ML20046C797
| ML20046C797 | |
| Person / Time | |
|---|---|
| Site: | 05200002 |
| Issue date: | 07/26/1993 |
| From: | Mike Franovich Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9308120152 | |
| Download: ML20046C797 (18) | |
Text
bYY f ra f
UNITED STATES
[)jg[t Ik1 j
NUCLEAR REGULATORY COMMISSION 1
- g WASHINGTON, D.C. 205S5-0001 July 26, 1993 Docket No.52-002 APPLICANT:
ABB-Combustion Engineering, Inc. (ABB-CE)
PROJECT:
CE System 80+
SUBJECT:
PUBLIC MEETING 0F JUNE 17, 1993, TO DISCUSS HYDR 0 GEN CONTROL AND 50.34(f) REQUIREMENTS FOR THE CE SYSTEM 80+ STANDARD PLANT DESIGN On June 17, 1993, a public meeting was held at the Duke Engineering & Services (DE&S) facilities in Charlotte, North Carolina, between representatives of the U.S. Nuclear Regulatory Commission (NRC) and ABB-CE.
The purpose of the meeting was to discuss. ABB-CE's progress on resolving hydrogen issues for compliance with 50.34(f) requirements. provides a list of attendees. contains the material presented by ABB-CE.
System 80+ Hydroaen Mitiaation System and 50.34(f)
Under 10 CFR 50.34(f) Additiona7 THI Requirements, ABB-CE is required to demonstrate that the System 80+ design has the capability to limit uniformly distributed hydrogen concentrations in the containment from exceeding 10 percent assuming 100-percent active fuel-clad metal-water reaction.
The System 80+ hydrogen mitigation system (HMS) is designed to meet 50.34(f) and is composed of 42 igniters (21 pairs) distributed through various locations inside the containment. The igniters are classified as non-Class IE equipment and receive 120 VAC vital power.
For loss-of-offsite power scenarios, the HMS is capable of being powered from the emergency diesel generators or the alternate ac source (gas turbine).
For station blackout with a failed or unavailable gas turbine, the HMS is powered off the two station batteries (separate from the 4 channel batteries) through the _dc to ac inverters.
Through engineering judgement, DE&S evaluated selected regions of the CE System 80+ containment and the need for igniters in each location.
Hydrogen mixing during and following the degraded core scenarios were not evaluated beyond engineering judgement. provides the igniter analysis and locations for the containment.
For containment performance during deflagration, ABB-CE calculated a global, adiabatic burn for 100 percent of active fuel metal-water reaction below 15-percent bulk average concentration in a dry environment. ABB-CE performed this calculation to demonstrate containment survivability and subsequently used engineering judgement for placement of igniters to optimize hydrogen removal to prevent detonable mixtures.
b$h f
A 9308120152 930726 PDR ADOCK 0S200002 A
PDH
' July 26, 1993 Issues The staff presented several hydrogen issues that ABB-CE should address:
(1) What impact would rapid deinertion (e.g., containment sprays) of the containment have on hydrogen concentrations and the potential for detonable mixtures.
In response, ABB-CE stated 100-percent clad would yield a maximum of 15-percent hydrogen concentration (bulk average) for a dry environment.
ABB-CE stated to get to 100 percent would require accident sequences where high amounts of steam are liberated and subsequent inerting would limit the combustible concentrations. However, the staff stated that further into the accidents, steam condensation will occur leaving hydrogen in the containment. ABB-CE will attempt to demonstrate that through the entire scenario, the role of the igniters is to limit concentrations between 5 and 7 percent to preclude detonable mixtures, and consequently, the hydrogen levels after deinertion would be below detonable mixtures.
(2)
Igniter operability, reliability, availability, and power sources are a concern.
The issue involves lack of power to igniters and inoperability for extended periods.
(3)
For hydrogen stratification, ABB-CE will have to support the assumption that gradients are not large enough to cause stratification in the System 80+ design.
(4)
Effects from local detonations is also a concern and critical areas within the containment should be evaluated.
[quipment Survivability and Goerability DE&S representatives presented the commercial dedication methods, maintenance, and surveillance requirements for hydrogen igniters at the McGuire and Catawba power stations.
For surveillance requirements, DE&S stated that the igniters circuits receive a continuity (circuit) check on a quarterly interval and that each igniter is tested every 18 months / refueling outage.
The 18-month igniter surveillance takes approximately one to two weeks to test all of the igniters.
A visual examination and temperature measurements are performed; igniters should exceed approximately 1700 'F to pass the surveillance.
For commercial dedication, there is a ten-hour burn-in test to qualify glow plugs with a 50-percent failure rate during qualification.
The qualified plugs fail at I to 2 per refueling outage where the entire 72 are tested.
The staff asked for the distribution of failures during the 10-hour time-line for the qualification test.
There is no igniter qualification testing beyond the 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />. All the igniters and transformers are replaced every four years for environmental qualification concerns.
-l
, July 26, 1993 The staff and ABB-CE did not agree on the need to have the igniters in the CE System 80+ technical specifications. The staff will need assurance that the HMS is maintained as a reliable and available system, and the technical specifications would provide such assurance. This issue will be the subject of future discussions.
General equipment survivability of severe accident features was discussed; namely, rapid depressurization system valves and cavity flood system (CFS) valves (qualified to operate submerged). ABB-CE stated that these valves and actuators are environmentally qualified in accordance with 10 CFR 50.49, since ABB-CE has defined the valves mission to function prior to the onset of degraded core conditions.
Power Supplies for Ioniters and Other Severe Accident Features ABB-CE has not yet fully accounted for battery sizing due to the igniters load contribution to the divisional / station batteries. However, CESSAR-DC does identify that the igniters are on the station batteries (via inverters), and DE&S is in the process of completing the battery capacity calculation.
Additional igniters may impact the battery capacity to be procured, and ABB-CE indicated the possibility to remove Ha gniters from station batteries; i
however, the staff did not endorse this option.
The staff also discussed the electrical loads and the placement of non-Class IE hydrogen igniters and the reactor cavity flood valves on Class IE busses, where potential faults may affect the vital sources. The staff stated that the preferred approach for advanced light-water reactors is not to have non-Class lE loads on Class IE busses due to the potential for electrical faults from non-lE loads affecting Class IE sources. ABB-CE stated they will evaluate the possibil1ty of changing the CFS actuators to ac motors.
Passive Autocatalytic Recombiners (PARS)
The staff discussed the potential use of PARS for System 80+.
The PAR device consists of catalyst cartridges enclosed within a stainless steel box frame.
Each catalyst cartridge consists of water resistant, palladium-coated aluminum oxide spheres. These porous pellets are coated with a non-metallic protective coating for moisture / environmental protection.
Protective coating melts away at elevated temperatures.
The staff stated that the Electric Power Research Institute report on the PARS (letter dated April 8,1993) is under review.
The possibility of a hybrid hydrogen mitigation system was discussed with a combination of igniters and PARS. Under this defense-in-depth option, the System 80+ containment would have a minimum set of igniters that would provide reasonable assurance to preclude detonable mixtures, and the PARS would provide added assurance of hydrogen removal during the event.
Such a hybrid system would offer diversity and redundancy.
1
~
. July 26,1993 The following commitments were made during the meeting:
(1) ABB-CE will determine if any additional igniters are needed. Support locations with material access authorization program (MAAP) analysis and some local cloud detonation analyses (cell size and geometry) and supplement previous methodology will be performed. ABB-CE will perform some detailed MAAP nodalization. The analysis will include detonations in areas such as the in-containment refueling water storage tank (IRWST) vents, the containment shell, the reactor cavity, etc.
(2) ABB-CE will present the case that igniters are not needed for the IRWST due to the steam inerted environment.
(3) ABB-CE will submit to the NRC an affidavit testifying to the proprietary nature of the plant arrangement drawings provided to the staff during the meeting, if the drawings have not previously been sent to the NRC's document control desk.
(4) The NRC staff will evaluate the equipment list identified in Chapter 19 for equipment survivability under global burn conditions.
(5) ABB-CE will address the Electrical Engineering Branch's concerns over the CFS valves dc motors. ABB-CE will review the appropriate NRC information notice on faults and evaluate the option to place the actuators on an ac source.
(6)
The staff requested additional information on the qualification of igniters.
Namely, the failure rate and distribution during the commercial dedication and what information is available on the qualified igniter's performance beyond the 10-hour burn in test.
In the interim between the meeting and the issuance of the associated summary, ABB-CE outlined their approach to further investigate the staff's concerns in a telecon held on June 22, 1993:
(1) ABB-CE will evaluate the results of the PISA test to justify the assumed 3-percent variation of hydrogen concentration.
(2) ABB-CE will use the G0THIC code to analytically evaluate stratification.
(3) ABB-CE will perform hand calculations of local detonations in the upper compartments, IRWST vents, and selected areas around the RCS including the crane wall.
(4) ABB-CE will perform a 20 to 30 containment node MAAP analysis.
(5) ABB-CE will reassess containment spray effects and the potential for creating a detonable mixture due to rapid steam condensation.
9 1 July 26, 1993 The staff indicated to ABB-CE that the NRC will convene a panel of experts from the NRC and the national labs to investigate the hydrogen phenomena.as applied to the CE System 80+ design.
(Original signed by)
Michael X. Franovich, Project Manager _
)
Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal' Office of Nuclear Reactor Regulation i
Enclosures:
As stated cc w/ enclosures:
See next page DISTRIBUTION w/ enclosures:
' Docket File-PDST R/F DCrutchfield PDR MFranovich RPerch, 8H7 PShea TWambach SMagruder TEssig RLSTRIBUTION w/o enclosures:
TMurley/FMiraglia RBorchardt JMoore, 15B18 EJordan, MNBB3701 MMalloy RBarrett, 8D1 JKudrick, 8D1 MSnodderly, 801 HAshar, 7H15 GBagchi, 7H15 0Chopra, 7E4 AMalliakos, NLN344 i
ACRS (11)
JNWilson kV(
SC: A hSSA LA:PDhDAR MXFra$
(DAR OFC:
PM:P SC:PDST:ADAR novich:tz TEssig NAME:
PShea
.f JKu
'k DATE:
07/31/9h 07/g93 07/ 0 93 07/2.4/93
/
0FFICIAL RECORD COPY:
DOCUMENT NAME: MSUM0617.MXF i
l
ABB-Combustion Engineering, Inc.
Docket No.52-002 cc: Mr. C. B. Brinkman, Acting Director Nuclear Systems Licensing ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Windsor, Connecticut 06095-0500 Mr. C. B. Brinkman, Manager Washington Nuclear Operations ABB-Combustion Engineering, Inc.
12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Mr. Stan Ritterbusch Nuclear Systems Licensing ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Post Office Box 500 Windsor, Connecticut 06095-0500 Mr. Sterling Franks U.S. Department of Energy NE-42 Washington, D.C.
20585 Mr. Steve Goldberg Budget Examiner 725 17th Street, N.W.
Washington, D.C.
20503 Mr. Raymond Ng 1776 Eye Street,' N.W.
Suite 300 Washington, D.C.
20006 Joseph R. Egan, Esquire Shaw, Pittman, Potts & Trowbridge 2300 N Street, N.W.
Washington, D.C.
20037-1128 Mr. Regis A. Matzie, Vice President Nuclear Systems Development ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Post Office Box 500 Windsor, Connecticut 06095-0500 g
O t
MEETING ATTENDEES JUNE 17, 1993 NAME ORGANIZATION M. Franovich NRR/PDST J. Kudrick NRR/DSSA T. Clinesber9 BNL M. Snodderly NRR/DSSA T. Crom DE&S L. Davis DE&S S. Ritterbusch ABB-CE R. Schneider ABB-CE M. Ravan Duke Power Co.
- O t
+
l
M Purnose Establish the required locations for the Hydrogen Mitigation System igniters in the Advanced Light Water Reactor (ALWR) containment. The ALWR containmentis a spherical containment with a volume of approximately 3.4 million cubic feet. The Hydrogen Mitigation System provides hydrogen control in the event of a degraded core accident.
M O. A. Condition The Hydrogen Mitigation System components are not nuclear safety related since they are not required to prevent or mitigate the consequences of a design basis
~~
accident.
~
M Methodolorv The following considerations will be taken into account in determining the igniter locations:
e hydrogen released to the IRWST from in-vessel hydrogen production e ex-vessel hydrogen production e LOCA effects at the igniter locations e potential ar6as of hydrogen pocketmg e a well mixed atmosphere can not be assured M
Anolicable Codes and Standards The code of federal regulations,10CFR50.34(f)
M Desien Criteria From 10CFR50.34m Provide a system for hydrogen control that can safely accomodate hydrogen generated by the equivalent of a 100% fuel-clad metal water reaction.
lof8
9 From CESSARm Section 6.2.5 Igniters are to be placed at the IRWST safety valve outlets and the IRWST spillway outlet in the holdup volume.
Local areas of potential high hydrogen concentrations will have two igniters, one from Group A and one from Group B.
M Assumotians The IRWST is assumed to be steam inerted for those sequences resulting in the discharge of the RCS inventory and hydrogen into the tank. Igniters are not to be located in this region.
Ia References ALWR nuclear island general arrangements. Drawing number 4248-00-1607.00, D200-series as of 2/7/92.
CESSAR section 6.2.5, Combustible Gas Control In Containuent, Amendment I, 12/21/90.
~
Duke Engineering and Services calculation 4248-04-1606.01-0001, Rev.1, IRWST/RV Cavity Storage Volume Calculations.
Duke Power Company analysis,"An Analysis Of Hydrogen Control Measures At The McGuire Nuclear Station."
M Evaluation For purposes of this analysis the containment has been broken up into the following regions. These regions are not necessarily separate compartments in the usual sense but are sufficiently different in character that each deserves some special consideration. The selected regions are:
e IRWST 2 of 8 j
l
e Holdup volume tank e HVAC distribution header e Region outside of the crane wall e Region inside the crane wall e Containment dome region The region inside the crane wall is further subdivided into :
e Reactor cavity e The 91+9 elevation e The 115+6 elevation e The pressurizer compartment e The letdown heat exchanger room o The regenerative letdown heat exchanger room Each region, and the need for igniters in the region,is evaluated separately.
M IRWST No igniters are required for this region if the assumption of an inert environment is valid. Attachment I contains an analysis of the igniter requirements for the IRWST should future analysis indicate that combustion in the IRWST can not be dismissed.
M Holdun Volume Tank The holdup volume tank is open to the 91+9 elevation through the enclosure screen. Hydrogen reaching the holdup volume should not acemnulate to unacceptable levels in this open arrangernent.
i No igniters are required in this region. The CESSAR requirement for igniters in this region should be deleted.
M HVAC Distribution Header The HVAC distribution header is a dead-ended region with numerous openings into the 91+9 elevation. Hydrogen flow rates into a dead ended region such as this are i
3 of 8
t
~
expected to be small. Because no flow to promote mixing of this region with the rest of containment will exist, hydrogen could accumulate slowly in the header. Because the surfaces in the header will be cold at the initiation of the event, significant steam condensation in the header may occur.
Because of the above considerations, igniters are to be located in fourlocations in the header at approximately 90 intervals.
M Recion Outside The Crane Wall There are four entry ways into this region from the 115+6 elevation. This region is open to the dome region at the top of the crane wall. Since hydrogen entering this region from the 115+6 elevation must pass through the openings in the crane wall, igniters in the vicinity of these openings should reliably ignite hydrogen at low concentrations. No mechanism for the hydrogen to bypass the igniter locations exists.
Igniters are to be located in the region outside the crane wall near the openings from the 115+6 elevation.
M Elevation 91+9
~
This region is in the area of the reactor coolant system piping. It is therefore closest to the likely hydrogen release location. Combustible concentrations could first be achieved in this area. If this is the case, ignition in this region would likely result in frequent localized burns. The resulting small burns would produce a mild containment response. The locations should be shielded from direct spray and pipe whip that may result during a reactor coolant system break. The IRWST relief valves are located at this elevation. Igniters located here satisfy the requirement for placing igniters at the relief valve discharge, as stated in section 5.0.
Four igniter locations are to be provided at this elevation.
If this region could be assured ofigniting first, other igniter locations, may not be required. Two conditions arise which make this situation uncertain. First, the i
4 of 8 i
hydrogen may be released in such a direction and with such velocity that it may bypass this region and accumulate elsewhere in containment. Second, this region could become steam inerted during the RCS blowdown making ignition in this region impossible. Therefore, other regions of the containment are to have igniters in order to assure that combustion occurs.
M Elevation 115+6 This region of the containment is connected to the 91+9 elevation, the dome region, and the region outside of the crane wall. Significant accumulation in this region is unlikely. Burns initiated at the other igniter locations should easily propagate into this region if the conditions will support combustion.
No igniters are recnited in this area.
M Pressurizer Comnartment The pressurizer compartment is a tall compartment closed at the bottom and open at the top on two of the four sides of the compartment. Such a configuration is not' likely to result in hydrogen accumulating within the compartment.
The tube pull space is connected to the 91+9 elevation through an openimg that is 5.5 ft. in diameter. This space is adequately protected by the igniters on the 91+9 elevation.
No igniters are required in the pressurizer compartment.
M Letdown Heat Exchantrer Room It is assumed that a LOCA in this room would eventually fail the door which leads from this room to the 91+9 elevation. Otherwise such a small room would certainly be steam inerted and incapable of supporting combustion. Hydrogen released into this room could accumulate to undesirable concentrations.
Igniters are to be located here to protect against this possibility.
5 of 8
4 4
Ha Recenerative Letdown Heat Exchancer Room It is assumed that a LOCA in this room would eventually fail the door which leads from this Room to the 91+9 elevation. Otherwise such a small room would certainly be steam inerted and incapable of supporting combustion. Hydrogen released into this room could accumulate to undesirable concentrations.
Igniters are to be located here to protect against this possibility.
BE Reactor Cavity
~
The reactor cavity region consists of the region below the vessel as well as the incore instrument chase. This.a a dead ended region where hydrogen accumulation is possible.
One igniter location in this region is recommended.
&ll Dome Recion The containment dome region is the highest point in the containment and also the area vhore the containment spray headers are located. The high elevation and po!-
i %w sicam concentrations make it likely that this region.will eventually see conwc N.ms of hydrogen that would provide for reliable ignition in those situations where the hydrogen has bypassed the otherigniterlocations. Ifigniters are located only at the top of this region ignition may not occur until the downward flame propagation limit, approximately 8 volume percent,is reached. This situation could be considered acceptable since the containment response should be relatively mild. Downward flame propagation speeds tend to be slower than those of upward flames; and the entire containment would not be at that concentration or the other igniters would have initiated burns earlier.
However, b der to allow the possibility of burns at even lower conc,entrations, igniters,
o elaced at an elevation low in the dome region of the containment.
~6of8
.l
This location should permit burns to occur in the dome at lower concentrations, closer to the upward flame propogation limit, approximately 5 volume percent.
Locations near the area where hydrogen is most likely to enter the upper region of the containment are most suitable.
Four igniter locations at the top of the dome af. 90 to each other and inside the radius of the crane wall are to be provided.
Two igniter locations near the top of the steam generators are to be provided.
Ei!
Results This evaluation has set those regions of the containmentin which hydrogen igniters are to be located. Table 1 provides a listing of the approximate igniter locations.
Precise locations can be established after all other equipment is located so that accessibility for maintenance and testing can be assured. Each location will have two igniters, one from each train.
h 7 of 8
p 4
Table 1 REGION COVERED RADIAL LOC.
AZIMUTH ELEVATION _
91+9 elevation 52 ft 70 100 ft 91+9 elevation 47 ft 130' 100 ft 91+9 elevation 47ft 230 100 ft 91+9 elevation 47 ft 310 100 ft HVAC dist. hdr.
69 ft 8
100 ft HVAC dist. hdr.
69 ft 105 100 ft HVAC dist. hdr.
69 ft 185 100 ft HVAC dist. hdr.
69 ft 275
' 100 ft Letdown HX Room 65 ft 150 100 ft
/
Regenerative LDHX Room 60 ft 200 100 ft
/
Reactor Cavity 43 ft.
8 94 ft
/
Outside Crane Wall 69 ft 25 125 ft
/
Outside Crane Wall 69ft 142 125 ft v
Outside Crane Wall 69 ft 225 125 ft
/
Outside Crane Wall 69 ft 310 125 ft v
Dome 24 R 0
252 R Dome 24 ft 90 252 ft Dome 24 ft
?Q 252 ft Dome 24 ft 270" 252ft Dome 46 ft.
90 192 ft.
Dome 46 ft.
270 192 ft.
i 8 of 8
a
--+44 G--
i e-e e
~
1 5
e 9
R
.y S
.h, I
b h
i h
h l
ATTACHMENT 1 f
a e
I e
8
-t 4
)
I l
5 I
?
I i
r<+
r e--
The purpose of this calculation is to provide a conservative estimate of the igniter requirements for the IRWST should they be required. The values selected for the various parameters required are selected from the noted references or are based'on past experience.
The following assumptions are to be applied in establishing the igniter spacing requirements for the IRWST:
o hydrogen is introduced to the IRWST at a maximum rate of 1 kg/sec, note 3 e normal IRWST water level is at elevation 82+6, note 1 e volume of water in IRWST at 82+6 is 72,965, note 1 e
total volume of the IRWST is 130,100 cu. ft., note 1 e flame propagation speed is 1 ft/sec, note 2 e burn initiation occurs at 8.5 vol. %, note 2 e initial water temperature of the IRWST is 80 F, note 3 (normal temperature,60 F to 110 F) e 8000 cu. ft. is the volume of RCS water discharged to the IRWST, note 3 note 1: from DESI calculation 4248-04-1606.01-0001, rev.1 note 2: samt value as that used in "An Analysis Of Hydrogen Control Measures At The McGuire Nuclear Station" for analyzing the igniter spacing for the ice condenser upper plenum note 3: an assumed value based on past experience Assume that the discharge of the RCS inventory has raised the IRWST temperature to 212 F. In addition, that 8000 cu. ft. of RCS inventory has been added to the IRWST volume.
water density at 80 F = 62.2 lb,,/ft' water density at 212 = 59.8 lbdft' The final water volume is:
72,965 x 62.2/59.8 + 8,000 = 83,893 cu. ft.
final freeboard volume is:
130,100 - 83,893 = 46,207 cu. ft.
1 i
,t
.a.
The ideal gas equation: P7 = mRT R = 766.4 ft*1b/(lb,* R) for hydrogen At 8.5 vol. % the mass of hydrogen in the freeboard volume of the IRWST is :
2 2 m = (14.7 psia *.085*46,207ft'*144in ffg )/(766.4 ft*1b/(Ib
- R)*672 R) m where 212 F = 672 R m = 16,1b, ikg/sec = 2.21b /sec If the hydrogen being consumed by the burn is to equal the hydrogen entering the IRWST, thus preventing further accumulation, then the burn time can be found by:
~
T% = 16.11b /2.21b /sec = 7.3 sec.
m If the hydrogen consumption is to match the hydrogen input then the igniters must be positioned so that the entire freeboard volume of the IRWST is burned in 7.3 seconds.
With a flame speed of 1 ft/see this requires that all points in the volume be no more than 7.3 feet from an igniter. It is estimated that approximately 60 igniter locations, 120 igniters, would be required to meet this requirement.
4 6
2