ML20207A179
| ML20207A179 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 05/21/1999 |
| From: | Pulley H UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-99-1015, NUDOCS 9905260185 | |
| Download: ML20207A179 (7) | |
Text
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7 "d USEC
. A Global Energy Company May 21,1999 GDP 99-1015 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Dock.et No. 70-7001 Event Report ER-99-06 Pursuant to 10CFR76.120(d)(2) enclosed is the required 30-day written event report pertaining to the inoperability of process gas leak detection (PGLD) heads required to be operational when operating above aimosphere. The Nuclear Regulatory Commission Headquarters (NRC-HQ) operations office was notified of the event on April 27,1999 (NRC No. 35639). Commitments contained in this submittal are in Enclosure 2,
. Any questions regarding this matter should be directed to Larry Jackson at (502) 441-6796.
Sincerely, 5
\\{l Howard Pulley General Manager j
Paducah Gaseous Diffusion Plant j
Enclosure:
As Stated cc: NRC Region Ill Office NRC Resident inspector-PGDP l
9905260185 990521 PDR ADOCK 07007001 i
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PDR P.O. Box 1410, Paducah, KY 42001 Telephone 502-441-5803 Fax 502-441-5801 http://www.usec.com Omces in Livermore, CA Paducah, KY Portsmouth, OH Washington, DC u
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Docket 70-7001 L
GDP 99-1015 e
Page1of5 EVENT REPORT ER-99-06 f-DESCRIPTION OF EVENT '
' On April 27,1999, at approximately 0900 hrs., a process gas leak detector (' PGLD) head alarm for head YE-45, was received in the area control room (ACR), Building C-333. A determination was made that YE-45 served the number 2 purge and evacuation (P&E) pump, which was out of service (Mode 3) and technical safety requirement (TSR) 2.4.4.1 was not applicable; therefore, limiting conditions for operation (LCO) were not entered. PGLD head YE-45 alarms on the Unit 5, Cell 1, PGLD signal conditioner. The Unit 5 Cell 1, PGLD system was required to be operational since the cascade was operating above atmosphere (cascade Mode 2). The PGLD
-YE-45 alarm would not reset and the alarm in the ACR remained in an alarm condition (locked in).! This ' condition precluded operators from receiving notification of additional PGLD alarms from Unit 5, Cell 1 in the event of a uranium hexafluoride (UF6) release. At approximately 0922 hrs., the Plant Shift Supetintendent (PSS) declared PGLD YE-45 inoperable. The LCO was not
- entered within the required one-hour time period, because the operators did.not realize that the safety function of the PGLD for Unit 5, Cell I had been rendered inoperable when the alarm for
. YE-45 had not been reset. The Nuclear Regulatory Commission Headquarters (NRC-HQ) operations oflice was notified of the event in accordance with 10CFR76.120(c)(2) (NRC Event
- No. 35639).
l On -April 27,1999, at approximately 0800 hrs., testing of the Building C-333 PGLD heads s
. required by TSR 2.4.4.1, was initiated. The PGLD heads are required to be " test fired" twice each shift when operating in cascade Mode 2. The surveillance test was successfully completed for Unit 5, Cell 1, and the operators were completing the surveillance of the remaining systems in Unit 6. When PGLD head YE-45 fired, the operator in the ACR verified receipt of the alarm.
However, instead of responding to the alarm, according to the alarm response procedure (ARP),
the operator in the ACR directed the operator on the floor to return to Unit 5, Cell 1 to determine the cause for the alarm. The floor operator reported that YE-45 had fired and attempted to reset j
the system. After several unsuccessful attempts to reset the head, the operators completed the PGLD surveillance sheet, noted the problem, and reported the problem to the First-Line Manager j
(FLM). The operators and FLM reviewed the TSR and correctly determined YE-45 was not required to be operational according to the TSR; therefore, LCO action steps were not entered.
However, Unit 5, Cell I was operating above atmosphere; therefore the PGLD system associated with inis cell was required to be operable in accordance with the TSR. The FLM was cognizant of the fact that when a PGLD head remained in an alarm condition it precludes receipt of other i
valid PGLD alarms within the~ACR for the cell. However, the FLM stated that he entered and exited the ACR several times and failed to notice that the alarm light remained illuminated. At l
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Docket 70-7001 GDP 99-1015 Page 2 of 5
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approximately 1100 hrs., a second FLM entered the ACR and questioned the reason for the
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illuminated PGLD alarm light on the ACR panel, which led to the discovery that the PGLD head remained in an alarm condition. At approximately 1100 hrs., the PSS was notified that the PGLD head was left in an alarm condition and a smoke watch was established for Unit 5, Cell 1, as required by LCO. It was later determined that the cause for the PGLD head to fire was probably due to welding activity that was underway in the immediate vicinity.
The problems experienced with PGLD head YE-45 were properly reported to the FLM by the operators and the situation was discussed, including researching operability requirements in the TSR. The FLM did not understand that Unit 5, Cell 1 PGLD alarm was locked in until it was pointed out by a second FLM. The operators involved in the surveillance test knew the Unit 5, j
Cell 1 ACR alarm was locked in but failed to understand the impact on the system's operability j
and assumed the issue was resolved when YE-45 was declared inoperable at 0922 hrs. One of j
the operators on duty at the time of this event implied that he did not understand when a PGLD alarm remained actuated it locked out receipt of additional alarms.
The safety significance of this event was the loss of PGLD audible alarm capability for Unit 5, Cell I for one hour and thirty-eight minutes. The loss of alarm capability is mitigated by the twice-a-shift PGLD system surveillances (maximum time between surveillances is eight hours).
Additionally, the most likely places for incidental releases to occur are from "B" seals, or
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buffered expansion joints on "B" lines. Instrumentation used to control and monitor these j
system's alarms in the ACR would alert operators to a UF release.
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CAUSE FOR THE EVENT
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A. Direct Cause The direct cause for this event was an actuated PGLD head alarm (YE-45) for P&E pump.
When the head would not reset, a condition existed which precluded receipt of an additional PGLD system alarms for this unit and cell in the event of a UF release. Because Unit 5, Cell 6
1, was operating above atmosphere, the PGLD system associated with this cell was required to be operational in accordance with TSR 2.4.4.1.
e-Docket 70-7001 GDP 99-1015 Page 3 of 5 B. Root Cause The root cause for this event was less than adequate training. Prior to the event, the Unit 5, Cell I surveillance test was successfully completed. When PGLD head YE-45 fired a second time, instead of responding according to the ARP, the ACR ' operator directed the floor operator to return to Unit 5, Cell 1 to determine the cause for the alarm. Additionally, subsequent to the event an operator implied that he did not realize that once a PGLD alarm was locked in it will not alarm upon receipt of additional alarms.
C. Contributing Cause A contributing case for this event was a communication problem between the supervisor and the operators. The operators attempted to reset PGLD head YE-45 and were unsuccessful.
The problem was reported to the FLM and the situation discussed, which included researching
~ the operability requirements of the TSR. The supervisor did not realize that Unit 5, Cell 1 PGLD alarm was " locked in" until informed by a second manager.
CORRECTIVE ACTIONS -
A. Completed Corrective Actions.
- 1; On April 27,1999, as an interim compensatory measure, Cascade Operations Long Term Order (LTO)99-003 was published. The LTO implemented the following policy:
- a. Receipt of a PGLD alarm shall be considered an actual alarm and will be responded to in accordance with the ARP. The only exception will be the actual performance of the PGLD surveillance on the equipment.
- b. _When operability of any component is in question, all PGLD heads associated with the signal conditioner are to be declared inoperable and actions' under the TSR implemented. Once implemented, the PSS may downgrade the operability to a single component if the remainder of the system has been tested to verify operability.
- c. Once each hour the First-Line Manager (FLM) and the ACR operator will complete a walkdown of the ACR alarm panel. Walkdowns shall ensure compensatory measures are taken when alarms are locked in and shall specifically include a review of PGLD alarms. Walkdowns shall be documented hourly in the ACR and the FLM logs.
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t, Docket 70-7001 GDP 99-1015 -
Page 4 of 5
- d. Additional oversight of TSR surveillance 2.4.4.2-1 will be conducted by the ' Assistant Plant Shift Superintendent (APSS) twice each shift.' At the discretion of the APSS, an.
FLM from an adjacent facility may provide the required oversight.
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e.1 The operator performing verification of receipt of PGLD alarms in the ACR will sign the " Cascade UF6 Detection System Test Firing Data Sheet," form along' with the
. building operator performing the PGLD head test at each cell panel. This will ensure-proper documentation and receipt of the ACR alarms during the test.
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' 2. By May 4,1999, approximately 90 percent of Cascade Operations personnel had received I
a " lessons _ learned" briefing on this event. Based on these actions, LCO 99-003 has been -
lt revisc0 to retain only actions A.1.a, A.1.b.;' action A.I.c was modified to eliminate the FLM's walkdown and maintenance of the FLM log.
- 3. CP4-CO-CN-6020t, Rev.1, "TSR Surveillance-Test Firing of PYR-A-LARM Type 1, High Voltage UF6 Detection Systems in C-331, -333, -335, -337," was published with an effective date of May 14,1999. This revision proceduralizes paragraph A.I.e.
B. Planned Corrective Actions ~
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- 1. By June 30,1999, Operations will complete a lessons learned briefing for all Cascade i Operations personnel who have not been briefed (see completed corrective action 2.,
1 above). The briefing will be conducted by a " stand down" and documented.
- 2. By November 17,1999 Operations will review training modules / procedures for UF6 eak l
detection, criticality accident alarm system, and freezer /sublimers, for adequacy in providing guidance to personnel for determining the operability of the system based on system indications (indicating lights, alarms). Additional actions will be input into the plant corrective action program for correction of any identified deficiencies.
L EXTENT OF EXPOSURE OF INDIVIDUALS TO RADIATION OR RADIOACTIVE MATERIAL None l
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Docket 70-7001 GDP 99-1015 Page 5 of 5 LESSONS LEARNED Most cascade buildings contain PGLD heads not required to be operational under the TSR.
However, PGLD heads not required under the TSR could cause TSR required systems to become inoperable if the PGLD head fires and fails to clear on cell _ signal conditioners covering equipment operating in cascade Mode 2.
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Docket 70-7001 j
GDP-99-1015 Page1of1 i.
List of Commitments Event Report ER-99-06
- 1. l By June 30,-1999, Operations will complete a lessons learned briefing for all Cascade Operations personnel. The briefing will be conducted by a " stand down" and documented.
2.1 By' November 17,-1999, Operations will review training modules / procedures for UF6 leak
. ' detection, criticality accident alarm system, and freezer /sublimers, for adequacy in providing guidance to personnel for determining the operability of the system based on system indications (indicating lights, alarms). Additional actions will be input into the plant corrective action program for correction of any identified deficiencies.
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