ML20054M704
| ML20054M704 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 07/02/1982 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Delgeorge L COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8207140252 | |
| Download: ML20054M704 (12) | |
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D NRC PDR L PDR ASchwencer NSIC RLTedesco/JKerrigan Docket Nos.: 50-373/374 PRC DGt.senhut/RPurple LB#2 Readin9 BSiegel EHylton Mr. Louis 0. De1 George ABournia Director of Huclear Licensing DLynch Connonwealth Edison Company CWoodhead, OELD P.O. Box 767 I&E Chicago, Illinois 60690 ACRS (16)
Region III
Dear tir. De1 George:
Subject:
Concerns Regarding the Adequacy of the Design flargins of the Mark I and II Containment Systems A number of concerns regarding the adequacy of the General Electric Mark III containment design have been raised by tir. John Humphrey, a former employee of GE. When these concerns came to the attention of the NRC staff on the Grand Gulf docket, we initiated a series of telephone conference calls and neetings.
While these concerns were first directed by Mr. Humphrey towards Grand Gulf, in subsequent discussions he extended his concerns towards other facilities.
After considering Mr. Humphrey's concerns, we concluded that this infomation is potentially generic and may have applicability to all dockets with boiling water reactors which use the GE pressure suopression containment systems (i.e., the GE flark I, II and III containment systems).
The enclosure to this letter contains 22 categories into which Mr. Hunphrcy's concerns were coalesced on the Grand Gulf docket as of June 21,1982, less those itens which are clearly associated with a !! ark III containment.
In-some instances, we have modified an original concern to make it more applicable to the Mark I and 11 containments and have added some footnotes which generalize Mr. Humphrey's concerns. We request that you respond within seven (7) days of receipt of this letter with your proposed schedule for submitting a program to address those concerns which we have identified as being potentially applicable to your facility.
If you have any questions on this matter, please I
contact the assigned project manager. Mr. Byron Siegel (301-492-7534) is the contact for operating Mark I f acilities and Mr. M.D. Lynch (301-492-9793) is the contact for all other facilities.
l This infomation is being requested under Section 50.34(b)(2)(i) of 10 CFR l
Part 50 and was approved by atB under a blanket clearance 3150-0011 which l
expires April 30, 1985.
Sincerely, i
Original signod by Robert L. Tedeno 8207140252 820702 Robert L. Tedesco PDR ADOCK 05000373 Assistant Director for Licensing P
PDR Division of Licensing g y
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OFFICIAL RECORD COPY uscm mi-mmo l NRC FORM M OO@pRCM 0m
La Salle W1.Y 2
m Mr. Louis 0. De1 George Director of Nuclear Licensing Commonwealth Edison Company P. O. Box 767 Chicago, Illinois 60690 cc: Philip P. Steptoe, Esquire Suite 4200 One First National Plaza Chicago, Illinois 60603 Dean Hansell, Esquire Assistant Attorney General 188 West Randolph Street Suite 2315 Chicago, Illinois 60601 William G. Guldemond, Resident Inspector LaSalle NPS, U.S.N.R.C.
P. O. Box 224 Marseilles, Illinois 61364 O
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EUFJERIY.,f4ETAI!p.2KT CONCERNS i
1.
jf f ects of Local Encreach ents en Peel Svell Loacs 1.1 1.2 e
1.3 N/A for Mark I and Mark II Containments 1.4 1.5
'1.6 1.7 2.
Safety Relief Valve Discharts ~_ine Sleeves 2.1 N/A for Mark I and Mark II Containments 2.i 2.3 DESIGy1TE:) ORIGINAL L
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Certified 3 -
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i 3.
ECCS Relief Valve Discharge Lines Below the Suppression Pool Leve 3.1 The design of the STRIDE plant did not consider vent cleariig, condensation oscillation and..chugqigg loads which =ight be ' produced by the actuation of these relief valves.
3.2 The STRIDE de:ign provided only nine inches of sub=crgence above the RER relief valve disch rge lines ct low suppreccion pool icvels.
3.3. Discharge frc= the RER relief valves may produce. bubble discharge or other sub=erged structure leads on equip =ent in the suppression pool.
3.4 The RER heat exchanger relief valve discharge lines are provided with vacuu: breakers to prevent negative pressure in the lines when discharging stea= is condensed in the pool.
If the valves experience repeated actuation, the vacuu: breaker sizing may not be adequate' to prevent drawing slugs of water back through the discharge piping.
These slugs of water may apply i= pact loads -to the relief valve or be discharged back Tnto the pool at the pezt relief valve actuation and
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apply i= pact loads to submerged structurps.
3.5 N/A for Nark I and II Containments.
3.6 If the RER heat exchanger relief valve discharge stea= to. the upper levels of the suppression pool following a design basis accident, they vill significantly aggravate suppression pool temperature stratification.
3.7 The concerns related to the RER heat exchanger relief valve, discharge lines should also be addressed for all other relief lines that exhaust into pool. (p.132 of 5/27/82 transcript) 4.
Suppressic'n Pool Te=perature Stratification R
4.1 The present containment response analyses for drywell break accidents.
assume that.the ECCS syste=s transfer a significant quantity of water fro = the suppression pool to the lower regions of the drywell through the break.
This results in s pool in the drywell which is essentially isolated fre: the suppression pool at a te=perature of approximately 135'F.
The contain=ent response analysis assu=es that the dryvell pool is thoroughly mixed with the suppression pool.
If the inventory in the dryvell is assu=ed to be isolated and the re=ainder of the heat is discharged to the suppression pool, an increase in bulk pool te=perature of 10*F =ay occur. [1 4.2 The existence of the drywell pool is predicated upon centinuous operation cf the ECCS.
The current e=ergency procedure guidelines require the operators to throttle ECCS operation to maintain vessel level berow level S.
Consequently, the drywell pool =ay never be for=ed. [2 4.3 All Mark III analyses presently asse=e a perfectly =1xed unifor=
suppression pool.
These analyses assu=e that the te=perature of the suction to the RER heat exchangers is the sa=e as the bulk pool tenperature.
In actuality, the temperature in the lower part of the pool
~.
where the suction is located vill be as much as 7 *F cooler than the bulk pool te=perature. Thus, the heat-transfer through the RER heat exchanger vill be less than expected.
4.4 The long term analysis of' containment, pressure / temperature response assures that the vervell airspace is in ther=al equilibritm with the suppressien pool water at all ti=es.
The calculated bulk pool tc=perature is used to deter =ine the airspace te=perature.
If pool ther=al stratification vere considered, the surface te=perature, which is j
in direct contact with the airspace, vould be highet..Therefore the airspace te=perature (and pressure) would be higher.
4.5 A nu=ber of faotors may aggravate suppression pool thermal stratification.
The chugging produced through the first row of horizontal vents vill not produce any mixing from the suppression pool layers below the vent row. An upper pool dump may contribute'to additional suppression pool temperature stratification. The large volume of water from the upper pool further submerges' M beat exchanger effluent-discharge which Vill decrease mixing of the botter, upper regions of the pool.
Finally, operation of the containment spray elic;Lnates the heat exchanger effluent discharge jet which contributes to 2-4 ri n g. /_3 4.6 The initial suppression pool temperature is assumed to be 95'F while the '
maxi =um expected service water te=perature is 90*F for all GGNS accident analyses as noted in FSAR table 6.2-50.
If the service water te=perature is consistently higher than expected, as occurred at Kuosheng, the RER syste= may be' required to operate nearly continuously in order to maintain suppression pool temperature at or below the maximum permissible value.
4.7 All analyses completed for the Mark III are generic in nature and do not consider. plant specific int'eradtions _of t~ne RER suppression pool suction and discharge.
4.8 Operation of the RER. system in the containment spray mode vill d.acrease the beat transfer coefficient through the RER heat exchangers due to decreased system flow.
The FSAR analysis assumes a constant heat transfer rate from the suppression pool even with operation of the containment spray.
4.9 The effect on the long ter= contain=ent response and the operability of the spray syste= due to cycling the containment sprays on and off to maxi =ize pool cooling needs to be addressed. Also provide and justify the criteria used by the operator for svitching fre= the contain=ent spray code 'to pool cooling mode, and back again.
(pp.147-148 of 5/27/82 transcript) 4.10 Justify that the current arrange =ent of the discharge and suchion points of the pool cooling syste= maxi =izes pool mixing.
(pp.150-155 of 5/27/82 transcript) n
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'5.
Drvva11 to Contnin=nnt Evpass Lenkagn
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5.1 The worst case of dryvell to contain=ent bypass leakage has been established as a s=all break accident.
An inter =ediate break accident vin actually produce the most s%gui(icant dryvell to contain=ent leakage prior to initiation of contain=ent sprays.
5.2 Under Technical Specification li=its, bypass leakage correspe= ding to A/ 8 - 0.1 ft.
cenetitute acceptchie opercting conditions.
5:211er-than-IEA-siced breaks can maintain break flev into the dryvell fer leng time periods, however, because the PJV vould.be denressurized cver a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> period.
Given, for exa=ple, en SEA vith A/[iU = 0.1, projected ti=e period for conta4--ant pressure to reach 15 psig is 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
In the latter 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of the depressurization the conta4---nt would presunably experience ever-increasing overpressurization. /4 5.3 Leakage from the dryven to containent vin increase the temperature and pressure in the contai=ent. The operators win have to use the contain=ents spray in order to mainta'in containrint te=perature and pressure control.
Given the decreased effectiveness of the PER system in acco:plishing this objective, in the contain=ent spray mode, the bypass leakag, may increase the cyclical duty of the contad-ment sprays.
5.4 Direct leakage from the dryven to the containmnt may dissipate hydrogen.
outside the region where the hydrogen recombiners take suction. The anticipated leakage exceeds the capacity of the dryven purge ce= pressors.
This could lead to pocketing of hydrogen which exceeds the concentration-li=it of 4% by volu=e. f 5 5.5 Equip =ent may be exposed to local conditions which exceed the l
environ = ental qualification envelope as a result of direct dryvell to l
contain=ent bypass leakage.
5.6 N/A for Mark I and Mark II Containments 5.7 5.8 The possibility of high te=peratures in the dryvell without reaching the 2 psig high pressure scra= level because of bypass leakage throttsh the dryvell vall should be addressed.
(pp.168-174 of 5/27/82 transcript) 1 1
1
6.
RFR Per=1ssive on Contain=ent Sorav 6.1 We understand that GE has recommended for Mark III containments that the combustible gas control systems be activated if the reactor vessel water level drops to within one foot of the top of the active fuel.
Indicate what your facility is doing in regard to this recommendation.
6.2 General Electric has recc ended that an interlock be provided to require contain=ent spray prior to starting the rece=biners becaus,e of the large quantities of heat input to the contain=ent.
In~ correct i=ple=entation of this interlock could result in inabil:.ty to operate the reco=biners without contain=ent spray. /5 6.3 The rece=biners =ay produce " hot spots" near the reco=biner exhausts which =ight exceed the environ = ental qualification envelope or the contain=ent design te=perature. g 6.4 For the contain=ent air monitoring,sygem furnished by General Electric, the analyzers are~not capable of measurir;g hydrogen concentration at volu=etric stea= concentrations above 607..
Effective measure =ent is precluded by condensation of steam in the equipment.
6.5 Discuss the possibility of local te=peratures due to reco=biner operation being higher than the te=perature qualificatics profiles for equipment in the region around and above the recombiners.
State what instructions, if any, are available to the operator to actuate containment sprays to keep this te=perature below design values.
(pp.183-185 of 5/27/82 transcript) /5 7.
Contain=ent Pressure Response 7.1 The wetwell is assu=ed to be in thermal equilibrium with a perfectly
=ixed, unif,orm te=perature suppression pool. As noted under topic 4 the surface te=perature of the pool will be higher than the bulk pool te=perature.
This may produce higher than expected contain=ent te=peratures and pressures.
7.2 The ce=puter code used by General Electric to calculate environ = ental qualification para =eters considers heat transfer from the suppression pool surface to the contain=ent atmosphere. This is not in accordance with the existing licensing basis for Mark III environ =ents1 qualification.
Additionally, the bulk suppressien pool te=perature was used in the analysis instead of the suppression pool surface te=perature.L6 7.3 The analysis assu=es that the wetwell airspace is in ther=al.
equilibriu: with the suppression pool.
In the shert ter= this is non-censervative for Mark III due to adiabatic ce=pression effects and finite ti=e required for heat and cass to be transferred between the pool and contain=ent volu=es. L6 8.
Contain=ent Air Mass Effects 8.1 This issue is based on consideration that so=e Tech Specs allov eperation at para =eter values that differ fro = the values used in assu=ptions for TSAR transient analyses.
Nor= ally analyses are done assu=ing a nominal
contain=ent pressure equal to ambient (0 psig) a temperature near -4mm operating (90*F) and do not li=it the dryvell pressure equal to the contai==ent pressure.
The Tech Specs operation under conditions ruch as a positive containment pressure (l i psig), te=peratures less than y
maxi =u= (60 or 70*F) and dryv' ell'p'ressure can be negative with respect to the contain=ent (-0.5 psid). All of thes~e differences veuld result in transient respcuse dif ferent than the FSAR descriptions.
6.2 The draf t GONS technical specifications per=it operation of the. plant with centain=ent pressure ranging between 0 and -2 psig.
Initiation of contain=ent spray at a pressure of -2 psig =sy reduce the containmen:
pressure by an additional 2 psig which could lead to buckling and f ailures in the cegrain=ent liner plate.
8.-
If the containment is =aintained at -2 psig, the top row of vents could ad=it blevdown to the suppression pool during an SBA without a LOCA signal being developed.f7 8.4 Describe all of the possible methods hbth before and after an accident of
. creating a c.ondition of low air mass inside the containment. biscuss the effects on the centain=ent design external pressure of actuating the contain=ent sprays.
(pp. 190-195 of 5/27/82 transcript) 9.
Final Dryvell Air Mass 9.1 The current FSAR analysis is based upon centinuous injection of relatively cool ECCS vater into the drywell through a broken pipe folioving a design basis accident.
Since th'e operator is directed to throttle ECCS operation to maintain the reactor vessel water level to about the level of the steam lines, the break will 'be releasing satur.ated steam instead of releasing relatively cool ECCS water.
Therefore, the~ drywell air which would have been purged and then drawn back into the drywell, will remain in the wetwell and higher pressures than anticipated will result in both the. wetwell and the drywell.
9.2 The continuous ste= ring produced by throttling the ICCS flow will cause increased direct leakage from the drywell to the wetwell. This could result in increased wetwell pressures.
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'9.3 1: appears that sc=e' confusion exists as to whether SBA's and stuck open l
SRV accidents are treated as transients or design basis accidents.
l Clarify how they are treated and indicate whether the initial conditions vere set at ne=inal or licensing values.
(pp. 202-205 of 5/27/82 transcript) 10.
Dryvell Flooding caused by U ver Pool Du=p 10.
N/A for Mark I and Mark II Containments
=
10.2 N/A for Mark I and Mark II Containments 11.
O erational Control of Drywell to Contair:=ent Differentiri-Pressures P2:k III lead definitions are based upon the levcis in the suppressien peel and the drywell veir annulus being the same.
The GGI;S technical specifications per=it elevatien differences between thase-pools.
This nay effect load definitien for vent clearing. [8 12.
Suturession Pool Makeup LOCA Seal In N/A for Mark I and' Mark II Containments
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13.
ijinetySecondSprayDelay N/A for Mark I and Mark II Containments 14.
RER Eackflow Through Containment Spray A failure in the check valve in the LPCI line to the reactor vessel could result in, direct leakage from the presrure vessel to the containment atmosphere. This leakage might occur as the LPCI motor operated isolation valve is closing and the motor operated isolation valve.in thg.
conta'in=ent spray line is opening.
This could produce unanticipated increases in the containment sp. ray.
15..
Secendary Containment Vacuum Ereaker Plenum Response The STRIDE plants had vacuu breakers between the contain=ent and the secondary centain=ent. With suf ficiently high flows through the vacuum breakers to contain=ent, vacuun could be created in the secondary containment.
16.
Effect of Suppression Pool Level on Te=perature Measufement Se=e of the suppression pool te=perature sensors are located (by I;E reco==endation) 3" to 12" below the pool surface to provide early warning of high pool temperature.
Bewever, if the suppression pool is drawn down below the level of the temperature sensors, the operator could be misled by erroneous readings and required safety action could be delayed.
17.
E=ergency Procedure Guidelines f9 The EpGs contain a curve which specifies limitations on suppressi6n~ pool level and reactor pressure vessel ytessure. The curve presently does not adequately account for upper pool dump. At present, the operator would be required to initiate automatic depressurization~ when the only' action required is the opening of one additional SRV.
18.
Eff ects of Insulation Debris /10 18.1 Tailures of reflective insulation in the drywell may lead to blockage of the gratings above the weir annulus.
This may increase the pressure required in the drywell to clear the first row of drywell vents and perturb the existing load definitions.
18.2 Insulation debris may be transported through the vents in the drywell vall into the suppression pool.
This debris could then cause blockage of the suction strainers.
- 19.. Submergence Ef fects on Chugging Loads 19.1 N/A for Mark I and Mark II Containments 19.2 N/A for Mark I and Mark II Containments 20.
Loads on Structures Piping and Equipment in the Drywell During Reflood N/A for Mark I and Mark II Containments 21.
Containment Makeup Air For Backup Purge Regulation Guide 1.7 requires a backup purge H re: val apability.
2
. This backup purge for Mark III is via the drywell purge line which Bischarges to the shield annulus which in turn is exhausted through the standby gas treatment system (SGTS).
The containment air is blown into the dryvell via the drywell purge compressor to provide a positive purge.
The compressors draw from the containment, however, without e
hydrogen lean air makeup to the contain=ent, no reduction in contain=ent hydrogen concentration occurs.
It is necessary to assure that the shield annulus volume contains a hydrogen lean mixture of air to be admitted to the contain=ent via containment vacuum breakers.
For Mark I and II facilities, discuss the possibility of purge exhaust being mixed with the intake air which replenishes the containment air mass.
22.
Miscellaneous Emergency Procedure Guideline Concerns g The EPGs currently in existence ~ have been prepared with the intenf 6f
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coping s.-ith degraded core accidents. They may contain requirements' conflicting with design basis accident conditions.. Someone needs to carefully review the EPG's to assure that they do noi ec::fiict with the expected course of the design basis accident.
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TABLE OF FOOTNOTES APPLICABLE TO MARK I AND MARK II CONTAINMENTS Footnote Comment 1
This concern is related to the trapping of water in the drywell.
2 This issue applies only to those facilities for which EPG's are in effect.
l 3
For Mark I and II facilities, confine your response on this issue to those concerns which can lead to pool stratification (e.g.,
operation of the containment spray).
4 For Mark I and II facilities, refer to Appendix I to Section 6.2.1.lc of the Standard Review Plan (SRP).
I 5
This concern applies to those facilities i
at which hydrogen recombiners can be used.
6 This issue as phrased applies only to a Mark III facility. However, the concern can be generalized and applied to the earlier containment types.
For Mark I and II facili-ties, indicate what methodology was used to calculate the environmental qualification parameters including a discussion of heat transfer between the. atmosphere in the wetwell and the suppression pool.
7 Not applicable to Mark II facilities.
8 For Mark I and II facilities, consider the water in the downcomers.
9 This issue as phrased applies only to a l
Mark III facility. However, the concern can be generalized. Accordingly, discuss what actions the reactor operator would take in the event that the limitations on the suppression pool level and the pressure in the reactor vessel are violated.
10 This issue as phrased applies only to a Mark III facil ity.
However, the concern can be generalized.
Accordingly, discuss how the effects of insula-tion debris could perturb existing load defini-tions or could block suction strainers.
In responding to this issue, you may refer to existing generic studies; e.g., the study done for the Cooper facility.
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