IR 05000249/1986006

Safety Insp Rept 50-249/86-06 on 860128-0213.No Violations or Deviations Noted.Major Areas Inspected:Review of Potential Damage Caused by 860120 Fire in Drywell Expansion Gap

ML17199F652
Person / Time
Site:	Dresden
Issue date:	02/26/1986
From:	Guldemond W, Patterson J, Ramsey C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML17199F651	List: IR 05000249/1986006 ML17199F650
References
50-249-86-06, 50-249-86-6, NUDOCS 8603030173
Download: ML17199F652 (10)

Text

U.S. NUCLEAR.REGULATORY COMMISSION REGION Iii

. Re~ort No. 50-249/86006(DRSS)

.D.ocket No. SQ-:249 L,i c~nse No. DPR-25

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Li d~n$ee: *,Commonw~a l tti :Edi son ~ompa~_y * *

P. 0. * Box-767

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Chi ca~o, IL. 6_0690 Facility Nanie:. *or~s*d~h;;*Nuclear .P~~*;~ *s~*~:~i-6n,"* u~~i.{ 3,

• 'Inspection Location: * Morris, *1L

.Inspect ion 28, * 29 and Februa:ry 7 and 13, 1986

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Date Approved By:.

Ope rational Date

• . Inspection Summary Inspecton on January 28,* 29 and February 7 and 13, 1986 (Report N ~249/86006(DRS))

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Areas Inspected:

Announced special safety inspection conducted to review potential damage to. the facility originating from a fire in the dryw~ll *. *

expansion gap on Jan*uary 20, 198 The inspection involved 60 inspector-hours by six NRC inspector Results:

No ~iolatinns or deviations were id~ntifie (

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DETAILS Persons Cont~cted

. CECo Sept~, Station Manager...

R. Flessner, Servi~es Superintendent J.. Brunner, Assistant Services Superintendent T. Hauser, Fire Protection Engineer *

R. Mi rochi na, SNED D. Wilgus, SNED M. Dillion, Station Fire Marshal J. Schrange, Health Physicist Rolf Jensen and As~octate~

J. Klien; Consultant NRC E. Hare, Resident Inspector S. Stasek, Resident Inspector L. McGreg-or, Sen1 or Resident Inspector L~ndsmari~ Region III Project M~nager *. January 20, 198.6 Drywell Expansion Gap Fire. Ap~ar~nt Origin of the Fire At approximately 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br /> on January20, 1986, with Unit 3 shutdown*.

and defueled, an air arc cutting activity began on containment pipe

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penetration No. ll3 (

118 11 reactor water cleanup system pipe) :inside *the_*

reactor water cleanup system (RWCU) -

118 11 heat exchanger roo At 0905 '.

hours workers in the area observed smoke.in the vicinity of the pipe penetratio The shift-engineer's office and the control rodm were *

notified.at approximately 0916 hour0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.48538e-4 months <br />. Initial Response The fire watch for the air arc cutting activity apparently discharged

• a dry chemical' extinguisher on or in the vici.hity of pipe penetration No. 11 Subsequently, a fire brigade.leader arrived to investigate the fire and determined that the fire had been extinguishe At approximately 1000 hour0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />s~ the station fire marshal was notified by the shift engineer of smoke in the Unit 3 reactor buildin A hours the reactor building ventil~tion system, whi~h had b~eh turned off to support Standby Gas Treatment System testing, was turned on to remove smoke from the Unit.3 reactor building and drywe 11, a 11 personnel were evacuated from the Unit 3 torus and drywell areas, and air samples were taken to verify the quality of air for personnel safet *

At 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br />, the shift engineer contacted the station fire marshal and informed him that the smoke was clearing from the Unit 3 reactor building. Apparently the fire brigade leader and station construction concluded that the problem was under control because the fire watch had earlier discharged a dry chemical extinguisher on or in the vicinity of the pipe penetration in the RWCU heat exchanger room and smoke was being cleared from the reactor building and the drywell by the reactor building ventilation syste At approximately 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br /> personnel were allowed to reenter the drywel At 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> station technical staff personnel discovered a hot spot in the drywell in the vicinity of penetration No. 11 Workers complained of intense heat 4 to 5 feet away from the drywell steel liner. At 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br />, all personnel were again evacuated from the drywell because of the overheated drywell liner. A construction staff person took general use (not calibrated) pyrometer readings in the vicinity of pipe penetration No. 113 on the inside of the drywell liner (unexposed side) between 1230 and 1315 hour0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br /> The highest reading recorded was 440-450° The heated drywell liner condition alerted the station fire marshal to investigate what could be burning on the other side of the drywell liner. His review of Section 5 of the Dresden FSAR identified the presence of polyurethane foam installed inside the drywell expansion gap between the steel liner and the concrete shell. Drywell Expansion Gap Design The outer surface of the steel drywell liner is enclosed.in 8 feet of structural and shielding concret Thermal expansion of the drywell liner as a result of normal reactor operations will cause the liner to expand both radially and verticall To accommodate this expansion, during construction, an expansion gap was provided between the structural concrete and the drywell steel liner. The sizing of the expansion gap was based on the maximum drywell steel liner temperature following a postulated loss of coolant acciden Materials Used to Fill the Drywell Expansion Gap To maintain sufficient space for liner expansion, prefabricated polyurethane foam sheets were installed over the entire liner exterior surfac Epoxy impregnated fiberglass tape was applied over all joints in the foam and one-fourth inch to 3/8 inch fiberglass-epoxy prefabricated cover panels were installed over the foam panel The fiberglass panels were made of fibrous glass in chopped fiber form with an isophatallic resin as a binde Tests were conducted at the site on mockups of the drywell steel liner/polyurethane foam/fiberglass panels to determine their displacement from the pour of structural and shielding concret The test results showed that the fiberglass was displaced less than 1/4 inch *from the pouring and curing of the concrete. Therefore, it was assumed that the drywell expansion gap design space was maintained during constructio * Determination Made that Polyurethane Foam Panels Were Burning Inside the Drywell Expansion Gap As a result of the station fire marshal 1s review of Section 5.2.3.6 of the FSAR, he determined that hot slag (molten metal) from the air arc cutting activity on pipe penetration No. 113 in the RWCU heat exchanger room had come in contact with and ignited the polyurethane foam material in the drywell expansion ga The typical drywell pipe penetration detail (figure 5.2.3.27 of the FSAR) shows a 2 inch gap between the pipe sleeve and the penetration sleeve, which provides a direct path to the polyurethane foam materia Furthermore, the drywell expansion gap is not air tigh The fiberglass panels installed over the polyurethane foam material do not form a barrier that will exclude air from coming in contact with the polyurethane foam materia The 45 degree angle that pipe penetration No. 113 is installed through the drywell adds credibility to this hypothesis as to the origin of the fir Extinguishment of the Fire c~

Since the fire was determined to be in a concealed space that was impossible for the fire brigade to reach, the station fire marshal directed the fire brigade leader to start applying water from a 1 1/4 inch (3/4 inch inside diameter) rubber hose (supplied by the demineral ized water system at 100 PSI) to the 2 inch gap between the pipe sleeve and the penetration sleeve on penetration No. 11 This action was initi~ted between 1230 and 1300 hour0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> As the fire marshal was not certain that water applied through this penetration would extinguish the fire, additional hose streams supplied by the *

fire water system at 100 PSI were applied above and adjacent to the penetration {pipe penetration Nos. 133, 122, 144 and 143).

At, 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />, the licensee decided to monitor the drywell liner temperature on the inside of the drywel At 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, inside drywell liner temperatures were recorded at 140, 110 and 90° At 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br />, the licensee's corporate fire protection engineers and the station fire marshal considered the fire to be extinguished due to declining inside drywell liner temperature At 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />, inside drywell liner temperatures were determined to be normal and the application of water to the drywell expansion gap was discontinue No offsite fire department assistance was requested and no emergency event was* declared by the licensee at any point during this even Potential Damage Resulting From the Fire At the time of the inspection the licensee had not determined the extent of damage resulting from the fir In two principal areas inside the drywell (approximately 10 feet in diameter and 10 feet apart), charred, discolored, blistered or burned away paint was visible on the drywell line The drywell steel liner is approximately 1 1/8 inch thick carbon steel.

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Polyurethane foam materials are synthetically produced from glycols and diisocyanate It has been established by actual fires and certified fire testing laboratories that urethane foam materials ignite easily and burn vigorously with the production of dense black smoke and a very black, viscous melt product which can burn with the intensity of a flammable liquid (Reference Underwriters Laboratories Inc. and Factory Mutual Laboratories Inc. 1969-74 studies on the Flammability of Cellular Plastics). Burning polyurethane materials also produce corrosive and toxic oxides of nitrogen, together with other toxic gases and corrosive that are harmful to metal It appears that this fire began some time after 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br />, when the air arc cutting activity began on pipe penetration No. 11 It burned with some intensity and it is suspected that high temperatures were reached inside the drywell expansion ga It is not known how much polyurethane foam material was consumed by the fire or how far the fire spread vertically or horizontally around the drywel The 4! hours burn time from 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br /> to 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> (when water was first applied through penetration No. 113) indicate that substantial burning may have occurre Apparently, a substantial amount of water was applied to the drywell expansion gap to extinguish the fire (approximately 500 gallons per minute (GPM) for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> or 240,000 gallons). However, according to the licensee, only 20,000 gallons of excess water was removed from the torus basement by the radwaste system the day after the fir The licensee did provide the inspectors with a draft copy of proposed work to be performed by Sargent and Lundy (S&L Project No. 7368-30)

to evaluate the integrity of the Unit 3 drywell for affects from the fire. This evaluation did not appear to consider some of the specific NRC concerns detailed in Paragraph 3 of this report and is not scheduled to be completed until March 31, 198 Emergency Preparedness Implications The inspector reviewed records associated with the event; interviewed several available persons knowledgeable of the event; and reviewed the Station's Emergency Action Levels (EALs) and the notification requirements of 10 CFR 50.72 for applicabilit The event was not classifiable as an emergency per the current EALs for the Fire Condition (No. 5) for the following reasons: offsite fire fighting assistance was not requested; equipment was not degraded such that a Limiting Condition for Operation (LCO) required a reactor shutdown; equipment was not degraded such that 1a cold shutdown or hot shutdown could not be achieved or maintained; and required safety systems were not potentially affected. Since all fuel had been removed from the reactor vessel for some months, there was no need to be able to achieve and maintain shutdown and no reactor safety systems were required to be in operatio The event was not classifiable as an emergency per the current EALs for the 11miscellaneous 11 Condition (No. 18) which was worded as follows:

"any other conditions of equivalent magnitude to the criteria used to define the accident category as determined by the Station

Director."* The Unusual Event EAL for Condtion No. 18 listed a number of circumstantes th~t warrarited intrease~ awareness on the part of State and/or local offsite official The Alert EAL for Condition.No. 18 listed several circumstances which warranted precautionary activation of the qnsite Te_chnical Support Center (TSC) and near site Emergency Operations Facility (EOF).

the Site

• Area Emergenc:y EAL for*Condition No. 18 addressed~ activation of *

these Emergency.Response -Facilities~ radio l ogfca l * mon"itori ng teams, and precautionary notification of the public near the sit The General Emergency EAL for Condition No. l8 addressed.an imminent core melt si-tua:tion:.. No EAL associated with Condition No.* 18 was.

applicable to the f.ire i11cident..

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Si nee no EAL was app 1itab1 e, an emergency dec*l arat ion and activation of the Generating Stations Emergency Plan (GSEP) did not occu Consequeritly, initial notifications of the Illinois Department of Nuclear Safety and Illinois Emergency Services and Disaster Agency were neither required nor perform.e Similarly, initial. *

notification of the NRC Operations *center was not.required per 10 CFR 50.72(a); however, the licensee did nqtify the Station's Senior Resident Inspector between 4 p. m. * crnd 5 p. m. on January 2 That individual informed his superviso Neither the licensee nor the aforementioned Region III personnel deemed it necessary to promptly notify the NRC Operations Center per the requirements of 10 CFR 50.72(b) or Cc).

Due to the e~tensive nature of maintenance being performed on the Unit 3 reactor coolant System, and the fact that the vessel had been completely defueled for some months,

regional emergency preparedness staff have also concluded that the req~irements of 10 CFR 50.72(b) and (c) were riot ~pplicable to this situatio *

The wording of the Unusual Event EAL for Condition No. 18 was nbt in c 1 ose agreement with regulatory guidance found. in NU REG 0654, Revi s'i on 1. * The 1icensee 1 s E~L stated, in part, that 11 a condition that warrants increased awareness on the part.of the State and/or.*

local offsite offieials. 1-1 Rele,vant regulatory guidance for the Unusual Event classification states, in part.; that "other plant conditions exist that warrant increased awareness onthe*pa:rt_of a plant operating staff (emphasis added) -0r State and/or local offsite authoritie * During the course of the l.i censee 1 s response to the fire incident, there were a number of meetings in the TSC invo1ving Station management and/or technical staff; personnel were evacuated from the reactor building for a time; the licensee's General -Office was informed of t~e inci.dent; and personnel made repeated entr'ies into the drywe 11 to obtain temperature readings to he 1 p determine whether the fire still existe There was clearly increased

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awareness and -activity by p 1 ant operating and other p 1 ant staffs i response to the fir Had the Un.usual Event EAL for Condition No. 18 included the phrase "plant operating staff,

11 per the regulatory guidance, there would be no questi-0n wheth~r or not the NRC Operations Center and appropriate State agencies needed to be promptli informed of the fire incident, per the requirements of 10 CFR 50.72 and 10 CFR 50, Appendix E, Paragraph IV. * *

• Therefore, to prevent recurrence of any uncertainties regarding the need for the*licensee to promptly inform the NRC Operations Center and appropriate State agencies of significant tespohses by Station operations personnel to abnormal.conditions onsite, the phrase 11p l ant operating staff 11*.should b'e adc:fed to the Unusua 1 Event.EAL for Condition No. 1 NRC Request For In.formation To Be Prov*ided By The Licensee Prior lo Unit 3 *

Startup From The Current Outage

In view of the damage that may have.occurred to t.he drywe 11 steel 1 i ner,

.the structuraJ and shielding concrete, electrical and pipe penetrations, or other structures and equipmeht required for safe operation -of the Unit, the licensee is requested tQ provide to Region l1I.a detailed assessment of this event that will include a-confirmation of short term and long term operability of the affected struC:tures, systems and/or component This assessment ~ust include an evaluation of the following co~cerhs for Region III and Office of Nuclear Reactor Regulation.review prior to restart

• of _Unit 3 from the* current outage:

• Detailed throne 1 ogy of the Fire.Ev*ent Provide a.detailed chronology of the January.20, 1986 Unit 3 drywell

• expansion gap fire occurr~nce ahd describe the sequence of events that led to the decision that offsite*fire department assistance was not needed... Durat-ion and Intensity of the Fire DE!termine the duration, physical extent, and intensity of the*fire and includ~ in this assessment the highesl metal and concrete temperatures reached during.the fir If no systematic approach was taken to record actual temperatures reached.during the fire, determine the

.highest* temperature that the steel and.concrete structures may have been exposed* to based on published (i.e. Underwriters Labo~atories Inc., Factory Mutual Laboratories Inc.) free burning polyurethane foam ca 1 orifi c heat va 1 ues for a fire of this du rat ion. * Provide an estimate of what changes occurred in the material properties of the steel, concrete, electrical and p'ipe penetrations, drywell penetration wells: and.other affected equipment or component For the norma 1 op¢r~t ing."an.d, acc,i dent :.condi t io~,: detefmi ne the temperature profile' thrqugh 'the :dry'well st:eel liner wHh and without polyurethahe* present in order to show any changes in drywell expansion from the original design... ~erform a, stru_tt.ur:al arJaly5is which evaJuates *the.state of stress of the.drywe11*~stee_l": Jjne*r

during the :ffre and compare this with the yield strengths of the**

mater.i.a 1.

• Corrosive Species Introduced Into the Drywell Expansion Gap Determine the type and quantity of corrosives that were introduced into the drywell expansion gap as a result of the fire and its extinguishment. Determine the short and long term effects of these corrosive species on the structural integrity of the drywell steel liner structural and shielding concrete, electrical and pipe penetrations, drywell penetration welds and other affected equipment and component Effects of Spalling Concrete and Polyurethane Residue Remaining Inside the Drywell Expansion Gap Determine the effects of polyurethane and fiberglass residue as well as 11 hard spots" that may have been created by spalling concrete into the drywell expansion ga Determine the effects of potential 11 hard spots 11 on the drywell steel 1 iner under pressure and temperature loads during normal operating and accident conditions and determine the compressive strength these 11hard spots 11 must have to be of concer Amount of Water Applied to the Drywell Expansion Gap to Extinguish the Fi re Determine any thermal shock that may have occurred to the drywell steel liner and determine the amount of water used to extinguish the drywell expansion gap fire; how much of this water was removed; how much remains unaccounted for and what actions will be taken. to remove any remaining moisture in the drywell expansion gap or in the surrounding structural and shielding concret Basic Drywell Liner and Structural and Shielding Concrete Design Functions Determine to what extent (if any) the fire may have otherwise degraded the drywell steel liner's ability to provide a barrier which controls the release of fission products to the secondary containmen Determine to what extent if any, the fire may have otherwise degraded drywell electrical or pipe penetrations and the structural and shielding concrete design function Compliance with the Safe Shutdown Requirements of Appendix R to 10 CFR Part 50 Determine the effects of a fire of this nature on safe shutdown capability as prescribed in Section III G.2 of Appendix R to 10 CFR 5 During normal operation, this section requires redundant cables, including non-safety circuits that could adversely affect safe shutdown capability that are located in the same fire area outside of the primary containment, to be separated by a 3-hour fire barrier; be encased in a 1-hour fire barrier with automatic fire detection and suppression installed in the fire area; or be separated by a distance of more than 20 feet with no intervening combustible or fire hazards with automatic fire detection and suppression installed in the fire

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are For normal operation of both Dresden Units 2 and 3, explain how such electrical cables and circuits passing through the drywell expansion gap are in compliance with the requirements of Appendix R so that a fire of this nature will not affect safe shutdown capability during normal operation Potential Repairs Needed Determine the need for repairs (if any) to the drywell steel liner, structural and shielding concrete, electrical and pipe penetrations or other affected equipment as a result of the fir Include in this assessment a time frame for completion and the impact of such repairs on normal reactor operation Results of Water and Polyurethane Residue Samples Provide the results of any and all extinguishing water and fire residue samples collected as a result of the fire for NRC revie Corrective Actions Taken to Prevent Reoccurrence Describe in detail the corrective actions that will be taken to prevent fires involving polyurethane material in the drywell expansion gap, including interim measures currently in plac Provide an assessment of the extent and results of the radiolytic and thermal decomposition of materials in the drywell expansion gap in Unit 2 and an estimate of the effects of such decomposition on fire potential and containment structural integrit.

Provide a list of other plant locations where polyurethane or other combustible foam materials are installed in concealed space Identify whether these materials were explicitly addresse~ as part of our fire hazards analysi Items a through 1 above will be tracked as an open item (50-249/86006-0l(DRS)). Emergency Preparedness Concerns Add the phrase, "plant operating staff", to the Unusual Event Emergency Action Level for Condition No. 1 This is an open item (50-249/86006-02(DRSS)). Open Items

Open items are matters which have been discussed with the licensee, which will be reviewed further by the inspector, and which involve some action on the part of the NRC, the licensee, or bot Open items disclosed during the inspection are discussed in Paragraph 3.

9 Exit Interview The inspectors met with licensee representatives at the conclusion of the inspection on February 7, 1986, and summarized the scope and findings of the inspectio The licensee achknowledged the statements made by the inspector The inspectors also discussed the likely informational content of the inspection report with regard to documents reviewed by the inspectors during the inspectio The licensee did not identify any such documents as proprietar On February 13, 1986, in a telephone conversation with the licensee, additional concerns regarding compliance with the requirements of Appendix R to 10 CFR Part 50 were discussed with the license