ML20216C215
| ML20216C215 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 02/27/1998 |
| From: | Polston S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-98-1015, NUDOCS 9803130333 | |
| Download: ML20216C215 (3) | |
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W USEC A ciob.i en.rry comp.ny February 27,1998 GDP 98-1015 United States Nuclear Regulatory Commission Attention: Document Control Desk
'Vashington, DC 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001 Event Report ER-98-04 Pursuant to SAR, Section 6.9, Table 1, Criteria J.2, enclosed is the required 30-day written Event Report covering the actuation of the autoclave position 2 East, steam pressure control safety system in Building C-337-A. The Nuclear Regulatory Commission (NRC) was notified of the event on February 2,1998 (NRC No. 33637). The evaluating / troubleshooting is continuing to determine the root cause for the actuation. A revised report is targeted to be submitted by March 27,1998.
Any questions regarding this matter should be directed to Larry Jackson at (502) 441 6796.
1 Sincerely, f
to *e Polsto General Manager Paducah Gaseous Diffusion Plant Enclosure cc:
NRC Region III Office NRC Resident Inspector-PGDP
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9803130333 980227 PDR ADOCK 07007001 C
(({h k k kk, P.O. Box 1410 Paducah, KY 42001 Telephone 502-4415803 Fax 502-4415801 hnp://www.usec.com Offices in Livermore, CA Paducal., KY Portsmouth, OH Washington, DC MAR a9 d
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Docket No. 70-7001 GDP 98-1015 Page 1 of 2 EVENT REPORT ER-98-04 DESCRIPTION OF EVENT i
On January 22,1998, autoclave position 2 East, Building C-337-A was uc;i.tred cperational after
-l previously being declared inoperable on January 12,1998, because of a pressure control loop i
malfunctiori. Prior to being declared operational, the 6-pin connector and in-line amplifier at the i
P-515 pressure transducer were replaced and post-maintenance testing successfully completed. On February 1,1998, at 1920 the autoclave steam pressure alarm on position 2 East, Building C-337-A was received in the Operations Monitoring Room (OMRj when the autoclave steam pressure went to approximately 7 psig. The primary and secondary steam controllers were on automatic; the st:am pressure digital reading was found reading -3.75 psig on the steam controller; the strip chart recorder was approximately 6.75 psig; and the control valve was fully open. The operators initiated immediate actions according to procedures CP4-CO-AR8337A and CP4-CO-CN3038. At 1950, the Plant Shift Superintendent (PSS) declared the system inoperable. At 2015 hours0.0233 days <br />0.56 hours <br />0.00333 weeks <br />7.667075e-4 months <br />, the cylinder valve was closed, purged, the pigtail was disconnected after jetting and opening the autoclave, and autoclave position 2 East was removed from service (Mode 2). Due to malfunction of steam pressure / temperature control loop instrumentation, the steam pressure in the auteclave had increased to the alarm set-point (approximately 7 psig) and actuated the steam pressure control safety system.
On February 2,1998, at 0736, the Nuclear Regulatory Commission (NRC) Headquarters Operations j
office was notified of the event in accordance with SAR, Section 6.9, Table 1, Criteria J.2 (see NRC I
No. 33637).
An event investigation team was formed to determine the root cause for the steam pressure control
'i safety system actuation. The strip chart on autoclave position 2 East was evaluated. This chart i
records the autoclave pressure, cylinder pressure, and autoclave temperature. Prior to the event the steam pressure controller was controlling the steam within acceptable limits. The chart indicated that the pressure in the autoclave rose to the pressure set-point (approximately 7 psig), at which time -
the steam pressure control safety system was actuated. The steam pressure control safety system closed the steam isolation valves and the thermovent block valve, and placed the autoclave in a safe condition.
On February 3,1998, troubleshooting was initiated to determine the cause of the safety system actuation._ The P-514 and P-515 pressure loops were evaluated to determine the probable cause for g
_ the differences between the strip chart (P-514) and digital (P-515) steam pressure controller readings.
The position 2 East, in-line amplifier and transducer were removed for testing in the Instrument Maintenance' shop. The in-line amplifier tested satisfactorily. A shert was discovered in the signal
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l Docket No. 70-7001' GDP 98-10lS.
Page 2 of 2 l
wiring from the_ transducer to the amplifier. The short disappeared when the cable was disconnected from the transducer which indicates that the short existed in the transducer; however, the transducer successfully passed a pressure test, as well as a heat test up to 220 degrees. The electrical wire -
connecting the in-line amplifier and the transducer successfully meggered.
On February 6,1998, the transducer was returned after consultations with the manufacturer (Sensotec) for destructive analysis and additional testing. On March 2,1998, Sensotec will visit the plant site to present the results of their analysis and testirig. Additionally, Sensotec will examine.
existing transducer installations to determine whether installation problems exist.
1 On February 19, b98, a transducer similar to the one that is suspected to have failed in autoclave
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position 2 East was subjected to additional testing in the Instrument Maintenance shop. The tests
-- performed were to determine how hot the transducers get when they are soldered into copper tubing.
- A thermal imaging camera was utilized to record the effect of the heat on the transducer and to determine whether the interior of the transducer is adversely affected because ofintense heat. Initial results indicate that the internal temperature of the pressure transducer could exceed 400 degrees -
when fittings are being brazed if " hot sink" compound, or other precautions are not taken to shield the heat from the transducer. The possibility exists that high temperatures could have adversely affected the wiring and connections located inside the transducer. Additional analyses of the information are being conducted to determine the effects of the extreme temperature on the transducer.
The pressure transducer was installed as part of the Instrument Upgrade Project and has been in service since October 1997.
On February 11,1998, after replacing the F 015 pressure transducer, autoclave position 2 East was declared operational by the PSS subsequent to successfully completing post-maintenance testing.
CAUSE O' F EVENT A. Direct Cause i
Because the manufacturer of the transducer (Sensotec) has not completed an analyses of the suspect
_ part and the conclusions as a result of the application of heat to the transducer in the Instrument Maintenance shop has not been developed, the cause for the safety system actuation has not been determined.' Therefore, additional investigation is required to determine the root cause for the event.
The target date for submission of a revised report is March 27,1998.
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