ML20205C308
| ML20205C308 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 03/26/1999 |
| From: | Jonathan Brown UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GDP-99-2015, NUDOCS 9904010151 | |
| Download: ML20205C308 (4) | |
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\\ A Global Er rgy Company March 26,1999 GDP 99-2015
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U. S. Nuclear Regulatory Commission f
Attention: Document Control Desk
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Washington, DC 20555-0001 Portsmouth Gaseous liiffusion Plant (PORTS)
Docket No. 70-7002 Event Report 99-04 Pursuant to the Safety Analysis Report Section 6.9, Table 6.9-1, J(2), Enclosure 1 provides the required 30 day Event Report for an event that resulted from the actuation of a Cascade Automatic Data Processing smokehead in the X-330 Tails Area at the Portsmouth Gaseous Diffusion Plant.
There are no new commitments contained in the report.
I Should you require additional information regarding this event, please contact Scott Scholl at (740) 897-2373.
Sincerely, 93 J. Morris Brown Ocneral Manager Portsmouth Gaseous Diffusion Plant
Enclosures:
As Stated
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NRC Region III Office NRC Resident Inspector - PORTS 9904010151 990326
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010002 P.O. Ilox 800, Portsmouth, OH 45661 Telephone 614-897-2255 Fax 614-897-2644 http://www.usec.com Offices in Livermore, CA Paducah, KY Portsmouth, OfI Washington, DC
GDP 99-2015 Pageiof3 Event Report 99-04 Description of Event At 1006 hours0.0116 days <br />0.279 hours <br />0.00166 weeks <br />3.82783e-4 months <br /> on February 24,1999, the Tails mezzanine smokehead SSWE alarm actuated in the X-330 Process Building Area Control Room 2. At 1009 hours0.0117 days <br />0.28 hours <br />0.00167 weeks <br />3.839245e-4 months <br />, the operator assigned to Tails investigated the alarm utilizing appropriate personnel protective equipment (PPE). No smoke was observed, no odors were detected nor were abnormal conditions discovered. Operators evaluating the Cascade Automatic Data Processing (CADP) printouts for smokehead SSWE determined from the voltage drop that an outgassing may have occurred. Operators further investigated the valves inside the heated Tails housing and observed a trace amount of UO F on the stem of valve SBE-16.
2 2 At 1205 hours0.0139 days <br />0.335 hours <br />0.00199 weeks <br />4.585025e-4 months <br />, based on the observed evidence, the smokehead actuation was determined to be a 1
valid Safety System actuation caused by outgassing of the SBE-16 valve. Safety System actuations are reportable in accordance with the Safety Analysis Report (SAR), Section 6.9, Table 6.9-1, J(2).
Just prior to this event, the Tails cylinder located in Tails Withdrawal position #3 had been burped to remove excess light gasses. During routine burping operations, the pressure inside the associated process piping increases from below atmosphere to above atmosphere. When this occurred, a very small leak from valve SBE-16 caused a small outgassing of UF during the pressure transient, which was not detected outside the heated housing, but which actuated the smokehead inside the housing.
Smokeheads SSWB or SSWE had previously actuated three times on February 19,1999. Each time the outgassing was investigated, but evidence of a leak could not be detected. CADP printouts were evaluated and no conclusions could be made to determine whether a leak had occurred. The investigation continued until it was noted that the actuations occurred during burping operations.
On February 22 the piping was leak checked, but again no evidence of a leak was found. Following the actuation on February 24 housing panels were again removed and the piping was re-inspected using mirrors to examine hidden areas behind valves in close quarters. Evidence of a minar outgassing that was not previously visible was found on the SBE-16 valve. The material that outgassed was a small amount ofdepleted UFe t a nominal enrichment of 0.4% U-235. The SBE-16 a
valve is a 1-inch Xomox Tufline plug valve. It is located insidc a heated housing and is not accessible for routine visual inspections.
Cause of Event The direct cause of the CADP actuation was a UF release from the valve stem packing of the SBE-16 valve. P;evious operating experience has indicated that the use of this type of valve in UF6 WithdrawM Station applications can result in small leaks as a result of stem packing wear. In this event, the leak was very minor and could initially be detected only by the highly sensitive CADP smokeheads. Per.;onnel responding to the CADP alarms could not determine if a leak existed until 2
GDP 99-2015 Page 2 of 3 Event Report 99-04 the buildup of UF. reaction products or, the valve stem became sufficient to be visually detectable.
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i The root cause of the outgassing was that the corrective action to replace the Tails valves has not been implemented yet. It had previously been identified that valves incorporating stem packing may
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develop leaks as the stem packing wears. A project was initiated to replace this type of valve with a more durable valve which utilizes a bellows seal. When installed, the bellows seal will reduce the likelihood of minor leakage.
The project to install the bellows sealed valves is part of a long-term project for upgrading all three 4
withdrawal stations. Currently, Tails Withdrawal, the final station in the project, is scheduled for completion by July 1,2001. A review of event reports for the past two years did not reveal any additional instances of Safety System actuations caused by valve stem packing leaks. Considering the low frequency and negligible safety consequences of these valve packing leaks, it was determined that the valve replacement project schedule did not need to be accelerated. Personnel protection when responding to any similar leaks which may occur is assured through the use of PPE.
The potential for minor leaks has been previously recognized and discussed in the SAR. This outgassing of UF was similar to the types ofleaks described in SAR Section 4.1.1.3.1. which states "Small amounte of UF and other toxic materials such as HF, CIF and UO F can be released during 6
3 2 2 sampling operations, seal changes, failure to obtain sufficient cell and piping UF negatives, ruptured copper tubing, and possibly through buffer systems. These releases are prevented primarily by use of engineering and administrative controls. To protect the operator in the unlikely event a release does occur, operating specifications require that personnel performing operations and maintenance, where the possibility of releases exists, wear protective equipment such as an individually fitted gas mask. The releases in these cases may mean that a few grams of UF will escape to the atmosphere.
6 There are no TSR systems,(Safety Systems) to prevent the release of UF while performing these 6
types of operations. Engineering and administrative controls are considered adequate."
Corrective Actions 1.
On March 16,1999, the SBE-16 valve was re-sleeved. The valve was declared operable on March 23,1999, after a successful post-maintenance test.
2.
By July 1,2001, bellows sealed valves will be installed at Tails Withdrawal as part of the Withdrawal Station Improvement Project (Project X-34470).
a GDP 99-2015 Page 3 of 3 Event Report 99-04 Extent of Exposure ofIndividuals to Radiation or Radioactive Materials Data from a continuous air monitor positioned at Tails and IIealth Physics surveys indicate that there was no airborne radioactivity above posting limits for the area.
Lessor.s Learned There were no lessons learned from this event. Operations responded to this event in accordance with plant policies and procedures. No outgassing was observed. The release was small and could only be detected by the CADP smoke detector and, after significant investigation, verified by observation of hydrolyzed UF on the surface of the valve.
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