ML20195B911
| ML20195B911 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 05/28/1999 |
| From: | Pulley H UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-99-1017, NUDOCS 9906030209 | |
| Download: ML20195B911 (5) | |
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!e CSEC A Global Energy Company May 28,1999 GDP 99-1017 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001 Event Report ER-99-08 Pursuant to Safety Analysis Report (SAR), Section 6.9, Table 1 Criteria J.2, enclosed is the required 30-day written event report pertaining to the actuation of the water inventory control system (WICS), Building C-337-A. The Nuclear Regulatory Commission IIeadquarters (NRC-IIQ) operations office was notified of the event on May 7,1999 (NRC No. 35692). 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, A
K oward Pulley General Manager Paducah Gaseous Diffusion Plant
Enclosures:
As Stated cc: NRC Region III Office NRC Resident Inspector - PGDP f
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P.O. Ikix 1410, Paducah, KY 42001 Telephone 502-441-5803 Fax 502-441-3801 hnp://www.usec.com Omces in 1.ivermore, CA Paducah, KY Portsmouth, Oli Washington, DC
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s Docket 70-7001 GDP 99-1017 Page1of3 EVENT REPORT ER-99-08 DESCRIPTION OF EVENT On May 7,1999, at approximately 1345 hrs., a high primary condensate audible and visual water inventory control system (WICS) alarm was received in the Opciat ens Monitoring Room (OMR) fhr autoclave position 1 East, Building C-337-A. The autedave was operating in Mode 5 (heating) for approximately 55 minutes prior to the WICS alarm. The operators responded according to applicabie procedures; jetted and opened the autoclave; and placed the autoclave into a safe condition. All safety systems performed as designed. At approximately 1435 hrs., the Plant Shift Superintendent (PSS) declared the system inoperable. On May 7,1999, at 2207 hrs., the Nuclear
. Regulatory Commission Headquarters (NRC-IIQ) operations office was notified of the event in accordance with Safety Analysis Report (SAR), Section 6.9, Table 1 Criteria J.2 (NRC No.
35692).
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'Imubleshooting revealed that the steam controller settings, specifically the proportional band (PB),
was set at a value higher than the steam control system required. The PB is an adjustment on the steam controller, which is specific for each individual autoclave and controls the reaction rate of the steam control valve. With the steam control proportional band at a high value, the steam control valve manufactured by Masoneilan, CamFlex Valve (model no. 35-35212), reacted to commands in a sluggish manner compared to normal valve operations. As a result, the steam supply could not i
enter the autoclave rapid enough to meet the demand for heat from the cylinder located inside the autoclave. At the point where the cylinder is transitioning through the triple point (phase change of UF from solid to gas and liquid), the cylinder demanded a greater heat (steam) load, which 6
produced copious amounts of condensate. A feature of the condensate system is the steam pressure assists in expelling condensate out of the autoclave. In this instance, the sluggish steam control valve did not allow steam to enter the autoclave rapidly enough to force the condensate out of the drain, while keeping up with the heat (steam) demand of the cylinder; therefore, the condensate lost some ofits motive force to drain. When this occurs, a WICS alarm actuates.
Each autoclave has its own PB setting that must be determined by fine tuning until the steam control valve is under control and produces the autoclave steam pressure and temperature desired.
Slight changes over time as a result of normal autoclave operation, such as degradation of steam control components, will change the reactiveness of the system. The PB settings for the controller do not perform a safety function.
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t Docket 70-7001 GDP 99-1017 Page 2 of 3 On May 13,1999, after successfully testing the operability of the WICS; adjusting the steam controller settings (proportional band adjustment); and determining that there were no degradations of the autoclave's components, the autoclave was declared operational.
The safety significance of this event is considered negligible because the safety systems performed as designed.
CAUSE FOR THE EVENT A. Direct Cause The direct cause for this event was the steam controller PB settings were higher than desired.
The higher settings caused the steam control valve to react slower to demands for heat, thereby allowing steam condensate build-up.
B. Root Cause The root cause for this event was lack of a preventative maintenance (PM) program designed to evaluate autoclave proportional band settings. Although this event is an isolated occurrence, a PM program will reduce the possibility far recurrence involving other autoclaves.
CORRECTIVE ACTIONS A. Completed Corrective Actions
- 1. On May 13,1999, the steam controller settings on autoclave position 1 East were adjusted and results reviewed to ensure a more rapid steam control valve response to demands for steam.
B. Planned Corrective Actions
- 1. By June 25,1999, Engineering will establish preventative maintenance (PM) to periodically examine and adjust, if necessary, the feed and sample autoclave steam control valve proportional band control.
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l Docket 70-7001 GDP 99-1017 J
l Page 3 of 3 EXTENT OF EXPOSlJRE OF INDIVID11AI,S TO RADIATION OR RADIOACTIVE MATERIAL None LESSONS LEARNED 4
Non-safety operational settings, if not set to optimum conditions, may impact operations by challenging safety systems.
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J Docket 70-7001 GDP 99-1017 Page1of1 List of Commitments Event Report ER-99-08
- 1. Ily June 25,1999, Engineering will establish pt fentative maintemince (PM) to periodically examine and adjust, if necessary, the feed and sample autoclave steam control valve proportional band control.
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