ML17286A732

LER 90-022-01:on 900930,pressure Decrease Occurred in Containment Instrument Air Sys When Nitrogen Cryogenic Tank Was Inadvertently Depleted.Containment Nitrogen Inerting Procedures PPM 2.3.1 & 2.3.7 revised.W/910422 Ltr

ML17286A732
Person / Time
Site:	Columbia
Issue date:	04/22/1991
From:	John Baker, Fies C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-022, LER-90-22, NUDOCS 9105010160
Download: ML17286A732 (17)

Text

ACCELERATED ISTRIBUTION DEMONS'PRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9105010160 DOC.DATE: 91/04/22 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION FIES,C.L. Washington Public Power Supply System BAKER,J.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-022-01:on 900930,ESF actuation occurred re pressure being decreased in containment Instrument Air sys.Caused by less than adequate procedure. Obtain more liquid nitrogen &

containment nitrogen procedures revised. W/910422 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR I ENCL ( SIZE:

TITLE: 50.7'3/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 ENG,P.L. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 '

NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFBll 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DST/SELB SD 1 1 NRR/DREP/PRPBll NRR/DST/SICB 7E NRR/DST/SRXB SE 2

1 1

2 1

1 N~ILE SPLBSD1 02 1

1 1

.1 RES/DSIR/EIB 1 1 R 01 1 1 EXTERNAL: EG&G BRYCE, J. H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 (ogfkoo1~ P NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US'TO REDUCE O'ASTE! CONTACT THE DOCUMENT CONTROL DESK, ROO~I Pl 37 (EXT. 20079) TO ELli~'IINATEYOUR NMK FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

3VASHINGTON PUBLIC POWER SUPPLY SYSTEM P.o. Box 96S ~ 3000 George 11'ashingfon Way ~ Richland, tl'ashington 99352 Docket No. 50-397 April 22, 1991 Document Control Desk ',

S. Nuc 1 ear Regulatory Commi s sion Nashington, D.C. 20555

Subject:

NUCLEAR PLANT- NO. 2 LICENSEE EVENT REPORT NO. 90-022-1

Dear Sir:

Transmitted herewith is'icensee Event Report No.90-022 Revision 1 for the NNP-2 Plant. This report provides more complete information on this event as discussed during meetings associated with Inspection 90-28 and the SALP review.

Very truly your ,

gaul J. M. Baker (N/D 927M) blNP-2 Plant Nanager Jt"8: 1 r

Enclosure:

Licensee'vent Report No. 90-0?2-1 cc: Hr. John B. Hartin, NRC Region V Nr. C. Sorensen, NRC Resident Inspector (H/D 901A)

INPO Records Center Atlanta, GA Hs. Dottie Sherman, ANI Nr. D. L. Williams, BPA (H/0 399)

NRC Resident Inspector walk over copy pof(

g $ k.

~

..i a.' ~

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NRC FORM356 V.S, NUCLEAR REGULATORY COMMISSION (64) 91 AI'PROVED OMB NO. 3(504104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION AEQVESTI 500 HRS. FORWARD LICENSEE. EVENT REPORT tLER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (Ps530), V.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (II POCKET NUMBER l2) PA Washman ton Nuclear Plant

'"L'('I Engineered Safety eature ctuatson Un>t 2 o 5 o o o39 7>oFll o ontas nment nstrument s r Caused by Depleting the Nitrogen Cryogenic Tank EVENT DATE (5) LEA NUMBER (SI AEPOAT DATE (7) OTHER FACILI'TIES INVOLVED (4(

MONTH DAY YEAR YEAR N: SEOVENTSAL rrr+R NUMBER REVISION cpn NVMSER MONTH OAY YEAR FACILITYNAMES DOCKET NUMBERISI 0 5 0 0 0 022 229 i

0 930 9 0 9 0 01 0 4 1 0 5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PURSUANT T 0 THE REDUIREMENTS of 10 cFA gi /Cntcs ont oi mort o/ snt /orrowinp/ (ll MODE IS) 20.402(SI 20.405(cl 50.73(s l(2( lir) 73.7((S) 1 POWE R 20,405I ~ )(1)(ll 50.34(c)(ll 60,73(sl(2) (r) 73.71(cl LfvEL 7 0 20.405( ~ ) Ill(ill 50.35(c)(2) 50.73(el(2) (riil OTHER /Sotciiy in Apssrecs orrery tnd in Teel, HRC Poim 20.405( ~ l(1 ) lill) 60.73 I~ ) (2) (I) 60.73( ~ )(2l(rill)IAI 3664/

20.405 Isl(l l(lr) 50.73( ~ I(2)(ill 50.73 I ~ 1(2) lrill)IS) 20.405( ~ Illl(r) 5073(e I(2)(III) 50.73(e)(2Hsl LICENSEE CONTACT FOR THIS LEA (12I NAME TELEPHONE NUMBER AREA CODE C. L. Fies Com liance En ineer 50 937 7- 2501 COMPLETE ONE LINE FOll EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13l MANUFAC EPORTABLE COMPONENT MANVFAC EPORTABLE CAUSE SYSTEM COMPONENT TO NPRDS SYSTEM TVRER TURER TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED SV B MISSION DATE IISI YES /I/ yes, comprtst EXPECTED SUSM/SS/OH DATE/ NO ABsTRAGT /Limit so ft(s(s sptcts, i,t tpprosi'mtstiy Risttn sinpit spree syptirrintn iinNI (16)

At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on September 30, 1990, while plant operators were inerting the primary containment during a reactor startup, a pressure decrease, occurred in the Containment Instrument Air (CIA) System. The pressure loss occurred when the Nitrogen Cryogenic Tank (CN-TK-1) (the normal supply used for containment inerting and for CIA) was inadvertently depleted. This pressure decrease caused the safety related part of the CIA system to be isolated and automatically placed the backup bottled nitrogen source into service. This action is considered an Engineered Safety Feature Actuation.. Further evaluation showed that the pressure maintained by the bottled nitrogen source in Division II did not meet design requirements because of a misadjusted pressure regulator.

The root cause of the depleted nitrogen supply in CN-TK-1 was less than adequate procedures that did not contain precautions for containment inerting with low tank levels. A second root cause 'was less than adequate supervisory oversight and a contributing root cause was an equipment design deficiency associated with the alarm setpoi nt on CN-TK-1. The root cause of "the low nitrogen pressure in Division II was an equipment design deficiency associated with the Pressure Control Valve CIA-PCV-28. The root cause of the event where plant operators did not respond to the abnormal condition alarm was a knowledge based error.

NRC FORM 366A U.S. NUCLEAR AEGULATORYCOMMISSION (649) APPROVED OMB NO. 31504104 E X PI A ES: 6/30/92 ESTIMATED BUADEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUESTl 50$ HRS. FOAWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P630), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK AFDUCTION IIROJECT (31500106). OFFICE OF MANAGEMENTAND BUDGET WASHINGTON DC 20503' FACILITY NAME (I) DOCKET NUMBER (2I LER NUMBER LSI AGE ISI YSA II SEGVSNTlAL 6 'ar rrEY1$ 10rr NUMeell 'o5 rrvM err Washington Nuclear Plant Unit 2 o s o o o 397 9 0 0 2 2 0 1 02 oF TEXT IN more epece Ie reerrrled, rree eddlo'one( HRC %%de SSSA Sl (IT)

Abstract (continued)

Immediate corrective action was taken to obtain an additional supply of nitrogen.

Procedures and the level setpoint were also changed to make sure plant operators are aware of the CN-TK-1 level and the possibility of loss of pressure. The Pressure Control Valves (CIA-PCV-2A and CIA-PCV-28) have been evaluated and will be secured in their proper regulating position. Plant operating personnel were counseled on the need to strictly follow the guidance in Plant Procedures.

The event posed no threat to the health and safety of either the public or plant personnel.

Plant Conditions Power Level -70 5 Plant Hode 1 Event Descri tion At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on September 30, 1990 Plant Operators were in the process of inerting Primary Containment following reactor startup on September 28, During the inerting process, shortly after shift change, the inventory of Containment Nitrogen Tank One (CN-TK-1) was lowered to a level which led to an ESF actuation due to low system pressure in the Containment Instrument Air (CIA) System.

The Shift Support Supervisor noted that the CN-TK-1 was somewhat lower than'ormal at 150" (325" being full) following shift turnover at approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />. He had previously assigned two Equipment Operators to follow Primary Containment inerting. One was assigned to follow the job at the Nitrogen Cryogenic Tank (CN-TK-1) skid, using Plant Procedure PPH 2.3.7, "Nitrogen Inerting System". The other Operator used Plant Procedure PPH 2.3.1 "Primary Containment Venting, Purging, and Inerting", which had work to do in several locations. The CN-TK-1 Low Level alarm was set to actuate at a level of 220"., Thus the alarm is normally on during the inerting process.

At the start of swing shift the Shift Support Supervisor believed that there was enough inventory in the tank to complete any further inerting. The Drywell oxygen was approximately 7.5X of tota'I Drywell volume at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br />, with the system designed to control the oxygen at approximately 2 percent. The Technical Spec,ification limit is 3,5 X oxygen.

At 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br /> the Equipment Operator at the CN-TK-1 skid questioned the Shift Support Supervisor as to how much inerting there was left to do, because the Tank level was getting rather low, reading approximately 40" at that time. The PPH provided no guidance as to minimum values for the tank, He was to'ld by the Supervisor that inerting would be completed shortly, so the process could continue.

NRC Form 366A (649:

f NRC ORM 366A U.S. NUCLEAR RFGULATORY COMMISSION APPROVED OMB NO. 3(500(06 (BJ)9)

EXPIRES: 6/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (3ISOOIO(), OfFICE OF MANAGEMENTAND BUDGET, WASHINGTON,DC 20503.

FACILITYNAME (I) OOCKE'T NUMBER (2)

LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL II6 V IS IO N NUM 6 II NUM 6 II Washington Nuclear Plant Unit 2 0 6 0 0 o 9 7 9 0 0 2 2 0 1 oF 1 1 TEXT /// JINuu space /J tuqukaf, utu afiWond HRC RNIII 366AB/ (\2)

It was shortly following this exchange, via telephone, at approximately 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br />, that Control Room personnel received "Cryogenic Tank N2 Press Low" alarm, which activates at 155 psig (+ or 6 psig). Subsequently, the A and 8 ADS Headers isolated at 1618 hours0.0187 days <br />0.449 hours <br />0.00268 weeks <br />6.15649e-4 months <br /> and at 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br />, respectively. At that time the Division II CIA ADS Timer cycled the Nitrogen Backup bottles ON to maintain ADS Nitrogen pressure. This event is considered an ESF actuation at WNP-2. Eventually, the Div.

II CIA ADS Header stabilized at 121 psig. The Division I CIA Header, which is much tighter, stabilized at approximately 150 psig.

When the Containment Nitrogen (CN) system looses pressure, Plant Operators must take manual action to provide a backup supply of air from the Control Air System (CAS) to prevent the Hain Steam Isolation Valves (HSIVs) from closing. At 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br />, Plant Operators cross connected the CAS system to the CIA system per Plant Procedures, PPH 2.8.2, Containment Instrument Air. This lineup connects non-safety related loads to th'e CAS through the CIA system air dryers. This procedure states that "Normal CIA pressure while being supplied by CAS is 80 psig. Normal CAS header pressure is 100 psig. MSIV closure will occur at approximately 50 psig.R Plant operators observed the CIA pressure decrease and were concerned about the pressure drop across check valves (CIA-V-742 and CIA-V-743) downstream of the CIA Dryer tower and filter units.

Because of their concern about pressUre drop Plant Operators installed an air path jumper between the Service Air (SA) System and the CIA receiver tank (CIA-AR-1) through CIA-V-19. This jumper bypasses the dryer units and provides air through an Air Receiver (CIA-AR-1) to the non-safety related part of CIA. At 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br /> CIA non-safety related header pressure was stabilized at approximately 105 psig using Service Air. Operations management then stationed Equipment Operators at the SA hose connections for continuous monitoring.

'Ihe CN System is a non-safety related system that provides a one million standard cubic foot supply of nitrogen for the plant. It provides a high volume source of nitrogen to inert the containment and also provides a regulated supply of nitrogen to specific loads inside Containment. The non-safety related part of the Containment Instrument Air (CIA) header supplies pneumatic pressure to the Inboard Hain Steam Isolation Valves (HSIVs) and the Hain Steam Safety/Relief Valves {SRVs).

The "safety related" part of the CIA system is composed of two separate headers which, combined, supply the nitrogen to operate seven Hain Steam Safety Relief-Valves (HSRVs) in the Automatic Depressurization System (AOS) mode of operation.

The AOS is a portion of the backup Emergency Core Cooling System (ECCS), an Engineered Safety Feature, designed to quickly reduce reactor pressure in the unlikely event of fai lure of the High Pressure Core Spray {HPCS) System. The AOS is composed of seven (7) specially designated HSRVs that provide rapid depressurization of the primary system. The safety related part of the CIA system normally receives nitrogen from the non-safety related part of the system via CIA-V-39A(B). The "A" devices are used to designate safety related Division I, and the "B" devices designate Division II. When a loss of pressure is detected by pressure switches CIA-PS-39A( 8), valves CIA-V-39A(B) are automatically closed. The isolation of these valves, by system design, occurred at approximately 1618 hours0.0187 days <br />0.449 hours <br />0.00268 weeks <br />6.15649e-4 months <br /> when the pressure droooed to 137 osiq.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6 JIB) APPROVEO OMB NO. 3)504106 EXPIRES: E/30/02 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT {LER) FNFORMATION COLLECTION REOUEST: 50A) HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE, FIECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (F430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (31504106), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON,OC 20503.

FACILITY NAME (I) DOCKET NUMBER (21 LER NUMBER (6) ~ AGE (3)

YEAR $25: SEOUENTIAL 'O'IT err REVISION NUM ER NUM ER Washington Nuclear Plant TEXT /// more e/>>ce Je

- Unit r)V/rerL oee eOE//Iior>>/ HRC Fonrr 366A 2/ (12) 2 p,pp pp 397

~

~ 9002201 4 oF At 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br />, when the Logic for Division II Initiation was satisfied (The logic being 2/3 of: (l)CIA-PS-228 less than 137 psig; (2)CIA-PS-218 less than 140,psig; or CIA-V-39B closed) the CIA-PROG-18 was automatically initiated and the Oiv. II system went on backup bottles. The pressure in the Oiv. II header dropped to a low of 117 psig at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> and then, eventually, stabilized at 120 psig. The system should maintain header pressure at 150 psig. The Div. II System stayed at 120 psig 24 hrs., as shown by the pressures recorded by Transient Data for'pproximately Acquisition System {TDAS). Control Room Alarm 4.820.Bl, Window 10-4 '-'CIA Div 2 Out of Service" was on for approximately 24 hrs. due to "N2 Div. 2 Supply Press Low" which alarms at a pressure less than or equal to 137 psig, or when the Programmer selects the last bottle. With this alarm on it means that the backup bottles were not providing sufficient pressure to the Oiv. II header. The response to 4,820.81, 10-4, step number 4 .calls for checking the pressure regulating valve CIA-PCV-28, and to consider bypassing if necessary. For the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period that the alarm was lit, this was never done, nor'was the alarm responded to.

A truckload of liquid nitrogen, which had been previously ordered, was scheduled for delivery on October 1, 1990. It arrived on schedule and at 1125 hrs operators began filling CN-TK-1. The CIA system was placed back into service at approximately 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on October l.

Immediate Corrective Action

l. Immediate action was taken to obtain additional liquid nitrogen.

2. The Containment Nitrogen Inerting Procedures {PPH 2.3.1 and 2.3.7) were revised to clearly provide a lower limit for CN-TK-1 level. Specifically, a caution statement was added to the procedures which, reads: "When inerting the containmeni',, closely monitor the Liquid Nitrogen Storage Tank Level. Do not drain liquid level to less than or equal to 50 inches at CN-LIS-l. If the tank level is lowered beyond the point where normal pressure is maintained, as indicated by CN-PI-l, containment CIA header pressure will be lost."

Further Evaluation and Corrective Action A. Further Evaluation The actuation of the Safety Related portion oF CIA is being reported per the reqUirements of 10CFR50.73(a)(2)(iv) as an "event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF). ...R. In ~

addition, this event is being reported under 10CFR50.73(a)(2)(i)(B) as "Any operation or condition prohibited by the plant's Technical Specifications..."

NRC Form 366A (645

0 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (669) APPROVED OMB NO. 3150410i EXPIRES: 4/30(92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT HLER) INFORMATION COLLECTION REOUESTI 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINuATION AND REPORTS MANAGEMENTBRANCH (F430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555, AND TO 1ME PAPERWORK REDUCTION PROJECT (3(50010lI, OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (II DOCKET NUMBER (21 LER NUMBER (6) ~ AGE (SI YEAR SEQUENTIAL b)~ IIEVISION NUM 4 II SI( NUM44II Washington Nuclear Plant - Unit 2 o s o o o 397- 90 0 2.2 0 1 5OF 1 1 TEXT N mon <<+co JI mouood, uoo oddlo'one HJIC FomI 36SASI IITI

1. The first part of this further evaluation is concerned with the part of the event associated with low level in CN-TK-l.

The Liquid Nitrogen Tank (CN-TK-1) was inadvertently reduced to less than desired levels because of less than adequate plant procedures.

The procedures being used, PPM 2.3.1 and PPH 2,3.7, did not provide the Equipment Operator(s) adequate information for them to realize, on their own, what the minimum acceptable tank level was, before the process of inerting had to be terminated. The Equipment Operators knew that the tank inventory was approaching a marginally, low condition, but the procedures did not provide guidance nor instruction on what was the minimum level before stopping the process.

b. The Shift Support Supervisor could have stayed at the CN-TK-1 skid and followed the Inerting process through to it's conclusion.

Instead, he elected to have the two operators,.who were qualified on the system, follow the procedures for Primary Containment inerting, contacting them by telephone when needed. The Supervisor had physically been to the skid at the start of the shift, at 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br />.

After he assigned the operator to the job, he did not return until the occurrence of the event, At the start of the job he noticed that there was less than a desired amount of inventory of liquid nitrogen, but that there was probably enough to complete inerting. He did not return to the skid again, until the event occurred, being busy in performing his other duties throughout the plant. He did stay in contact with both Equipment Operators prior to event initiation.

The root cause for the inadvertent draining of the 'Liquid Nitrogen Tank was determined to be procedural. The purpose of Plant Procedures PPN 2.3.1 and 2.3.7 is to provide operations personnel with instructions that will guarantee successful completion of the task being described. These plant procedures lacked a caution or instruction step for providing instruction for the Equipment Operators to NOT go below a certain minimum tank level.

An additional cause for the depletion of the Nitrogen Tank was less than adequate supervisor oversight on the part of the Shift Support Supervisor. Because he devoted his attention to completing duties of a lesser priority, he choose to spend less time following the inerting process. The Shift Support Supervisor should have given the inerting of the Primary Containment a much higher priority of importance and followed the job much closer than he did.

NRC F oiIII 366A (6 Eo

NRC FORM366A US. NUCLEAR REGULATORY COMMISSION (669) APPROVED 0MB NO. 31504)OE EXPIRES: 6/30)92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REOUEST: 50J) HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (F4301. U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTiON PROJECT (31504)04), OFFICE OF MANAGEMENTAND BUDGET,WASHINGTON,DC 20503.

FACILITY NAME (I) DOCKET NUMBER (1) LER NUMBER (6) ~ AGE (3)

YEAR ~w re EEOVENTrAL o> rrEvrEION

>+0 NUM ER ~

NVM Err Washington Nuclear Plant- - Unit 2 p p p p p 39790 02 2 01 0 6 pF TEXT N more Eoece Je rer)rr(rer6 rree Jrr'orreJ NRC %%drm 36(LES) (IT)

e. A contributing cause to the depletion of the liquid nitrogen tank level event was the nitrogen tank Low Level Alarm, 4.813.Hl Window 3-3, "Cryogenic Tank N2 Leve'I Low" which was set to actuate at 220".

This alarm level is too high since the level of the tank reaches 220", from a max level of 325", rather quickly in the initial stages of inerting Primary Containment. Normally, the highest tank level readings recorded on the Outside Tour Log Sheet are 3000 which is only 80" above the 220" alarm setting. At 220R Operations would be in the initial stages of Inerting and the low level alarm would actuate. Operations would'ontinue on with Inerting with the alarm on for the remainder of the process. Thus, its purpose is lost .to the Control Room Operators. The alarm at 220" did not make Operations do anything other than to, verify the level in the tank and notify the appropriate personnel to order additional liquid nitrogen.

2.. The second part of this further evaluation is concerned with the low pressure in the Division II CIA header.

'a ~ When the initial event occurred on October 1, 1990 the Plant Operations manager requested a review of the situation by the System Engineer. A Plant Technical/Engineering evaluation of the CIA data on October 12, 1990 showed that pressure maintained in the Oivision II CIA header was below the design basis value. Engineering Calculation 5.46.05.stated a pressure of 127 psig was required to satisfy the system safety function. This value is based on a Safety Relief Valve (SRV) actuating pressure of 88 psid and a peak containment .pressure of 39 psig. Plant operators were not aware of the minimum design basis pressure of 127 psig for the system when the event occurred on September 30, 1990.

Further evaluation on October 12 indicated that the pressure regulator for Oivision II (CIA-PCV- 28) was not adjusted properly causing the low pressure in the header. At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on October 12, 1990 AOS Oivision II was declared inoperative due to low header pressure and Technical Specification Action Statement 3;5.1.e.2 was entered which required HOT SHUTOOWN within the next twelve hours. An emergency work request was generated to investigate the pressure setpoint of CIA-PCV-28. It was immediately apparent that it was not set at the proper pressure and an adjustment was completed to establish a pressure of 150 psig in the Oivision II header. AOS Division II was declared operable at 1242 hours0.0144 days <br />0.345 hours <br />0.00205 weeks <br />4.72581e-4 months <br /> on October 12, 1990.

NRC Form 355A rf AS

NRC FORM 366A US. NUCLEAR REGULATORY COMMISSION APPROVED DMS NO.31600)04 (SJ)9)

EXPIRES: 4/30/62 ESTIMATED SURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUEST: 50.0 HRS. FORWARD COMMENTS REGARDING SURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH IP430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (3)600105), OFFICE OF MANAGEMENTAND SUDGET,WASHINGTON, DC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (6) PAGE IS)

YEAR NUM 5R '~

55OVENTIAL bM RSVI5ION NUM 5R TEXT //I mor5 RP555 0 nqvkat, Nw ~

Nashin ton Nuclear Plant Unit HRC Fofm SSSA2/ ()T) 2 o 5 << o 3 9 7 9 0 0 2 2 01 7 OF C. root cause associated with this low pressure setting was an equipment design deficiency. The location of this valve placed it in A

a position where "inadvertent adjustment" could occur by bumping or hitting the Tee handles on the valve. The valve should have been designed to prevent this type of "adjustment."

d. During this time plant operating personnel were under the guidance of Abnormal Condition Procedure 4.820.81, Mindow 10-4 "Containment Instrument Air Division II Out of Service".. Step g5b states that if pressure is less than 140 psig, action should be taken to use backup systems to restore low NSIV/SRV header pressure. This was done, as explained above through the use of CAS and SA. Step g5c states that if inerting is in progress restore nitrogen tank pressure. Actions were taken to make sure additional nitrogen was, ordered. Step g3 says to "Check for proper control of CIA-PCV-28, consider bypassing if necessary". This refers to bypassing the regulating valve CIA-PCV-28 by opening the 1/2R bypass valve CIA-V-7338 and, thereby, increasing Div. 2 prcssure'he reason that this was not done was their concern for repressurization of the header, which might cause the Div. 2 header isolation valve (CIA-V-398) to reopen. The reopening of CIA-V-398 could create a condition where the entire backup supply would eventually be depleted. The error in this diagnosis, which was discovered at a later date, was that the pressure sensing instrument, for CIA-V-398 which could cause the valve to open, is on 'the side of the valve that would not 'have seen the pressure increase. Up until this, Operations had taken all the correct actions and exercised every precaution for maintaining CIA system pressure and Plant safety.

e. Further evaluation showed, however, that for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> the "CIA Div, 2 Out of Service" alarm was on. Step gl of the procedure for RN2 Div 2 Supply Press LowR relates that the alarm annunciates pressure less than or equal to 137 psig and Step g4 states, "Check for proper control of CIA-PCV-28. Consider bypassing if necessary". They failed to realize that the alarm for N2 Div. II was independent of the loss of N2 Tank level problem. Therefore, they failed to use Abnormal Condition Procedure 4.820.81, which would have corrected the cause of the alarm, and returned the system pressure to normal. CIA Division II header pressure was at 120 psig and the bypass around CIA-PCV-28 could have been opened/throttled to raise the pressure and restore normal pressure per the procedure instructions. Additionally, Step g6 could have alerted Operations personnel to the fact that with alarm window 10-4 ON (actuated),

pressure may not be within the requirements of Technical Specification 3.5.1., therefore, some form of action was required.

NRP f Rrm 3IJSA iRSP

NRC FORM 366A U4. NUCLEAR REGULATORY COMMISSION (689) APPROVED OMB NO. 31504106 EXPIRES: E/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUESTI 500 HRS. FORIVARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20655, AND TO THE PAPERWORK REDUCTION PROJECT (3)504)04), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (\) DOCKET NUMBER (2) LER NUMBER (SI PAGE (3)

SEQUENTIAL NUM E II e PI IIEVISION NUM E II Washington Nuclear Plant Unit 2 o s o o o 9 0 0 2 2 01 08 oF1 TEXT /// more soece /I IN)o/red, Iree erSdR/orM/ HRC Avm 366A'I/ ((2)

f. TOAS documentation confirms that OIV. II Header pressure did in fact

, drop to approximately 120 psig and remain that way until approximately 1600 on October 1, 1990. Supporting this is the fact that on October 12, 1990, 12 days after the event, CIA-PCV-2B was found to be set to regulate Div. II ADS pressure at only 120 psig (127 psig was minimum required at the time). A Haintenance Work Request (HWR) AR1148 was initiated and adjustments completed on October 12, 1990, At that time the system was returne'd to a 150 psig regulating pressure.

g. The cause for annunciators not being corrected for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> was personnel related attributed to a Knowledge Based Error. Knowledge Based Errors occur when' worker is put in a new or novel situation where limited information is available, limited response time available, and he must rely on his system knowledge to work. The response to the loss of N2 and CIA header pressure taxed the Operation personnel's knowledge and teamwork abilities.

h. An Engineering evaluation (Supply System Hemo SS2- PE-90-0998) after the event on October 17, 1990 showed the required minimum pressure in the ADS pneumatic supply header is 134 psig. This higher pressure takes into account the line losses between the accumulators and the point where the header pressure is measured.

3. A further'evaluation was performed of the portion of the event associated with the use of Service Air (SA) to provide a backup to CIA. CAS was lined up to supply pressure to the CIA main header to ensure the Hain Steam Isolation Valves (HSIVs) had adequate air pressure to stay open.

However, the pressure continued to drop and the Shift Hanager made a decision to have a jumper installed from the Service Air (SA) system to the CIA system. Operations reasoning for doing this was that no CAS air flow was initially observed and conceivably the check valves downstream of the dryer unit could have remained closed or the pressure drop across the dryer units could be excessive. They evaluated the moisture content of the air before connecting the SA system to CIA.

4. The containment was inerted to an oxygen content below the Technical Specification limit of 3.5$ prior to nitrogen depletion and stayed below that value for the duration of the event.

5. There were no structures, components or systems that were inoperable prior to the start of the first part of this event associated with the loss of the contents of CN-TK-1. The loss of nitrogen clearly contributed to the second part of the event associated with low pressure in the Division Il CIA header.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (649) APPROV ED DMS NO. 3) 500106 EX PI RES l 6/30/92 LICENSEE EVENT REPORT (LER) ESTIMATED SURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUEST: 500 HRS. FORWARD COMMENTS REGARDING SURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENTSRANCH (P430I, U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104(, OFFICE OF MANAGEMENTAND SUDGET.WASHINGTON, DC 20503.

FACILITY NAME l(I DOCKET NUMSER (2I LER NUMSER (Sl PAGE (Si EEOVENTIAL rIEVrE ION

'c>P: kvM Err PRATE rrvM EA Washin ton Nuclear Plant Unit 2 o s o o o 397.90 0 2 01 09 OF N moro g>>co JI o(rrrrod, Ir>> oddrrr(rr>>J HRC Form 305ASI (IT(

'ExT B. Further Corrective Action

1. Pressure Regulating Valve {CIA-PCV-28) was adjusted to its proper setpoint of 150 psig.

2. An Instrument Setpoint Change Request was prepared and implemented to move the low level alarm on CN-TK-1 from 220 inches to 80 inches.

3. Plant Procedure, PPH 2.3.7, Nitrogen Inerting System was modiFied with a Caution note which states: "Performance of the remainder of this procedure section requires the Shift Support Supervisor remain informed regarding inerting equipment operability, tank filling operations, operator assignment and responsibility."

4. Procedures for using CAS as a backup to CIA were evaluated to see if changes needed to be made to better define when and how the backup is to be accomplished. No changes were required.

5. Plant operating personnel were counseled on the need to strictly follow the guidance provided in Abnormal Condition Procedures.

6. Plant Procedure PPH 1.3.1, Conduct of Operations was revised to add a new section to track ROut of Service Instruments and Alarms".

.7. Plant Procedure {PPH 4.820.81-10-4), Containment Instrument Air Division 2 Out of Service, was reviewed to assure actions required in response to low nitrogen supply are clear. No changes were required to the procedure.

8. A review of surveillance procedures was conducted to provide additional

~

assurance that regulating valves on the saFety related part of CIA {CIA-PCV-2A and 28) are set correctly to maintain pressure, Plant Procedure PPH 8.3.49 checks the operation of these valves. A change will be made to the valves to secure them in a fixed position.

Safet Si nificance This is no safety significance associated with this event. The accumulators for the ADS valves each have a check valve between the accumulator and the header where the relief valve is located. The operation of this equipment is verified by Surveillance Test 7.4.0.5 '3, CIA-V-40 Operability Test. This test was completed available for successfully in Duly 1990. Thus, nitrogen pressure would have been initial automatic operation of the ADS valves.

NRC form 366A (&6&

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION

)689) AI'PROVED OMB NO. 3)600104 EXPIRES: E/30/92 ESTIMATED SUADEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUEST: 500 HRS. FORWARD COMMENTS AEGARDING BURDEN ESTIMATE TO THE AFCORDS TEXT CONTINUATION AND REPOATS MANAGEMENT BRANCH IP430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT l3150dl0r), OFFICE OF MANAGEMENTAND BUDGET,WASHINGTON, DC 20503.

FACILITY NAME 11) DOCKET NUMBER 12) LEA NUMBER )6) PAGE IS)

YEAR SP. SEOVENTIAL N V M 9 E el REVISION NUM E el Washin ton Nuclear Plant TEXT /// more r/Iree /r reqokaL ere ~ - Unit NRC Fome 355A'r/ ) IT) 2 0 6 0 0 0 3 9 7 9 0 0 2 2 01 11 OF EIIS Information Text Reference EIIS Reference

~Sstem ~Com anent Containment Instrument Air (CIA) LD Nitrogen Cryogenic Tank (CN-TK-1) LK TK Containment Nitrogen Inerting System (CN) LK CIA Pressure Control Valve 28 (CIA-PCV-28) LD 'V and (CIA-PCV-2A)

Hain Steam Isolation Valves (HSIVs) SB CIA Check Valves {CIA-V-742, 743) LD Safety Relief Valves (SRVs) SB Automatic Oepressurization System (ADS) BG High Pressure Core Spray System (HPCS) BG CIA Valves 39A and 8 (CIA-V-39A(B)) LD. V CIA Pressure Switches 39A and 398 LO PS (CIA-PS-39A(B))

Control Air System (CAS) LD Service Air System (SA) LF CIA Receiver Tank (CIA-AR-1) LD TK CIA Valve 19 (CIA-V-19) LD V CIA Pressure Switches 22A and 228 LO PS (CIA-PS-22A(B))

CIA Pressure Switches 21A and 218 LD PS (CIA-PS-21A(B) )

CIA Programmers lA and 18 LD PHC

{CIA-PROG-lA(18))

CIA Pressure Indicator 218 (CIA-P-218)) LD PI CIA Pressure Indicator 318 (CIA-P-318)) LD PI CIA Remote Nitrogen Cylinder 20A and 208 LO TK (CIA-TK-20A(8))