ML20202F209
| ML20202F209 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 02/11/1998 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1007, NUDOCS 9802190151 | |
| Download: ML20202F209 (3) | |
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r s CEEC A Global Energy Company February 11,1998 U iited States Nuclear Regulatory Commission SERIAL: GDP 981007 Attention: Document Control Desk Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)- Docket No. 70-7001 - Event Report ER-98-01 Pursuant to SAR Section 6,9, Table 1, Criteria J.2, attached is the required 30-day Event Report covering the actuation of the autoclave 2 East steam pressure control safety system in Building C-337-A. The Nuclear Regulatory Commission (NRC) was notified of the event on January 13, 1998 (NRC No. 33521). The evaluating / troubleshooting is continuing to determine the root cause of the actuation. A revised report is targeted to be submitted by March 20,1998, Should you require further information on this subject, please contact Larry Jackson at (502) 441-6796, Sincerely, 4M Steve Polston 9802190151 980211 General Manager gm 0700k Paducah Gaseous Diffusien Plant
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NRC Region III ll ll ll llllll llll NRC Senior Resident Inspector, PGDP i=.o a.-
P.O. Box 1410, Paducah, KY 42001 Telephone 502-441-5803 Fax 502-441-5801 http://www.usec.com OfTices in Livermore, CA Paducah, KY Portsmouth, OH Washington, DC
Docket No. 70 7001 Attachment'l Page1of2 l
i EVENT RFPORT ER 98 01 DESCRIPTION OF EVENT On January 12,1998, autoclave position 2 East, Building C 337 A, was being returned to
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operation atter previously being declared inoperable on January 2,1998, because of a limit 1
switch failure on the head to shell closure. Following the maintenance work to repair the limit switch, a successful rost maintenance test was conducted. On January 12,1998, at 1508, the Plant Shin Superintendent (PSS) declared autoclave position 2 East operational. At 1705, steam was placed into the autoclave and at 1710, the steam controller in the Operations Monitoring Roo r (OMR) went to approximately 7 psig and an autoclave steam pressure alann was received.
The primary and secondary steam controllers were on automatic; the steam pressure digital reading was 4,75 psig on the steam controller; the strip chart recorder was approximately 6.5 psig; and i control velve was fully opcn. The operators initiated inunediate actions according to procedures CP4 CO AR8337A and CP4 CO CN3038. M 1755, the cylinder valve was closed, purged and the pigtail was disconnected afterjetti.. and opening the autoclave. At 1825, autoclave position 2 East was removed from serv!ce (Mode 2). Due to a malfunction of the -
stea n pressure / temperature control loop instrumentation, the steam pressure in the autoclave had increased to the alann set point (6.5 7.5 psig) and actuated the steam pressure control safety
'ystem, as designed. All safety system components perfonned as designed to place the e.utoclave M a safe condition. On January 13,1998, at 0325 the Nuclear Regulatory Commission (NRC) licadquaners Operations office was notified of this event in accordance wia SAR Section 6.9, Table 1, Criteria J.2.
- An event investigation team was fonned to determine the root cause for the steam pressure control safety system actuation. The strip chart for autoclave position 2 East was evaluated.
This chart records the autoclave pressure, cylinder pressure and autoclave temperature. Prior to the event, the steam pressure controller was controlling the steam withir. acceptable limits. The chart indicated that the pressure in the autoclave rose to the pressure set point, at which time the steam pres::ure control safety system was actuated. The steam pressure control safety system closed the steam isolation valves and the thermoveut block valve.
On January 13,1998, troubleshooting was initiated to detemiine the cause of the safety system actuation. The P 514 and P 515 pressure loops were evaluated to determine the probable cause
- for the ditTerences between the strip chart (P-514) and digital (p 515) steam pressure controller readings. It was initially believed that the cause of the pressure control safety system actuation was due to a pressure control loop malfunction (See NRC No. 33521). The safety system s-w yn, - - <.,,, -
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Docket No. 70 7001 Attachment'l l
Page 2 0f 2 actuation may have been the result of the failure of the P 515 autoclaw presswe instrument loop, speellically an elect.ical short existed in the 6 pin "Souriau" model 85 bo6At 0 6S50, connector at the P 515 pressure transducer. When an electrical short occurred o.. the P 515 loop, the signal which was created was sent to the steam controller. The r. team controller saw the signal as a low pressure input, which is the signal to indicate a demand for steam. Steam was added to the autoclavet however, the electrical short did not allow the signal to change. Thus, the autoclaec prenured up to the autoclave steam pressure control safety system actuation set point of approximately 7 psig.
T On January 22,1998, afler replacing the 6 pin connector and in line amplifier at the P 515 pressure transducer, autoclave position 2 East was declared operational by the PSS subsequent to successfully completing post maintenance testing.
The in line amplifier and 6 pin connector was installed as part of the Instrument Upgrade Project and have been in service since October 1997. No previous electrical short in the connectors has been reported.
On February 1,1998, at 1920 the autoclave steam pressure alarm on position 2 East, Building C 337 A was received in the OMR when the steam pressure went to approximately 6.75 psig.
The primary and secondary controllers were on automatic; the steam pressure digital reading was 3.75 on the steam controller; the strip chart.: corder was approximately 6.75 psig; and the control valve was fully open. The operators initiated actions according to CP4 CO AR8337A and CP4 CO-CN3038. At 1950, the PSS declared the system inoperable. At 2015 the cylinder was closed, purged, and the pigtall was disconnected afterjetting and opening the autoclave.
Due to malfunction of the steam pressure / temperature control iaop instrumentation, the steam pressure in the autoclave had increased to the alarm set point (approximately 7 psig) and actuated the steam pressure centrol safety system. NRC lleadquarters operations oflice was notified of the second event on February 2,1998, at 0736 in accordance with SAR Section 6.9, Table 1, Criteria J.2.
CAUSE OF EVENT A. Direct Cause Because the second event (February 1,1998) occurred prior to the submittal of the 30-day report for the first event (January 12,1998), additional investigation is required to determine if the cause for the two safety system actuations is possibly due to a common failure mode. The target date for submission of a revised report is March 20,1998,
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