ML20079H154

Rept on Unit 1 High Drywell Temp

ML20079H154
Person / Time
Site:	LaSalle
Issue date:	12/22/1983
From:	COMMONWEALTH EDISON CO.
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ML20079H087	List: ML20079H121 ML20079H139 ML20079H154
References
NUDOCS 8401230342
Download: ML20079H154 (23)

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Commonwealth Edison Company LaSalle County. Station - Unit 1 REPORT ON UNIT 1 HIGH DRYWELL TEMPERATURE TABLE OF CONTENTS Section '

Page

.. I. INTRODUCTION -

1 II. DISCUSSION OF EVENT

1. Discovery of Results of the High Temperature 2 2

3.

Characterization of Event Condition 2 Causes of Excessive Temperatures 2 III. EVALUATION OF EFFECTS,AGAINST PLANT DESIGN

1. Structural Capability 3

2. Drywell Cooling System Capability 4

3. Biological Shield Capability 4

4. Electric Cable Capability 4

5. Equipment Capability 4 Table III-l 5 IV.

CORRECTIVE ACTION AND EXPECTED RESULTS

1. Structural Corrective Actions 6

2. Decreased Drywell Temperatures

a. Improved Air Flow Distribution 7

b. Penetrations Through the Biological Shield 7

c. Gaps in Installed Insulation 7

_d. Peripheral Gap on RPV 8

e. Reduction of Sensible Heat Lo~ ads 8

3. Electric Cable Replacement 8 Table IV-1 9 Table IV-2 9

4. Equipment Replacement 10 Table IV-3 10

5. Temperature Monitoring

• 11 Table IV-4 12 Table IV-5 , 13 V. UNIT 1 RESTART OPERATING PLAN

1. Justification for Unit 1 Restart 14

2. Temperature Monitoring Plan 15 VI.

SUMMARY

CONCLUSION FOR UNIT NO. 1 RETURN TO SERVICE

1. Specific Reason for High Temperature Condition 16

2. Completion of Short Term Fixes for Temperature Improvement

3. 16 .

4.

Cable Replacement and Evaluation of Adequacy 16 Equipment Evaluation

5. 16 Expected Schedule for Return to Service 17 VII. LONG TERM PROGRAM 17 ANNFY 18 8401230342 840113 PDR ADOCK 05000373 g PDR - - - - - - - ~

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, Commonwealth Edison Company '

LaSalle County Station - Unit 1

, - REPORT ON . UNIT 1 HIGil DRYWELL TEMPERATURE I, INTRODUCTION The subject of the LaSalle County Station - Unit 1 high l

.. .drywell. temperature problem was discussed among Region III '

of.the NRC, CECO, and S&L during a management meeting held at Region III on-Monday,. November' 21, 1983._ An initial briefing on the problem of the degradation of the elecbri-cal' cables and equipment in the upper levels of the Unit 1 drywell was made by CECO (Reference NRC Region III letter of December 2,1983 to C. Reed from A. B. Davis). In  :

accordance with commission instructions, page 12 of that letter, this reportJaddresses.the short term actions taken '

to. enable restart of LaSalle Unit 1. In addition, though

', not. requested, the report. acknowledges the long term cor-rective actions briefly mentioned at the management meeting.

4 LaSalle County Unit 1 has experienced excessively high temperatures in the upper areas of the-drywell. The safety effect of these high temperatures is'to degrade the cabling i.

and the electrical and mechanical components.

1 The short term plan for Unit 1 restart was presented by

- CECO ' at the November meeting. It included,

', e investigating the reasons for the high temperatures, ,

7 e de' fining the extent of the problem, e -taking short term corrective actions to eliminate '

i the cause- ,

.e evaluating the remaining life of retained equipment

. e ensuring through a temperature monitoring program "

that cabling and components do not exceed their remaining qualified life prior to the end of the

!. *- first fuel cycle.

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' CECO's long term solution-is intended to preclude possible future high temperatures, thus preventing accelerated de-gradation of electrical-cables, and mechanical and elec-p trical equipment and also ensuring the functional capabi-lity of the containment pressure boundary. ,

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I II. . DISCUSSION OF EVENT

1. Discovery of Results of the High Temperature .

During a recent shutdown of the LaSalle Unit 1, visual damage to electrical cables was noted by station per-sonnel. The physical evident was degradation of the

-insulation and jacketing on some' control cables. CECO's outline briefing to Region III on November 21, 1983 was based on these preliminary observations. Sinco then a systematic inspection of the Unit 1 drywo11 and equipment

.. was conducted. The inspection consisted of looking for discolored, cracked, or stiff electrical insulation, and cable jacketing. Flexible electrical conduit.and equip-ment were also examined for signs of degradation. Vari-ouc junction boxes were opened to verify that cables in the conduit was undamaged. The primary containment liner and concrete structures in the upper drywell region were visua'lly idspec'ted for'o6vious indications of elevated temperature effec ~ts.

2. Characterization of Event Conditions The operating temperature reading from drywell monitors were used'to establish a temperature profile for the drywell (See Figure 1). Some additional temporarily in-stalled thermocouples around the safety relief valves were-also utilized for temperature indications. A correlation was made of available temperature data and observed visual damage. The bulk high temperature effects appear to be limited to elevation 804 feet and above with some local problems below that level. The degradation problem is caused by excessive heat in the upper drywell regions and at localized hot spots. The local hot spots on some cables coincided with physical contacts on hot piping or high temperature surfaces.

Only the upper area of the drywell had a volumetric or bulk overtemperature.

3. Causes of Excessive Temperatures High drywell temperatures resulted from excessive heat traceable to several conditons:

• - a) poor air flow distribution within the drywell due to unanticipated heat loads, b) _ inadequately sealed penetrations including some un-insulated penetrations in the bioshield wall, c) numerous gaps in installed thermal metallic reflec-tive insulation including uninsulated components such as open flashing at clamps, gaps at whip res traints, miuuing flashing at inuulation seams,

missing flashing at tap and test connections, missing flashing at valves, and also crushed and -

damaged insulation,

,, d) , a full perimeter thermal insulation gap around the RPV, 4

e) and because of the above deficiencies, a greater sensible heat load than anticipated. The original design sensible heat load was equal to approximately 3,627,250 3ut/hr. It was later determined the un-anticipated sensible heat load at 100% power was approximately 5,204,100 Btu /nr. which contributed to the high drywell temperature.

III. EVALUATION OF EFFECTS AGAINST PLANT DESIGN An evaluation of the effects of high temperature against the design basis for LaSalle was made to ausure adequacy of the plant features to sustain such an event. The scope of the evaluation included review of the following capa-bili ties :

e the primary containment structure o the drywell cooling system o the biological shield e

the electric cable e mechanical and electrical equipment in the drywell

1. Structural Capability l

The primary containment was designed for an operating I

temperature of 135*F for its internal atmosphere while at power and an accident transient temperature of 340*F. The assumption being that the containment walls l could attain thermal equilibrium with the internal at-l mosphere for the long periods associated with power

( operations, but that the thermal spike associated with L ., a transient event would not sustain wall temperatures of the magnitude of the atmospheric maximum.

A maximum upper level atmosphere temperature of 351*F was extrapolated from the observed lower elevation temperatures taken from the drywell sensors. Consider-ing an atmospheric temperature of 351*F which conser- s vatively translates to an average wall temperature of i

210

• F in the con re te , the properties of the LaSalle concrete indicate that less than ten percent strength loss occurs hence,

a) The containment wall has the capability to with-stand the ef fects of that temperature, b) The containment wall has the capability to with-stand all design loadings.

The liner was designed to withstand a design accident temperature of 340*F. The reserve capacity of the liner is such that at an extrapolated temperature of 428'F the calculated strains do not exceed liner plate allowables for factored loads.

2. Drywell Cooling System Capability The drywell cooling system capability is as stated in paragraph II.3.e. The drywell chiller capacity is 6,600,000 Btu /hr. Adjustment of the drywell airflow is the mechanism to control and obviate drywell over-temperature

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3. Biological Shield capability The biological shield was designed for a temperature of 275'F. The shield temperatures were less than this design temperature. Therefore, there iu no adverse ef fect on the biological shield wall.

4. Electric Cable Capability Plant systems' cablea whether safety-related or non safety related were puchesed to the sanle specifica-tions (IEEE-383, 1974). The test available cable was selected with a design rating of 90*C (194*F). Speci-alty cables such as the head vent thermocouples and

'he vibration monitoring signal cables are uniquely c

run in separate conduits it high drywell elevations and  :

these are n'ot of concern for this overtemperature event.

The service life for various types of cable was evalu-ated as a part of the environmental qualification program for LaSalle. That lifetime calculation includes the normal service and the most limiting accident (LOCA or llELB) parameters according to Arrhenium methodology that is acceptable to the Commission for the estimation of component life. In as much as cable applications and lifetimes vary, a specific or a bounding calcula-tion must be made for each type of cable.

5. Equipment Capability The Mark II containment design approach pul posefully removed safety-related equipment from the drywell to improve reliability. Only a few items remain insida L

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9 the drywell: the main steam isolation valves, the safety / relief valves, other isolation valves, and .

control actuators, solenoids,'and related switchec and cables. Mechanical snubbers are also located inside the drywell.

As was electric cabling, these items of equipment were evaluated for decreased service life (plus bounding accident effects) as a result of the high thermal ex-

. . posure of the Unit 1 Grywall. This review was mudc _n the same context as the NRR approved " Justification for Interim Operation" which recognizes the current qualifi-cation status of the equipment and the reliance on functionally independent, physically separated equipment available to perform the intended safety functions.

Except for piping snubbers, no safety-related mechanical components were functionally affected.

The following sa ety-related electrical equipment, while still functional has a decreased service life due to the overtemperature conditions; other equipment with over 40 years. remaining life under routine maintenance and surveillance practicos is not listed.

Table III-1 Exist. Remaining Service Qualified Item Model Temp. Life . nacision

. Valve Motor SMul 166"P 30.7 Yrs. Retain Operators SMB000 163*F 36.3 Yrs.

SRV Solenoid IMF-2 173 F 1.5 Yrs. Retain SRV Position LISA 173*F Alternate capability provided, Switch still being qualified, retain.

, MSIV Solenoids ASCo-8300 185*F Not overtemperatured by con-

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. ditions, retain MSIV Limit EA-740 185*F 3.5 Yrs. Retain

• • Switches RPV Head Vent SMB000 280 F Mis-classified, Refurbished Motor Operators valves are safety-related but these opera-

- tors are non i safety-related

Exist. Remaining Service Qualified Item Model Temp. Life Decision Misc Valve NAMCO 1460F only one limit Limit Switches EA-180 Retain -

uwitch (ln33P019) 10 safety related.

It has 2.0 years remaining life; others are for operator display except for one non safety related function.

Primary Coolant ASCo 146*F Sample HVA S.4 Yru. Re tain Solenoid Valve 205-852 Testable' Check ASCo HVA- 225*F Valves normally Bypass Solenoid 206-852 Retain closed, fail closed.

. Valves

"',' Used only during cold shutdown and luak testing of isolation valve Drywell Air Weed 148E.

Temp. Monitor- E4B to 7.2 to 21.7 Yrs. Retain These are part of ing Thermocouple 173*F drywell temp.

monitoring program Drywell RD-23 159"F i

Radiation Alternate monitor, Retain to still undergoing Detector 181*F qualification Some snubbers in the upper elevations have recently been found locked up and subsequently replaced. Based on the latest available temperature projection and this failure i experience, upper level snubbers were evaluated for re-placement. l' The snubbers have a maximum operating temperature limit of 300 F. Those snubbers exposed to greater than 300*F  !

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' ambient air temperatures, based on extrapolated tempera- '

ture data, have been replace ~d and are epected to last through this fuel cycle.

In addition snubbers that are in the )

vicinity of elevation 830 feet, where no temperature data was available, were also replaced because locked up snubbers were discovered in the vicinity. See Table  !

1 IV-3 for list of replaced snubbers.

IV.

CORRECTIVE ACTIONS AND EXPECTED RESULTS s

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1. Structural Correction Actions No correction action is required for the primary contain-ment because the structural capability was not affected I

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tar this high drywell temperature event.

2. Decreased Drywell Temperatureu .

a. . Improved Air Flow Distribution

.. .To improve the air ciruelation into the upper dry-

• well levels, four'16 inch flexible steel supply air ducts were installed within the drywell. Normal air flow from colder, lower drywell regions is

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blown via these ducts into the upper drywell to re-duce.the local temperatures there. In addition, existing air discharge flow was readjusted to de-

,. crease discharge flow resistance due to interfer-ences or to improve the radial flow distribution in the upper drywell. On December 9, 1983, a post-fuel-load modification was issued for the installa-tion of these scismically supported ficxible ducts.

See Figure 2 for layout of ducts,

b. Penetrations thr$$gh the Biological Shield Penetrations through the biological shield were surveyed and corrected to ensure that intended '

seals are now in place. The neutron curtains and insulation. covers for thene penetrations inhibit air flow inside the bioshield to external zones and thus decrease radial convective heat transfer,

c. Caps in Installed Insulation Thegapsinpipinginsulationandi$sulationtransi-

. . tions from piping lines to equipment bodies had been documented in the initial drywell thermal survey on Novenber 28, 1983 and in re-survey for corrective fixes on December 2, 1983. The corrective fixes in-  !

cluded the following: adding metallic heat shields to upstream piping for three testable check valves to reduce local hot spots; adding metallic insula-tion to fill gaps on pipeline insulation near hangers, ,

snubbers, clamps, valves, whip restraints and tee-joints; adding flashing,,at edges of installed insula-tion at transition joints, equipment interfaces, and tap connections, and replacement of crushed or damaged insulation pieces to close seams in existing metaille ins ula tion . This work on the testable check valves was covered by a modification released on December 15, 1983 The field corrections on gaps were accomplished under a plant work request utilizing drawings marked up i during the cited surveys.

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d. Peripheral Gap on the RPV The peripheral gap on the RPV hood insulation was -

corrected by adding flashing to inhibit out flow of heat at tho tcp of the cylindt ural part o f the

.. , vessel. This fix should decrease the drywell sensible heat load significantly as it precludeu the chimney effect of vessel heating of air which enters at the bottom of the vessel and rises inside the RPV insulation.

k Reduction of Sensible Heat Loads The preceding corrective measures on the insulation for piping, equipment, and the reactor pressure vessel are expected to reduce the senisble heat load to approach the anticipated sensible heat load value previously mentioned.

a .

The net estimated change in average drywell temperature is +5 "F based upon decreased heat load through im-proved insulation and the increased mixing of the upper drywall air with the bulk drywell air. The anticipated temperature in the upper drywell zone, on a volumetric average basis will decrease to about 185*F. Because of variations in radial distribution and becauuu of the uncertainty of the accumulative effect from the aug-mented vertical ducting, the actual temperature values must be determined Th area.ere is no safety relatedbyequipment temperature monitoring. located in this

3. Electric Cable Replacement '

Damaged safety-related cables were removed above drywell elevation 796 feet and new cables were installed. The termination points were junction boxes, penetrations and equipment lugs, i.e., cable segments were replaced to splice points located in junction boxes or at penetra-tions. The original design criteria was preserved in that no splices were made inside conduits or in cable trays. Cable splices were 'made near primarf containment penetrations; these will be removed during the first refueling outage.

The damaged non-satety-related cables above elevation I

796 feet were also replaced with new cables. Exceptions

.. to this replacement criteria were the cables for the plant welding grid, special. head vent thermocouple leads inside conduits, test cabling for integrated leak rate test, and special cables for loose parts monitoring systems.

The visual inspection results were used to determine the -

elevation at which cable replacement would be mandatory.

This was validated via the calculation of qualified life

'- for tha cable. The replacement elevation of 796 feet is shown' to be conservative (minimum of about 11 year) by the following data.

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, Table No. IV-1

, Qualified Calculated Life at Existing Existing Maximum Service Option Elev. . Temp. Temp. Temp. for 18 Mo. Life Existing Cable 804'-6" 266*F* None Replace New Cable,, ,

804'-G" 266*F 151 Days 239*F Existing' Cable 796'-0" '202*F 11 Years 239'F New Cable 7968-0" 202*F 11.4 Years 220'.

• llighest observed temperature at any azimuth during entire period of drywell overtemperatures For those cables retained et lower elevations, the remain-ing cable life was calculated for the 'postulatedIover-temperature conditions asaumed continuous while at rated power and with the'LOCA exposure at the end of life.

Conservative calculation indicates-the past overtemperature exposure used approximately an equivalent 0.4 years of life. The table below shows the remaining life for some typical cables for the existing drywell temperature.

Table No. IV-2 Retained Cable: Okonite, Rockbestos, Samuel Moore Maximum Temp. Maxir.um Temp.

Calculated Qualified Allow, for Allow. for Existing Life After Continuous - Continuous Service November 1, Service of Service of

. Elev.. Temp. 1983 18 Months 2 Years

'790' 186*F 23.6 Yrs. 239'F 233*F 760'- 157*F >40 Yrs. 239"F 233*F Raychem (Coax) Instrument Cable 790' 186"F 13.0 Yrs. 240*F 232*F

j. 770' 160*F >40 Yrs. 241*F 233'F With temperature reductions resulting from the previously enumerated short term fixes, these lifetimes can be in-creased markedly. This table shows the most pessimistic future condition for retained cables.

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The conclusion for the cabling is: first, safety-related cables which were damaged have been replaced as required.

• NJn safety-related Cabling on* essential or display

• equip-ment was also replaced. The replacement cable has

, , sufficient life at thle expected drywell temperatures m

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following the enumerated fixos to last beyond the remaindor of the current fuel cycle. A tempera- ,

ture monitoring program has boon defined to evalu-

' ate the results from the short term fixes. A scheduled shutdown after approximately three months will enable a visual appraisal of conditions and possible further air flow adjustments or thermal insulation adjustments for local hot spots.

Secendly cablen 'ecre retained inside the drywelloa the basis that sufficient life remains to not only complete this fuel cycle but to not markedly affect the long range capability of the initially installed cable.

These retained cables will be reinspected and re-placed as necessary prior to startup following the first refueling outage.

4. Equipment Replacement The following mechanical snubbers woro replaced as a result of the drywell overtemperature conditions:

Tablo IV-3 Snubber No. Elev. (ft.)

MS05-1002S 810 NB13-100lS 832 NB13-1002S 832 NB13-1904S 829 NB13-1006S 828 NB13-1025S 813 NB13-1027S 811 NB13-1028S -

814 NB13-1031S 311 NB15-1002S 830 NBlS-1005S 828

, NB15-1008S 827

-NB23-1003S 808 NB-125-Il07S 816

k Snubber No. Elev. (ft.)

RI24-ll20S 321 48 e RI24-ll21s 821 RI24-ll22S 821 RI24-ll24S 826 RI24-1511S 810 No mechanical equipment has had to be replaced ex-cept - for snubbers 5 Temperature Monitoring The need for te[perature monitoring has been stated previously with respect to the short term correc-tive actions. Augmented temperature monitoring will be performed for the following purposes-e to evaluate the effectivenese of the short range-fixes e to monitor actual temperatures to assure safety-related equipment does not degrade beyond pre-defined thresholds-

• , e to evaluate actual degradotion rates for dry-well cabling and equipmen t e to provide volumetric thermal data inputs for the long range fix.

The thermal monitor network is an array of approxi-mately 50 thermocouples located at various eleva-tions and azimuths in the drywell.- These are

-grouped at various-elevations to measure the verti-i-

cal temperature gradien't in the drywell to establish !

temperatures where safety related equipment is

• . installed. Additionally, some thermocouples are in contact with the equipment itself to provide local temperatures.

This is the case for one SRV solenoid.

and one MSIV limit switch. See Tables IV-4 and 5.

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Y TABLE IV-4 i

i EXISTING TEMPERATURE MONITORING SENSORS AND LOCATIONS

.-Total cerder of existing sensors = 26 .

Sensor No. Elevation

, Azimuth Location ITE-VPO41"

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817'-4" 45* Supply duct to licad Area.

ITE-VPO42 817'-4" 120* Supply duct to Head Area.

,. '1TE-VP084 817'-4" 240* Supply duct to !! cud Area.

ITE-VP081 804'-6" 65*

1 Annulus outlet.

ITE-VP082 804'-6" 185* Annulus outlet.

1TF-VP080 804'-6"- 305* Annulus outlet.

1TE-VPO45 801'-6" 15* * , Upper Drywell 10' from wall.

1TE-VPO46 801'-6" 135' Upper Drywell 10' from wall.

1TE-VP083 801'-6" 255' Upper Drywell 10' from wall. .

1TE-CM058 776'-9" 50* 13' from wall.

1TE-CM059 776'-9" 152' .

13' f; m wall. i ITE-CM060 776'-9" 320* 13' from wall.

1TE-CM061 772 -5" 246* 13' from wall.

1TE-VP077' 745'-6" 10*

MSIV 1B 8' from wall.

ITE-VP076 745'-6" 350*

MSIV 1A 8' from wall.

ITE-VP043 745'-6" 30' Lower Drywell 5' from wall.

ITE-VPO44

+ '

745'-6" 135* LowerDrywell5'ftImwall.

)

1TE-VP078 745'-6" 255' Lower Drywell 5' from wall.

1TE-VP075 776'-6" 135*

Recirc. Area IB 4' from wall, l'[E-VP074 745'-6" 317" Recire. Area lA 4' from wall.

1TE-VP040 750'-0" 55*

Lower Annul w .' Upper CRD Area.

1TE-VP039 750'-0" 319* Lower 4 v s. / Upper CRD Area.

, 1TE-VP079 750'-0" 185* Low %-

aue._ : , Upper CRD Area.

1TE-VP037 742'-0" 305* CRD Area.

1TE-VP033 742'-0" 65*

, CRD Area. s ITE-VP072 742'-0" 185* CRD Area.

a __ _ - _ _ _ _ _ _ _ _ - . _ - - - - - - - - - - -

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TABLE IV-5 -

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Now Tcmparatura'Eonitoring Sansors andLLocntion_s

Total number of new se'nsors =.35 Sensor No. Elevation Azimuth Location 2

1TE-VP200 822'-0" 0* Head Area *

, 1TE-VP201 807'-0" 350* ,

Mount on IE51-F355 limit switch housing (actal temperature)

1TE-VP202 810'-0" 30* Upper drywell above 1B21-F001, 1B21-F002, 1B21-F005, lE51-F066 and 1E51-F35S ITE-VP203 804'-6" 135' Upper drywell 5 ft. from wall 1TE-VP204 795'-0" 30* . Upper drywell above and between 1B21-F013 Bland 1B21-F013J j 1TE-VP205 795'-0" 315* Upper drywell above 1B21-F013C 1TE-VP206 784'-6" 30* SRV area above 1B21-F013J, mount sensor approx. 2 ft. from 1TE-VP207 ITE-VP207 784'-6" 30* Mount on SRV 1B21'F013J solenoid housing (metal temperature) 1TE-VP20 8 790'-0" 135* Mount above lE21-F000, lE21-F051, lE51-F063 and lE51-F076 1TE-VP209 790'-0" 255* Mount above lE22-F005, lE22-F354 and lE22-F038 1TE-VP210 785'-0" 315' . Mount above SRV 1B21-F013C and lE21-F013G i 1TE-VP211 742'-0" 350* Mount on FSIV lE21-F022D, limit' switch housing (metal temperature) .

1TC-VP212 782'-0" 25' 1TE-VP213 793'-8" O' Inside shield wall, hang through shield door fo,r middle annulus Inside the 30" x 32" duct 1TE-VP214 793'-S" 180* Inside the.30" x 32" duct 1TE-VP215 760'-0" 80* SRV "M" (air temperaturebexisting ITE-VP216 780'-0" 300* SRV "E" (air temperaturebexisting h

} ITE-VP217 815'-0" 30*

1TE-VP21C 810'-0" 13T.*

2 ft. from containment wall 2 ft. from containment wall y

} 1TE-VP219 810'-0" 255 2 ft, from containment wall 1TE-VP22C 804'-6" 255* 2 ft. from containment wall 1TE-VP221 C15'-0" 315* 2 ft. from containment wall -

l 1TE-VP222 810'-0" 315* 2 ft. from containment wall 1TE-VP223 815'-0" 185* 2 ft. from containment wall 1TE-VP224 810'-0" 185* 2 ft. from containment wall i

1TE-VP225 807'-0" 350* Mount near limit switch for lE51-F355 (air temperature), mount l approximately 2 ft. from 1TE-VP201

! 1TE-VP226 015'-0" 135* 2 ft, from containment wall 1TE-VP227 815'-0" 255' 2 ft. from containment wall 1TE-VP229 804'-G" 30' Annulus outlet ITE-VP229 804'-6" 315* Annulus outlet

! ITE-VP230 801'-6" 30* Upper drywell, 5 ft. from wall ^

1TE-VP231 776'-9" 30* Mount 13 ft. from wall 1TE-VP232 742'-0" 350* Mount near MSIV IB21-F022D limit switch (air temperature) mount

. approximately 2 ft. from ITE-VP211 i

1TE-VP233 74 5'- 6" 30' Lower drywell 5 ft. from* wall j 1TE-VP234 7.76'-6" 135* ,

Mount 13 ft. from wall

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.V. UNIT'l RESTART OPERATING PLAN l.. Justification for Unit 1 Restart With the short term modifications to the drywell air handling equipment to cool the upper drywell region and with the closure of-insulation gaps and the addi-tion of flashing to decrease the sensible heataload into the drywell atmosphere, the Unit i drywell cool-ing capability is' configured to preclude a recurrence

.of the overtemperature in the drywell.

'With the replacement of damaged cables and snubbers in the upper drywell and with justification for retention of slightly degraded, though fully operational cables and equipment in the lower drywell regions, LaSalle Unit 1 in configured for restarting. The restart plan presented at the November management meeting included the following provisions: .

a. -All safety-related cable and components will have a remaining qualified life of 18 months at appro-priate-temperatures. This has been met for even the worst case where r.o improvement results from the short term HVAC fixes descri6ed herein. With '

improved drywell temperatures.this remaining qualified life will extend considerably for the replaced as well as the retained cables and equip-ment.- ,

, b. A surveillance program will be established to en- '

, . sure that all cabling and components do not exceed their qualified life prior to the end of the first refueling outage. This has been accomplished two ways

first, by decreasing the heat load in the locations of previous overtemperature, including the physical rerouting of those cables previously experiencing local hot spots; and secondly, by cable and equipment replacement to assure that qualified life remains sufficient to complete this fuel cycle. The temperature monitor-ing program is a part of this effort to verify by actual operating observations that this goal is met.

c. Should the temperature in an area where safety

, related equipment is located exceed the limiting temperature on which the 18-month life is based for that equipment, for more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, an analysis for continudd operation will be completed '

within 'seven days or the unit will be temporarily shut down for a visual inspection and correction of the anomalaus condition (s). This provision is met through equ operation procedurus that implement

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the temperature monitoring program. (See Annex)

d. A' general visual inspection of the safety-related components and cabling will be conducted at approximately.three months and nine months after '

~. the Unit 1 restart to ensure that thermal 'agra-dation of qualified equipment is still wi sin the

" remaining qualified life" of the equipr at. It is anticipated that air flow and local insulation may need further refinement af ter the Unit i ra-start. The complexity of the air flow distribu-tion within the drywell lends itself to iterative refinements based on the results of the tempera-ture monitoring ef forts. Adjustment within three months is considered to be conservative in con-sonance with provision C above which covers any immediate need to protect safety-related equipment.

2. Temperature Monitoring Plan The temperature monitoring plan is based upon observ-ing the vertical temperature profiles in four quadrants of the drywell, then defining characteristic tempera-tures for those drywell elevations where safety-related equipment is located. This operating. plan then cross-correlates these characteristic tempe~ratures to the safety-grade readout, in the control room, of the con-tainment temperature monitors (CM-058, 059, 060 and 061) .

This correlation enables the operator to reference the drywell characteristic temperatures via safety-grade monitors that have annunciator capability in the con-trol room. -

Determination of the drywell temperature profiles and these characteristic temperatures will occur during heat up and attainment of thermal equilibrium for the fully rated power condition via normal operating pro-cedures on Unit 1. Once the correlation of characte-ristic temperatures to the CMO monitors is made, the basis is established for operational decisions regarding I

drywell temperature according to the existing technical

! specification with the CMO monitors.

• • As experience accrues after the short term fix, and based on the accumulated thermal monitoring history, it will be possible to compute new service life for critical safety-related equipment on the basis of l actual temperature histograns. An in-cycle shutdown is planned for approximately 90 days after startup, at which time an evaluation can be made based on visual .

inspection and accumulated temperature data to project the need for temperature controls during the remainder of the fuel cycle. See Annex A for Technical Specifi-

! cations applicable to the Temperature Monitoring Plan to ensure equipment qualification.

l .

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, VI.

SUMMARY

CONCLUSION FOR UNIT.NO. 1 RETURN TO SERVICE

1. Specific Reason for High Temperature Conditions '

The primary causes of the high temperature condition

" were tne poor air distribution at-the upper level causing air s tratification, localized hot spots caus-ing high local temperatures above ambient, and yarious gaps in-the mirror installation around valves, pipe whip rentraints, etc. which contributed to the

.. excessive sensible heat.

2. Completion of Short Term Fixes for Temperature Improvement The various thermal insulation defects discovered via two surveys of the drywell have been repaired. Addi-tional flexible ductwork to bring. cooler air to the upper levels has-been installe, 'n addition, changes to HVAC supply air discharges have uten made to further enhance the air distribution. The combination of

.these short term fixes is~cxpected to produce consider-able temperature improvements in the drywell. The goal is to bring the maximum mean temperature at the uppermost zone in the drywell to below 185*F.

3. Cable Replacement and Evaluation of Adequacy Safety-related cables which were visibly damaged have been replaced above dryuell elevation 796 feet. At -

lower drywell elevations, the safety-related cable

' has been evaluated and determined to have adequate remaining life to complete the first fuel cycle. Also, a few specific cables below elevation 796 feet had to be-replaced due to local hot spots. The replacement cables have been rerouted. to prevent recurrence of local hot spots. An evaluation of adequacy has been completed to justify retention of cable below 796 feet elevation. The remaining service life (with LOCA included) is sufficient to extend well beyond the first fuel cycle even in the worst case where drywell high temperatures persist in spite of this short term fix.

., 4. Equipment Evaluation Safety-related electrical equipment has been evaluated and - determined to have sufficient qualified life to permit cycle.

unit operation to at least complete this fuel The only mechanical equipment requiring re-placement was snubbers in ,the upper drywell area which s had been found locked up due to exposure to the high temperatures. No piping was found unacceptable as a result of the locked up snubbers.

L .

S. Expected-Schedule for Return to Service Based on the repair of insulation defects, additional fixes for 14nproved air distribution for temperature improvement, replacement of affected safety-related cables and affected mechanical snubbers, Unit 1 is ready for restart. The unit is configured for opera-tion through the scheduled first fuel cycle. An interim outage in 1984 will be used to appraise the effectiveness of the short term-fixes and the effects of further thermal degradation on safety-related cables and equipment. A temperature monitoring program will be used for apprai; sing remaining equipment life and the success of the sho'rt term fixes.

VII. LONG TERM PROGRAM The corrective actions described previously are primarily short term corrections to, enable Unit 1 to return to

. service. The long term objective is to comple tely elimi-nate the high ambient air temperature. The principal approach is to provide adequate air handling (and mixing) in the drywell and to assure that adequate cooling capabi-lity exints to ab: sorb the sensible heat load and any latent heat. Additional long term cooling capabilities under consideration include :

1) Additional coolers in the upper area of the drywell.

Additional cooling capacity there is limited by the available space and the available cooling capacity of the RBCCW system.

2)_ Increased fan capacity for general circulation in' the drywell to achieve greater cooling capability with existing installed equipment.

3) Adding booster fans in the ductwork to achieve an improved air circulation to certain critical areas.

4) Adding additional cooling coils to the existing main cooling units to increase the cooling capaicity.

Any one or a combination of the described corrections may

- eventually be used. The temperature measurement program will be used to obtain baseline data to assist in the

. definition of long term fixes.

There are two additional long term corrections under review.

The first covers eliminating snubbers above the 804 feet bulk head and replacing them with struts where possible. Pre-liminary indications are that adequate design margin exists to allow this. The second is e3imination of position switches on certain valves. These switches show valve

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only and are.not actually required for a safety In ' fact,- on Unit 2 the bypass valving, warm-up valves, and these switches-have already been climinated Las non-essential because they are used only during leak testing during shutdown.

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D Annex A Technical Specifications

1. Drywell Averago Temperatu.-e. (3/4.6.1.7)

The average Drywell Temperature will be verified to be less than or equal to 1350F as required by this specif3 cation.

The. identified locations for determining ccupliance withthis specifications and

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its basis have not changed. .

2. Area Temperature Monitoring (3/4.7.7.)

This report is submitted as requested in reference (c) and should be considered to fulfill the requirements for a Special Report to the 3cmmission as specified in T.S. 3.7.7.a. The report identifies the previous Temperatures in the Drywell and the methodoly used to demonstrate con-tinued operability. The Temperature locations identified in T.S. 4.6.1.7 will be used to verify compliance with Table 3.7.7.-1 limit of 1500F for item A.S.a Drywell. The temp-erature limits for safety related equipment are identified in this report and ensures that, as a minimum based on previous thermal exposure and an projected life usage, all equipment will remain qualified through the first cycle. These temperature limits

. will be considered as the temperature limit referenced in T.S. 3.7.7.b. This action is justified on the basis that this report demonstrates operability as required by T.S.

3.7.7.a. and that the basis for T.S. 3.7.7.

is area temperatures for Safety-Related Equip-ment and not the entire Drywell. The Tempera-ture Monitoring Program will verify that these temperature limits ar- not exceeded and corre-

' lated to Control Room CMO Monitors (4).

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v a e-1 The Temperature limits are:

F_wls.m.P.n.t. Ie.mfr.a_tr.e_.h!_ml_t_.

Valve Motor Operators . + 227 F SRV' Solenoids + 173 F MSIV Limit Switches + 275 0F Primary colant Sample + 170 F Valve Solenoid Drywell Air Temp. + 213 F Monitoring Thermoccuple Cable N. + 235 F

=

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