ML20248F000
| ML20248F000 | |
| Person / Time | |
|---|---|
| Site: | Surry, 05000000, Trojan |
| Issue date: | 09/29/1989 |
| From: | Padovan L NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | |
| Shared Package | |
| ML20248E940 | List: |
| References | |
| TASK-AE, TASK-T916 AEOD-T916, NUDOCS 8910060162 | |
| Download: ML20248F000 (5) | |
Text
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E.1 AEOD TECHNICAL REVIEW REPORT UNITS:
Multiple TR REPORT NO.:
AEOD/T916 DOCKET-NOS:
Multiple DATE: September 29, 1989 LICENSEES:
Multiple EVALUATOR / CONTACT:
L.Padovan NSSS/AE:
Multiple
SUBJECT:
DEBRIS IN CONTAINMENT RECIRCULATION SUMPS
SUMMARY
On July 8,
- 1989, during cleanup ' activities after a refueling outage at the Trojan nuclear power plant, debris was discovered in the containment recirculation sump.
Items ' found in the sump included insulation, pieces of metal wire, pipe fittings, and pieces of fabricated steel.
Two pins, taped to hangers located above the recirculation sump, were also located.
A few days later, a second inspection of the sump revealed duct tape and a piece of muslin material in the sump.
f -
i The containment recirculation sump and associated
- screens, shelves, and ' curbs, are designed to provide a source of water, with a minimum acceptable amount of debris, to the containment spray system and residual heat removal system during the recirculation phase of a loss of coolant accident.
Debris in the containment sump could be drawn into the suction of the containment spray pumps and the residual heat removal pumps during the recirculation phase.
This potentially could cause a partial or complete loss of one or more of the containment spray, residual heat removal, or safety injection systems.
As a result of the identified concern:s, AEOD initiated this study to investigate the frequency of occurrence, and generic applicability, of debris accumulation in containment recirculation sumps.
In addition to the Trojan occurrence, the study evaluated seven other licensee event reports (LERs) which were identified through a Sequence coding and Search System (SCSS) review of the LER data base from 1980 to 1989.
With the exception of occurrences at the Surry 1 and 2 plants, l
none of the other LERs were found to involve actual accumulation of debris in containment sumps.
At Surry, foreign objects identified and removed from the sumps included nuts, bolts, wire, j
metal
- pieces, and wood.
The sources of the debris were determined to be from early plant modifications made at a time L
when adequate foreign material exclusion programs were not being implemented.
The Surry events were specifically addressed in NRC Information Notice No. 88-87,
" Pump Wear and Foreign Objects in Plant Piping Systems."
At the Trojan
- facility, immediate corrective actions have been completed, and long term programmatic actions are in process.
Accordingly, no further AEOD action on the subject of debris in containment sumps is warranted at this time.
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DISCUSSION i
1.
Description of Tro-lan Occurrence On July 8, 1989, with the plant in a cold shutdown condition nearing the er.d of the 1989 refueling outage, debris was
)
discovered in the containment recirculation sump (Ref.1).
The debris was located in the pipe chase near the suction to the containment spray and residual heat removal systems.
Items found in the sump included insulation, pieces of metal j
wire, pipe fittings, and pieces of fabricated steel.
Two
]
hanger pins, taped to hangers above the containment sump, were also found and removed with the sump debris.
i on July 10, 1989, quality assurance personnel performed a follow-up inspection of the containment sump, and identified duct tape on a valve inside the sump, and found muslin material just inside the pipe chase.
These materials were likewise removed, and combined with the previously removed foreign materials for examination.
Quality assurance inspectors determined the material had been in the sump long enough to collect dust and rust.
As a result of subsequent discussions, the licensee concluded the foreign material found in the containment recirculation sump was most likely there during the last fuel cycle.
On July 14,
- 1989, after the plant entered Mode 4
(hot shutdown), the resident inspector found additional items in the containment sump.
These items included nylon tie wraps, washers, and welding rod, which were subsequently removed.
On July 17, 1989, as a result of an investigation into the hanger pins, the licensee further determined that the sump baffle did not have the 3/16 inch mesh screen installed on the top portion of the baffle, and some of the mesh screen in the side baffles was torn or missing.
On July 19, 1989, NRC inspectors identified additional debris in the containment sump, consisting of weld rod stubs, steel wire, and pipe fittings (Ref. 2).
Some of this material was encrusted with boric acid crystals.
The licensee's analysis of the containment sump debris situation revealed inadequacies with procedures, post-work cleanliness requirements, system walkdowns, inspector qualifications, work and tool control, foreign exclusion, management oversight, and incomplete construction of the sump.
As corrective actions, the missing mesh screen was installed on the recirculation sump, and procedures were revised to enhance containment inspections.
Training of inspectors was improved, and walkdowns of various systems were performed, again.
A program to upgrade the Design Basis Document l
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Program was implemented, also.
-2.
Opera _t;fonal Data The Sequence Coding ~and Search System was utilized to perform a search of the LER database from 1980 to 1989, for debris in the containment sumps.
In particular, the search focused on foreign ' material in 1) containment, 2) equipment drains, 3) the decay heat removal system, and 4) the containment spray system.
Seven additional LERs were determined to be relevant to this' study.
The seven occurrences were grouped into the following categories:
-Foreign material in containment recirculation sumps.
The Surry 1 (Ref. 3) and Surry 2 (Ref. 4) occurrences involved foreign objects located in the containment sumps.
These occurrences were discussed in NRC Information Notice No. 88-87 (Ref. 5).
-Potential for fibrous or aluminum foil insulation transportation to the sump screens.
Personnel at Millstone 1 (Ref.6) and Susquehanna 2 (Ref.7) determined that the potential existed for insulation inside containment to become loose and be transported to the screens of the containment sump.
This issue was previously addressed by NRC Generic Letter 85-22 (Ref. 8).
-Debris inside containment which could' not be transported to the containment sump screens.
A Sequoyah 2 LER (Ref.
9) described a condition where debris and loose equipment was discovered inside the containment upper compartment.
- However, subsequent licensee analysis of the available pathways to the containment sump revealed the material could not be transported to the sump during accident conditions.
-Debris inside containment identified prior to potential transport to the containment sump screens.
LERs from D.C.
Cook 1 (Ref. 10) and l
D.C. Cook 2 (Ref. 11) described situations where debris and inadequately restrained items were found inside containment.
However, no items were found inside the containment sump.
FINDINGS AND CONCLUSIONS j
With the exception of the Surry occurrences, none of the seven i
other LERs were found to involve actual accumulation of debris in containment sumps.
As previously indicated, the Surry occurrences were addressed in Information Notice No. 88-87.
At
the Trojan
- facility, immediate corrective actions have been L
completed, and long term programmatic actions are in process.
k Accordingly, no further AEOD action in this regard is warranted at this time.
REFERENCES 1.
Trojan Nuclear Plant Licensee Event Report 89-16, " Inadequate Procedure and Personnel Errors Result in Power Operation With the Containment Recirculation Sump Protective Screen Not Installed,"
Docket No.
50-344, Portland General Electric Company, August 16, 1989, 2.
U.S.
Nuclear Regulatory Commission Region V Inspection Report No. 89-22,
" Meeting on August 24, 1989," Docket No. 50-344, September 1, 1989.
3.
Surry Power Station, Unit 1, Licensee Event Report 88-17-01,
" Debris in Containment Sumps Due to Inadequate Inspection Program,"
Docket No.
50-280, Virginia Electric and Power Company, November 7, 1988.
4.
Surry Power Station, Unit 2,
Licensee Event Report 88-24, "A
and B Inside Recirculation Spray Pump Found With Internal Damages," Docket No.
50-281, Virginia Electric and Power Company, November 4, 1988.
5.
U.S.
Nuclear Regulatory Commission Information Notice No. 88-87, " Pump Wear and Foreign Objects in Plant Piping Systems,"
November 16, 1989.
6.
Millstone Nuclear Power
- Station, Unit 1,
Licensee Event Report 88-04-01,
" Potential Fouling of ECCS Suction Strainers,"
Docket No.
50-245, Northeast Nuclear Energy Company, May 27, 1988.
7.
Susquehanna Steam Electric Station, Unit 2,
Licensee Event Report 88-10, "Delaminating Foil on Insulation in Primary Containment," Docket No. 50-388, Pennsylvania Power and Light Company, July 15, 1988.
8.
U.S.
Nuclear Regulatory Commission Generic Letter 85-22,
" Potential For Loss of Post-LOCA Recirculation Capability Due to Insulation Debris Blockage," December 3, 1985.
9.
Sequoyah Nuclear Plant, Unit 2, Licensee Event Report 85-05,
" Debris Inside Containment,"
Docket No.
50-328, Tennessee Valley Authority, March 14, 1985.
10.
D.C.
Cook Nuclear Plant, Unit 3, Licensee Event Report 81-08, (untitled),
Docket No.
50-315, Indiana Michigan Power Company, April 15, 1981.
11.
D.C.
Cook Nuclear Plant, Unit 2, Licensee Event Report 83-41,
.-.t._
.g-i-
(untitled),
Docket' No.
50-316,
-Indiana Michigan Power Company, May 6,
- 1983, i
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1 1
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