ML17194A197
| ML17194A197 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/02/1981 |
| From: | Danielson D, Yin I NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17194A196 | List: |
| References | |
| 50-237-81-25, NUDOCS 8110140221 | |
| Download: ML17194A197 (5) | |
See also: IR 05000237/1981025
Text
U.S. NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
REGION III
Report No. 50-237/81-25
Docket No. 50-237
Licensee:
Commonwealth Edison Company
Post Office Box 767
Chicago, IL
60690
Facility Name:
Dresden Station, Unit 2
Inspection At:
Dresden Site, Morris, IL
Inspection Conducted:
September 6-7, 1981
Inspector: I. T. Yin ~ ~
d)Jifd-.. ~-~/A----
Approved By:
D. H. Danielson, Chief
Materials and Processes Section
Inspection Summary
License No. DPR-19
Inspection on September 6-7, 1981 (Report No. 50-237/81-25)
Areas Inspected:
Licensee actions relating to the.repair of the damaged
HPCI turbine steam supply line piping suspension system. The inspection
involved 14 inspector-hours onsite by one NRC inspector.
Results:
No items of noncompliance or deviations were identified.
'811
DETAILS
Persons Contacted
Cof!llllonwealth Edison Company (CECO)
- R. Ragan, Assistant Superintendent - Operations
- E. D. Eenigenburg, Assistant Superintendent - Maintenance
- J. Wujciga, Operating Engineer
- J. Doyle, QC Supervisor
- R. Meadows, Maintenance Staff Engineer
T. Cusla, Technical Staff
K. Zinvas, Technical Staff
M. Strait, SNED Engineer
D. L. Farrar, Assistant Superintendent - Administration/Technical Support
N. Schneider, Technical Staff
J. R. Williams, QA Inspector
EDS Nuclear, Inc. (EDS)
- T. Ginsberg, Site Coordinator
T. Goto, Engineer
Sargent and Lundy Engineers (S&L)
P. Gazda, Engineer
- Denotes those who attended the management exit interview on September 7,
1981.
Functional or Program Areas Inspected
Review of licensee actions relating to repair of the damaged Unit 2 HPCI
turbine steam supply line pipe suspension system.
Reference Region III
Immediate Action Letter to CECO dated September 4, 1981.
See Attachment
to this report.
1.
Observation of Work
a.
The inspector performed walkdown of the pipe line from pipe
anchor outside the drywell to the first floor penetration at
Floor Elevation 503'-6".
The approximate configuration of
the system was as follows:
(1) After the elbow from the outboard isolation valve, the
pipe runs 27' south with an approximate 3' offset.
(2) It then runs in a generally west direction for 62'.
(3)
Then in a southerly direction for 26'.
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(4)
Then in a westerly direction for 51' before dropping
through the floor penetration.
The damaged suspension systems included:
Pipe whip restraints 2305-M-209 and 219 near the beginning
and end of run (2) above.
Piping sway braces 2305-M-213 and 220 at the middle and.end
of run (2) above.
Pipe sway brace 2305-M-232 at pipe riser after run (4) above.
b.
The inspector stated that subsequent to this observation hard-
ware repair and modification had brought the system back to
original design conditions.
For details of hardware repair and
modification, see Paragraph 3 of this report.
Based on the inspection findings, the following original design layout
and structural areas appeared to be questionable:
(1)
There was a total horizontal pipe run of approximately 140 feet
with little or no slope.
The steam line condensate drainage
appeared to be poor.
This is an unresolved item (237/81-25-01).
(2)
The design of the pipe whip restraint system appeared question-
able since they failed in the absence of the higher LOCA loading
conditions.
Review of the design is planned.
This is an
unresolved item (237/81-14-02).
(3)
The system was suspended horizontally by sway braces without
seismic snubbers.
Due to their low spring stiffness (similar to
the variable spring hangers), they appeared to be under designed
for restraining piping movements during OBE ,and SSE.
The system
seismic design appears questionable.
Further review of the design
is planned. This is an unresolved item (237/81-25-03).
(4)
The failure of the sway braces demonstrates questionable hanger
installations during construction, in that welding was performed
at the threaded connections where material separation occurred
under load.
2.
Cause Assessment
In conjunction with system observation and in discussion with the site
staff, the inspector determined that the damage was probably caused by
severe line vibrations created by water, steam and mixed flow turbu-
lence during periodic operability tests on valves, pump, and flow
capacities.
The determination was based on the observation that:
(1) damage occurred away from the turbine isolation valve where 2" of
water was measured in the pipe by UT, and (2) the absence of concrete
breakaway at the failed pipe whip restraint ceiling attachment plate
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anchor bolts, could indicate repeated loading that could have loosened
the grip of the expansion type concrete anchor bolts.
Based on the above determination, the inspector stated that the
licensee should provide fatigue analysis that considers the present
vibratory and prior water hammer loading effects to assess the
remaining system safe operation transient life cycles.
This is an
unresolved item (235/81-25-04).
3.
Review of Records
In conjunction with the observation of system conditions, the inspector
reviewed the following repair and hardware modification records, and had
no adverse comment:
a.
VT and MT of pipe suspension components and pipe sections that
had experienced or were expected to see the highest stresses.
This suggested by EDS in a letter to CECO, "Dresden Unit 2 - HPCI
Turbine Steam Supply Operability Assessment," dated September 5,
1981.
This satisfied Item 1 of the Immediate Action Letter.
b.
Inspection, torque testing, and tightening of all shell type
concrete anchor bolts on sway brace structural attachment plates.
c.
Repair of pipe whip restraint 2305-M-209, including tightening
of all wedge type anchor bolts to 300 ft-lb.
The embedment
length of the 1" diameter bolts was measured to be 4-1/8", 3-1/4",
3-1/8", and 5".
These installations were verbally accepted by S&L.
d.
Modification of pipe whip restraint 2305-M..:219.
The ceiling
attachment plate was increased from 8" x 8" x 1-3/4" with four
1/2" diameter bolts to 15" x 15" x 1-3/4".
Due to the difficul-
ties encountered during installation, the eight bolts installed
consisted of three 5/8" diameter bolts, four 1/2" diameter bolts,
and one 5/8" diameter bolt was inoperable because it was not
fully engaged.
e.
Adjustment of variable spring hangers 2305-M-207, 211, 214, 216,
and 221 to the design cold position settings.
f.
Repair of longitudinal linear indications of 3" and 1" along
the pipe elbow center line near the pipe lug connecting sway
- brace 2305-M-220.
A maximum of 0.008" thickness was ground
off.
The wall thickness at the repaired section was measured
to be 0.710".
The minimum calculated required wall thickness
is 0.433".
g.
Repair of a small gouge or tool mark at the pipe near the
containment penetration anchor.
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Items b through g above satisfy Items 2 and 3 of the Immediate Action
Letter.
h.
Installation of a 3/4" drain line at the bottom of the 10" HPCI
steam supply where 2" water was detected by UT.
Two valves in
series were installed to provide throttling of water/steam flow.
A hose discharge was connected to the torus floor sump.
Sub-
sequent to the inspection, a l" drain line was connected to Valve
M0-2-2301-3 instead of using the hose connection to the floor sump.
4.
Procedures Review
The inspector reviewed CECO procedures:
Special Operating Procedure, SOP 81-8-75, "Draining of Condensate
from HPCI Steam Line 2-2305-10 Inch", Revision 0.
"Operating Order No. 22-81 for Dresden Units 2 and 3", dated
September 4, 1981.
The procedures included visual inspection of the newly installed drain
line during normal operating conditions and UT of the water level in
the line at operating temperature.
The inspector stated that he had no
adverse comment as a result of the review.
The above procedures and the daily surveillance committed to by the
licensee for the l" drain line (discussed in Paragraph 3.h above) to
detect steam condensate flow, satisfies Item 4 of the Immediate Action
Letter.
Unresolved Items
Unresolved items are matters about which more information is required in
order to ascertain whether they are acceptable items, items of noncompli-
ance, or deviations.
Four unresolved items disclosed during the inspection
are discussed Paragraphs l.b(l), l.b(2), l.b(3), and 2.
Exit Interview
The inspector met with licensee representatives at the conclusion of the
inspection~ The inspector summarized the scope and findings of the
inspection.
The licensee acknowledged the findings reported herein.
Attachment:
Immediate Action Letter
NRC to CECO dtd 9/4/81
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