ML20070V835
| ML20070V835 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/06/1991 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| Shared Package | |
| ML20070V836 | List: |
| References | |
| NUDOCS 9104120145 | |
| Download: ML20070V835 (6) | |
Text
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ATTACHMENT.
B ALTIMORE CAS AND ELECTRIC CHARLES CENTER
- P.O. BOX 1475
- BALTIMORE, MARYLAND 21203 1475 NUOLEAR SAFErY & Pl.ANNING DrPARrMENT cotvtat nars wetAA 90 wit Aud April 6,1991 imm, w U. S. Nuclear Regulatory Commission Washington,DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50 318 Recuest for_ Regional Waiver of Compilpag.e
REFERENCE:
(a) Ixtter from Mr. O.C. Crect (BG&E) to Document Control Desk, dated April 5,1991, same subject Gentlemen:
This letter replacca Reference (a) in its entirety. Reference (a) is hereby withdrawn.
Baltimore Gas & Electric (BG&E) Company requests a Regional waiver of compliance from certain requirements of Cahert Cliffs Unit 2 Techniad Specification 3.6.1.7," Containment Purge System."
- niat SpectGcation requires, in MODES 1,2,3, and 4, that "The containment purge supply and exhaust isolation valves shall be closed by isolating air to the air operator and maintainmg the solenoid air supply valve deenergized." We request a waiver to allow operating the contairunent purge supply and exhaust isolation vahes in Mode 3 (Hot standby) and Mode 4 (Hot shutdown) for the purpose of purging the Unit 2 containment, and to conduct local leak rate testing (and repairs, if required) of the containment purge vahes upon cornpletion of the purge. If any of the four containment isolation valves fails its local leak rate test, that failed vahr will be repaired within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or the unit will be in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. This also constitutes a waiver from Technical Specifications 3.61.1, " Containment Integrity," inasmuch as containment purge applies to that Specification.
CIRCUMSTANCES Unit 2 is in MODE 3, in the process of starting up for Cycle 9 operation following shutdown in March,1989. During the refueling outage, new msulation was installed on the Unit 2 Reactor Coolant System piping. In addition, substantial maintenance involving penetrants and lubriamts in the plant has been conducted. As the plant has been heated up from cold shutdown, off gassing from the new insulation and heat up of fimd residues has unexpectedly resulted in high levels of carbon monoxide inside the containment building. While some work can be completed wearing breathing equipment, in order to allow for personnel access to complete all necessary maintenance and 9t04120t45 910409 PDR ADOCK 05000310 p
PDR l.
APR 6 '91 8: 44 FROM CCNPP< NRM NOF-2FLR PAGE.003 l
Document Control Desk April 6,1991 Page 2 surveillance items the containment must be purged. If the containment is not purged in MODE 3 or 4, the unit will have to be cooled down to MODE 5 (cold shutdown) then beated back up, causing an unnecessary transient on the plant. This would also delay starting up Unit 2.
The situation could not be avoided. Similar insulation was installed on Unit 1, but far less new insulation was necessary and the phenomenon did not occur. Previous outages resulted in lower concentrations of contaminants, but it was impractical to quantify the expected concentrations or to eliminate them before plant heatup. Herefore, no basis existed for expecting this phenomenon during this startup.
SMYrY SIGNIFlCANCE ANUElTmr1Al,CONSFQFMQ.ES u
ne containment purge system includes a supply penetratbn with a supply fan and two 48 inch butter 0y velves for containment isolation, one ms,de and one outside contamment, and an chaust i
x:netration with an exhaust fan and two 48 inch buttert.y valves for containment isolation, again one nside and one outside containment.
Pur ' g the Unit 2 containment willinvohc opening these 48 inch air operated butter 0y valves at the su and the exhaust containment penetrations. These are openings that are normaDy shut in M DES 1 through 4 due to Loss of Coolant Accident (LOCA) considerations. If a LOCA occurs while purging, a releasc of a portion of the containment atmosphere would be possible before the vahes are shut.
Unit 2 has been shut down for over two years. The decay heat of the reactor is very low. Therefore the chances of overheating of the fuel, fuel failure, and introduction of fission products into the reactor coolant are also low. The activity in the reactor coolant is also low. If a LOCA did occur, the overall activity concentrations of any released containment atmosphere wuuld be very low relsthe to previous accident analysis conditions. Also, the actual time of purging will be minimized, further reducing the chance that the worst casc of a LOCA while purging could occur.
An evaluation was performed to assess the consequences of a LOCA while purging containment for the present decay heat and Reactor Coolant System conditions, he source term considered to leak from the containment in the current LOCA analysis consisted of 100% of noble gases and 50% of halogen Ossion product gases contained in the fuel. These fission products were decayed the appropriate amount to reflect curTent mnditions and conservatively assumed to be totally released to the environment in analyzing the effects of a potential LOCA during purge. He results for whole body dose were 4.2 rem, which is greater than the present accident analysis result of 2.2 rem but is far below the 10 CFR Part 100 timit of 25 rem. The thyroid dose result was lower than the present analysis result due to the decay of iodine, the primary contributor to that dose.
A walkdown of the plant's main ventilation system was conducted to evaluate the potential effects of its failure in the event of a LOCA steam pressure transient during purging. ne location of the piping was determined to make any effect on the controlviUnit 1, which is operating, unlikely. That
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APR G '91 0 45 FROM C CNPP n4RM t40F-2FLR PAGE.004-Document Control Desk April 6,1991 Page 3 equipment necessary to maintain reactor coolant [nventory and decay heat removal for Unit 2 would also x unlikely to be incapacitated.
COMPENSATORY ACTIONS After the final purge and prior to Unit 2 entry into MODE 2, the containment purge supply and exhaust isolation valves will be local leak rate tested.
Boric acid concentration will be maintained greater than 2000 ppm and all Control Element Assemblics will be fully inserted until satisfactory local leak rate testing of all purge valves.
DIMATION OF WAIVER This waiwr is requested for as long as Unit 2 doer not enter MODE 2 (Startup) or for seven days, whicbcver occurs first. Purging will be scheduled to optimize containment carbon monoxide removal while minimizing purge time. He ma}ority of the required purging is expected to be completed with the initial purge, but additional purges may be necessary to address any delayed oft gassing.
BASlS FOR NO SIGNIFICANT HAZARDS CONSIDERATIONS Tbc proposed waiver has been evaluated against the standartis in 10 CFR 50.92 and has been determined to not imulve a significant hazards consideration, in that operation of the facility in accordance with the proposed waiver:
(1)
Would not invohs a significant increase in the probability or consequences of an accidentpreviously evaluated.
The probability of previously evaluated accidents is not affected by this walver, because the change m containment ventilation does not impact any LOCA initiation scenano.
The consequences, however, are affected. An evaluation was performed to assess the consequences of a LOCA while purging containment for the present decay heat and Reactor Coolant System conditions. %e source term considered to leak from the p'
containment in the current LOCA analysis consisted of 100% of noble gases and 50%
of halogen fission product gases contained in the fuel. Dese thslon products were decayed the appropriate amount to reflect current conditions and conservatively assumed to be totally released to the environment in analyzing the effects of a potential LOCA during purge. The results for whole body dose were 4.2 rem, which is greater than the present accident analysis result of 2.2 rem but is far below the 10 1
l
i$PR 6 'b 8: 46 FROM CCNPP/HRM HOF-EFLR PdGE,Ob5 Document Control Desk April 6,1991 j
Page 4 CFR Part 100 limit of 23 rem. The thyroid dose result was lower than the present analpis result due to the decay ofiodine, the primary contributor to that dose.
Additionally, the likelihood of failure of the fuel assemblics which would result in the fission product release is substantially reduced because of the lower heat Eencration of the fission products in the fuel. Consideration of a similar case when analyzing long decapd fuel (3 years decayed) indicates that they would be sufficiently cooled in air to prewnt fuel failure.
Therefore, there is not a signiticant increase in the probability or consequences of an accident previously evaluated.
(2)
Wordd not create the possibility of a new or different type of accident from any accident previously evaluated.
1 bis waiver would not result in a change to the plant itself and involves an operation that is routinely carried out in other MODES. Therefore it would ret create the possibility of a new or different type of accident from any accident previously evaluated.
(3)
Would not involve a significant reduction in a margin ofsafety.
Containment integrity is essential for limiting the potential reh:ase of activity to the environment during a LOCA.
A LOCA during power operations results in pressurization of the containment with activated reactor coolant plus the potential for fuel cladding failure as decay heat is generated and reactor coolant pressure is reduced. Cladding failure could relcase fission products to the Reactor Coolant Systern, then possibly to the containment and then possibly to the environment as well.
Calvert Cliffs Unit 2 has not been operated at power for over two years.- Therefore there is very little decay beat in tbc reactor and the level of activity in the reactor coolant system is low. The amount of purging time will be limited and analysis has shown that the worst case LOCA while purging would not result in exceeding off site dose rate limits. Given these considerations the affect on margin of safety of purging -
containment while in Mode 3 or 4 is not significant.
ENVIRONMENTAL CONSEOUENCFE The purge operation will introduce fresh outside air into the upper containment, while drawing air from the lower levels and exhausting it through the plant's main vent, via high efficiency filtering and
Documsat ControlDesk April 6,1991 Page5 radiation monitoring devices. ne effect of the relecse of the small amounts of carbon monoxide in question to the environment wi.U be negligible and not irreversible.
SA*TIY COMMrCQ1RtMtM l
This proprxed walver of Technical SpeelScaten 3.6.1.7 and 3.6.1.1 for Unit 2 and our discunion of significant hazards considerations have been reviewed by our Plant Operations and Safety Review Committee. They concur that utilization of this waiver will not result in an undue risk to the health and safety of the public.
-Very truly purs, D
GCC/ DIE / dis Attachment cc:
D. A Brunc, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. O. McDonaki, Jr., NRC T. T. Martin. NRC L E Nicholson, NRC R. I. McLean, DNR J. ii. Walter, PSC
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- .9 Document Control Desk April 6,1991 Page 6-bec
J. A.Tiernan/A.J.Slusark M. J. Micrnicki W. R. Corcoran/F. J. Munno C. H. Cruse /P. E Katz i
R. C DeYoung
- R. M. Douglass/R. F. Ash R. P. Heibel/T. N. Pritchett C P. Johnson C C Lawrence,III/A. R. Thornton W. A.Thornton/E. I.Baucrcis R. B. Pond, Jr/S. R. Buxbaum, Jr.
L B. Russell /J. R. Iemons O.L Adams A. B. Anuje J. E Baurs J.J. Connolly R. E Denton G. L Detter G. J. Falibota L D.Grabcr D, V. Graf R.C Johnson (2)
B. S. Montgomery R. E Nage!-
R. C L Olson P. A. Pieringer L O. Wenger D. L. Shaw
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