ML20210P254
| ML20210P254 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 08/21/1997 |
| From: | Allen D UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 97-13, GDP-97-2018, NUDOCS 9708270030 | |
| Download: ML20210P254 (7) | |
Text
s United States Enrichment Core in n
? Democracy Centet 6903 Rockledge Drive Bethe6da, MD 20817 Tel: (3011664 3200 Fan:(301)664 3201 August 21,1997 GDP 97 2018 United States Nuclear Regulatory Commission l
Attention: Document Control Desk i
Vashington, D.C. 20555 0001 l
Portsmouth Gascous Diffusion Plant (PORTS)- Docket No. 70 7002 Event Report 97-13 Pursuant to Safety Analysis Report (SAR), Section 6.9, Table 6.91, J(2), Enclosure 1 provides the required 30 day written Event Report (ER) lbr an event involving an autoclave high condensate level shutoff actuation at the Portsmouth Gascous Diffusion Plant. Enclosure 2 is a list of commitments made in the report.
Should you require additional information regarding this event, please contact Scott Scholl at (614)897 2373.
Sincerely, Dale Allen General Manager Portsmouth Gaseous Diffusion Plant DIA:SScholl:me ec:
NRC Region 111 C. Cox/D. llartland, NRC Resident inspectors, PORTS lil!!lllli'll!!HIl'El!!,Il 9708270030 970821 1
PDR ADOCK 07007002 C
PDR Offees in uvermore, Caldomia Paducah, Kentucky Portsmouth, Ohio Washington, DC
i
, United States Nuclear Regulatory Commission August 21,1997 Page Two Distribution NRAP Reading Room
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J. Adkins,llQ J. Anzelmo, PORTS i
J. llolling, PORTS -
M. Iloren, PGDP
- S. Ilrawner, PODP D. Davidson, PORTS
-J. Dietrich, LMUS.
L. Fink., PORTS L
R. Gaston, PORTS
. M.11asty, PORTS t
P. Ilopkins, PORTS
. J. Ilutsebaut, PORTS 3
J. Labarraque, PGDP
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II Lantz, PORTS
. R.- Lipfert, PORTS R. McDermott, PORTS J. Miller,llQ J. Mize, PGDP
- J. Morgan, PORTS J. Oppy, PORTS S. Polston, PODP L:
_11. Pulley, PODP
'A. Rebuck Main, ilQ R. Robinson, PORTS I
S. Routh,' llQ S. Scholl, PORTS
-II. Sykes, PGDP -
D, Thompson, PORTS R. Wells, llQ.
. Plant Shift Superintendents PORTS Records Management
. o:\\ users \\nra\\ ports \\9713 er i.
4 Docket No. 70 7002 Page 1 of 4 Event Report 9713 Description of Event l
On July 21,1997, at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, X 344 Autoclave (AC) #3 was in Mode 11, heating a 48 inch Uranium llexafluoride (UF.) cylinder when the audible alarm for steam shutdown was received.
Operators responding to the alarm found the "A" and "B" condensate level probe lights on, indicating the high condensate level shutofr(llCLS) safety system had actuated. Steam supply block valve FSW163 was verified to be in the closed position, stopping steam flow to the autoclave as designed. The actuation of the llCLS safety system is reportable in accordance with the Safety Analysis Report (SAll), Table 6.91, J (2).
The condensate level shutoffsystem is provided to prevent over pressurization or a nuclear criticality in an autoclave following a postulated UF, release. Excess water is undesirable in case of a UF.
release from the cylinder that could cause either high hydrogen fluoride pressure as the result of the reaction between UF. and water or the excessive moderation of an unsafe mass of uranium, thereby causing a criticality within the autoclave. The system function is to detect either a drain line plug or restriction and to shutoff the steam flow to the autoclave.
Cause of Event The direct cause for the 11CLS safety system actuation was the accumulation of debris in the condensate strainer. Maintenance removed the in line strainer and discovered that condensate flow was prevented by debris which had completely filled the internal volume of the strainer.
The root cause of the event was that an abnormal amount of rust accumulated within AC #3 causing the condensate strainer to become rapidly plugged. In the past the accumulation of rust on the autoclave strainers was observed to be a gradual process. Normally an autoclave can be expected to operate for at least six months before strainer cleaning would be required, llowever, in this event AC #3 strainer became restricted aller approximately three heating cycles.
Prior to this event, on July 18,1997, the AC #3 interior shell and head were cleaned. The autoclave was then steam heated to wash any residual debris into the strainer. The strainer was then removed and cleaned. The debris collected was typical for that autoclave and the strainer was not plugged.
On July 21,1997, AC #3 was heated for approximately one hour before the llCLS actuation occurred.
This event is similar to three previous events that were documented in Event Reports 97-04,97-07 and 97-08, in these events the accumulation of rust in the condensate strainers was also the cause for these llCLS actuations.
The autoclave interior and UF cylinders are made of steel which provides the source of rust within the autoclaves. Paint from the autoclave interior and cylinders also provides a source of debris.
Docket No. 70-7002
. Enclosure 1 Page 2 of 4 Event Report 9713 When rust or paint flakes off, it accumulates in the autoclave shell and eventually collects in the condensate strainer. Since the amount of rust within an autoclave is a function of the autoclave age and operating history, it is expected that the higher rate of rust generation will continue.
Previous llCLS actuations caused by restricted strainers resulted in implementation of an autoclave interior shell cleaning program and increased strainer inspection frequency. Interior shell cleaning was considered as a way to reduce the amount of rust that could accumulate in the strabers.13ecause l
of the a-'
lave design, interior shell cleaning is limited to accessible surfaces. In addition, the cleaning process was suspected of loosening more debris and contributing to the problem. To alleviate these concerns, the autoclave is now steam heated following each cleaning to wash any l
residual debris into the in line strainer. The strainer is then inspected and cleaned as necessary, it I
has also been determined that thoroughly cleaning each UF. cylinder is not practical. As a result, cleaning operations are not completely effective at limiting rust accumulation from all sources.
Since the accumulation of rust cannot be readily controlled, engineering has determined that the condensate strainer design should be changed to accommodate an increased amount of rust. The X-344 nutoclaves have one inch strainers which are smaller than the two inch strainers installed on the other nine autoclaves. The one inch strainers have an internal volume of approximately 1,7 cubic inches.
On June 4,1997, a larger two inch strainer was installed on X-344 AC# 1. The new strainer has a larger mesh size and an internal volume of approximately 18.8 cubic inches. An engineering evaluation of the quantity of debris collected in the new strainer during weekly inspections and shcIl cleanings was performed. The evaluation concluded that the amount of debrir collected in the strainer was less than 25 percent of the volume of the new strainer. Engineering concluded that the new larger strainer prevented ilCLS actuations that would have occurred if the one inch strainer had been installed. The volume of debris collected from the strainer and condensate drain lines following this event was approximaiely 4.4 cubic inches, which would not be enough to cause an 11CLS actuation if the new two inch strainer had been installed.
Following this event, the remaining three autoclaves were shutdown until the new strainers could be installed. The new strainers have been installed on AC #3 and AC #4, and will be installed on AC #2 prior to its retum to service. As part of the evaluation of the new design, the strainer will continue to be inspected weekly to ensure the new design is efTective at preventing rapid strainer plugging. This inspection frequency will continue for all X 344 autoclave strsiners until an appropriate inspection frequency can be determined based on the rate of debris accumulation.
AC #3 was also bomscoped to determine if there was any other debris in the condensate drain line other than what was found in the one inch condensate strainer. During the boroscoping an ink pen, half moon shaped piece of naterial, and some liber material were found. The ink pen was found above the first containment valve. These items were not large e ough to have contributed to the llCLS actuation.
I
Dockei No. 70 7002
. Enclosure i page 3 of 4 Event Report 9713
'lhe discovery of these items was of particular concem since problems with foreign material entering the condensate drain lines had been identified as a cause to a previous !ICLS actuation (Event Report 97 11). As part of th; corrective actions for that event, all autoclave condensate lines were inspected and foreign material removed. Additional controls to prevent foreign material entry into the condensate line were also implemented. Interim controls were established by issuing work instructions to operators to require the removal of any known or suspected foreign material entering the autoclave condensate drain system. More fonnal procedure controls were also planned but had not been implemented prior to this event. The discovery of these items in the condensate drain line indicates these interim controls did not have the desired effect.
Autoclave til and #4 were boroscoped to determine if foreign material entered the condensate system since the implementation ofinterim administrative controls. No foreign material was ibund. An inspection of X 344 AC t/2 will be performed prior to returning the autoclave to service.
Corrective Actions 1.
On August 1,1997, a new condensate strainer incorporating a larger volume, surface area and mesh size was installed in X 344 AC ll3 and AC ll4.
2.
On August 21,1997 Autoclave operating procedures weic revised to add steps to ensure that autoclaves are inspected for foreign material prior to autoclave start up.
3.
lly September 19,1997, a lesson learned will be created and reviewed with operations personnel on foreign material exclusion for autoclaves.
4.
Ily August 22,1997, operating instructions will be developed to provide additional guidance for preventing foreign material from entering the autoclave interior.
5.
Ily October 15,1997, additional guidance for preventing foreign material fiom entering the autoclave will be incorporated into procedures.
6.
Ily August 30,1997, engineering will evaluate the X 342, X-343, and X 344 autoclave designs and foreign material exclusion programs, including current planned modifications, and determine what additional changes may be necessary to prevent foreign material from entering the condensate drain system. (Duplicate of corrective action no. 4 from Event Report 97-11).
7.
Based on the results of the evaluation, a schedule for implementing necessary design changes will be developed by September 30,1997. (Duplicate ofcorrective action no. 5 from Event Report 97-11).
o
_O -
I Docket No. 70 7002
. Enclosure 1 Page 4 of 4 Event Report 9713 8.
Prior to retuming AC #2 in X444 to service, the condensate system will be inspected for foreign material and a new condensate strainer incorporating a larger volume, surface area and mesh size will be installed. This is currently scheduled to be completed by October 18, 1997.
Extent of Exposure ofIndividuals to Radiation or Radioactive Materials There were no exposures to individuals from this incident to radiation or radioactive materials.
Lessons Learned
- Operation with the new two inch condensate ir. line strainer has proven that the larger strainer can accommmiate the amount ofdebris accumulation which is currently experienced by the autoclaves without restricting flow.
- l,.'
(
Docket No. 70 7002
. Enclosure 2 Page1of1 Event Report 9713 List of Commitments 1,
11y September 19,1997, a lesson learned will be created and reviewed with operations persor.nel on foreign material exclusion for autoclaves.
2.
Ily August 22,1997, operating instructions will be developed to provide addi'lonal guidance for preventing foreign material from entering the autoclave interior.
3.
Ily October 15,1997, additional guidance for preventing foreign mateilal from entering the autoclave will be incorporated into procedures.
4.
11y August 30,1997, engineering will evaluate the X 342, X 343, and X 344 autoclave designs and foreign material exclusion programs, including current planned modifications, and determine what additional changes may be necessary to prevent foreign material from entering the condensate drain system. (Duplicate of corrective action no. 4 from Event Report 971I).
(
5.
liased on the results of the evaluation, a schedule for implementing necessary design changes will be developed by September 30,1997. (Duplicate of corrective action no. 5 from Event Report 9711),
d 6.
Prior to returning AC #2 in X 344 to service, the condensate system will be inspected for foreign material and a new condensate strainer incorporating a larger volume, surface area and mesh size will be installed. This is currently scheduled to be completed by October 18, 3
1997.