ML20236H663
| ML20236H663 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 07/06/1998 |
| From: | Pulley H UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1052, NUDOCS 9807070300 | |
| Download: ML20236H663 (7) | |
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USEC A Global Energy Company l
July 6,1998 GDP 98-1052 United States Nuclear Regulatory Commission Attention: Document Control Desk l
Washington, D.C. 20555-0001 l
Paducah Gaseous Diffusion Plant (PGDP)
J Docket No. 70-7001 Event Report ER-98-18 Pursuant to 10CFR76.120(d)(2), Enclosure 1 provides the 30-day Event Report related to the disabling of the C-337 criticality accident alarm system (CAAS) horns. The Nuclear Regulatory Commission (NRC) was notified of the event on June 7,1998 (NRC No. 34358).
Commitments contained in this submittal are identified in Enclosure 2. Any questions regarding this matter should be directed to Larry Jackson at (502) 441-6796.
Sincerely, f
I Howard Pulley General Manager Paducah Gaseous Diffusion Plant
Enclosures:
As Stated cc:
NRC Region til Office NRC Resident Inspector - PGDP V[
9807070300 990706 i
PDR ADOCK 07007001 C
.[b C] I I
P.O. Ilox 1410. Paducah, KY 42001 Telephone 502-4415803 Fax 502-441-5801 hnp://www.usec.com Ofikes in Livermore, CA Paducah, KY Portsmouth. OH Washinpon, DC i
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Docket No. 70-7001 GDP 98-1052 Page 1 of 5 EVENT REPORT ER-98-18 DESCRIPTION OF EVENT On June 6,1998, at approximately 1330 hrs., C-337 process building operators were pressurizing the cell coolant (R-114) station with plant air through a 2-inch gate valve to leak rate the system following maintenance. While opening the valve and monitoring a down-stream pressure indicating gauge, the valve malfunctioned in the open position and could not be closed. The operators noted the air pressure was continuing to rise. They became concerned that the rising pressure in the R-114 station would blow the R-114 system rupture disc that they thought was set at 80 psig and had been a problem in past years. The operators decided to open a nearby air vent valve to expel pressure from the air line and preclude over-pressurizing of the R-114 rupture disc. This vent line extends upward approximately 20 feet and is open to the building atmosphere. The operators called the area control room (ACR) to notify their front-line manager (FLM) of the problem. The operator informed the FLM that the air supply valve had malftmetioned and to preclude blowing the R-114 rupture disc, he had opened the air vent valve. The FLM heard the operator state that a valve had malfunctioned, but did not hear or understand that the air vent valve had been opened. He then exited the ACR and heard air being vented into the building.
The FLM went to the R-114 station where the operators showed him the broken valve and also the vent valve they had opened. The vent valve is approximately 2 feet below the malfunctioning valve.
After unsuccessfully attempting to operate the failed valve, the FLM, along with an operator trainee who had been observing the leak rating operation, traced back the air line to an unlabeled 3-inch valve on the plant air header which he had the trainee close. This stopped the air which was being
- e. riled into the building through the open vent line. The FLM was aware of a current plant issue reteted to the air capacity required to maintain operability of building horns under Justification for Continued Operation (JCO) for Compliance Plan Issue 46. These horns are used to augment local criticality accident alarm system (CAAS) alarm audibility. He believed he was in a situation that required immediate action. His concem was that the air being released to atmosphere would reduce the plant's total air capacity below the level required to maintain CAAS alarm audibility.
At about 1340 hrs., a Utilities supervisor informed the plant shift superintendent (PSS) that one of his operators had reported that a C-337 operator had called the C-600 Utilities control room and requested them to monitor the plant air pressure due to a broken air valve in C-337, and that air was being vented. The PSS attempted to contact the C-337 FLM about this reponed air problem. The l
C-337 ACR operator stated that the FLM was out in the building and that he had been instructed to l
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Docket No. 70-7001 GDP 98-1052 Page 2 of 5 l
monitor the bu lding air pressure. 'Ihe PSS asked the ACR operator to get in contact with the FLM i
and have him call the PSS.
At 1341 hrs., a CAAS trouble alarm from C-337 CAAS cluster "AK" was received in the C-300 central control room. The PSS requested that Instrument Maintenance (IM) personnel investigate the trouble alarm. At 1400 hrs., the FLM called the PSS and reported that he had closed an isolation valve on an air line which only fed air to the R-114 station, stopping the air leak, and that the problem was under control. Not feeling comfortable with this information, the PSS sent the shift engineer to C-337 to investigate the situation and determine exactly which valve had been closed, and what equipment had been afTected.
At 1458 hrs., IM personnel sent to investigate the "AK" cluster trouble alarm, reported to the PSS that they thought the plant air supply to the cluster local horn was off, and that they had opened a Unit 2 auxiliary / air line and found no air pressure on the line, indicating that the plant air supply to all of Unit 2 had been isolated. The building instrument air to the unit was not afTected. Being concerned that this could potentially affect the building CAAS horns and given the lack of information from the building, the PSS declared the CAAS inoperable for audibility. At 1459 hrs.,
the PSS initiated the action steps associated with the general limiting conditions for operation (LCO) described in Technical Safety Requirements 2.4.4.2b. The failure of the FLM to communicate the problem to the PSS in a timely manner is not seen as a generic problem, and will be corrected via coaching by management with the FLM involved.
At 1530 hrs., it was determined that the 3-inch plant air valve closed by the operator trainee, as directed by the FLM, was the Unit 2 main air supply valve which had disabled two of the CAAS building air horns being used to augment local CAAS homs and removed the air supply to the local CAAS horns on clusters "AK" and "Y". The local horn function was maintained by nitrogen backup. The malfunctioning valve was replaced and plant air restored to the CAAS building and local horns. The CAAS was declared operable at 2230 hrs. on June 6,1998.
The Nuclear Regulatory Commission 11 headquarters (NRC-IlQ) operations office was notified of the event, as required by 10CFR76.120(c)(2), at 1224 hrs. on June 7,1998. NRC notification No. 34358 was assigned to the event.
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CAUSES OF EVENT i
A. Direct Cause The closure of the 3-inch plant air valve to C-337, Unit 2 removed the air from the building air horns credited for providing CAAS audibility for the building.
B. Root Cause A human performance evaluation system analysis of this event identified four root causes. The first root cause relates to the FLM's failure to apply the plant's stop, think, act and review (STAR) policy. Had he applied STAR, he may have realized that the problem could have been j
resolved by simply isolating the R-114 station from the plant air supply via one of two R-114 station isolation valves located only a few feet away from the malfunctioning valve and then closing the vent valve opened by the operator. This would have stopped the air venting, which l
he was concemed about, without the need to close an unlabeled valve. The FLM last attended STAR training in February 1996. Additionally, STAR is included in general employee traimng, j
l which is required for all employees every two years.
The second root cause relates to the FLM's failure to listen to the operators and gain a clear understanding of the problem. He stated that he did not hear the operator say that he had opened 1
the valve during the initial phone communication. He also failed to adequately assess the l
situation when the operator explained to the FLM face-to-face what had happened and the action taken at the R-114 station. This failure to gain a clear understanding of what had happened, led him to conclude that he was in a emergency situation requiring other immediate action.
1 The third root cause relates to the FLM's lack of knowledge of the air system configuration at the R-114 station. The FLM thought the unlabeled valve he ordered closed would only isolate the plant air supply from the R-114 station; when, in fact, the 2-inch valve that malfunctioned was the valve designed to isolate the air system from the R-114 system. The FLM has been trained on the plant air system and has had a great deal of experience related to the building air system during his seven years as an operator and two years as an FLM. The investigation team feels this lack of knowledge could have been overcome by application of the STAR concept.
The fourth root cause relates to the failure to properly label or tag the 3-inch plant air valve serving Unit 2. The two air supply valves to "AK" and "Y" CAAS clusters and the air valves to the two building air horns were being controlled by removal of the isolation valve handwheels and application of tags stating that the closure of these valves would impact the operability of l
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Dock.et No. 70-7001 GDP 98-1052 Page 4 of 5 CAAS. The 3-inch plant air valve serving all of Unit 2, including these other air supplies, was not labeled or caution tagged.
i CONTRIBUTING CAUSES A contributing cause relates to the fact that the R-114 rupture disc and relief valves were replaced in May 1996 to raise the system relief pressure from 80 psig to 140 psig and the C-337 operators involved could not recall being informed of the change.
This caused the operators to think that, as in the past years, the plant air system, which operates at approximately 90 psig, could over-pressurize the R-114 system. Had the operators been aware of this change, they would have realized that the malfunctioning valve would not cause system over-pressurization and that immediate action to stop the pressure rise was not necessary. The operator at the R-114 station, at the time the valve malfunctioned, was last trained on the R-114 system in November 1995 and the FLM attended this training in February 1996, both prior to the system modification.
1 The Engineering modification package included documentation that the change was communicated to cascade operations management, as required. Operations management communicated the change to their personnel via a procedure change and required reading. The subject operator and FLM signed as reading and understanding the procedure change. Thus, the operators lack of knowledge is not related to a breakdown in the management system.
CORRECTIVE ACTIONS A. Corrective Actions Taken
- 1. This event was discussed in the shift briefing with the FLMs on all four shifts. The STAR policy was discussed in the session.
B. Corrective Actions Planned
- 1. By September 1,1998, the STAR training module will be incorporated into the cascade Operations Training Development and Administrative Guide for annual refresher training.
- 2. By October 30,1998, visual aids will be posted throughout the plant to emphasize the STAR concept.
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Docket No. 70-7001 l
GDP 98-1052 l
Page 5 of 5 i
- 3. By August 5,1998, unit plant air header valves that supply air to CAAS horns will be labeled for C-331, C-333, C-335, and C-337.
- 4. By July 30,1998, the modification of the R-114 system rupture disc from 80 psig to 140 psig will be communicated to cascade personnel, via required reading.
- 5. By July 30,1998, training module 601.ll.0le, " Operation of the R-il4 Pump," will be j
revised to state that the R-114 system rupture disc pressure setting is 140 psig.
I EXTENT EXPOSURE OF INDIVIDUALS TO RADI ATION OR RADIOACTIVE M ATERI ALS There was no release of radioactive material er c.xposures to radiation during this event.
LESSONS LEARNED Personnel must stop, think and fully assess abnor nnl situations before taking action.
i Communication between personnel must be clear and understood before taking action.
Modifications to plant equipment must be communicated to plant personnel.
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i Docket No. 70-7001 GDP 98-1052 Page1 ofI l
List of Commitments Event Report ER-98-18 l
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- 1. By September 1,1998, the STAR training module will be incorporated into the cascade Operations Training Development and Administrative Guide for annual refresher training.
- 2. By October 30,1998, visual aids will be posted throughout the plant to emphasize the STAR concept.
- 3. By August 5,1998, unit plant air header valves that supply air to CAAS horns will be labeled for C-331, C-333, C-335, and C-337.
- 4. By July 30,1998, the modification of the R-114 system rupture disc from 80 psig to 140 psig will be communicated to cascade personnel, via required reading.
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- 5. By July 30,1998, training module 601.11.01e," Operation of the R-114 Pump," will be revised to state that the R-114 system rupture disc pressure setting is 140 psig.
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