Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
ACCESSION #: 9704160113
United States
Enrichment Corporation
2 Democracy Center
USEC 6903 Rockledge Drive
Bethesda, MD 20817
United States Tel: (301) 564-3200
Enrichment Corporation Fax: (301) 564-3201
George P. Rifakes Dir: (301) 564-3301
Executive VICE PRESIDENT, Operations Fax: (301) 571-8279
April 11, 1997
SERIAL: GDP 97-0063
U.S. Nuclear Regulatory Commission
Attention: Document Control Desk
Washington, D.C. 20555-0001
Paducah Gaseous Diffusion Plant (PGDP)
Docket No. 70-7001
Written Notification of 10 CFR 21 Report
The purpose of this letter is to provide Written Notification to
satisfy the requirements of 10 CFR 21.21(d)(3)(ii) of a reportable defect
that was discovered at the Paducah Gaseous Diffusion Plant (PGDP). This
Written Notification is a follow up to the Initial Notification sent to
the NRC by letter GDP 97-0036, dated March 14, 1997.
The defect is associated with the packing nuts on 1 inch valves used
on UF sub 6 cylinders. The firm supplying the items is Hunt Valve Co,
Inc., 1913 E. State Street, Salem, Ohio, 44460. The defect was initially
discovered on January 19, 1997.
The nature of the defect was cracking of the valve packing nut.
Metallurgical analysis of the cracked nuts has shown intergrannular
cracking to be the degradation mechanism. Packing nuts with
intergrannular cracks were found in cylinder valves which had been used
in various stages of the enrichment process. In addition, intergrannular
cracking was found in the packing nuts of cylinder valves removed from
new cylinders to allow internal inspection of the cylinders. The removed
cylinder valves were in storage and had not been exposed to the plant
process chemicals or handling practices which affect the packing nut.
This indicates that the problem is probably a material or manufacturing
problem with the nuts. Three valve packing nut materials are currently
used: monel, ASTM B150 613 alloy, and CDA 636 alloy. An inspection of
valves from other suppliers that are manufactured from all three
materials indicate that the cracking problem is observed only in the 636
alloy nuts on valves supplied by Hunt Valve Co., Inc.
U.S. Nuclear Regulatory Commission
Attn: Document Control Desk
March 11, 1997
GDP 97-0063 Page 2
Failure of the stem packing nut during plant operations to fill or
empty a UF sub 6 cylinder could allow the stem packing rings to be
forcefully ejected from the valve, resulting in a UF sub 6 release, a
hazard to plant personnel, and a challenge to plant safety systems.
Failure of a cylinder valve packing nut and ejection of the valve packing
with an open valve on a full cylinder would constitute a failure of a UF
sub 6 confinement system, and, therefore, could create a substantial
safety hazard. Cracking of the stem packing nut on closed cylinder
valves does not pose a hazard since the packing gland is isolated from
the UF sub 6 cylinder contents.
The 1 inch cylinder valves are used in the 30B Portsmouth Gaseous
Diffusion Plant (PORTS) cylinders and the 48X 48Y, 48G, and 48H PGDP
cylinders. The 1 inch cylinder valves are procured by PGDP for use on
all of the cylinders identified above at both PGDP and PORTS. The valves
are provided by PGDP to the cylinder vendors for installation on new
cylinders supplied to PGDP and PORTS. The 1 inch cylinder valves are
supplied by PGDP to PORTS for any replacements required on the 30B
cylinders. The total number of applications is bounded by the number of
valves supplied with CDA 636 packing nuts by Hunt Valve Co. The total
number of valves provided was 4500. The number of valves with CDA 636
packing nuts currently in service is less than 4500 due to valves removed
for cylinder inspections, repairs, replacements, etc. The exact number
in service is currently unknown. The 1 inch cylinder valves are not used
on any of the other cylinder designs.
The corrective action that has been taken at PGDP is to prohibit
feed and withdrawal operations for cylinders equipped with 1 inch Hunt
Valve Co. valves equipped with CDA 636 packing nuts. CDA 636 packing nuts
are replaced with monel or ASTM B150 613 packing nuts prior to use of a
valve in feed or withdrawal operations. Long Term Orders have been
established in accordance with the governing procedure to ensure
compliance with the prohibition. The Long Term Orders require checking
of the cylinder valve prior to use to identify any Hunt valves equipped
with CDA 636 packing nuts and prohibit their use. The valve body is
clearly marked with the name of the manufacturer and the nut is marked
with the material designator. Therefore, Hunt valves equipped with CDA
636 packing nuts can be readily identified and excluded from use.
PORTS has been notified of the Hunt Valve Co packing nut defect. A
PORTS Daily Operating Instruction was issued for the X-342, X-343, and X-
344 facilities to implement stop work notices which require inspection of
all cylinder valves prior to heating, filling, and transferring of
cylinders. Any cylinder found to have a 1 inch Hunt cylinder valve with
a CDA 636 packing nut installed will not be heated, filled, or
transferred. Caution tags are installed on all prohibited valves, and
operations may not continue until the valve packing nuts have been
replaced with approved replacements (i.e., non-CDA 636 material). A
procedure containing guidelines for inspection and rejection of cylinders
was revised to include the requirement to immediately replace any packing
nuts on Hunt cylinder valves stamped with "636", or hang a caution tag on
the subject valve and reject the cylinder. Hunt cylinder valves with the
CDA 636 packing nuts were removed from stock. The valves will not be put
back into stock until the packing nuts are replaced with another
material.
U.S. Nuclear Regulatory Commission
Attn: Document Control Desk
March 11, 1997
GDP 97-0063 Page 3
PGDP efforts to determine the root cause of the failure mechanism
are continuing. These efforts are focused on the nut fabrication methods
and the raw material production. The suspect population of 1 inch
cylinder valves may be narrowed to a subset of the current 4500 valves as
a result of the investigation. In the event that some number of the 4500
valves can be excluded from the potentially defective population, the
corrective actions may be revised at that time to allow the use of Hunt
Valve Co. 1 inch cylinder valves with CDA 636 packing nuts from the
population excluded from being potentially defective. The prohibition on
the use of valves with nuts from the suspect population for withdrawal or
feed will be maintained. This corrective action is adequate to preclude
a UF sub 6 release due to the identified defect.
The associated PGDP 10 CFR 21 evaluation checklist and a copy of
pertinent PGDP problem reports are enclosed. New commitments made in
this letter are to continue the ongoing corrective actions described
above to prohibit the use of cylinders with 1 inch Hunt Valve Co. valves
with CDA 636 packing nuts at both PGDP and PORTS. Any questions related
to this subject should be directed to Mark Lombard at (301) 564-3248.
Sincerely,
George P. Rifakes
Executive Vice President, Operations
Enclosures: as stated
cc: NRC Region III Office
NRC Resident Inspector - PGDP
NRC Resident Inspector - PORTS
Mr. Randall M. DeVault (DOE)
ENCLOSURES
PGDP PART 21 CHECKLIST AND RELATED PROBLEM REPORTS
UE2-EG-GE1039, Rev. 1 Page 17 of 18
[illegible print]
10 CFR PART 21 EVALUATION CHECKLIST
Page 1 of 2
Following questions provide the criteria for evaluation of 10 CFR
Part 21 reportability:
A.1 No x Yes Has the NRC already been informed of this condition
pursuant to 10 CFR 21 (for example, by a supplier)?
A.2 No Yes If yes, has USEC or LMUS been named as a recipient of
the defective item?
A.3 No x Yes Has this condition already been reported to NRC in
accordance with procedure UE2-MC-RE1030?
If the answer to Questions A.1 and A.2 are "Yes", or the answer to
Question A.3 is "Yes", the condition need not be reported under 10 CFR
21. Attach objective evidence of notification of the NRC and complete
Part #.
If the answers to Questions A.1, A.2, and A.3 are "No", continue with the
evaluation.
B.1 No Yes x Is the identified condition a deviation or failure to
comply associated with a basic component (including
design, analysis, inspection, testing, fabrication,
replacement parts, or consulting services)?
If the answer to Question B.1 is "No", the condition is not reportable
under 10 CFR 21; attach basis for conclusions and proceed to Section E.
If the answer to Question B.1 is "Yes", continue the evaluation.
No Yes x If the answer to Question B.1 is "Yes", has the basic
component been delivered to USEC/LMUS and accepted
for use in the plant or an activity (includes USEC-
dedicated commercial grade items)?
If the answer to Question B.2 is "No", the condition is not reportable
under 10 CFR 21; attach basis for conclusions and proceed to Section E.
If the answer to Question B.2 is "Yes", condition is potentially
reportable. Continue with the evaluation.
C. Further, does the activity or basic component contain any of the
following types of conditions? (Deviation means a departure from
the technical requirements included in a procurement document.)
No Yes x 1) The installation, use, or operation of a basic
component containing a deviation?
No x Yes 2) A condition or circumstance involving a basic
component that could contribute to exceeding a
safety limit as defined in the GDPs Technical
Safety Requirements (TSRs)?
No x Yes 3) A failure to comply with any applicable
regulation, order, or certificate issued by the
NRC?
If all of the answers in this section are "No", the condition is not
reportable; attach basis for conclusion and proceed to Section E. If any
answers are "Yes", continue with the evaluation.
[illegible print]
UE2-EG-GE1039, Rev. 1 Page 18 of 18
UE-141 (11-22-96) Page 2 of 2
Could the deviation or failure to comply create a substantial safety
hazard resulting in any of the following (assume there is no
redundant or back-up systems):
No x Yes 1) Exposure in excess of 10 CFR 20.1201 limits
No x Yes 2) Exposure of an individual in an unrestricted
area to more than 0.5 rem in one calendar year
(10 CFR 20.1301(c))
No x Yes 3) Release of radioactive material to an
unrestricted area in excess of the limits in 10
CFR 20, Appendix B, Table 2
No Yes x 4) A deficiency which seriously compromised the
ability of a UF sub 6 confinement system to
perform its designated function
No x Yes 5) Other (explain)
If all answers in this section are "No", the condition is not reportable;
complete Part E. If any answer is "Yes", condition is reportable.
Continue with evaluation.
E. Evaluation results and recommendation. Recommend condition be
reported?
No Yes x If answer is "Yes", sign this part and continue to
follow procedure, UE2-EG-GE1039. Sign the evaluation
checklist and forward to the Manager, NRA. If answer
is "No", evaluation is complete. Sign the evaluation
checklist and forward to Commitment Management for
closure of Problem Report.
Attach written summary of evaluation and basis for conclusions.
Investigator:
Name Signature Date
Independent Reviewer:
Name Signature Date
NRA: Name Signature Date
(illegible print)
10CFR PART 21 EVALUATION CHECKLIST
Page 3 of 3
SUMMARY OF EVALUATION AND BASIS FOR CONCLUSIONS
The 1 inch cylinder valve used on UF sub 6 cylinders is equipped with a
packing not which [illegible] the packing gland follower and packing
rings. USEC-651, Rev 7, Uranium Hexafloride, A Manual of Good Handling
Practices, section 5.4.6, discusses past defects in 1 inch cylinder
valves and the potential adverse effects. One past defect was packing
nuts which have split during service. It is identified that this
condition could allow the stem packing rings to be forcefully ejected
from the valve, resulting in a UF sub 6 release.
Failure of a cylinder valve packing nut and ejection of the valve packing
with an open valve on a full cylinder, would constitute a failure of a UF
sub 6 confinement system. Therefore, the cylinder valve packing nut is a
basic component for which failure could create a substantial safety
hazard.
The cylinder valves were procured by the Paducah Gaseous Diffusion Plant
as commercial grade items and were dedicated for use on the UF sub 6
cylinders. The dedication process has been completed for any valves
installed on UF sub 6 cylinders thereby establishing the applicability of
10 CFR 21 to these components.
On 1/19/97, a UF sub 6 release was detected during pigtail purging
operations on a full cylinder. The release was visible as a small wisp
of smoke after the pigtail was pressurized above atmospheric. The
cylinder valve was closed and the release was terminated. Inspection of
the valve revealed a visible crack in the valve packing nut. An
investigation was initiated to determine the cause of the valve nut
failure. A similar failure occurred on 2/7/97 and was included in the
investigation.
The 2 failed nuts were examined metallurgically and were found to exhibit
intergrannular cracking. Both of these nuts are from Hunt valves and are
CDA 636 material.
Valve packing nut inspections were performed as part of the investigation
in order to determine the extent of the problem, Eddy current inspection
techniques were used in addition to visual inspections to help identify
potentially degraded valve packing nuts. As a result of the inspections
additional cracked valve packing nuts were identified. The following is
a summary of the additional nut inspection:
o 136 Hunt CDA 636 nuts from valves from Paducah Gaseous Diffusion
Plant cylinders have been inspected by eddy current. 13 of these
have exhibited cracks. One of these was on a cylinder stored in the
[illegible] yard and the cracks were detected visually. Another,
detected by eddy current, was on a "new" valve in storage following
removal to allow inspection of a new UF sub 6 cylinder.
Metallurgical analysis was performed on the "new" nut and confirmed
the presence of intergrannular cracks.
o 25 Hunt B150 613 nuts were eddy current tested and no eddy current
indications were detected. One of these was subjected to
metallurgical analysis and no cracking was detected.
o 28 Superior valve nuts of CDA 636 were eddy current tested and no
indications were detected.
o 20 Hunt 636 nuts were examined from customer cylinders. 3 showed
indications including 1 with a visible crack. 2 of these were
metallurgically examined and the indications confirmed. Three nuts
that showed no indications were examined metallurgically and only
one showed very slight indications that would not be picked up by
eddy current.
Three valve packing nut materials are currently used; monel, ASTM B150
613 alloy, and CDA 636 alloy. The cracking problem has been observed
only in the 636 alloy nuts on valves supplied by Hunt Valve Co., Inc.
The intergrannular cracking has been detected in Hunt CDA 636 cylinder
valve packing nuts which have been used in various stages of the
enrichment process and in the packing nuts of "new" cylinder valves
removed from new cylinders to allow receipt inspections. The removed
valves were placed in storage and were not exposed to plant process
chemicals or handling practices affecting the packing nut. This
indicates that the problem is a material or manufacturing problem with
the nuts. No defects or failures have been identified in nuts of CDA 636
material on other vendors valves or in nuts of alternate materials on
Hunt valves.
A total of 4500 valves were supplied by Hunt Valve Co. with CDA 636
packing nuts. Investigation and analysis is continuing to determine if
the entire population is susceptible to the intergranular cracking
problem or if the affected population is a subset of the 4500. Until
further analysis determines otherwise, it will be assumed that the entire
4500 is affected.
[illegible] Business Prioritization System Page 1
Problem Report Response Sheet
ISSUE TITLE...: SMOKE RELEASED FROM Response Due: / /
CYLINDER VALVE ON PP-2569
ASSESSMENT....: PROBLEM REPORTS JANUARY -
DECEMBER 1997 [UC97A00001]
ISSUE TO......: UC9710318 MANAGER......: PENROD SR
FINDING NO....: PR-CO-97-0289 FUNC. ORG....: 12' v
Operations
STATUS........: CANC GROUP........: __ - [Unassigned]
TYPE..........: PR - Problem Report
SUB-TYPE......: NO - Notification ORIGINATING
FUNC. ORG....: 12 - Operations
PRIORITY......: 0 ORIGINATING
GROUP........: 793 - UF6
Handling Shifts
LOCATION......: INITIATED BY.: 28539
BUILDING......: C-310 DISCOVERY
DATE.........: 01/19/1997 2200
MAIL STOP.....: C-331
PROCEDURE/
SPEC/DRAW....:
ROOT CAUSE DETERMINATION
TapRoot Code(s):
FLAGS
DESCRIPTION
UPGRADED TO EVENT REPORT PAD-ER-1997-001
A small wisp of smoke was released from the cylinder valve on
cylinder PP-2569. PGLD YE-75 over the [illegible] withdrawal
position pigtail was actuated. The operations were in the process
of evacuating/purging the pigtail on a full product cylinder. The
wisp was observed after the pigtail was pressured above atmosphere.
A noticeable crack circumvents the packing nut. The operators
exited the area and donned additional PPE. The pigtail was purged
using subatmospheric doubling purges and the cylinder valve
confirmed closed. Cylinder was disconnected with no further
incident and defective valve cap and caution tag was placed on the
cylinder. [Illegible] and uranium samples were pulled with negative
results. The ARP was followed and the PSS notified.
ACTIONS TAKEN
NONE
RECOMMENDED ACTIONS
Replace cylinder valve on pp-2549. Analyze [illegible] of valve cap
PSS JUSTIFICATION/COMMENTS
Urine samples were obtained. UF6 detection safety system was
actuated and operated as designed. 24 hour event report PAD-1997-
002 issued. Criteria met Appendix E 1 (a) Unusual and Appendix F, J
(2) 24 hour. Small wisp released from cracked packing nut when
pigtail pressured up. [Illegible] smears were negative. This PR
should be evaluated for 10CFR21 responsibility.
REMARKS
MANAGEMENT RESPONSE
Issue Revised 02/05/1997 at 13:12:29 Printed 02/19/1997 at 11:41:31
UC97I0699 Business Prioritization System Page 2
Problem Report Response Sheet
ISSUE TITLE...: C-310 RELEASE FROM Response Due:
CYLINDER VALVE PR-591 04/04/97
ASSESSMENT....: PROBLEM REPORTS JANUARY -
DECEMBER 1997 [UC97A0001]
ISSUE TO......: UC97I0699 MANAGER......: PENROD SR
FINDING NO....: PR-CO-97-0640 FUNC. ORG....: 12 -
Operations
STATUS........: PART GROUP........: 070 - Operations
Management
TYPE..........: PR - Problem Report
SUB-TYPE......: __ - [Unassigned] ORIGINATING
FUNC. ORG....: 12 - Operations
PRIORITY......: 0 ORIGINATING
GROUP........: 793 - UF6
Handling Shifts
LOCATION......: INITIATED BY.: 28539
BUILDING......: C-320 DISCOVERY
DATE.........: 02/07/1997 0827
MAIL STOP.....: C-331
PROCEDURE/
SPEC/DRAW....: CP4-CU-
CN2010 Rev. 0
ROOT CAUSE DETERMINATION
TapRoot Code(s):
FLAGS
CAQ
DESCRIPTION
A small wisp of smoke was released from the cylinder valve on
cylinder PK-S91 during purging operations. This activated FOLD YE-
73 in the #3 withdrawal position ventilation duct. The wisp was
observed after the pigtail was pressured above atmosphere. A
noticeable crack circumvents the packing nut.
ACTIONS TAKEN
Operations immediately exited the area. Alarm was responded to per
procedure. HF samples and wipes were negative. The pigtail was
purged using subatmospheric doubling purges. Cylinder was
disconnected with no further incident.
RECOMMENDED ACTIONS
Replace cylinder valve packing nut on PK-591. Investigate failure
of packing nut.
PSS JUSTIFICATION/COMMENTS
24 Hour Event Report per UE2-MC-RE1036, Appendix E criteria 2. 5.
unusual (a), and Appendix F criteria J.2. Appropriate response was
made. HF and HP surveys were negative. Precautionary urine samples
were obtained from the two workers who were present.
REMARKS
03/06/97: Per PRSC, assign to Operations for disposition. This PR
will be closed to PR-00-97-0648 which is a SCAQ.
03/06/97: DOE reportable events due to DOE on/after 03/03/97 (date
NRC assumed regulatory oversight) have been downgraded to problem
reports. PR-CO-97-0440 has been placed back in PART status and will
be taken back to the Screening Committee for SCAQ determination,
action plan due date, etc. Event Report FAD-ER-1997-094D
(OC97I06100 has been cancelled.
MANAGEMENT RESPONSE
Issue Revised 03/06/1997 at 15:49:37 Printed 03/13/1997 at 10:44:09
UC97:1002 Business Prioritization System Page 1
Problem Report Response Sheet
"31" PROBLEM REPORTS
ISSUE TITLE...: PACKING NUT ON CYLINDER Response Due:
PP-2520 ON 6 YARD CRACKED 03/20/1997
ASSESSMENT....: PROBLEM REPORTS JANUARY -
DECEMBER 1997 [UC97A0001]
ISSUE TO......: UC97I1002 MANAGER......: BROWN JR
FINDING NO....: PR-SU-97-08588 FUNC. ORG....: 37 -
Engineering
STATUS........: PART GROUP........: 814 - Mechanical
& Process
TYPE..........: PR - Problem Report
SUB-TYPE......: __ - [Unassigned] ORIGINATING
FUNC. ORG....: 38 - Production
Support
PRIORITY......: 0 ORIGINATING
GROUP........: 340 - Process
Technical & NDA
LOCATION......: INITIATED BY.: 28539
BUILDING......: C-743-E DISCOVERY
DATE.........: 02/18/1997 1445
MAIL STOP.....: C-710
PROCEDURE/
SPEC/DRAW....:
ROOT CAUSE DETERMINATION
TapRoot Code(s):
FLAGS
CAO
DESCRIPTION
The packing nut on cylinder PB-2520 in the E yard was found cracked
around the circumference (at approximately the cap thread) through
approximately 80% of the section. This is a "Hunt" valve alley "6-
36" nut. (Lot #390795-8). This packing nut failure was found while
inspecting Paducah Plant cylinders with an eddy current probe for
indications of cracked nuts, but was clearly visible with crack
opening of approximately 1/8". The cylinder appeared to be empty.
ACTIONS TAKEN
NONE
RECOMMENDED ACTIONS
NONE
PSS JUSTIFICATION/COMMENTS
Found during a random sampling of Hunt valves with the "6-36"
packing nut. No sign of any leakage. 10 ton cylinder. Per NMC&A
records, is an empty cylinder with notation requiring a valve
change. This should be evaluated for 10 CFR 21 and 71.95
applicability.
REMARKS
02/20/97: Part A is assigned to Operations and Management response
provided at PRSC. No further actio required. Part 6 is assigned to
Engineering to evaluate for 10 CFR applicability.
MANAGEMENT RESPONSE
Name of person providing response:
Issue Revised 02/20/1997 at 09:59:34 Printed 02/20/1997 at 13:23:43
FUEL CYCLE FACILITY EVENT NUMBER: 31954
FACILITY: PADUCAH GASEOUS DIFFUSION PLANT NOTIFICATION DATE: 03/14/97
RXTYPE: URANIUM ENRICHMENT FACILITY NOTIFICATION TIME: 13:30
[ET]
COMMENTS: 2 DEMOCRACY CENTER EVENT DATE: 03/14/97
6903 ROCKLEDGE DRIVE EVENT TIME: 00:00
BETHESDA, MD 20817 (301)564-3200 [CST]
LAST UPDATE DATE: 04/11/97
CITY: PADUCAH REGION: 3
COUNTY: McCRACKEN STATE: KY NOTIFICATIONS
LICENSE#: GDP-1 AGREEMENT: Y
DOCKET: 0707001 WAYNE KROPP RDO
JOSEPHINE PICCONE EO
NRC NOTIFIED BY: MARK LOMBARD KEVIN RAMSEY (FAX) NMSS
HQ OPS OFFICER: STEVE SANDIN
EMERGENCY CLASS: NOT APPLICABLE
10 CFR SECTION:
CDEG 21.21(c)(3)(i) DEFECTS/NONCOMPLIANCE
EVENT TEXT
10 CFR PART 21 NOTIFICATION REGARDING STRESS CORROSION CRACKING OF
CYLINDER VALVE PACKING NUTS
IT HAS BEEN DETERMINED THAT STRESS CORROSION CRACKING OF THE 1-INCH
CYLINDER VALVE PACKING NUTS USED IN VARIOUS STAGES OF THE
ENRICHMENT
PROCESS HAS, IN ONE CASE, RESULTED IN A REPORTABLE RELEASE OF UF6.
THIS
PROBLEM HAS ONLY BEEN OBSERVED IN THE 636-ALLOY NUTS ON VALVES
SUPPLIED
BY HUNT VALVE CO., INC.
* * * UPDATE 1740EDT 4/11/97 FROM MARK LOMBARD To S. SANDIN * * *
THE LICENSEE SUBMITTED AN UPDATE VIA FAX. NOTIFIED R3DO(MADERA) AND
FORWARDED TO NMSS(RAMSEY).
UNITED STATES ENRICHMENT CORPORATION
Two Democracy Center o 4th Floor o 6903 Rockledge Drive o Bethesda, MD
20817
Fax Memorandum
DATE: April 11, 1997
TIME: 5:39 pm
TO: NRC Operations Center FAX:
PHONE:
FROM: Mark Lombard FAX: 301 564-3210
PHONE: 301 564-3248
NUMBER OF PAGES (including cover sheet): 10
SUBJECT: Part 21 written report attached, for concurrence. Please call
me if you have any questions. The hard copy will follow by mail.
*** END OF DOCUMENT ***
