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_j 4-108 2/14/85 i

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] ACCEPTANCE CRITERIA FOR TASK 10 EVALUATION OF DRYWELL RESPONSE TO DEGRADED CORE ACCIDENTS

]

1. Accident scenarios which introduce hydrogen into the drywell shall be described. Scenarios will be based on line breaks that are consistent with a recoverable degraded core. The largest break considered shall be limited to a size equivalent with the throat of a single safety relief valve.

2. Vessel blowdown and drywell response prior to vessel depressurization shall be predicted with a recognized analysis code. Realistic assumptions shall be used in calculating the drywell's response to vessel blowdown.

3. Vessel blowdown and core heatup following depressurization of the reactor coolant system will be predicted with a degraded core analysis meeting the acceptance criteria for Task 7. ]

[) Vessel blowdown to the drywell shall include the period of 1

~

, recovery from the degraded condition.

4. The drywell response shall be calculated using an analysis code meeting the acceptance criteria for Task 5. ' Parameter studies shall be completed to determine variations in plant unique features such as the hydrogen mixing system or vacuum breakers. -

4

5. The potential for existence of combustion phenomena unique

,' to the drywell shall be evaluated. Criteria for the existence of l inverted diffusion flames in the drywell shall be established.

These criteria shall include definition of oxygen inflow rates, ]

bulk compartment hydrogen concentration, and air inlet n'ozzle ]

geometries required to sustain an inverted diffusion flame. If ]

these criteria are satisfied, the effect of inverted diffusion flames on the drywell environment shall be defined using i .

3 4-125 2/14/S5 I

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= .

m existing experimental data and analytical techniques or from a suitable test. Drywell essential equipment exposed to a potential inverted diffusion flama environment will be shown to meet the acceptance criteria of Task 11.

6. The pool swell transient shall be defined based upon expected combustion in the drywell. Drywell and containment structures and components shall be evaluated to determine that pool swell does not impose structure, equipman't or support

, loadings greater than previously analyzed., This may be accomplished by demonstrating that pool swell loads do not exist or that pool swell loads are enveloped by the present design loads, or that essential structures and components survive the pool swell event. The LOCA design basis drywell to containment ]

. pressure differential will be compared to the differential ]

pressure transient' produced by hydrogen combustion. No pool ]

j m swell loadings will be evaluated if the drywell to containment ]

differential pressure for a design basis event exceeds the ]

4 hydrogen combustion differential pressure for the length of the ]

transient. ]

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ACCEPTANCE CRITERIA FOR TASK 11 EQUIPMENT SURVIVABILITY ANALYSIS PROGRAM

}

1.

A' list of equipment required to survive hydrogen generation ]

events shall be prepared for each plant. Equipment meeting the following criteria shall be included on this list:

I

- Equipment and systems which must function to mitigate the consequences of the event

- Equipment and structures required to maintain the integrity of the containment pressure boundary 1

- Systems and components required to maintain the core in a i

j safe shutdown condition ij

'i _

- Instrumentation and systems which will be used to monitor

U.) the course-of the event and provide guidance to the ]

operat6r for initiating actions in accordance with the ]

Emergency Procedure Guidelines ]

4

- Components whose failure could preclude the ability of 1 the above systems to fulfill its intended function ]

The effects of hydrogen combustion are limited to the

! containment and drywell. .Only equipment located in these two

- compartments shall be evaluated for i nclusion on the j

survivability list.

l Degraded core accidents evolve over a- relatively long period of time before zircaloy oxidation begins. Many components will have performed their safety function before hydrogen combustion can begin. If these components are not required to function

. , - , during or after hydrogen combustion, and if failure of the '

i ~d 4-140 2/14/85 l

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component will not compromise plant safety or adversely affect the performance of equipment required to survive hydrogen ]

combustion, then the component will not be required to survive ]

these accidents. )

!' 2. The equipment and its internal component temperature ] t responses will be calculated using an accepted heat transfer

. code. This code shall be capable of solving steady-state and I

transient heat conduction problems including radiant heat i! transfer in one, two and three dimensional cartesian or cylindrical coordinates. The analysis code shall be capable of f

analyzing time dependent boundary conditions.

Equipment models shal1 be based on equipment drawings and )

i manufacturer's data which account for the as-installed )

! orientation and mounting arrangement. Models shall be ]

~

,  ; constructed considering the most appropriate coordinate system, )

component materials, internal heat generation, internal volumes 1 or air spaces, and specific thermal properties of the materials )

of construction. Boundary conditions shall be established for ]

all conducting surfaces. ]

3. The number of components to be modeled and/or analyzed may ]

be limited if one of the following criteria is met:

j A. The identical component model has been previously analyzed with a more limiting thermal environment and found to be acceptable.

l B. A similar, more thermally responsive component model, j has been determined to provide conservative thermal response results which meet the survivability criteria, i

Components may be judged to be similiar if the thermal ]

mass of two components, materials for two components, )

4-1 41 2/14/85

i n

or overall geometry for twq components can be shown to be comparable or conservative.

4. The thermally limiting component shall be a component ]

or subassembly of a piece of equipment required to survive ]

hydrogen combustion which is determined most likely to fail during a hydrogen combustion temperature transient.

5. Thermal environments produced by deflagrations, diffusion ]

, flames and inverted diffusion flames shall be defined for the locations of equipment required to survive these tra1sients.

4 The deflagration thermal environment shall be defined based on containment response analysis produced in Task 8. The diffusion I flame thermal environment shall be defined by scaling up of test ]

data from appropriate tests in the 1/4 scale test facility and )

meeting the acceptance criteria identified in Task 9. The )

inverted diffusion flame thermal profile for the drywell shall be defined based upon experimental data or analyses using the j acceptance criteria identified in Task 10. All of the thermal profiles shall be defined based on realistic experimental data or analyses. Factors of conservatism need not be applied to the definition of the thermal environments.

6. Equipment and components shall have demonstrated the ability ]

to survive a hydrogen burn temperature transient if one of the following criteria is met:

l A. The equipment surface temperatur's is equal to or below the equipment qualification temperature.

i i

B. If the surface temperature exceeds the equipment qualification, temperature, then the equipment or .

1 component will survive a hydrogen burn if the

,- temperature response of the most thermally limiting 4-142 2I14/85 J

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I

. component is equal to or below the component qualification temperature.

C. The equipment surface temperature is equal to or below the equipment survivability temperature. The survivability temperature shall be defined as a temperature, higher than the qualification temperature, at which the equipment has been demonstrated to operate by analyses or testing. ,

Component qualification temperature shall consider the period of ]

time that a component is maintained at a specific temperature. ]

7. Equipment and components shall demonstrate the ability to )

survive a hydrogen burn pressure transient by meeting one of the following criteria:

A. The equipment experiences a peak pressure or ]

differential pressure, as determined from containment )

deflagration analysis acceptable per criteria )

identified in Task 8, below the equipment qualification )

pressure. ]

B. The equipment can be shown to be insensitive to pressure increases

6. If a piece of equipment or critical component cannot be ]

shown to survive, then measures shall be identified to assure survivability. These measures may include but are not limited to:

A. Protecting the component by use of:

1) Shields

2) Insulation

3) Cooling 4-143 2/14/85

.m B. Replacing the component with equipment which will )

survive the hydrogen burn environment. ]

C. Relocating the component to a milder environment l

l 4-144 2/14/85 l.

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ACCEPTANCE CRITERIA FOR TASK 12 VALIDATION OF ANALYTICAL METHODS 1

1. To validate the methodology used to construct equipment thermal response models, the predicted response of a mathematical model of a complex calorimeter in known thermal

. environments resulting from hydrogen dif fusion flames shall be compared with the measured response of the actual calorimeter.

The methodology will be verified if the predicted response is conservative compared to the measured response. This validation

process shall be completed in two thermal environments with different radiative and convective contributions to the total surface heat flux.

2. The methodology used to predict the equipment thermal response using mathematical models of the equipment and thermal

} environments derived from containment deflagration response predictions from CLASIX-3 analysis shall be validated.

Validation can be accomplished by showing the predicted response of a mathematical model of the complex calorimeter, using a predicted thermal environment from CLASIX-3 analysis of a known condition 'in the 1/4 scale facility, is conservative compared to the measured response of the complex calorimeter on the 1/4 scale facility.

3. Combustion parameters for CLASIX-3 predictions as follows shall be acceptable for validating CLASIX-3: ]

t .A. Hydrogen volume percent. required for ignition 6 v/o B. Hydrogen volume percent required for propagation 6 v/o C. Hydrogen fraction burned .65

)

4-153 2/14/85

l I

1 D. Minimum oxygen volume percent for ignition 5 v/o E. Minimum oxygen volume percent to support 0 v/o combustion F. Flame speed 6 ft/sec Heat removal from the 1/4 scale facility shall be consistent ]

with the methodology used for full scale containment analysis. ]

The containment spray carryover fraction in the facility shall ]

be determined.

1 A CLASIX-3 prediction shall be completed using the same ]

assumptions as used in previous licensing analysis. ]

Specifically, combustion shall be initiated when hydrogen ]

concentration reaches 8 v/o with 85 % of the hydrogen burned. ]

4. The CLASIX-3 predictions of 1/4 scale test temperatures and ]

pressures shall be compared with measured temperatures and ]

pressures. The intent of this comparison shall be to ]

demonstrate that CLASIX-3 conservatively predicts compartment ]

average peak temperatures and pressures. Temperatures produced ]

by any localized hydrogen combustion shall be compared with the ]

compartment averaged temperature response. ]

I

! 4-154 2/14/95

[ ACCEPTANCE CRITERIA FOR TASK 13 COMBUSTIBLE GAS CONTROL EPG

}

1. A symptom based emergency procedure guideline which provides ]

guidance to the reactor operator on utilization of hydrogen control equipment shall be developed. The guideline shall specifically provide guidance on use of the hydrogen igniters, the drywell hydrogen mixing systems and the hydrogen recombiners. Operator actions shall be initiated based upon plant symptoms which are independent of a specific accident sequence.

]

2. The operator actions specified in the . emergency procedure ]

guidelines shall preserve containment integrity and equipment function to the greatest extent possible. The guideline shall indicate limits for securing equipment in order to preserve equipment function and maintain containment integrity.

, ~. '

3. The emergency procedure guideline shall provide guidance to the operator for all postulated accidents and transients including accidents and transients which are outside the existing design basis. This is in accordance with the requirements of NUREG-0737. All accident scenarios and plant conditions considered in developing the emergency procedure guidelines need not be considered in licensing analysis of hydrogen generation events.

.)~ ~

• 4-163 2/14/S5 Om ae ,e e

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ACCEPTANCE CRITERIA FOR TASK 14  !

NEVADA TEST SITE DATA EVALUATION

]

1. Data obtained by EPRI from a series of tests conducted in a ]

large scale hydrogen dewar and intended to provide generic information on the performance and thermal response of selected nuclear plant equipment under a range of hydrogen burn environments shall be evaluated. i

)' 2. Nuclear plant equipment used in the Nevada Test Site (NTS)

', tests will be reviewed and equipment and cables which are

'b similar in manufacture and design to equipment utilized by HCOG member utilities shall be identified. Equipment and cables not applicable to HCOG member utilities shall also be identified.

3. Equipment and components used in the NTS test series and

+

similar to equipment and components used by HCOG member utilities shall be eval.uated to determine all failures which l- occurred in tests where the hydrogen concentration was less than I 10 volume percent. The cause of failure and, if available, the

. manufacturer's evaluation of the failure, shall be identified.

f

4. Premixed combustion tests for hydrogen concentrations at ]

or below 10 volume percent shall be evaluate,d for equipment ]

! performance and thermal response. Since the distributed igniter i system provides reliable ignition for hydrogen concentrations at

{ 6 volume percent, concentrations above 10 volume percent are not j realistic for recoverable degraded core accidents.

I 5. Data from premixed and continuous hydrogen injection tests shall be reviewed to provide a comparison between assumptions J  ;

4-170 2/14/85

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r-

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~ The following

',_ used in licensing analysis and test results.

{ items will be compared with the NTS data results:

4 A) The concentration at which ignition occurs

] Apparent flame speeds in the facility

< B)

C) Burn completeness for various conditions D) Effects of steam injection on combustion E) Effects of fans and sprays on combustion s

4 0

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4-171 2/14/85

\ .;

5

r MARK lli CONTAINMENT HYDROGEN CONTROL OWNERS GROUP som a. nodes enoi, mon c/o wssissippi Power and Light e P.O. Dox 1640 e Jockson, %ssissippi 09205 601 969 2458 February 14, 1985 BGN-028 U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C'. 20555 .

-~

Attention: Mr. Robert Bernero

Subject:

Hydrogen Control Owners Group Submittal of Revised Acceptance Criteria For Hydrogen Control Program Plan ,,

References Letter BGN-024 from S.B. Bobbs to Mr. B.R. Denton

, The reference letter transmitted the Hydrogen Control Owners' Group (BCOG) Hydrogen Control Program Plan. Several meetings o have been held with members of your staff over the course of the last three weeks to discuss this program plan. As a l result of these meetings numerous changes have been proposed l to the acceptance criteria. Some of the changes have been proposed by members of your staff and some of the changes have been proposed by BCOG to correct typographical errors, grammatical errors or ommissions.

Enclosed with this letter are proposed revisions to the acceptance criteria for all fourteen tasks identified in the program plan. The proposed revisions in the acceptance criteria provide a basis for agreement between BCOG and your staff. BCOG requests that your staff expeditiously review the l revised acceptance criteria.

In order to support the 1/4 scale test program, it is necessary to have NRC approval of the revised acceptance m

S O N J f Jf'Iy % If 3S pp.

criteria for Tasks 1, 7, 9, and 12 prior to scoping tests which are currently scheduled to begin on March 15, 1985.

BCOG plans to submit a revised program plan to incorporate the results of the recent meetings with the NRC by March 1, 1985.

, BCOG requests that the NRC provide a Safety Evaluation Report documenting acceptance of the complete program plan by April 9, 1985.

This submittal was compiled by BCOG from the best infornietion -

available for submittal to the Nuclear Regu]atory Commission.

The submittal is believed to be complete and accurate, but it is not submitted on any plant specific docket. The information contained in this letter and its attachments _.. -

should not be used for'evaluatfon of any specific plant unless the information has been endorsed by the appropriate member utility. BCOG members may individually reference this letter in whole or in part as being applicable to their specific plants.

, BCOG appreciates the NRC staff's support to date in reviewing the program plan. We look forward to concluding the review effort and establishing a mutually acceptable program plan.

i Sincerely, d b I Chairman, BCOG Attachment p 'cc: Mr. Carl R. Stable Bydrogen Control Program Manager D. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C. 20555 l

Er. Charles G. Tinkler Containment Systems Branch D. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation

. Washington, D. C. 20555 Mr. John Cummings, Project Manager

- Bydrogen Studies, Division 4441 Sandia National Laboratory Albuquerque, NM 87185

t

- ACCEPTANCE CRITERIA POR TASK 1 ESTABLISH MOST PROBABLE HYDROGEN GENERATION EVENT I

r 1 i

1. Hydrogen generation events which involve amounts of hydrogen production up to the equivalent of oxidizing 75%'of active fuel cladding shall be defined. Probabilistic considerations shall be used to determine the most probable initiating event. Plant __

systems available to mitigate the event will be consistent with assumptions regarding event progression and recovery of lost vessel inventory makeup systems. The frequency of occurrence l for a-variety of postulated initiating events shall be based on.

existing BWR/6 prob'abilistic data and considered in conjunction with loss of all core makeup to determine the probability of core melt. The consolidated events with the highest probability of leading to hydrogen ~ generation without gross core melting shall be established. . - 3

2. Station blackout events and Anticipated Transients Without l l

Scram (ATWS) shall 'be demonstrated to be low probability events I which need not be considered as probable precursors to I recoverable degraded core accidents. The probability of these I events; leading to a recoverable degraded core acci' dent shall be i shown to be less than 1x10-6 events per reactor year. l

3. $perator actions to recover various ECCS systems and respond te' plant conditions will be consistent with symptom based emergency operating procedures or guidelines. The I consequences of reasonable variations in the timing for operator 1 actions to depressurize the vessel and to recover core I makeup shall be considered. l

! 4. A recoverable core geometry shall be maintained by assuring j that adequate core make-up is provided prior to the onset of i

6. ,

4-9

e.

gross core melting. Melt shall be defined as the percentage of  :

the core for which the metal cladding temperature exceeds the I melting point of zircaloy (21700K). Gross core melting shall be I that amount of core melt which would cause the core to be unrecoverable.

I I

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ACCEPTANCE CRITERIA FOR TASK 2 SELECT MITIGATION SYSTEM i

i

1. The mitigation system shall not create conditions which impose unacceptable loads on the containment structure.

2. Recognizing the Mark III containment is a " working containment", the hydrogen mitigation system shall not present a safety hazard to operating personnel in containment during periods of normal plant operation.

Inadvertent actuation shall not present a hazard to plant personnel working in the containment.

3. Mitigation syste~m actuation shall not produce unacceptabie' environmental effects on equipment required to:

A. protect the containment integrity B. recover the reactor core, C. mitigate the consequences of the accident D. evaluate and follow the course of the ,4ccident and l provide guidance to the operator for initiating actions I in accordance with the Emergency Procedures Guidelines l E. function in order to prevent failure of components. I required to function l This can be accomplished by showing that the results of l

\ -

4-16

mitigation system actuation does not exceed the environmental qualification envelope of essential equipment. Inadvertent actuation of the mitigation system during normal plant operations shall not adversely affect systems and components needed for safe operation of the p1;nt.

4. The mitigation system shall prevent accumulation of hydrogen I to detonable mixtures under conditions conducive to combustion l .

following a hydrogen generation event.

i

5. The hydrogen mitigation system shall not endanger the health ~~"

and safety of the public due to planned or inadvertent actuation and shall meet the requirements of 10CFR100 as applicable.

6. The hydrogen. mitigation system shall be capable- of-demonstrating its operability by periodic surveillance tests.

7. The hydrogen mitigation system shall be capable of maintaining the containment integrity in the environment present in the Mark III containment after a hydrogen generation event.

The mitigation system shall be environmentally and seismically qualified or capable of being qualified in accordance with the requirements of IEEE-323 and IEEE-344 as applicable.

8. The hydrogen mitigation system equipment and components shall be readily available and shall not require substantial efforts to procure or fabricate the equipment.

l l

L .

4-17 l

l

ACCEPTANCE CRITERIA FOR TASK 3 DESIGN HYDROGEN IGNITION SYSTEM i

1. In order to protect the i containment integrity, the spacing of igniters throughout the containment and drywell volume should assure that hydrogen ignition occurs that pocketing of hydrogen does not at occur. low concentration and .

igniters by a distance of 30 ft. with all Separation of shall be acceptable. The igniter sp6cing of 30 ft. need igniters operable maintained in the large, open area between the refueling not be --

floor and which the containment dome or in the lower regions of the drywell are subject to submersion following a loss of coolant accident. The separation distance between operable igniters i be 60 _may-ft. if' one Wivision of engineered safeguard feature AC

~l power is inoperable. The separation criterion may be modified I to 35 feet with all igniters operable or 70 feet if one division I of engineered safeguard feature power supply is inoperable in order to account 1 for construction interferences and support I availability.

I

2. Igniter locations shall not present a hazard to personnel working in containment during testing or inadvertent operation.

3. The hydrogen igniter device usedindistribuledignition systems must be capable of functioning in the environment present in a Mark III containment following a degraded core accident. In order to assure that the igniter will be-functional following the accident, the igniter and associated support components located inside the containment should be environmentally qualified in accordance with the requirements of f

Im 4-25

l l

IEEE-323. Supports for the igniter assembly should be designed I to withstand the appropriate design load combinations. The igniter device should be sealed to assure that the presence of containment sprays or an all steam environment does not adversely affect component operation. If the igniter device must be submerged or subject to pool swell, the component must be designed to withstand the anticipated submergence or pool I swell impact loads. The effects of high energy pipe whip and jet I impingement shall be considered. I

4. The operating temperature for the igniter device must assure reliable ignition of hydrogen at low concentrations. A minimum l surface temperature of 17000F at an applied voltage of 12.0v for the igniter shall be acceptable to meet this -

requirement.

• glowA min _ plug imum ' surface temperature of 15000F will be maintained at a minimum voltage of 10.8v.

5. The hydrogen ignition system shall be sufficiently redundant to assure that no single active or passive failure will prevent the system from performing its intended function. The ignition system shall be divided into divisional subsystems powered from redundant onsite and offsite emergency safeguard feature power supplies. In enclosed regions of the containment which may be susceptible to pocketing of hydrogen, separate igniters powered from redundant power supplies shall be installed.

6. The hydrogen ignition system shall have the capability to be initiated prior to onset of hydrogen production. Manual initiation of the system shall be acceptable provided that guidance is available to the operator on system initiation procedures. A minimum of 10 minutes shall be available between 1 I the time when the vessel level reaches the top of the active i fuel and the time when siginificant hydrogen production begins I for the most probable hydrogen generation event identified in l Task 1. l l

Le 4-26 l

7. The hydrogen mitigation system shall be designed as seismic Category I system and in accordance with IEEE-344 and shall be designed to withstand the effects of the SSE and remain functional.

8. The hydrogen ignition system shall be designed and procured as Safety Class 2, Quality Group B equipment.

9. The use of A.C. power for the igniter system is acceptable provided that criterion 2 in Task 1 is satisfied with respect to i station blackout being demonstrated to be sufficiently I improbable.

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10. Technical specification limits shall be established to assure that the hydrogen ignition system will be operable when

. required. This will include requirements that igniters in enclosed regions are operable and that sufficient igniters are operable in other regions of the containment to assure ignition

, of hydrogen at low hydrogen concentrations. Surveillance requirements shall be specified to assure that the system is operable during normal plant operation. Surveillance requirements shall also be established to assure that the igniters are capable of achieving the requi' red surface temperature.

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ACCEPTANCE CRITERIA FOR TASK 4 i

CONTAINMENT ULTIMATE CAPACITY ANALYSIS I

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1. The containment structural integrity shall be established by l i

analyzing the ultimate internal pressure capacity. The ultimate l internal pressure capacity shall be defined as that pressure 1 l where a general state of yield is reached by the limiting I structural section or component. Local components such as I containment air lock and hatch seals, and penetrations shall be l shown to maintain their structural integrity at pressures which I equal or exceed the ultimate internal pressure capacity. I

2. The calculational method for determining ultimate internal _. I pressure capability may. include the use of actual materfal I properties with suitable margins to account for uncertainties in

, modeling, in material properties, in construction tolerances,

.and so on. Another method which can be used is to demonstrate the following specific criteria of the ASME Boiler and Pressure Code are met:

A. Steel containments shall meet the requirements' of the ASME Boiler and Pressure Vessel Code Section III, Division 1, Subsubarticle N-3220, Service Level C Limits, considering pressure and dead load alone. The evaluation

, of instability is not required.

I B. Concrete containments shall meet the requirements of the ASME Boiler and Pressure Vessel Code,Section III, Division 2, subarticle CC-3720, Factored Load Category, considering pressure and dead load alone.

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3. For containments which do not have vacuum breakers to admit additional air mass into the containment volume, the containment structure shall be demonstrated to withstand an external pressure differential due to a hydrogen combustion event which depletes oxygen or reduces the partial pressure contribution of steam due to the operation of sprays or coolers, or loss of containment inventory due to leakage. For containments which do not have vacuum breakers, the external pressure is acceptable if the containment will withstand a 4 psid pressure. '-

4. The ultimate pressure capability of the drywell structure I shall be established or the structure will be shown to have a l pressure capability in . excess ,of the maximum pressure which~ l could result from hydrogen combustion in the drywell. This l maximum pressure may be estimated with a containment response l analysis which meets the acceptance criteria for Task 8. The I ability of the drywell to withstand external pressurization 1 j shall be evaluated. l

5. The containment ultimate internal capacity shall be demonstrated to be greater than the peak internal pressure loading resulting from hydrogen combustion as calculated with a l containment response analysis which meets 'the acceptance l criteria of Task 8. l

6. The potential for accumulation of hydrogen above detonable

' limits in enclosed regions of the containment shall be evaluated. Postulated detonations which could occur in these enclosed areas shall be evaluated or it shall be shown that hydrogen concentrations are controlled by the selected

, mitigation system such that the probability of detonations

occurring is sufficiently small to assure that the consideration  !

of detonations is not warranted. l l

f 4-34

ACCEPTANCE CRITERIA FOR TASK 5 SELECTION OF CONTAINMENT RESPONSE ANALYSIS CODE l

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1. The containment response analysis code used for evaluating hydrogen combustion effects shall model Mark III containment features important to hydrogen generation events. Specific -

features which shall be modeled by the code include:

A) Mark III compartments consisting of at least the drywell, wetwell and upper containment. The code shall have the capability to nodalize additional components.

B) Suppression pool, behavior and the effect of upper -poor ~

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C) Flows paths between compartments such as vacuum breakers, combustible gas control compressors, or the LOCA vent system.

D) Flows into or out of compartments from hydrogen / steam injection, containment sprays, spray carry over, or break flows.

E) Bydrogen combustion in each compartment F) Energy loss due to containment heat removal systems or heat sinks.

2. The containment response code shall be able to predict pressure, temperature; and concentration of constituent gases in each compartment modelsd_

km 4-41

3. The analysis code shall model energy addition to various compartments due to hydrogen combustion. Hydrogen combustion energy addition rates shall be controlled by external input parameters such as ignition criteria, burn time, and completeness of burn. Control volumes may be assumed to be perfectly mixed. l

4. The containment response analysis code used to evaluate effects of hydrogen control system operation shall be compared with other accepted containment response analysis codes. This

~~

comparison shall show that the selected containment response analysis code predicts containment response in agreement with predictions of accepted codes. The suppression pool modeling shall be shown to represent the behavior of the Mark-III-'

suppression pool.

5. The containment response analysis code used to evaluate I effects of hydrogen control system operation shall be compared I with large scale test data relevant to the Mark III containment. i This comparison shall be completed in accordance with the )

I acceptance criteria identified for Task 12. l 9

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4-42

ACCEPTANCE CRITERIA FOR TASK 6 HYDROGEN COMBUSTION TESTING I

1. A program to evaluate completed and on-going industry l

efforts concerning hydrogen generation events, combustion testing, and equipment testing shall be conducted. Data which affects the analysis of hydrogen combustion phenomena or the design and use of a distributed igniter mitigation system shall be reviewed for applicability to Mark III hydrogen control programs. __.

2. Information required to support burn parameter input and selection for containment response analysis shall be identifi_ed.__.

This will include da'ta to support selection of:

a) minimum concentrations of hydrogen for ignition b) completeness of burn c) flame propagation velocity d) steam effects on ignition

3. Mark III unique hydrogen combustion phenomena shall be evaluated. Phenomena which shall be evaluated include potential inverted diffusion flames in the drywell, potential standing diffusion flames above the suppression pool, and combustion of hydrogen rich / oxygen limited combustion conditions in the drywell.

i Le 4-57

4. The combustion phenomena in the Mark III containment shall be evaluated to determine if adequate oxygen can be recirculated to the suppression pool surface in order to support steady diffusion flames.

5. The ability to ignite hydrogen rich mixtures in steam rich ,

and oxygen lean atmospheres shall be evaluated. Ability to ignite these mixtures in a condensing environment shall also be evaluated. Testing shall verify the values for combustion initiation assumed in analyses. -

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l ACCEPTANCE CRITERIA FOR TASK 7 GENERATION OF HYDROGEN RELEASE BISTORIES I

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1. Codes used to calculate hydrogen generation release histories shall model BWR/6 cores. The code shall physically model BWR/6 fuel assemblies, fuel channels, control rod blades -

and include representations of upper vessel components. The code shall have the ability to predict hydrogen produced by oxidation of the zircaloy cladding, the zircaloy fuel channels, and the stainless.s. teel control blade housing. The code shall-account for energy produced by decay of fission products in the fuel and energy produced by oxidation reactions. The code shall have the capability to analyze heat transfer by conduction out of the fuel and cladding, convective heat transfer between steam and and affected components, and radiant heat transfer. The code shall provide the capability to predict level in individual power bundles including two phase level and simultaneously balance water level in the bypass region. The code shall provide an accurate mass and energy balance throughout the control volumes. -

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Correlations used to predict hydrogen production shall be

! conservative. The Cathcart-Pawel correlation for hydrogen production as a function of temperature shall be acceptable for temperatures below the zircaloy phase transition temperature.

The Baker-Just correlation shall be extrapolated linearly to t

provide conservative predictions of hydrogen production at temperatures above the Baker-Just data.

! 2. Operator actiona assumed in calculating hydrogen generation i

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histories shall be consistent with guidance provided to the operator in symptom based emergency procedures. The operator shall be assumed to have depressurized the reactor pressure vessel prior to the start of core heatup. The vessel shall be assumed to remain depressurize6 throughout the subsequent core i heatup, hydrogen production, recovery of vessel injection, and quenching of the core. The operator will be assumed to devote all of his efforts to recovering vessel makeup once he has __

i recognized that inadequate core . cooling conditions exist. I Variations in the time for completion of operator efforts to i depressurize the vessel and to recover core makeup flow shall be  !

analyzed to determine the effect on hydrogen production.

3. The code utilized to predict hydrogen generation shall provide a reasonable representation of degraded core behavior.

The code shall model the oxidation rate as a function of zircaloy temperature and provide for oxidation termination at high temperatures. A conservatively high value of 2400oK cs a l maximum shall be used for this irreversible oxidation cutoff.

Justification for use of the irreversible oxidation cutoff shall I be provided by evaluating the accumulation of an oxide layer on 1

-the cladding surface. If a small oxidation layer is formed on I the cladding surface, the 2400oK oxidation cutoff shall be l valid. The code shall not be required to accurately model core l

geometry deformations which occur during core heatup including l l.

molten zircaloy relocation. l

4. Hydrogen generation histories evaluated for input to the 1/4

scale test program shall be limited to hydrogen generation 3 histories produced by recoverable degraded core accidents. In order for an accident to be recoverable, the core must be l .

4 4-72

maintained in a coolable geometry. Once 30% of the total zircaloy inventory in the active fuel region exceeds the melting temperature of zircaloy, i.e., 2170oK, a coolable core geometry l can no longer be assured.

5. The sensitivity of code predictions of hydrogen generation ~'

i histories for variations in significant code input parameters shall be evaluated. Variations in the following significant --

parameters shall be assessed:

A. Core nodalization, i.e., number of unit cells

~~ ~~~

B. Zirc'aloy oxidatioh cutoff-temperatures C. Core reflood flow rates D. Reflood recovery timing E. Assumed initial core water level F. Timing for initial core uncovering 4

G. Timing for assumed reactor vessel depressubization l H. Total amount of active core zircaloy inventory allowed 1 -

to melt and still consider the accident recoverable l shall be varied to 50% l

6. Hydrogen release histories which are selected for input to the 1/4 scale test facility shall correspond to degraded 4

coreaccidents which can evolve based on symptom based emergency procedure guidelines. The reflood flow rates for h J

release histories which are selected for input to the 1/ydrogen 4 scale 4-73 t a- .

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test program shall correspond to the flow rates from systems installed in the plant and capable of providing injection to the vessel within the required time frame. The flow rates shall be based upon system flow rates to an essentially depressurized vessel. Only systems which are available with all supporting components and systems which can operate during a loss of offsite power event shall be considered in defining available reflood flow rates. Reflood flow rates considered shall be __

further limited to those flow rates which can be placed in service in time to prevent the accident from becoming non-recoverable. The time required to place a system in service shall be based on the amount of time required to realign the system for injection to the vessel, the time required to make

any physical modifications to system configuration, and the time required for the system to be pressurized and begin providing flow to the vessel. The timing for initiating the vessel reflood shall assure that the accident remains recoverable in accordance with criteria 4 at the end of hydrogen generation.

7. A hydrogen release history which produces a total amount of I hydrogen equivalent to oxidizing 75% of the active fuel cladding I shall be calculated. This hydrogen release history shall be i calculated in a manner which accounts for mechanistic degraded I core phenomena to the maximum extent possible. l l

4-74

ACCEPTANCE CRITERIA FOR TASK 8 CONTAINMENT RESPONSE ANALYSIS I

1. Analyses to evaluate the consequences of hydrogen release to I the containment, from a metal-water reaction of up to 75% of the fuel cladding surrounding the active fuel region, shall be -

conducted. The analysis shall specifically address effects produced by operation of the hydrogen control system. - - -

2. Accidents involving hydrogen release to the drywell and to the suppression pool shall be evaluated. Assumptions regarding containment and drywell initial conditions shall be based upon . I realistic assomptio~ns. This analysis shall include the period I from the time of occurrence of the initiating event until recovery from the degraded condition.

3. A containment response code and meeting the acceptance criteria for Task 5 shall be used to analyze the containment pressure and temperature response.

4. Hydrogen combustion parameters used for containment analysis shall have sufficient supporting information to jpstify their use. The following parameter values are acceptable for containment analysis:

1) Minimum hydrogen volume fraction required 0.06 for ignition.

2) Minimum hydrogen volume fraction to support 0.06 flame propagation.

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3) Hydrogen fraction burned 0.65 (Burn completeness)

4) Minimum oxygen volume fraction to support 0.05 ignition.

5) Minimum oxygen volume fraction to support 0.00 combustion. - - -

6) Speed of propa'ation g (flame speeds) 6 ft/sec

5. Initial pressure conditions for oxygen, nitrogen and steam . l partial presures shall be calculated from initial compartment temperatures, pressures and relative humidities.

6. Hydrogen release histories used in containment response i

, analysis shall meet acceptance criterion 7 under Task 7.

7. Operator actions during the time period of' the hydrogen generation event shall be consistent with actions required by plant symptom based emergency procedures. These actions shall determine when vessel depressurization occurs, containment l

. sprays are actuated and when hydrogen mixing systems are I activated.

8. Sensitivity studies shall be conducted to determine the  !

change in predicted containment response due to changes in input parameters. Analysis of the following cases shall be sufficient to assure that uncertainties in containment response 1

analysis have been adequately characterized based upon the I expected range of input parameters and assumptions. I l

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4-84 n- ..

A) Steam and hydrogen release rates one half of the base case value for a 75% metal water reaction.

B) Steam and hydrogen release rates twice the base case value-for a 75% metal water reaction.

C) Steam and hydrogen release rates four times the base case value for a 75% metal water reaction. __

D) Hydrogen ignition criterion changed to 10 v/o and burnup to 100% from the values stated in Acceptance Criteria 5.

• E) Flame propagation criterion changed to 7.5 v/o and burnup to 75% from the values stated in Acceptance Criterion 5.

F) Flame speed increased to 12 ft/sec from 6 ft/sec.

G) Containment spray flow increased to flow from two trains.

B) Containment spray flow reduced to zero.

I) Containment spray carry-over reduced to zero.

J) Convective heat transfer coefficient to beat sinks' reduced to zero.

K) Radiant beat transfer beam lengths reduced by 1/2.

, The results of the sensitivity studies on predicted compartment l l temperatures and pressures shall be evaluated. l u

4-85

9. A. representative case for containment response analysis shall use specific geometric and system parameters for a typical Mark III design such as the Grand Gulf Nuclear Station (GGNS). This case shall be demonstrated.to conservatively predict the response of containment arrangements other than GGNS or plant specific containment response analysis shall be conducted.

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l ACCEPTANCE CRITERIA POR TASK 9 DIFFUSION FLAME THERMAL ENVIRONMENT (1/4 SCALE TEST PROGRAM) l l

1. The containment thermal environment resulting from .

diffusion flames anchored at the suppression pool surface during recoverable degraded core accidents shall be defined using experimental data. The thermal environment shall consist of

, convective heat loading from hot gases, radiation from the 1 diffusion flame, and radiation from hot gases and hot gratings or other components. Data shall allow definition of the thermal . environment .in areas of the containment where ~

equipment required to survive thesh accidents is located.

2. The scaling basis for the test facility shall assure that j the ratio of inertial and buoyant forces is preserved I between the scaled test facility and full scale. l

3. The scaled test facility used to define the diffusion flame thermal environment, shall represent the Mark III containment plants. The containment geometry for each Mark III plant shall be simulated or it shall be shown that differences between plant

geometries do not affect the thermal environment. The major blockages to flow such as the steam tunnel or concrete portions of individual floors shall be sim'ulated. Grating shall be e

4-104

simulated to preserve the ratio between open areas and blocked areas.

Containment cooling systems such as containment sprays or safety related unit coolers shall be simulated in the scaled test facility. The scaled lowest containment spray flow rate from any member Mark III containment plant with containment sprays or the scaled actual flow rate from a specific plant shall be used in the test facility in order to model the effect of heat --

transfer to the containment sprays. The sprays shall be demonstrated to produce bulk atmosphere mixing patterns which are representative of the bulk atmosphere mixing patterns expected at full scale.

The total heat transfer characteristics of the scaled test I facility shall be conservative with respect to the heat transfer characteristics of all full scale Mark III containment or representative of the actual heat transfer characteristics. It shall be demonstrated that the heat losses to the gratings, I walls and other heat sinks in the scaled test facility shall not i exceed the heat losses to gratings, walls, equipment and other I heat sinks in the full scale facility. Alternately, it may be i demonstrated that heat losses in the scaled test facility are I compensated for by other factors. A typical compensating factor I which could be considered is a comparison of heat sink capacity 1 included in the scaled test facility versus heat sink capacity 1 in the full scale plants. l The scaled test facility must have the capability to simulate

, variable hydrogen and steam flow into the facility. The hydrogen flow rate into the facility must be variable over the the range of expected hydrogen production rates. The hydrogen shall be injected into the facility at locations which correspond to the points of hydrogen release in the full scale plant.

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4. The repeatability of the test data shall be evaluated. A l set of tests with comparable initial conditions and identical I geometry shall be completed. Acceptable repeatability for l test data will be determined by comparing the- gas the l temperatures, velocities, and radiant heat fluxes. I Specifically, the following parameters will be compared for the i repeatability tests: l gas A) Peak temperatures in oF measured along a l circumference with the simulated SRV spargers at an I elevation just above the simulated BCU floor. Peak 1 temperatures shall be compared in the four chimneys and I in the region between azimuth 172.5o and 210o. l B) Peak radiant heat flux as measured by instrument R-184 in i the 315o chimney _.

l C) Peak ' gas velocity ~ measured by instrument W-184 in the 1 315o chimney l Test repeatability shall be acceptable if the range of each of l these parameters is less than or equal to 15%. If these l criteria are not met factors of conservatism shall be applied in defining the local thermal environment for asessing survivability of equipment.

5. The testing conducted in scaled facilities shall be l consistent with the course of events in a full scale plant based l upon emergency procedure guidelines. The ignition system shall be energized prior to injection of hydrogen. The simulated sprays shall be ' actuated' when the bulk average containment temperature reaches the temperature limit identified in the emergency procedure guidelines. The same number of spargers shall be open during testing as the number of spargers used to

depressurize the reactor pressure vessel plus one additonal sparger as appropriate to simulate a stuck open relief valve.

6. The parameters which could affect definition of the thermal I environment in a Mark III containment shall be evaluated in the scaled test facility. For each parameter which is evaluated, the test including that parameter shall be completed identically with tests which are conducted to assess repeatability. Each parameter may be judged to have no effect on the combustion transient. If the temperatures, gas velocities and-radiant heat flux measured in the test facility for all instruments at the

! BCU floor level are within the data scatter defined during I the repeatability tests, or these parameters are within 15% of I the mean value established during repeatability testing, the l l parameter will be assumed to have no effect. If the parameters are shown to have a significant effect, these parameters shall be addressed in the testing.

4-106

7. The thermal en:/ironment including gas temperature convective heat flux and radiative heat flux shall be defined for all areas in the wetwell and containment where equipment required to survive hydrogen ccmbustion is located. A limiting thermal environment in each area of the containment shall be established. The possible release points for hydrogen through stuck open safety relief valves, open ADS values, and release through LOCA vents shall be considered in establishing the __

limiting thermal environment. The effect of having two open relief valves under a het chimney, the effect of a single open relief valve below BCD floor grating, and the effect of i

simultaneous hydrogen release through the SRV spargers and LOCA,.

v.ents shall be evaluated in establishing the limiting thefmal environment.

i

8. Sufficient data on gas distribution throughout the wetwell and containment shall be obtained from tests with and without i operation of containment sprays to evaluate the effectiveness of

, hydrogen mixing with the containment atmosphere. A gas sampling system shall be included in the facility which is capable of measuring hydrogen, oxygen and water vapor concentrations at a number of different locations in the wetwell and containment.

The mixing data will be evaluated to demonstrate that mixing of the containment gases prevents significant accumulation of hydrogen. Hydrogen concentrations shall be shown to not exceed 8 v/o at elevations above the first row of igniters and that i detonatable mixtures do not exist. l l

l 9. Data shall be obtained from the test facility to validate analytical methods which are used by BCOG. An instrumented calorimeter with complex geometry shall be included in the facility. This calorimeter shall be used to validate the heat transfer methods used in calculating the temperature response of the component.

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ACCEPTANCE CRITERIA FOR TASK 10 EVALUATION OF DRYWELL RESPONSE TO DEGRADED CORE ACCIDENTS l

l

1. Accident scenarios which introduce hydrogen into the drywell shall be described. Scenarios will be based on line breaks that are consistent with a recoverable degraded core. The largest break considered shall be limited to a size equivalent with the -- .

throat of a single safety relief valve.

2. Vessel blowdown and drywell response prior to vessel depressurization shall be predicted with a recognized analys.is_.

code. Realistic assumptions shall be used in calculating the drywell's response to vessel blowdown.

3. Vessel blowdown and core heatup following depressurization of the reactor coolant system will be predicted with a degraded core analysis meeting the acceptance criteria for Task 7. l

Vessel blowdown to the drywell shall include the period of I recovery from the degraded condition.

4. The drywell response shall be calculated using..an analysis code meeting the acceptance criteria for Task 5. Parameter studies 'shall be completed to determine variatisns in plant unique features such as the hydrogen mixing system or vacuum breakers.

5. The potential for existence of combustion phenomena unique to the drywell shall be evaluated. Criteria for the existence of inverted diffusion flames in the drywell shall be established.

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( 4-124 1

These criteria shall include definition of oxygen inflow rates, I bulk compartment hydrogen concentration, and air inlet nozzle geometries required to sustain an inverted diffusion flame. If i l

these criteria are satisfied, the effect of inverted diffusion flames on the drywell environment shall be defined using existing experimental data and analytical techniques or from a -

suitable test. Drywell essential equipment exposed to a potential inverted diffusion flame environment will be shown to meet the acceptance criteria of Task 11.

6. The pool swell transient shall be defined based upon expected combustion in the drywell. Drywell and containment structures and components.shall be evaluated to determine that

~

pool swell does not impose structure, equipment or support loadings greater than previously analyzed. This may be accomplished by demonstrating that pool swell loads do not exist or that pool swell loads are enveloped by the present design loads, or that essential structures and components survive the pool swell event. The LOCA design basis drywell to containment l

pressure differential will be compared to the differential I pressure transient produced by hydrogen combustion. No pool I swell loadings will be evaluated if the drywell to containment I differential pressure for a design basis event exceeds the I hydrogen combustion differential pressure for the length of the I

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4 ACCEPTANCE CRITERIA FOR TASK 11 EQUIPMENT SURVIVABILITY ANALYSIS PROGRAM i

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1. A list of equipment required to survive hydrogen generation events shall be prepared for each plant. Equipment meeting the following criteria shall be included on this list: __

- Equipment and systems which must function to mitigate the consequences of the event

- Equipment and structures, required to maintain th'E'~

integrity of the containment pressure boundary

. - Systems and components required to maintain the core in a safe shutdown condition

- Instrumentation and systems which will be used to monitor the course of the event and provide guidance to the l operator for initiating actions in accordance with the i Emergency Procedure Guidelines ,,

- Components whose failure could preclude the ability of 1

, . the above systems to fulfill its intended function I L

l The effects of hydrogen combustion are limited to the containment and drywell. Only equipment located in these two compartments shall be evaluated for inclusion on the ,

survivability list.

Degraded core accidents evolve over a relatively long period of time before zircaloy oxidation begins. Many components will have performed their safety function before hydrogen combustion can begin. If these components are not required to function during or after hydrogen combustion, and if failure of the

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component will not compromise plant safety or adversely affect the performance of equipment required to survive hydrogen I combustion, then the component will not be required to survive I these accidents. l

2. The equipment and its internal component temperature responses will be calculated using an accepted heat transfer code. This code shall be capable of solving steady-state and transient heat conduction problems including radiant beat --

transfer in one, two and three dimensional cartesian or cylindrical coordinates. The analysis code shall be capable of analyzing time dependent boundary conditions.

Equipment mo'dels 'shall be based on equipment drawings and i manufacturer's data which account for the as-installed I orientation and mounting arrangement. Models shall be I constructed considering the most appropriate coordinate system, I i component materials, internal heat generation, internal volumes I or air spaces, and specific thermal properties of the materials l l of construction. Boundary conditions shall be established for I all conducting surfaces. l

3. The number of components to be modeled and/or analyzed may be limited if one of the following criteria is met:

i -

A) The identical component model has been previously analyzed with a more limiting th'rmal environment and found to be acceptable.

B) A similar, more thermally responsive component model, has been determined to provide conservative thermal response results which meet the survivability criteria.

Components may be judged to be similiar if the thermal mass i of two components, materials for two components, or overall. I geometry for two components can be shown to be comparable I or conservative.  !

O be 4-140

4. The thermally limiting component shall be a component or subassembly of a piece of equipment required to survive I hydrogen combustion which is determined most likely to fail during a hydrogen combustion temperature transient.

5. Thermal environments produced by deflagrations, diffusion -

flames and inverted diffusion flames shall be defined for the locations of equipment required to survive these transients.

The deflagration thermal environment shall be defined based on . _ _

containment response analysis produced in Task 8. The diffusion flame thermal environment shall be defined by scaling up of test I data from appropriate tests in the 1/4 scale test facility and .I meeting the . acceptance criteria, identified in Task 9. thy' l inverted diffusion flame thermal profile for the drywell shall be defined based upon experimental data or analyses using the acceptance criteria identified in Task 10 All of the thermal profiles shall be defined based on realistic experimental data or analyses. Factors of conservatism need not be applied to the definition of the thermal environments.

6. Equipment and components shall have demonstrated the ability to survive a hydrogen burn temperature transient if one of the following criteria is met: "

A) The equipment surface temperature is equal to or below the equipment qualification temperature.

B) If the surface temperature exceeds the equipment qualification temperature, then the equipment or component will survive a hydrogen burn if the temperature response of the most thermally limiting component is equal to or below the component qualification temperature.

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1 C) The equipment surface temperature is equal to or below the equipment survivability temperature. The survivability temperature shall be defined as a temperature, higher than the qualification temperature, at which the equipment has been demonstrated to operate by analyses or testing. l Component qualification temperature shall consider the period of I time that a component is maintained at a specific temperature. I __

7. Equipment and components shall demonstrate the ability to survive a hydrogen burn pressure transient by meeting one of the following criteria:

A) The equipment experiences a peak pressure or I differential pressure, as determined from containment I deflagration analysis acceptable per criteria identified l in Task 8, below the equipment qualification pressure. l B) The equipment can be shown to be insensitive to pressure increases

8. If a piece of equipment or critical component cannot be shown to survive, then measures shall be identified to assure survivability. These measures may include but are not limited to:

A) Protecting the component by use of:

1) Shields

2) Insulation

3) Cooling l

1 B) Replacing the component with equipment which will survive the hydrogen burn environment.

i C) Relocating the component to a mild'er environment 4-142 4

ACCEPTANCE CRITERIA FOR TASK 12 VALIDATION OF ANALYTICAL METEODS I

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1. To validate the methodology used to construct equipment thermal response models, the predicted response of a mathematical model of a complex calorimeter in known thermal environments resulting from hydrogen diffusion flames shall be --

compared with the measured response of the actual calorimeter.

The methodology will be verified if the predicted response is conservative compared to the measured response. This validation process shall be -completed in ,two thermal environments with' different radiative and convective contributions to the total surface heat flux.

2. The methodology used to predict the equipment thermal response using mathematical models of the equipment and thermal environments derived from containment deflagration response predictions from CLASIX-3 analysis shall be validated.

Validation can be accomplished by showing the predicted response of a mathematical model of the complex calorimeter, using a predicted thermal environment from CLASIX-3 analysis of a known condition in the 1/4 scale facility, is conservative compared to the measured response of the complex calorimeter on the 1/4 scale facility.

3. Combustion parameters for CLASIX-3 predictions as follows shall be acceptable for validating CLASIX-3: l A) Bydrogen volume percent required for ignition 6 v/o

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B) Hydrogen volume percent-required for propagation 6 v/o C) Bydrogen fraction burned .65 D) Minimum oxygen volume percent-for ignition 5 v/o E) Minimum-oxygen volume percent to support 0 v/o combustion --

F) Flame speed 6 ft/sec

• Heat removal from the 1/4 scale facility shall be consist.ent l

.with the methodo16gy used for full scale containment analysis. I The containment spray carryover fraction in the facility shall l be determined.

A CLASIX-3 prediction shall be completed using the same I assumptions as used in previous licensing analysis. 1 Specifically, combustion shall be initiated when hydrogen I concentration reaches'8 v/o with 85 % of the hydrogen burned. l

4. The CLASIX-3 predictions of 1/4 scale test temperatures and I pressures shall be compared with measured temperatures and I

pressures. The intent of this comparison shall be to I demonstrate that CLASIX-3 conservatively predicts compartment I average peak temperatures and pressures. Temperatures produced l

by any localized hydrogen combustion shall be compared with the I compartment averaged temperature response.  !

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l ACCEPTANCE CRITERIA POR TASK 13 COMBUSTIBLE GAS CONTROL EPG I

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1. A symptom based emergency procedure guideline which provides I guidance to the reactor operator on utilization of hydrogen control equipment shall be developed. The guideline shall specifically provide guidance on use of the hydrogen igniters, + - -

the drywell hydrogen mixing systems and the hydrogen recombiners. Operator actions shall be initiated based upon plant symptoms which are independent of a specific accident sequence. , ,_

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2. The operator actions specified in the emergency procedure I guidelines shall preserve containment integrity and equipment function to the greatest extent possible. The guideline shall indicate limits for securing equipment in order to preserve equipment function and maintain containment integrity.

3. The emergency procedure guideline shall provide guidance to the operator for all postulated accidents and transients including accidents and transients which are outside the existing design basis. This is in accordance with the requirements of NOREG-0737. All accident scenarios and plant conditions considered in developing ths emergency procedure guidelines need not be considered in licensing analysis of hydrogen generation events.

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ACCEPTANCE CRITERIA FOR TASK 14 NEVADA TEST SITE DATA EVALUATION I

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1. Data obtained by EPRI from a series of tests conducted in a l

large scale hydrogen dewar and intended to provide generic -

information on the performance and thermal response of selected nuclear plant equipment under a range of hydrogen burn _ _ _

environments shall be evaluated.

2. Nuclear plant equipment used in the Nevada Test Site (NTS) tests will be reviewed and equipment and

.s mi ilar in manufacture and design to equipment cables which .are utilized by ECOG member utilities shall be identified. Equipment and cables not applicable to BCOG member utilities shall also be identified.

3. Equipment and components used in the NTS test series and similar to equipment and components used by BCOG member utilities shall be evaluated to determine all failures which occurred in tests where the hydrogen concentration was less than 10 volume percent. The cause of failure and, if available, the manufacturer's evaluation of the failure, shall be identified.

4. Premixed combustion tests for hydrogen concentrations at l or below 10 volume percent shal.1 be evaluated for equipment I performance and thermal response. Since the distributed igniter system provides reliable ignition for hydrogen concentrations at 6 volume percent, concentrations above 10 volume percent are not realistic for recoverable degraded core accidents.

5. Data from premixed and continuous hydrogen injection tests shall be reviewed to provide a comparison between assumptions

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used in licensing analysis and test results. The following items will be compared with the NTS data results:

A) The concentration at which ignition occurs B) Apparent flame speeds in the facility C) Burn completeness for various conditions -

D) Effects of steam injection on combustion E) Effects of.- fans and sprays on combustion _ , , _ _ .

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