ML20091E759
| ML20091E759 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/22/1984 |
| From: | Tucker H DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8406010359 | |
| Download: ML20091E759 (8) | |
Text
6 DUKE POWER GOMPANY P.O. BOX 33189 CHARLOTTE, N.O. 28242 HAL B. TUCKER m zenows
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(704) 373-4538 May 22, 1984 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation
.U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Ms. E. G. Adensam, Chief Licensing Branch No. 4 Re: Catawba Nuclear Station Docket Nos. 50-413 and 50-414
Dear Mr. Denton:
Attached herewith are twenty (20) copies of Revision 11 to Duke Power Company's report, "An Analysis of Hydrogen Control Measures at McGuire Nuclear Station."
As noted in Revision 9, this report _ is applicable to Catawba Nuclear Station.
This ' revision provides responses to the questions submitted to Duke Power Company by letter dated May 8,1984 (E. G. Adensam, NRC/NRR, to H. B. Tucker, Duke Power Company). This information should be inserted in Section 7.0 of Volume 3.
Please advise if there are any questions regarding this matter.
Very truly yours, D.TMM Hal B. Tucker ROS/php Attachments cc: Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 NRC Resident Inspector Catawba Nuclear Station I
Mr. Robert Guild, Esq.
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Attorney-at-Law' P. O. Box 12097 Charleston, South Carolina 29412 Palmetto Alliance 21351 Devine Street' 1
Columbia, South Carolina 29205 y 84060103S9 840522
' PDR ADOCK 05000413 A.
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MrSHarold R. Denton, Directorn
.May 22, 1984'-
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-cc: -Mr. Jesse L. Riley Carolina Environmental Study Group 854 Henley Place
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Response to questions submitted by letter from NRC (Elinor G. Adensam) to Duke (H. - B. ; Tucker)- dated May 8,1984.
1.
With regard to the CLASIX code, the staff has previously requested clarification of the structural heat sink heat transfer models.
The following pertinent points have been derived from the responses:
- 1) Heat transfer is based on a temperature difference determined by (Tbulk T,,jj).
- 11) Heat ' transfer coefficients for degraded core accident analysis are determined from a natural convection (stagnant) correlation appli-
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cable to condensation heat transfer.
I iii) CLASIX does not explicitly model mass removal due to condensation heat transfer.
Based on the description of the.CLASIX structural heat sink model, it appears that the CLASIX model differs dramatically from generally ac-l cepted approaches and is not, as is' claimed, consistent with' standard methods such as those used in CONTEMPT.
The differences are related to the treatment of the three items cited above.
By comparison, previously accepted approaches are characterized by-the following:
i) Heat' transfer is based on (T i
atureoftheheatsinkis1elftthan,tjj),whenthe'surfacetemper-
-T sat; i.e., T,,jj < Tsat'
- 11) Heat transfer coefficients are based on condensation only' when I
wall < Tsat' fii) Condensed mass removal is based on condensation heat transfer with provisions for revaporizing a small-fraction of the condensate.
A more detailed description of accepted practice is contained in NUREG-3 4
-0588 and NUREG/CR-0255.
The effect of the CLASIX models would appear'to be the de-superheating of the atmosphere too rapidly thus reducing gas temperatures'and possibly altering the combustion characteristics.
\\
Considering the above discussion, provide the results of analyses, with acceptable models to determine the effectiveness of deliberate ~ ignition for the Catawba plant.
The analyses should address the effects of hy-drogen combustion on containment integrity and equipment' survivability'.
Furthermore, the analyses should be performed to address a spectrum of-appropriate degraded core accidents.- Specific items that should be Laddressed include:
a.
1Model input and analytical assumptions; b.
~Calcul_ated compartment atmosphere pressure,. temperature, and gas concentration transients; L
Equipment temperature response profiles; c.
lL l-I-
7.0.129 Rev. 11
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d.
Differential pressure-transients between compartments which will allow for an evaluation of AP effects on interior structures and mechanical components (e.g., doors, fans); and Considering the capability of the containment shell, crane wall, e.
and the operating deck, perform an analysis to determine the maxi-mum concentration of hydrogen which could be accommodated in a de-flagration.
Your estimate should consider realistic initial conditions and approximate combustion parameters.
Response
A justification for the use of the heat sink models in CLASIX was pre-sented to NRC when this question was first posed to Duke in Elinor G.
Adensam's letter of August 18, 1983.
That response appears on pages 7.0-129 - 7.0-133.
We have reviewed that response and continue to support the case that it makes for the adequacy of the original analysis.
Our conclusion is that no additional CLASIX analysis is required to justify the results of our original work.
We note, however, that the additional CLASIX analysis requested by the staff was performed by AEP using heat transfer models which were in accordance with the staff's request that the models conform to those of NUREG 0588 and NUREG/CR-0255.
The results of this analysis were reported I
to NRC by M. P. Alexich's letter dated march 30, 1984.
These results are very interesting in view of the theoretical arguments presented previously by Duke Power Company in support of the original CLASIX heat transfer models.
In their work, AEP compared directly the original heat transfer models with those requested by the staff using identical geometries, initial conditions, and release rates.
The AEP results indicate:
1.
Pressure and temperature profiles are generally similar for the two sets of heat transfer correlations.
2.
The original CLASIX analysis tends to underpredict the temperature in containment at the peaks associated with the hydrogen burning by about 100*F.
3.
The original CLASIX analysis tends to overpredict the baseline containment temperatures (the temperature of the containment between hydrogen burning).
This indicates that the original CLASIX heat sink models remove less energy from the containment atmosphere in l
the period immediately following a hydrogen burn and therefore l
provide a conservative baseline containment temperature profile.
4.
Further evidence of the conservatism of the original CLASIX heat sink models can'be found from examining the containment pressure response.
In every case, pressures during the hydrogen burn period l
were higher for the' original CLASIX analysis than for the analysis j
using the " corrected" heat sink models.' This indicates again that the original CLASIX heat sink'models remove less energy from the containment atmosphere per unit time than the heat sink models based on NUREG-0588 and those used in CONTEMPT.
7.0-130 Rev. 11 r
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3 i-i' In summary, analysis performed by AEP wherein a head-to-head comparison l
of heat sink models was made supports the position taken by Duke Power in its previous submittal concerning the question of CLASIX heat sink models (Revision 10).
These models have been shown to be conservative from both a theoretical and an analytical standpoint.
The higher peak temperatures during hydrogen burning predicted by the " corrected" heat sink models are i
of no consequence to the analysis of equipment survivability as our surviv-ability analysis used the adiabatic flame temperature (1400*F) rather than a lower temperature predicted from CLASIX results.
V The ability of the hydrogen ignition system has been shown to be effective r
F in controlling the concentration of hydrogen to levels less than 8.5% by volume in CLASIX analyses, small scale testing, and more recently, in the large. scale Nevada tests. Our structural analysis has consistently shown
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considerable margin in the containment design in its ability to withstand the pressures and differential pressures associated with hydrogen burning at this concentration.
To seek some maximum theoretical higher concent-ration which could be tolerated represents an unrealistic extension of our previous work and, at best, can be considered of academic interest only, and of no consequence in proving the adey acy of the concept of
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deliberate ignition.
Further support for the adequacy of the CLASIX code is presented in reference (a),.wherein CLASIX is compared with HECTR.
For identical F
input conditions, and in spite of considerably increased technical comp-lexity in many of the HECTR models, results from the two codes are nearly i
identical. We conclude that the models contained in CLASIX are suitable i
for use in analysis of beyond design basis conditions, and that further-i discussion of CLASIX is unlikely to affect our confidence in it as an-j.
analytical tool for the study of deliberate. ignition in ice condenser ~
containments.
2.
Provide a complete evaluation of fan (both air return and hydrogen I
skimmer as applicable) operability and survivability for degraded core accidents.
In'this regard discuss the following items:
y The identification of conditions which will cause fan overspeed, in a.
terms of differential pressure and duration, and hydrogen combustion events.-
l b.
The consequences of fan operation at overspeed conditions. The i
response should' include a discussion of thermal'and overcurrent breakers in the power supply to the fans, the setpoints 'and physical locations of these devices, and the fan loading conditions required i
to trip the breakers.
i i
c.
Indication to the operator of fan inoperability, corrective actions i
.which may be possible, and the times' required for operators to complete these actions.
(
'd. -
The capability of fan system components'to withstand differential pressure transients (e.g., ducts, blades, thrust bearings, housing),
l-in terms of limiting conditions and components.
7.0-1 31 Rev. 11
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Response
n
'This identical question was submitted by letter from NRC (Elinor Adens.am) i' to Duke.(H. B. Tucker) dated August 18, 1983.
It was answered in L.
Revisions 8 and 10.~
3.
Provide an analysis of the pressure differential loading on.the ice L
condenser doors created by hydrogen combustion in the upper plenum and upper compartment.
Describe and justify the assumed or calcu-l-
lated door positions.
Provide an evaluation'of the ultimate cap-
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ability of the ice condenser doors to withstand roverse differential
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pressures.
Discuss the probable failure modes and the consequences of such failures; including the impact on a) adjacent equipment and
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structures, b) ice bed integrity, and c) flow maldistribution.
i 1
-Response:
Referring to previous CLASIX results for measures of-the intercompart-i mental differential pressures results in unrealistically conservative answers.
This result is caused by the manner in which CLASIX models the lower inlet and intermediate deck doors.
The dynamics of door closing L
contains no inertial ters; therefore the doors close instantaneously
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whenever the net force in the closing direction is greater than zero.
l-For example, as soon as an upper plenum burn is initiated and upper i
plenum pressure increases, the intermediate deck doors closed instant-
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aneously.
The pressure rise in the upper plenum will therefore be conservatively high as venting into the ice bed will be precluded.
This t
effect was noted in the comparison of CLASIX analysis with similar analyses using HECTR and COMPARE reported in reference (a).
In addition,
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reference (a) states:
"During burns, CLASIX predicts fairly large pressure differentials between the compartments, which we would not expect to occur, j
given the large flow areas connecting tho' compartments.
HECTR-j predicts rapid pressure equilibration, and only small pressure differences between compartments.
As shown later, COMPARE also j
predicts rapid pressure equilibration".
1 i
Based on the discussion above, differential pressures obtained from l
CLASIX might be considered a gross upper bound for the differential pressures which would be developed in an actual hydrogen burn situation.-
l A review of previous CLASIX analysis reveals the following results.
For an upper plenum hydrogen burn initiated at'8.5% by volume, and a flame
't speed of 6 feet /second, the maximum indicated differentia 1 pressure across the intermediate deck doors is 1.2 psid.
As reported in an answer to a previous question, the reverse differential i
pressure capability of the intermediate deck door.is 6 psid. 'Ihere is
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-therefore substantial margin'in the intermediate deck to withstand the reverse differential pressure associated with an upper plenum burn, even i
under the bounding conditions of an analysis using CLASIX.'
i.
7.0-132 Rev. 11 m..
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For an upper compartment burn, which is shown to be precluded except under the most extreme a'ssumptions, the pressure rise time is relatively
- slow due to the length of time it takes for the flame to propagate throughout this large compartment.
Results of the EPRI Nevada large scale tests show that hydrogen is reliably ignited by top ignition at 6%
by volume in the presence of sprays or fans, and that the corresponding 4
flame speed is less than 10 ft/sec.
Pressure rise times are less than one psi /second generally for the cases where typical plant conditions have been modeled. We conclude that upper compartment burns cannot exert large differential pressures across the top deck doors, even if the doors are assumed to be fully closed.
In an actual hydrogen burn, the differ-4 i
ential pressure would be minimized by the increase in flow area caused by dislocation of the top deck blankets during the early portion of the accident.
4.
Identify the essential equipment needed to function during and after a de-i -
graded core accident.
Provide the location inside containment for this equipment.
Response
This information has been furnished previously to the staff on at least two occasions.
Refer to reference (b), Section 6.2, and to Section 5.2 j
of this volume.
5.
In view of the recent TVA test results with Tayco igniters which indicate.
j desirability of additional spray shielding, please discuss whether t
supplementary spray shields may be appropriate for the glow plug j
igniters.
~
Response
i None of the glow plug igniters found'by Duke Power.to be required for i
adequate coverage of the containment is exposed to.a spray environment.
The four additional igniters added to the upper compartment at the t
request of the staff are in the environment created by the containment j
sprays; however, we note the following:
i 1.
During the small_ scale testing reported in Chapter 2, there was i
no evidence that a spray environment had an adverse effect on l
the performance of the glow plug igniter.
l 2.
The tests performed in the large scale test vessel in Nevada,
?
in which ignition was started by glow plug igniters located at j
the' center and bottom' elevations (and thus in the spray) show' no evidence that containment spray inhibits the ignition of I
hydrogen by glow plug igniters..
I We conclude that no further testing or modification of the glow plug igniters is required for McGuire or Catawba.
I i
7.0-133 Rev. 11
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References:
(a) Camp, Allen L., Vance L. Behr, and F. Eric Haskin, MARCH-HECTR Analysis of Selected Accidents in an Ice Condenser Containment, Sandia National Lrboratories.
'An Analysis of Hydrogen Control Measures at McGuire Nuclear Station, (b)
Volume III, dated January 5, 1981 (this has been referred to as the " Grey Book").
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7.0-134
-Rev. 11
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