ML20127K381

Forwards IE Bulletin 75-04 & 75-04A Re Cable Fire at Browns Ferry

ML20127K381
Person / Time
Site:	Monticello, Prairie Island
Issue date:	04/03/1975
From:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:	Wachter L NORTHERN STATES POWER CO.
References
IEB-75-04, IEB-75-04A, IEB-75-4, IEB-75-4A, NUDOCS 9211200389
Download: ML20127K381 (5)

Text

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, UNITED STATES NUCLEAR REGULATORY COMMISSION REGION 111 799 ROOSEVELT ROAD GLEN ELLYN, ILLINOt$ 60137 APR 3 ypye

' )(o Northern States Power Company Docket No. 50-265 ATIN: Mr. Leo Wachter, Vies President Docket No. 50-282 Power Productios and System Docket No. 50-506 Operation 414 Micollet Mall Minneapolis, Minnamota 54401 Gentiament Enclosed are IE Bulletina No. 75-04 and No.75-04A which require action by you with regard to your power reactor facilities with an operating license.

Should you have questions regarding these Bulletins or the actions required of you, please contact this office.

Sincerely, James G. Esppler Easional Director Enclosures II Bu11stina No. 75-04 and No.75-04A Approved by GAO, 3-180225 (R0072), clearance expires 7/31/77. Approval was given under a h,h' ,j, blanket clearance specifically for identified generie problems, bec: Central Files IE Files PDR Local PDR

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< April 3, 1975 IE Bulletin No. 75-04 s

, CABLE FIRE AT BROWNS FERRY NUCLEAR POWER STATION .

DESCRIPTION OF CIRCUMSTANCES: .

Preliminary information from Tennessee Valley Authority regarding a fire which occurred on March 22, 1975, at their Browns Ferry site near Athens,

Alabama, indicates that the fire was started as a result of construction activities. The fire resulted in the shutdown of two operating nuclear plants and made several saf ety systems inoperative, including systems j normally used for decay heat removal during shutdown. The workmen were engaged in construction activities on a third unit not yet licensed f or operation by NRC.

Initial information indicates that during the installation and testing

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of cable through-wall penetrations an open flame ignited a flammable material used in the penetration seals.

ACTION TO BE TAKEN BY LICENSEES:

The following actions are requested of selected Licensees with operating power reactor f acilities and major construction activities at a common site:

1. Review your overall procedures and system for controlling construction activities that interface with reactor operating activities, with particular attention to the installation and d

testing of seals for electrical cables between compartments of the reactor building, e.g. , control room to cable spreading room.

2. Review the design of floor and wall penetration seals, with particular attention to the flammability of materials.

3. Evaluate your procedures for the control of ignition sources which may be used for leak testing or other purposes in areas containing flammable materials.

4. Report to this of fice, in writing within 20 days of the date of this Bulletin, the results' of your reviews or evaluations regarding items 1 through 3 above.

ACTIONS TO BE TAKEN BY LICENSEES MAY BE REVISED:

. The actions requested of Licensees above may be revised as additional details of the Broyns Ferry occurrence are available and evaluated by the NRC, /

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1 April 3, 1975 IE Bulletin No.75-04A CABLE FIRE AT BROWNS FERRY NUCLEAR PLANT l The following material supplements and modifies _IE Bulletin 75-04.

DESCRIPTION OF CIRCUMSTANCES I Additional, though still preliminary, information has become availabic

related to the fire which occurred at the Browns Ferry Site on March 22, 1975. The fire started in the cable spreading room at a cable penetration through the wall between the cable spreading room and the '

reactor building for Unit 1. A slight differential pressure is maintained (by design) across this wall, with the higher pressure being.

on the cable spreading room side. The penetration seal originally present had been breached to install additional cables required by a design modification. Site personnel were rescaling the penetration after cabic installation and were checking the airflow through a temporary seal with a candle flame prior to installing the permanent

sealing material. The temporary sealing material was highly combustible, and caught fire. Efforts were made by the workers to extinguish the fire at its origin, but they apparently did not recognize that the fire, under the influence of the draft through the penetration, was spreading on the reactor building side of the wall. The extent of the fire in the cable spreading room was limited to a few feet from the penetration; however, the presence of the fire on the other side of the wall from the point of ignition was not recognized until significant i damage to cables related to the control of Units 1 and 2 had occurred.

Although control circuits for many of'the systems which could be used for Unit 1 were ultimately disabled by the fire, the station operating personnel were able to institute alternative measures by_ which the primary system could be depressurized and adequate cooling water supplied to the reactor vessel. Unit I was shut down-

manually and cooled using remote manual relief valve operation =

and condensate booster pump, and control rod drive system pumps. Unit 2 was shut down and cooled for the first hour by the RCIC. After depressurization, Unit 2 was placed in the RRR

, shutdown cooling mode with makeup water availabic from the condensate booster pump and control rod drive system pump.

ADDITIONAL ACTIONS TO DE TAKEN BY LICENSEES

1. Because the occurrence appears to have resulted from modifications being made to an operating unit, all power reactors with operating licenses should address the. actions requested in Bulletin 75-04 as well as the nctions described below.

2. Review yourlpolicies and procedures relating to construction or maintenance and modification work to assure that activities which might affect the safety of a unit in operation, including the 6

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1E Bulletin No.75-04A April 3, 1975 4

ability to shut down and cool the unit are properly ,

controlled. Your review should consider particularly your policy on deferring construction, maintenance or modification work on a unit until a shutdown period except for emergency maintenance vital to continued safe operation or safe shutdown of the unit.

3. Review your policies and procedures to assure that for construction or modification and maintenance activities during plant operation, particular attention is given to the following areas

a. The degree of safety sign'ificance of affected and nearby cabling and piping,

b. The use cnd control of combustible materials.

c. The use and control of equipment that may be an j ignition source.

d. The assignment of personnel, knowledgeable of plant arrangement and plant operations, whose sole temporary responsibility is monitoring the safe performance of construction or maintenance and modification work, including attention to otherwise unattended areas adjacent to the work areas.

e. Provision of installed or portable equipment to provide the monitoring personnel with prompt communication with the operating staff in the control room.

f. Provision of adequate fire prevention'and fire suppreenion equipment, installed or portable, for the following locations

l (1) Areas where work is being performed.

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(2) Areas where occurrence of a fire has high safety significance, even though the probability of occurrence 2

is relatively small.

g, Recognition that a fire, even one involving electrical equipment, umy, if of suf ficient intensity require water as the ultimate suppression medium.

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4. Review your emergency procedures to assure that consideration for alternate methods for accompliching an orderly plant _ shutdown and cooldown are provided in case of loss of normal and preferred alternativg shutdown and cooldown systems for any reason (e.g. , a fire) . In this connection, assure that the minimum i

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s i 1E Bulletin No.75-04A April 3, 1975 information necessary to assist the operators in such shutdown actions, the minimum protection system actions required (e.g. ,

scram) and the spectrum of alternative paths availabic to the i operators to supply cooling water and remove decay heat dependent l on plant conditions are included in your emergency procedures.

I 5. Report to this office, in writinC, within 20 days of the date of this Bulletin, your schedule for review in each of the above areas.

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6. Upon completion of your reviews, provide this office with the .

' results of these reviews and the schedule for accomplishment of any revisions to your policies and-procedures, and any proposed changes to the facility, and the date by which the changes are scheduled to he completed. If this latter date is more than 30 days after the date of the initial report, provide a monthly summary report detail-

! ing your progress in the review and/or proposed procedure or facility modificationc. Reports requested by Bulletin No. 75-04 may be

incorporated with the initial response to this Bulletin.

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NSED NORTHERN STATES POWER COMPANY M 8 N N E A PO L18. MIN N E BOTA 58401 f

April 23,1975 .) /

Mr. J. G. Keppler Director - Region III Office of Inspection and Enforcement United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr. Keppler:

MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 The reviews and evaluation requested in items 1 through 3 of IE Bulletin 75-04 have been conoleted for the Monticello Nuclear Generating Plant.

In accordance with item 4 of the Bulletin, the results of these reviews and evaluation are hereby submitted.

Existing Administrative Directives governing installation and test procedures require identification of unusual mechanical, electrical, chemical, thermal, or other hazards associated with equipment and its environs. Instructions and precautions necessary to control these hazards are required to be included in the procedures. Existing Directives and instructions governing work authorizations require a second level of review by technical and operating personnel prior to commencing work related to equipment, instruments, and systems which are designated on a " critical" list. Cable spreading room penetrations have been added to this list.

Design of the floor and wall penetrations in the cable spreading room requires the penetrations be covered with a non-flammable material. Investigation revealed that penetrations which were scaled or rescaled subsequent to completion of original construction were sealed with a flame retardent material. A non-flammable covering has been applied to these penetrations.

A task force has been designated to review the areas identified in IE Bulletin 75-04A. Their review is expected to be completed by June 30, 1975.

Yours very truly, L.

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. Wachter Vice President - Power Production cc: UKE. A. Giambusso Mr. G. Charnof f Minnesota Pollution Control Agency Attention: Mr. E. A. Pryzina kh27

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Mr J G Keppler, Director REllll'a ' 3 Region III Office of Inspection and Enforcement , , ,

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Glen Ellyn, IL 60137 #'*...** M s

Dear Mr Keppler:

, py _GfY MONTICELLO NUCLEAR GENERATING PLANT e

Docket No. 50-263 License No. DPR-22 In accordance with Items 2 and 3 of IE Bulletin 75-03, the following informa-4 tion is submitted:

1. Eight solenoid valves of the type described are in use on safety related systems at the Monticello Nuclear Generating Plant.

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2. Correspondence with tbc Automatic Switch Company indicates that the

' proper disc springs are installed on the subject valves. The Auto-matic Switch Company also informed us that the 1cver to lower disc stem clearance problem is related only to those solenoid valves with resilient seats. The eight valves in question have metal-to-metal seating; therefore, no further actions are deemed necessary. It is noted that no ASCO solenoid valve failures have been experienced at the Monticello Nuc1 car Generating Plant.

Yours very truly, Y 40 L J wachter, Vice President Power Production 6 System Operation LJW/ma cc: [Giambusso G Charnoff Minnesota Pollution Control Agency p Attention: E A Pryzina y J-4406 4pd&3@ ' b'

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NORTHERN STATES POWER COMPANY M I N N E A POI.l e . M I N N E s OTA 5 5 401 May 15, 1975 ti Mr J G Keppler, Regional Director Office of Inspection & Enforcement J Region III United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Dear Mr Koppler:

MONTICELLO NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 The following information is hereby reported in response to IE Bulletin No. 75-05:

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. Bechtel Power Corporation is the original purchaser of all hydraulic shock suppressors installed at Monticello. Bechtel has supplied Northern States Power Company with the following information in regard to items 1.a. and 1.b. of the subject IE Bulletin.

a) Only one supplier of pipe.line suppressors was used for Monticello, namely Bergen-Patterson who supplied their

" Hydraulic Shock and Sway Arrestor (HSSA)" standard i units for this service.

l l The hydraulic suppressors are selected to allow necessary I thermal motions and to restrain velocities in excess of thermal motions. The hydraulic suppressors are set to allow unrestrained thermal growth rates of 10 inches per minute on all lines. Further, if these velocitics are encountered and the hydraulic suppressors actuate (lock), provision is built into the unit to allow continued thermal expansion at a rate of 4 to 6 inches /

minute at rated load to avoid excessive thermal stresses.

'Ihe anticipated scismic/ dynamic velocities will always be sufficiently higher. than the 10 inch per minute hydraulic suppressor setpoint to ensure that snubber actuation (locking) due to the anticipated seismic /

dynamic . event will occur.

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The minimum standard size hydraulic suppressor.is generally i selected for each application. The rated load for each standard size unit is approximately three quarters the i maximum. load allowed by a relief dev1ce before it operates to bypass fluid and prevent damage to the snubber. Accord-4 ingly, the safety margin for each unit is 1.3 and in many j cases .where the minimum standard- size is greater than the required load, the safety margin is larger, b) Testing of the hydraulic suppressors includes the following:

l l (1) Current Testing Procedure (applicable to all units tested after October, 1972 - Serial Numbers F84806

through F98991 G12039 and up) . The assembly and

' testing procedure for each individual unit is covered j by Rexnord Spec. Nos. 3831 and 3832. Briefly described, using this procedure, the operational-characteristics are established by physical test of each fully assembled unit. As part of the final- assembly of major components 4 operation, the cylinder is set horizontally in a calibrated test stand. The cap end of the cylinder is bracketed to the test stand base and the piston rod is coupled in

line to the piston rod of a power driven 8-inch bore

, hydraulic cylinder which is used to stroke the test.

unit. The velocity of the 8-inch bore unit can be varied by manually controlling the volume of fluid d

pumped for each. direction of stroke. A fluid pressure gauge for each direction of stroke.is-calibrated to read, ,

, directly in pounds force and piston rod-velocity is taken as a direct _ reading from a velocity instrument -

i package incorporated in the test stand.

The first check made is for piston rod alignment and

). binding. Prior to. the cylinder being charged with

fluid, the unit -is stroked using an automatic " bind

test" controlled drive setting on the test stand l for the particular size unit being tested. Excessive resistance to movement would be indicated by the open-l ing of a relie'f valve'and the shutting down of the pump motor.

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l. The cylinder is then charged during an extensive stroke i of the piston and the valve manifold attached and filled 2

by a pouring operation. A temporary test fitting is

, attached to the valve and 4500 psi' fluid pressure is applied for a 20-second period during which fluid containment is visually checked.

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The accurulator is then mounted and fluid filling is performed under pressure through the normal field filling a!' mite fitting. The unit is now in its fully assemoled and filled condition.

Af ter random stroking of the unit, the poppet valve closure test is conducted for each direction of stroke by slowly increasing the piston velocity and noting the velocity at the time of an instantaneous increase in fluid pressure denoting valve closures.

The bypass rate of flow in cach direction is then checked by first applying a high velocity rate to close the valve and then establishing the rated force capacity of the unit. As the unit is ottoked tt_ under the rated force condition, the velocity is checked and noted.

Tne unit is then cleaned off and allowed to stand a period of time on cican paper and then checked

. .. evidence of Icakage.

t (2) Tormer Testing Procedure (applicabic to all units tested prior to October, 1972 - Serial Numbers - All six-digit numbers without prefix letter and F60635 through F81302).

The operational characteristics of the assembled unit is established by determining the control valve fluid flow characte 4stics at the various phases of operation. This is done by setting up each individual control valve in a fluid test stand and physically capturing and measuring the fluid flow volume over a specific time period and comparing the results to establish minimum-maximum flow rates at the test pressure that are equivalcut to flow rates at actual design rated pressure. These values were originally determined by calculations and then by physical experiment using valves from units whose fully assembled characteristics had been established as being within the piston velocity tolerance ranges for the various phases of operation, such as valve closure and bypass rates. The cylinder is filled with fluid prior a to mounting of valve using a piston stroking operation and the valve is then mounted and filled using a pouring operation. The fluid containment integrity of the cylinders wich valve body attached is established by applying 3500 psi fluid pressure through the valve port to which the accunulator is normally attached and visually checking for Icaks over a specific time period.

The accumulator is then attached and charged with fluid, the unit is cicaned and allowed to stand for a period of time and then checked visually for Icakage.

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, NORTH' 1N OTATEO POWER COM' NY

's Mr J G Keppler '

May 15, 1975 In addition to the above described testing procedures performed on cach individual unit, dynamic testing

• has been performed on some selected units to demon-strate operational characteristics during shock load-ing and vibration conditions.

In regard to atem 1.c. of the subject IE Bulletin, Northern States Power Company has previously described the hydraulic shock suppressor surveil-lance program at Monticello in a letter from Mr L 0 Mayer to Mr J F O' Leary dated October 1, 1974. In addition, it is noted that the maintenance procedure used for snubber overhaul calls for stroking the reassembled snubber and verifying that the snubber will lock 6p.

Yours very t ruly, f &Y L J Wachter, Vice President Power Production 6 System Operation IJW/ma cc: A Giambusso G Charnoff Minnesota Pollution Control Agency Attn: E A Pryzina Asst Director for Construction & Operations

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