ML20053A637

Forwards Repts by R Strehlow Re Hydrogen Control Sys at Sequoyah Plant.Issues Raised by Repts Have Been Incorporated Into Review of Grand Gulf Hydrogen Control Sys

ML20053A637
Person / Time
Site:	Grand Gulf, Sequoyah, 05000000
Issue date:	05/17/1982
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Mcgaughy J MISSISSIPPI POWER & LIGHT CO.
Shared Package
ML20053A638	List: ML20053A637 ML20053A640 ML20053A643
References
NUDOCS 8205270043
Download: ML20053A637 (2)

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g 17 1CJ82 Docket File bcc: NRC PDR LB#2 File Local PDR DHouston NSIC EHylton PRC

' Docket fles.- 50-416/417 Wagner, OELD I&E ACRS (16)

RTedet 9 Mr. James P. McGaughy, Jr.

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to Assistant Vice President W. Butler S

Mississippi Power & Light Co.

C. Tinkler 6 NECgfY B

P. O. Box 1640 ED T_

Jackson, Missist.>ppi 39205 g

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Dear Mr. McGaughy:

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Subject:

Background Documents for. Hydrogen Control b

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Our Office of Polfgy Evaluation engaged Dr. R. Strehlow to provide an independent reYiew of the hydrogen igniter system (DIS) at the Sequoyah pl ant. The issues raised by Dr. Strehlow have been incorporated in our review of the Grand Gulf IIIS. So that you are fully aware of Dr. Strehlow's concerns, we are sending you copies of his 1981 reports dated January 9, May 1, and August 17 along with associated internal NRC corresponderce.

If you require any clarification of this matter, please contact M. D. Houston, Project Manager, (301)492-7564.

Sincerely,

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A. Sc encer, Chief Licensing Branch No. 2

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Division of Licensing

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Mr. J P. McGaugby Assistant Vice President Nuclear Production Mississippi Power & Light Company P. O. Box 1640 Jackson, Mississippi 39205 cc: Robert B. McGehee, Esquire Wise, Carter, Child, Steen and Caraway P. O. Box 651 Jackson, Mississippi 39205 Troy B. Conner, Jr., Esquire Conner and Wetterhahn 1747 Pennsylvania Avenue, N. W.

Washington, D. C. 20006 Dr. D. C. Gibbs, Vice President Middle South Energy, Inc.

225 Baronne Street P. O. Box 6100 New Orleans, Louisiana 70161 Mr. John Richardson Mississippi Power & Light Company P. O. Box 1640 Jackson, Mississippi 39205 fir. R. Trickovic, Project Engineer Grand Gulf Nuclear Station Bechtel Power Corporation Gaithersburg,' liaryland 20760 Mr. Alan G. Wagner Resident inspector Route 2, Box 150 Port Gibson, Mississippi 39150 e

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. UNITED STATES 8

Ii NUCLEAR REGULATORY COMMISSION

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Jan^uary 22, 1981 MEMORAriDUM FOR:

Ch' airman Ahearne Commissioner 'Gilinsky Commissioner Hendrie Commis~ioner Bradford s

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Edward J. Hanraha

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SUBJECT:

SPE REVIEW 0F HYDR 0GEti'C0tiTROL MEASURES FOR SEQUOYAH

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M hortly, the staff will brief the Commission with regard to whether the-January 31, 1981 license condition for Sequoyah has been satisfied, i.e.,

"TVA shall by testing and analysis show to the satisfaction of the tiRC staff that an interim hydrogen control system will provide with reasonable assurance protection against breach of containment in the event that a substantial quantity of hydrogen is generated" (emphasis added).

OPE comments with regard to a Commission decision-on this 1,icense condition -

are provided below.

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The immed' ate decision facing the fiRC is whether " reasonable assurance"of protection" required by the -January 31, 1981 license condition has been obt'ained through use of the IDIS.

In this regard, two principal aspects should be considered:

. Reasonable assurance against breach of containment due to direct over-

. pressure from hydrogen combustion, irrespective of equipment survivability.

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. Reasonable assurance against breach of containment due to failure of essential equipment to survive the effects of hydrogen combustion with the subsequent inability to maintain core integrity, possibly leading

-to eventual containment failure.

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Given the close connection.of ice condenser containment plants and the i

potentially significance of hydrogen effects, whatever decision is reached on Sequoyah should be applied to all ice condenser containment plants.

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In compliance witn its license conditions, TVA submitted to fiRR on December 1, 1980 its first quarterly report on.the research pro' gram for hydrogen j

control and'a revised Volume 2 of the Sequoyah Core Degradation Program l

Report which provides information on TVA's proposed Interim Distributed l

Ignition System (IDIS) as well as longer term efforts for a " final hydrogen l

control system."

In early January, the staff prepared a draft " Supplement fiol 4 to the Sequoyah Safety Evaluation Report (SER)" containing a preliminary evaluation of'the TVA submittals.

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Jim Milhoan (OPE) 7/O ^ ML30cM

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For,the Commission

• OPE Review OPE has reviewed the above documents with the assistance of Dr. Roger Strehlow, a nationally recognized expert in gas dynamics with particular enertise in^ hydrogen combustion.

Dr. Strehlow's evaluation report is attached.

Dr. Strehlow concluded that a well designed and maintained glow plug

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igniter system whic~h is energized only for testing or <hrring afavent"'

which has the. potential of generating.h,vdrpgen-is an effective way to protect the Sequoyah nuclear plants-from'the possibility of breaching the containment vessel due to inadvertent combustion of accumulated hydrogen.

(Dr. Strehlow also identified additional research needs and provided comments on combustion dynamics.)

t Dr. Strehlow's review was related primarily to the question of reasonable.

assurance against breach of containment due to direct overpressure from shydrogen combustion.

In this regard, Dr. Strehlow has identified mechanisms whi.ch could lead to explosion if a continuous flame is able to propagate in an ice condenser ty?e containment.

Even though he concluded the glow plugs will virtually eliminate the possibility of detonation in the contain-I recommend ment vessel, he recommended further research be accomplished.

the staff address Dr. Strahlow's comments before reaching a decision on

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"figl hydrogen control measures."

l With regard to. the second question (equipment sur.vivability)., Dr._StrAlow indicated that glow plug initiated burns will be much'less da'n'geroiTstfian- '

spark initiated burns because glow plugs will initiate burns at lower corfcentrations than sparks of the type that undoubtedly initiated the TMI' burn.

It appears that the lower the concentration at which hydrogen burns, the better chance of equipment survivability because of reduced D

flame propagation at low hydrogen concentrations.

Thus, glow plugs should be an improvement with respect to equipmentesurvivability.

Based upon our own review and that of Dr. Strehlow, I believe operation of the IDIS will reduce further any probability of breach of containment in the event that a substantial quantity of hydrogen is generated.

The question of whether the ' reasonable assurance" criterion has been satisfied appears to hinge on the question of equipment survivability.

(Equipment survivability is certainly improved by use of glow plug igniters.)

Equip-ment survivability will be addressed further in the next Supplement to the Sequoyah SER.

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Enclosure:

As stated cc: L. Bickwit l

S. Chilk

. Fraley

.4. Dircks H. Denton R. Tedesco W. Butler C. Tinkler C. Stahle

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Evaluation of the t.

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Igniter Concept for use in the j;

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Sequoyah Nuclear Plant I

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Mr. James Milhoan, P. E.

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January 9,19 81

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Overall Evaluaticn In my opinio.1, a well designed and maintained glow plug igniter system which is energized only for testing or during an event which has the potential of generating hydr' ogen is an ef fective way to protect the Sequoyah nuclear plants from the s.

possibility of breaching the contain~ ment vessel due to the inadvertent combustion of accumulated hydrogen.

Furthermore, it

./ is my opinion that the. implement'ation of this glow plug igniter

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technique will have no negative effects on overaY1 saf'ety in such a nuclear plant.

I base this opinion on the following information that was supplied to me by the Nuclear Regulatory Commission:

Tennessee Valley Authority, Sequoya.h Nuclear Plant Core Degradation Program, Volume I, Hydrogen Study, September 11, 1980

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News Release No.80-159, USNRC, September 11, 1980

. News Release No.80-163, USNRC, September 18, 1980 Safety evaluation report related to the operation Sequoyah Nuclear Plant, Units 1 and 2, Docket No. 50-327 and 50-328, Tenn'6'ssee Valley Authority, NUREG-00ll, Supplement No. 4, September,.19 80 Memorandum for:

ACRS members, from: J. C. Mark, Subject Notes on hydrogen burn with ignite'rs, December 4, 1980 Memorandum to:

AC'RS members, from:

H. Etherington, Subject Memorandum P. G. Shemwon to ACRS members :

" Quantity of H2 at TMI-2 and source."

Tehnessee Valley Authority, Sequoyah Nuclear Plant Core Degradation Program, Volume 2, Report on the Safety E. valuation of the Distributed, Ignition. System, December 15, 1980.

Tennessee Valley Authority, Sequoyah Nuclear Pl. ant, Research Program on Hydrogen Combustion and Control, Quarterly-Progress Report, December 15, 1980

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'Draf t ' copy 'of Supplement No. 4 to the Safety evaluation report by the Office of Nuclear Reactor Regulation, U, S. Nuclear Regulatory Commission in the matter of Tennessee Valley, Authority Sequoyah Nuclear Plant Units 1 and 2, Docket No's. 50-327 and 50-328, undated.

Attendance at the ACRS subcommittee meeting held in Washington, D. C. on January 6, 19 81.

A meeting with Mr. Tinkler and Nr. Butler of,the NRC staf.f on, the morning of January 7, 1.981.

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Other open literature references which he1 ped me form my opinion will be referenced in the detailed supporting statement that follows.

I also have opinions concerning the dynamics of a

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'gombustion explosion in a Sequoyah type conta'inment and new resqarch and data accumulation efforts which would be necessary to st'rengthen and quantify the justification for using glow plug These will also igniters as the~ only hydrogen control technique.

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Effe'ctiveness of the Glow Plugs.

The Singleton Lab, Fenwal and LLNL tests have shcwn the glow plugs that are being considered for the Sequoyah plant to be very r

effective' igniters down to 5% hydrogen even in the, presence of 15% dry steam.

Thus, in a real accident we now know - that the in the CV.

Further-igniters would initiate a partial burn at 5% H2 more, the Singleton lab' tests show that in a small vessel even 2 present initially a five minute " burn" reduces the.

with.3'5%

H H

concentration to about 0.1%.

This is very encouraging because 2

it shows that a. hot glow plug will act as an H2 scavenger even outside the flammability limit for upward propagation of about

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4% H Furt'hermore, sparks of the type that undoubtedly initiated 2

the Three Mile Island burn are not effective at such a low hydrogen

concentration.

It is important to note that glow-plug initiated burns will be much less dangerous than spark initiated burns.

This is because between 4-8% hydrogen in air burns with a very lazy upward propagating flame which spreads a'c a maximum hal'? angle of about 20 degrees and extinguishes when it reaches the top of the vessel.

This means two things:

1) the pressure rise will be minimal for such a burn, and.2) the hot product gases will be confined to this cone-shaped volume and subsequently will spread j

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'ajong the ceiling.

L. other words, the f, lame will not contact and therefore not heat most equipment that is in the containment vess'el.

Also, if the rate of hydrogen generation were slow so

'that the fans p'roduced A rather uniform hydrogen concentration, the b,u.rn would be almost continuous onie the hydrogen content

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reac'hed 4-5%.

. On the other hand, a fast leak which caused a localized higher concentration of hydrogen would also not be dangerous when ignited by the glow plug.

This is bgpause glow plugs strategically

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placed above potential ~ hydrogen scurees would ignite a high hydrogen concentration pltre on contact and only a localized high temperature burn would occur.

It is well documented (Cubbage and Marshall,1972) that such' a partial burn yields a pressure rise in a vessdl which is proport,ienal to the energy released by the localized burn (Joules) divided by the total volume of the vessel (m ).

Thus, a small localized burn cannot cause a. really large 3

pressure rise.

In my opinion, properly located and functioning glow plug igniters would reduce t.he probability of a burn leading to a

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transi' tion'to detonation to* virtually zero.

This io because the.

very weak flames produced by a 4-5% hydrogen burn cannot generate significant pressure waves or significant flow velocities ahead

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'1 of the flame.

This means that the mechanisms that lead to flame

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acceleration do not e'xist under these conditions.

In other words, 1

the weak 4-5% hydrogen flames will remain weak -ifre'spedtive~ ~of the environment'tha.t t' hey encounter.

Combustion dynamics in the Sequoyah containment vessel.

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The Sequoyah containment contains three main. compartments :

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1) t;he upper compartment,

2) the lower compartment, and 3) the l

ice' condenser.

The upper and lower compartments both have a rather low length-to-diameter (L/D) ratio and therefore if they y

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supporting only a simple over-pressure explosion.

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at Three Mile Island was essentially of this type and that is what happened there when the hydrogen concentration reached about 8%.

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In such a case, the flame propagates slowly enough such that the r*

pressure is relatively uniform spatially in the vessel during the burn and simply rises'with time (approximately as a' cubic of

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time; see Bradley and Pltcheson,1978 a, b).

This is true even Under if there is some acceleration due to turbulence generation.

tl se conditions, there are essentially no pressure waves generated.

4 Note that at TMI the transit time of a sound wave from top to bottom to top is about 0.2 seconds and the burn took about 10 seconds.

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lower compartments are not independent but are connected by '_he

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ice condenser.

In my opinion, this is a very dangerous configu-ration because it would generate pressure waves which could possibly lead to local over pressures that could breach the containment.

This is because the ice condenser contains hundreds of tubes (the spaces-between the baskets) which have a very large L/D anu hich could cause significant flame acceleration and"-

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po'ssibly even transition to detonation.

This mechanism has been adequately documented by Urtiew et al (1965,1967) and could cccur

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af ter primary ignition at or aboy,e 8% in either t,he lower or upper f

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compartment.

The sequence, without detonation,,is as.follows:

ignition in one compartment causes a slow pressure rise and starts

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a flow through the condenser, pressurizing the second compartment.

The flame then gets int _o the ice condenser at some location and

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accelerates in this turbulent ficw causing large turbulent jets to

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enter the'second compartment.

Once the 71Eme reach s he7/66 cad t

compartment, it is already pre-pressurized and the burning velocity is now so large that combustion in this compartment produces pressures that are up to a factor of 2-4 above the calculated r

maximum adiabatic constant volume pressure (Heinrich,1974).

There is another more recently discovered combustion dynamics possibility.

Knystantas et al (1979) have shown that large scale eddy folding of hot comb.ustion products into an already turbulent jet of, reactants can produce shockless initiation of detonation.

Here the mechanism is that radicals in the product gases trigger combustion reactions in 'the mixing volume an'd' a's 'the system

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explodes the pressure increase augments the combustion process..

This coupled au'gmdntation eventually culminates in a detonation For hydrocarbon-air mixtures, the critical eddy size is wave.

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large, about three meters in diameter.

Note that at the exit of the ice condensus, conditions would be right for the formation of such a large mixing region.

The required eddy size for

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hydrogen-air is not known but it would probably be smaller than the critical size for a hydrocarbon-air mixture.

Thus, i.n my opinion, the combustion dynamics of an explosien inwhichacontin[ousflameisabletopropagate (i.e.,

in a mixture containing greater than 8%. H ) is a very dangerous situ-2

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/ ation and would have t_he potenti'il to breach the "containmen.t

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vessel.

We know that glow plugs have been shown 'to yield partial burns when the flame is lazy and not dangerous.

This, coupled with the vulnerability of the facility to a dynamic combustion explosion, is 'ohe more point in favor cf, using glow plug igniters to protect the containment vessel from the adverse consecuences

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of an accidental spark-ignited burn.

Research Needs.

Glowplugtestingshouldbecont((nued.

Specifically, I agree with the LLNL recommendations for ' further work that was presented at the ACRS subcommittee meeting of January 6,1981.

I would also like to see some continuous burn tests at concentration less than 4% to determine how rapi' ly a glow plug will scavenge hydrogen at d

these.lbw concentrations.- In these tests, the ef fect of f an-induced flow across the plug.should also be invest'ig,ated..

Even,though I feel that the glow plugs will virtually elimi-nate the possibility of detonation in the containment vessel, I still feel that some work on detonation limits should.be performed..

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I do not'bolieve the 18% figure that is in the reports.

I feel that the limit iS much lower, possibly 12%.

At any rate, this uncertaint'y can be relatively easily answered by a few rather simple tests that should be performed.

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4 References

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Bradley, D.

and Mitcheson, A.

(1978a), Comb and Flame 32, pp. 221-236

Bradley, D.

and Mitcheson, A.

(1978b), Comb and Flame 32, pp. 237-255

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./ Cubbage, P. A. and Marshall, M. R. (1972), "P_ressures generated' in combustion chambers by the ignition of air gas' mixtures",

N-I. Chem E. Symposium Series #33, Inst. of Chemical Engineers, London, pp. 24-31.

Heinrich, H.

J.

(1974), " Bum Ablanf von Gas explosionen in mit Rohleitungen verbundenen Behadtern", BAM Berichte #28, Berlin (August 1974).

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Knystantas,

R. ; Lee,

J. H.; Guirao,[C'.T Freuklach, M.; and Wagner, H.

G.,

" Direct Initiation ef. detonat-ion by a-het - - - - '

turbulent gas jet", 17th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, Pa.,

(pages unknown).

Utriew, P.A.

and Oppenheim, A. K.

(1967), " Detonation Initiation by Shock Merging", lith Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, Pa.,

F' pp. 665-676.

Utriew, P.A.,

Laderman, A. J. and Oppenheim, A. K.

(1965),

" Dynamics of the Ge'neration of Pressure Waves by Accelerating Flames", 10th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, Pa., pp. 797-804 I

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