ML20199A154
| ML20199A154 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 11/05/1997 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-97-1038, NUDOCS 9711170076 | |
| Download: ML20199A154 (6) | |
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Ist $f'2 4414kOl November 5,1997 United States Nuclear Regulatory Commission SERIAL: GDP 971038 Attention: Document Control Desk Washington, DC 20555-0001 Paducah Gaseous Diffusion Plant (PGDP). Docket No. 70-7001 Event Report ER 97-16 Pursuant to 10 CFR 76.120(d)(2), attached is the required 30-day written report for the actuations of the Autoclave Steam Pressure Control System in C 333 A. 'This was initially reported on October 7,1997 (NRC No. 33039). Attachment 2 is a list of commitments made in this report Should you require further information on this subject, please contact Bill Sykes at (502) 441 6796.
Sincerely, I
l'M St '
Iston j
General Manager Paducah Gaseous Di!Tusion Plant SP:WES:MLB:mel Attachments (2) cc:
NRC Region 111 NRC Senior Resident inspector, PGDP t
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Docket No. 70 7001 Attachment,1-Page 1 of 4 Event Report ER 9716 BACKGROUND The autoclaves in the C-333A facility are used to steam heat cylinders of UF. In order to feed
-the UF. to the cascade. The autoclave also provides containment around the cylinder in the event of a release of UP. from the cylinder or cylinder connections during the feeding of the cylinder, Steam pressure within the autoclave $s limited by the autoclave steam pressure
~ control system which is required by Technical Safety Requirement (TSR) Limiting Condition of Operation (LCO) 2.2.3.3. By controlling the steam pressure, the steam temperature is
. limited to a maximum of 235'F for Category A cylinders and 230*F for Category B cylinders. (Cylindeu are categorized by the amount of UP. they contain compared to the fill limits.) This also pro.' ides an indirect means of. ontrolling the temperature of the cylinder below the safety limitw This, in turn, limits not only the UF. vapor pressure within the cylinder, but also the volume (density) of liquid UF., preventing loss of ullage and over-pressurization. According to the Safety Analysis Report (SAR) Section 3.2.5.3, if the autoclave pressure reaches 8 psig, the steam pressure control system closes the steam isolation
. valves and the thermovent line block valve and sounds an alarm. To meet this SAR requirement, the set-point for activation of the steam pressure control system is currently set at
-7 psig for Category A cylinders.
DESCRIPTION OF EVENT On October 6,1997, at approximately 1654, operators placed six in-service autoclaves into containment in response to a small UF. leak on Autoclave 3 South in C-333A. After mitigating the release, Autoclaves 2 North,2 South,3 North,4 North, and 4 South were returned to service after ensuring ' valve clarity in accordance with TSR LCO 2.2.4.11.
Autoclaves 2 South and 4 South were returned to service first with the feed cycle being reestablished at approximately 2030. Steam heating was reinitiated on Autoclave 4 North at approximately 2038 and on Autoclave 2 North at approximately 2040. At approximately
- 2045, the steam pressure control system on Autoclave 4 North actuated. Steam heating was initiated on Autoclave 3 North at approximately 2105. At approximately 2110, the steam pressure control system on Autoclave 3 North actuated.
The system engineer investigated the actuations to determine cause as required by alarm
. response procedure CP4-CO-AR8333A-13, "High Autoclave Steam Pressure." The system engineer determined that the autoclave systems were functioning properly and had actuated
- from a valid signal indicating a high steam condition (autoclave pressure :t7 psig). Since the
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Docket No. 70-7001 Page 2 of 4 equipment functioned properly during troubleshooting, the high steam condition was believed.
to have been the result of incorrect operator actions while returning the system to service.
After ensuring valve clarity in accordance with TSR LCO 2.2.4.11, cylinder heating was resumed _ on positions 4 North and 3 North at approximately 2345 and 2400, respectively. On October 7,1997 NRC was notified of the actuations of the Autoclave Steam Pressure Control System according to SAR Section 6.9, Table 6.91, Criteria J.2. (Reference NRC Worksheet 33039)-
An investigation team was formed to determine the root cause of the actuations of the steam.
pressure control system on Autoclaves 4 North and 3 North. All strip charts associated with the C-333A autoclaves which were being returned to service were evaluated. These charts
- record the autoclave pressure, the cylinder pressure, and the cylinder temperature. Both the 4 North and the 3 North charts indicated that the pressure of the autoclave had rapidly risen to the set point of 7 psig, at which time the steam pressure control system actuated shutting off the steam to the autoclave. A review of the strip chart showing the heat cycles on 4 North, which occurred prior to the event, indicated that the steam controller was controlling the steam within acceptable limits up to the time of the event. Prior to the event,3 North had undergone an instrument upgrade. Parameters associated with the upgrade were reviewed and found to be correct. A review of the steam controller inputs indicated that they were within tolerance limits. The P-515 and P 514 pressure loops were evaluated and appeared to be operating properly. Since steam was being applied to multiple autoclaves in a short period of time the
- steam supply was evaluated for adequacy and determined to be adequate and not a cause of the
- event, in summary, no equipment problems were found that would have caused the event. A review of problem reports and previous events involvP3 actuations of the steam pressure control system indicate previous actuations have been caused by either (1) faulty components; (2) having the steam controller set on manual but not set to 0.0 when the steam is turned on; or (3) setting the steam controller on automatic before the steam is turned on. Both of the last two scenarios would be incorrectly following the procedure for startup of an autoclave. The autoclave startup procedures require the steam controller to be set on manual and set on 0.0; then the steam to be valved on; and then the steam controller to be set to automatic. The accuracy and order of these steps is critical in preventing a steam pressure control system -
actuation. - Under normal operation, this startup process is covered under CP4-CO-CN2045a,
" Operation of the C-333A and C-337A Vaporizer Facilities." Under off-normal conditions, this procedure is supplemented by CP4 CO-ON3038, "C-333A/337A Interrupted Heat Cycle."
Both procedures are in hand procedures, f 0perators and front line managers who were involved were interviewed and indicated that the
. steps to place the steam on the autoclaves were completed in the proper order. However,
Docket No. 70 7001 Atta,chment 1 Page 3 of 4 following the placing of steam on the autoclaves, the off normal procedure requires the operator to closely monitor, from the OMR, the rise in steam pressure for approximately 15 minutes to ensure the pressure does not exceed 7.0 psig. This step of the procedure was not completed for either Autoclave 4 North or Autoclave 3 North.
CAUSES OF EVENT A. Direct Cause The initiator of the high pressure steam could not be conclusively determined.
B.
Root Cause The root cause of this event is failure to follow procedures. The in-hand off-normal procedure, "C-333A/C-337A Interrupted lleat Cycle," Step 3.32, requires the steam pressure to be closely monitored in the OMR for approximately 15 minutes to ensure the autoclave pressure does not exceed 7.0 psig. Ilowever, Operations personnel did not continue to monitor the steam pressure rise after setting the controller to automatic.
Although this did not cause the rise in steam pressure, it was a missed opportunity to possibly prevent the event by valving off the steam as the pressure abnormally increased.
Another area of concern is that there may have been inadequate command and control of the evolutions which occurred in restoring steam to multiple autoclaves.
The failure to follow the in-hand procedure in a " read a step /do a step" manner will be addressed in Corrective Action No. I as the Operations UF. Ilandling manager reemphasizes expectations for use of in-hand procedures with all UF. Ilandling ficat line managers. Additionally, Operations will conduct a crew briefing with all applicable Operations personnel to discuss the event and to define management's expectations on command and control related to multiple evolutions and strict adherence on use of proccdures. Corrective Action No. 3 will conduct job observations with all shifts in C-333 A to ensure expectations for use of in-hand procedures are met. The installation of the vaporizer PLC/ computer interface for data collec' ion will allow detailed reconstruction of vaporizer events. Corrective Action No. 4 will determine the relative priority of this project compared to other Operations projects.
CORRECTIVE ACTIONS 1.
By November 26,1997, the Operations UF.11andling manager will reemphasize expectations for use of in-hand procedures with all UF. l{andling front line managers.
Docket No. 70-7001 Attachmen; 1 Page 4 of 4 2.
By November 26,1997, Operations will conduct crew briefings with all applicable Operations personnel to discuss the event (ER 97-16) and to define management's expectations related to command and control and adherence to procedures.
3.
By January 29,1998 Operations will conduct job observations on each shift in C-333A to ensure expectations for use of in-hand procedures are being met.
4.
By January 29,1998. Operations will evaluate priorities rel:ted to the installation of the PLC/ computer interface for the vaporizers which will provide detailed data for event reconstruction.
EXTENT OF EXPOSURE OF INDIVIDUALS TO RADIATION OR TO RADIOACTIVE MATERIAI_S No exposure to radiatitu or to radioactive materials occurred related to the actuation of the steam pressure control system.
i FSSONS LEARNED Important information should be captured either through a timely event critique and/or monitoring systems that record system parameters and component operation, in-hand procedures must be used in n " read a step /do a step" manner. Adequate command and control must be established over the evolution of operations in restoring multiple systems.
Docket No. 70-7001.
- Page1of1, K
List of Commitments 1.
By November 26,1997, the Operations UF. Handling manager will reemphasize expectations for use of in-hand procedures with all UF. Handling front line managsrs.
A 2.
By Noveinber 26,1997, Operations will conduct crew briefings with all applicable j
Operations personnel to discuss the event (ER-97-16) and to define management's expec*.ations related to command and control and adherence to procedures.
- 3.
By January 29,1998, Operations will conduct job observations on each shift in C-333A to ensure expectations for use of in-hand procedures are being met.
4.
By January 29,1998, Operations will evaluate p-iorities related to the installation of the PLC/ computer interface for the vaporizers which will provide detailed data for event
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reconstruction.
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