ML20198J600
| ML20198J600 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 10/15/1997 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-1037, NUDOCS 9710210160 | |
| Download: ML20198J600 (5) | |
Text
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Padwah Ltc ok P.o Ik>n 1410 Padwah. KY 42001 Tet $02 4415803 I at: 502 441 5801 October 15,1997 United States Nuclear Regulatory Commission SERIAL: GDP 971037 Attention: Document Control Desk Washington, DC 20555-0001 Paducah Gaseous DifTusion Plant (PGDP)- Docket No. 70-7001 - Revision I to Event Report ER-97-14 During a review of NRC Event Report ER 97-14 (NRC No. 32627) issued to the Commission on August 7,1997, we have discovered an incorrect procedure reference and number which we want to bring to your attention. Under Corrective Actions Planned in Enclosures 1 and 2, Action No.
2 incit. des a reference to a problem reporting sy': tem procedure, UE2 IIR-Ci1040. This reference and number is incorrect.
The action statement has been corrected in the attached revised event report to read:
"By October 15,1997, the Corrective Action Process Procedure, UE2-HR-CIl031, will be revised to require an evaluation of generic implications for equipment related issues."
Should you have questions concerning this issue, please contact Bill Sykes at (502) 441-6796.
Sincerely, Steve Polston V
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General Manager Paducah Gaseous L)iffusion Plant Attachments SP:WES:MLB: mig cc:
NR. Region 111 NRC Senior Resident inspector, PGDP 9710210160 971015
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PDR ADOCK 07007001 C
- Docket No. 70 7001 -
Page1of3 Event Report ER-97-14 Rev.1 DACKGROUND The C-360 sampling and transfer facility heats UF. p.roduct feed cylinders in steam autoclaves.
These autoclaves are equipped with an autoclave steam pressure control (ASPC) safety system described in SAR Section 3.6.7.4. This safety system is used to stop the steam flow to the autoclave while heating a cylinder prior to reaching pressures which could result in reaching the maximum allowable working pressure of the cylinder. The ASPC system closes the steam isolation valves and sounds an alarm if the autoclave steam pressure reaches tne set point of a maximum of 8 psig. This is accomplished by a pressure transmitter which actuates a pressure switch and a redundant direct tied pressure switch which trips if the autoclave pressure reaches the set pressure (currently 7 psig). The switches send signals, via the associated relays, to de-energize the solenoid valves which supply air for the air powered stenm isolation valves, thereby isolating the steam supply.
DESCRIPTION OF EVENT On July 14,1997, at 1920, C-360 facility operators began heating (Mode 5) a 14-ton UF. feed cylinder in autoclave No.1. At approximately 1930, they noticed that the steam pressure indicator was not responding normally and was showing an autoclave steam pressure of 4 psig, and not increasing. Aller consulting with the front-line manager, a decision was made to stop the heat cycle to investigate the pressure indicator problem.
As they were beginning to interrupt the heat cycle, an automatic ASPC safety system actuation occurred. The operators then initiated steps to remose the autoclave from service, pending investigation. This automatic safety system actuation was reported to the NRC operations office at 0922 CDT on July 15,1997, and NRC Event 32627 was assigned. No UF release occurred and no adverse safety consequence resulted from this event.
DESCRIPTION OF CAUSE An inspection of the autoclave pressure control instrumentation components revealed that a short piece of flexible plastic tubing located inside the strip chart recorder pressure to current transducer (PY-115 A) had deteriorated and ruptured. The subject transducer is a Rochester Instrument Systems Model No. SC5410. When the tubing burst, all signal air to the steam pressure transmitter (PT-115A) loop was vented resulting in an input pressure of 0 psig. The pressure input to autoclave temperature control transducer relayed this O psig pressure signal to the temperature controller (TIC-117). In turn TIC-117, signaled the temperature control valve (TCV-117) to open fully. Without a valid signal to close or control steam flow, TCV-117 remained fully open until the ASPC safety system actuated as designed at the 7 psig set-point.
Docket No. 70 7001 Page 2 of 3 This caused an alarm and isolated the steam supply from the autoclave by closing steam isolation valves XV-153 and FV-105. All safety system components opersted as designed to place the autoclave in a safe configuration. The subject transducer (PY-1ISA) is not within the "Q" safety system boundary. The failure of the short piece of flexible tubing has been attributed to hardening and embrittlement, due to age. This pressure transducer (PY-115A) was most likely installed in the 1980 time-frame. The manufacturer (Rochester) was consulted and stated, even though they do not recommend any preventive maintenance (PM) relative to this flexible tube, most users inspect and, when needed, replace this tubing. No PM task existed for this component at the time of this event. This type of transducer is only used in C-360, and not at the C-333-A or C-337-A feed vaporizer facilities.
The C-360 facility maintenance personnel indicated that two similar failures had occurred in the 1992 time-frame. These failures occurred during system calibration and testing and did not cause safety system actuations. The flexible tubes were replaced on the affected ir.struments, but no action was taken to inspect or replace the tubes on the other ten Rochester SC5410 transducers in service in C-360. There are three of these transducers on each of the four C-360 autoclaves.
At the time these failures occurred (1992), there was not a management system in place to capture this type of condition and ensure that appropriate generic actions would be implemented, i.e., replace the flexible tubes on all of the other similar transducers and create a PM task for the periodic inspection of this tube and replacement as necessary.
In April 1995, the Problem Reporting system was implemented to document this type of condition and ensure appropriate corrective actions are implemented to prevent recurrence. To further strengthen this process, a revision to the problem reporting procedure is underway to require an evaluation of generic implications to other similar components, or system and development of corrective actions to address the results of the evaluation.
Additionally, actions are underway to develop a component failure analysis and trending procedure and process. The procedure (CP2-EG-EG1039) is scheduled to be issued by August 15,1997. This progra a will cause " Component Failure Reports" to be created in addition to problem reports. The component failure reports will be used to initiate a causal analysis; an evaluation of current PM requirements and effectiveness for possible change or upgrade as necessary; tracking of component failures to enable the site to trend repeat failures; and reviews of vendor component failure reports among other related evaluations. The plant Reliability Engineering group will be responsible for the management of this process.
DIRECT CAUSE The c.utomctic actuation of the autoclave steam pressure isolation system resulted from the rupture of a llexible plastic tube located inside the pressure to current transducer (PY-115A), due l
to age.
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< Docket No. 70 7001-Page 3 cf 3 ROOT CAUSE The root cause is attributed to the lack of a management system to documeat component failures for failure analysis and development of corrective actions to ensure that the generic implications of the component problem are evaluated. The problem reporting and component failure analysis program will provide this management system.
CONTRIBUTING CAUSE The lack of a preventive maintenance task to inspect and replace, when required, the flexible plastic tube inside the pressure to current transducer (PY-115A) allowed the tubing to deteriorate over the years and eventually rupture.
CORRECTIVE ACTIONS PLANNED 1, By September 30,1997, issue and implement the component failure analysis and trending procedure (CP2-EG-EG1039).
- 2. 13y Octoberf15f1997, the Corrective Action Process Procedure, UE241R-CIl031pvill be reyised to require an evaluation;of generic implications for equipment related issues.
- 3. By September 15,1997, Engineering will develop and provide to Operations the PM inspection / replacement criteria related to the flexible plastic tube inside all C-360 Rochester SC5410 transducers.
- 4. By September 30,1997, Operations will issue a PM task request to conduct the inspection of the C-360 Rochester SC5410 transducers, per the criteria developed by Engineering (reference Action No. 3 of this report).
- 5. By October 31,1997, the flexible tubing inside the C-360 Rochester SC5410 transducers will be nplaced with tubing specified by Engineering.
LESSONS I EARNED Component failures which impact safety related equipment must be documented and analyzed for potential generic implications to other similar components.
EXTENT OF EXPOSURE OF INDIVIDUALS TO RADIOACTIVE MATERIAL S None
I 4'
l Docket 70-7001 Atta:lunent 2 Page1of1 ER 97-14 List of Commitments CORRECTIVE ACTIONS PLANNED
- 1. By September 30,1997, issue and implement the component failure analysis and trending procedure (CP2-EG-E01039).
- 2. By October.15s 1997, the Corrective Action Process ProgedurelUE2 HR-C11031Dvill be revised to require an evaluati,on of generic. implications for equipment related issues.
- 3. By September 15,1997, Engineering will develop and provide to Operations the PM inspection / replacement criteria related to the flexible plastic tube inside all C-360 Rochester SC5410 transducers.
- 4. By September 30,1997, Operations will issue a PM task request to conduct the inspection of the C-360 Rochester SC5410 transducers, per the criteria developed by Engineering (reference Action No. 3 of this report).
- 5. By October 31,1997, the flexible tubing inside the C-360 Rochester SC5410 transducers will be replaced with tubing specified by Engineering.
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