ML20154M680
| ML20154M680 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 10/09/1998 |
| From: | Toelle S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | Devault R ENERGY, DEPT. OF |
| References | |
| DOE-98-0034, DOE-98-34, NUDOCS 9810210006 | |
| Download: ML20154M680 (8) | |
Text
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%/USEC A Global Energy Company L
October 9,1998 p
DOE 98-0034
.b4i Mr. Randall M. DeVault M
Regulatory Oversight Manager Oak Ridge Operations U. S. Department of Energy Oak Ridge, Tennessee 37831-8651 Portsmouth Gaseous Diffusion Plant (PORTS)
Docket No.70-002 1
Response to Confirmatory Action Letter Regarding the Vabrication, Testing and Application of Highly Enriched Uranium Cylinder Adaptors
Dear Mr. DeVault:
The United States Enrichment Corporation (USEC) received a Confirmatory Action Letter from the Department of Energy (DOE) on October 1,1998 (Reference 1), addressing the failure of an adaptor used to connect a 12-inch cylinder during the X-705 highly enriched uranium (HEU) cylinder cleaning activities.
On October 2,1998, a discussion was held between yourself and Mark Lombard of USEC to discuss items P
in Reference 1 that required clarification. Based on tl.at conversation and the results of USEC's assessment of this issue, USEC is providing the resolution of all issues outlined in Reference 1 in Enclosure 1 to this 3
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letter. With the resolution of these issues in Enclosure 1, USEC intends to continue the HEU cylinder i
cleaning operation in X-705.
f New commitments made in this letter are provided in Enclosure 2 If you have any questions regarding this matter please contact Mark Lombard at (301) 564-3248.
. Sincerely, n
5.A.
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p Steven A.Toelle h
Nuclear Regulatory Assurance and Policy Manager
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Enclosures:
As Stated 5:
>y cc: Mr. Robert C. Pierson (NRC)
Jg DOE Site Safety Representative, PGDP and PORTS g\\
NRC Resident Inspector - PGDP and PORTS
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E NRC Project Manager-PGDP and PORTS 9010210006 981009' l
PDR ADOCK 07007002 C
PDR 6903 Rockledge Drive, Bethesda, MD 20817-1818 Telephone 301564-3200 Fax 301-564-3201 http://www.usec. corn Offices in Livermore, CA Paducah, KY Portsmouth, OH Washington, DC o
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Mr. Randall M. DeVault October 9,,1998 DOE 98-0034, Page 2 1
REFERENCES a.
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Regarding the Fabrication, Testing, and Application of Highly Enriched Uranium Cylinder Adaptors,"
September 29,1998.
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Resolution of DOE Issues
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- 1. DOE Concern:
Use of the alternate adaptor design may continue provided that each
,i adaptor is tested as follows:
N 60 foot-pounds of torsionalload 100 pounds of axialload, and
'60 pounds at 9-inches of bending moment.
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USEC Response:
Each of the alternate design adaptors was successfully tested to the above limits and the results are available for review on site.
- 2. DOE Concern:
Use of the altemate adaptor design may continue provided that USEC issue a Daily Operating Instruction which specifles the necessary precautions to preclude an adaptor from being used in a manner approaching testing limits listed in DOE Concern 1.
USEC Response:
A Daily Operating Instmetion (DOI) has been prepared which states that torque shall not be applied to the cylinder valve adaptor itself during the installation and removal from the cylinder. This will preclude the testing limits specified in DOE Concern 1 from being exceeded.
- 3. DOE Concern:
Use of the alternate adaptor design may continue provided that all affected personnel are trained to the requirements of the DOI discussed in DOE Concern 2.
USEC Response:
All affected personnel were trained to the DOI discussed in DOE Concern i
2.
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- 4. DOE Concern:
Use of the alternate adaptor design may continue provided that each 4
adaptor is labeled with precautions concerning the installation
- .,j requirements.
4 USEC Response:
A caution tag or sticker has been attached to each alternate design adaptor
- ijg indicating that torque shall not be applied to the adaptor itself during the installation and removal from the cylinder.
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DOE 98-0034 i
Page 2 of 4 Resolution of DOE Issues
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- 5. DOE Concern:
Use of the alternate adaptor design may continue provided that the DOI
?:-I discussed in DOE Concern 2 is reiterated at pre-job briefings.
USEC Response:
The DOI discussed in DOE Concern 2 will be reiterated during shift tumover which serves as the pre-job briefing for ongoing activities such as cylinder cleaning.
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- 6. DOE Concern:
Use of the alternate adaptor design may continue in the interim for up to eight weeks from September 14,1998.
l USEC Response:
The attemate adaptor design will not be used beyond November 8,1998.
Any existing alternate adaptors will be tagged "Out of Service" and/or removed from the X-705 West Annex before November 8,1998.
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- 7. DOE Concern:
Utilization of the altemate adaptor design after November 8,1998 will require further concurrence from the DOE.
USEC Response:
Ifit is determined that it is necessary to use the alternate adaptor design after November 8,1998, USEC will request approval from DOE on or before October 26,1998.
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- 8. DOE Concern:
The interim actions (outlined in DOE Concerns 1 through 5 above) are conditional upon the completion of a root cause analysis of the original adaptor's brazed weld failure to ensure that lessons learned have been incorporated into the design and in-service application of the adaptors.
USEC Response:
A preliminary root cause analysis on the failed original adaptor has been
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completed, and the results have been utilized in the design of the new,
,g improved adaptor. A failure analysis of the failed original adaptor is also
'4 being completed to confirm the results of the preliminary root cause analysis and ensure that lessons learned have been incorporated into the design and in-service application of the new, improved adaptors. The failure analysis will be completed by USEC and the root cause analysis
.L will then be finalized.
\\1 Based on a conversation between Randall DeVault (DOE) and Mark q
Lombard (USEC) on October 2,1998, the root cause analysis does not 4
need to be finalized prior to using the alternate adaptor design as long as the interim actions outlined in the USEC responses to DOE Concerns 1
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DOE 98-0034 g
Page 3 of 4
^M Resolution of DOE Issues El through 5 are implemented. Accordingly, the new, improved design adaptors can be used prior to finalizing the root cause analysis as long as m.
,3 the actions outlined in the USEC responses to DOE Concerns 9 through 11 are followed.
As part of the preliminary root cause analysis, USEC performed a thorough visual inspection of the failed original adaptor and lessons learned from that inspection were utilized in the alternate and new, improved adaptor designs. While it is not anticipated that the finalized root cause analysis will result in any additional changes to the new, improved adaptor design, lessons teamed from the finalized root cause analysis will be reviewed and factored into revisions of the new, improved adaptor design if necessary. The results of the finalized root cause analysis will be available on site for review. A brief discussion of the information gathered from the visual inspection ar.d preliminary root cause evaluation follows.
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The original adaptor was fabricated from 1/2" schedule 40,304L stainless steel pipe with a 304L stainless steel plug welded into one end. Le opposite end had pipe threads for a quick disconnect. A hole was drilled for a stores stock monel gland to be silver brazed in the side of the pipe.
A visual examination after the failure of the originct adaptor occurred h,
indicated a poor fit between the stainless steel pipe and the monel glcnd.
Also, the silver brazing did not flow evenly around the joint, possibly j
indicating insufficient heat in the brazing process. Based ~on this 5, 1 ~
information, the preliminary conclusion is that the root cause of the original adaptor design failure was the dissimilar metaljoint design. This j
design led to poor manufacturing and brazing techniques and inadequate Q
post-fabrication inspection.
If The alternate adaptor was fabricated from the same dissimilar materials using the same brazing technique as the original adaptor. However, as immediate remedial actions, a more precise machine fit between the stainless steel pipe and the monel gland was achieved prior to silver Q
brazing. The hole in the pipe for the monel gland to fit into was held to
,I a +.005" tolerance and was machined to a depth of approximately.340".
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This arrangement approximated a socket type joint that would provide j-optimum strength for the silver brazedjoint. Physical stress tests of the C
alternate adaptor design were conducted to the testing limits listed in DOE Concem 1 above and the integrity of the brazed joint in shear, 9
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'4-1 DOE 98-0034 Page 4 of 4 Resolution of DOE Issues g
j;p bending and torsion was verified. After the stress tests were conducted i
j the assemblies were successfully hydrostatically tested to 225 PSIG and the welds were visually inspected and accepted by the dye penetrant method.
I The new, improved adaptors are fabricated by machining all the lE component parts from 304L stainless steel. The body of the adaptor is socket welded to the gland thus eliminating the silver brazing of the d
stainless steel pipe and the monel gland. Engineering calculations were j:
performed and verified the strength of the new design exceeds the testing j
limits in DOE Concern 1 above. In addition, the new, improved adaptors j
j were successfully hydrostatically tested to 225 PSIG and the welds were
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visually inspected and accepted by a welding inspector.
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- 9. DOE Concern:
The new, improved adaptor design should have engineering calculations to verify its welded joint strength is adequate for this cylinder cleaning I
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application or have completed load-testing equivalent to that above.
USEC Response:
Engineering calculations were performed that verify that the strength of 3
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the new, improved adaptor design exceeds the testing limits in DOE Concern 1. These calculations are available on site for review.
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- 10. DOE Concern:
Non-destructive examination requirements should be met for the new, improved adaptor design.
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USEC Response:
The welds of the new, improved adaptor design were visually inspected and accepted by a welding inspector and the adaptors were successfully
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2 l1 hydrostatically tested to 225 PSIG. All pertinent records are available on site for review.
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- 11. DOE Concern:
The DOI described in DOE Concem 2 should continue to apply to the use 3
of the new, improved adaptor.
M USEC Response:
The DOI described in DOE Concem 2 will be revised after the new, tFl' improved adaptor is approved for use to state that torque shall not be k
applied to the new, improved adaptor during the installation and rem 6 val Q
from the cylinder.
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l DOE 98-0034 Page 1 of2 l
New Commitments Made in this Letter g
The following new commitments made in this letter have been completed:
- 1. Each of the altemate design adaptors was successfully tested to the following limits (the results L
are available for review on site);
. 60 foot-pounds of toisionalload 100 pounds of axialload, and 60 pounds at 9-inches of bending moment.
- 2.' A Daily Operating Instruction (DOI) has been prepared which states that torque shall not be
!O applied to the adaptor itself during the installation and removal from the cylinder. All affected personnel were trained to the DOI.
- 3. - A caution tag or sticker has been attached to each altemate design adaptor indicating that torque
,i shall not be applied to the adaptor itself during the installation and removal from the cylinder.
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- 4. Engineering calculations were performed that verify that the strength of the new, improved
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adaptor design exceeds the testing limits in item 1 above. These calculations are available on site for review.
- 5. The welds for the new, improved adaptor were visually inspected and accepted by a welding
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. inspector and the adaptors were successfully hydrostatically tested to 22$ PSIO. All pertinent
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records are available on site for review.
b The following new commitments made in this letter are not completed:
- 6. The DOI discussed in DOE Concem 2 will be reiterated during shift.tumover. This is an y
ongoing commitment to be performed until HEU cylinder cleaning in X-705 is completed.
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- 7. The alternate adaptor design will not be used beyond November 8,1998 without prior DOE approval. If it is determined that it is necessary to use the alternate adaptor design after November 8,1998, USEC will request approval from DOE on or before October 26,1998.
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- 8. Any existing alternate design adaptors will be tagged "Out of Service" and/or removed from the L.,
_ X-705 West Annex by November 8,1998 unless USEC requests an extension for use of the
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alternate design adaptors as outlined in Item 7.
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DOE 98-0034
.Page 2 of 2 New Commitments Madeinjjais Letter
- 9. USEC will finalize the root cause analysis on the failed original adaptor to ensure that lessons leamed have been incorporated into the design and in-service application of the new, improved adaptor design. Lessons teamed from the finalized root cause analysis will be reviewed and factored into revisions of the new, improved adaptor design if necessary. The results of the finalized root cause analysis will be available on site for review by December 31,1998.
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- 10. The DOI described in Item 2 above will be revised afle the new, improved adaptor is approved for use to state that torque shall not be applied to the new, improved adaptor during the installadon and removal from the cylinder. This action will be completed by November S,1998 unless USEC requests an extension for use of the alternate adaptor design as outlined in Item 7.
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