ML20086E615
| ML20086E615 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 02/15/1973 |
| From: | Walker R PUBLIC SERVICE CO. OF COLORADO |
| To: | Kruesi F US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086E612 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8312070448 | |
| Download: ML20086E615 (15) | |
Text
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PUBLIC SERVICE COMPANY OF COLORADO P. O.
sOM S40
- OENVER.
COLORAOO e0901 February 15, 1973 Mr. F. E. Kruesi Directorate of Regulatory Operations D ' g [p f U.S. Atomic Energy Commission Washington D.C.
20545
Subject:
Deficiency Report 10 CFR 50 Control & Orificing Assembly, Reserve Shutdown System Fort St. Vrain Station
Dear Mr. Kruesi:
Pursuant to the reporting requirements of 10 CFR 50, Part 50.55, we are submitting herewith twenty (20) copies of the subject _ report involving the reserve shutdown system portion of the control and orificing assemblies at the Fort ' Saint Vrain Station.
Although final corrective action has.notLbeen completed at this time, we feel that the problem and the proposed' corrective measures are sufficiently defined ' that the attached report can be considered complete and final.
We'will, of course, keep the.
local Directorate advised.of-any further. developments.
We trust the attached report will provide you wi'.h sufficient.
information, and will. fulfill the reporting requirements of 10 CFR 50.
-Very truly-yours,-
k % N 4.ll W R. F. Walker, Vice' President.
. Engineering Planning 1
tric Department DW CC Mr. John Flora, Directorate; Region IV Su%o'8M*d385EJm S
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DEFICIENCY REPORT 10 CPR 50 PART 50.55 Facility:
Fort. Saint Vrain Nuclear Generating Station
Subject:
Control and Orificing Assemblies Report Date: February 15, 1973 Incident:
Excessive bleed-off time of helium pressure from the rupture disc of the reserve shutdown hoppers during tests.
General Description The control and orificing assemblies were installed in their respective refueling penetrations.
The PCRV cavity was at atmospheric conditions, and the Preliminary Operating Test (POT 12-01) was being econducted for the control and orificing a'ssemblies as a part 6f the overall plant testing program.
At the time the defici ency was discovered that portion of POT 12-01 concerning testing of the reserve shutdown system was being conducted.
The POT calls for pressurizing the reserve shutdown hoppers with helium to test the capability of the system to pressurize the hopper and the relative integrity of the rupture disc.
With reference to the attached drawing, SLR 1201-100, helium for the reserve shutdown system is intro-duced into the hopper via the reserve shutdown line.
The hopper is vented back to the normal helium purge line via an orifice as shown in Detail A.
The purpose of the orifice is to permit pressure equalization across the rupture disc in the reserve shutdown hopper during normal operation, and yet provide sufficient flow restriction to permit pressurization of the hopper, and hence bursting of the rupture disc, when the reserve shutdown helium pressurization system is ' energized.
The POT called for pressurizing the hopper to some predetermined pressure (well below the rupture disc burst pressure) and measuring the rate of pressure bleed-cf f via the orifice.
In a few instances it was noted that the bleed-off time was excessively short and considerably below the predetermined limits.
1 Cause Determination and Tmmediate Action Taken
~
It was subsequently determined by i suspect control and orificing assem,nvestigation of two of the blies that the orifice had slipped from its design position into the counterbored area provided for the threaded connector (see Detail A).
As a result-helium flow was bypassing the orifice causing excessively f ast pressure bleed-off time.
Inspection revealed that due to' a combination of tolerances on the orifice, the' depth of the counterbore, and the depth to which the threaded connector was screwed into the assembly resulted in clearance between the end of the connector and the counterbore.- This clearance
()
Page 2 I*
D2ficiency Re t
Control & Ori icing Asc mblies was such to allow the orifice to slip from its position into the counterbored area.
A temporary washer / shim was inserted in the counterbored area between the orifice and the threaded connector on two of the assemblies.
Subsequent tests on these two assemblies were suCCe ss ful.
Evaluation of Consequences Although the actual testing during the POT does not provide conclusive evidence that the reported deficiency could have resulted in f ailure of the reserve shutdown system, it is possible that the orifice could slip from its design postion into a position that could result in sufficient bypass flow such that the hoppers could not be pressurized.
Under these conditions the reserve shutdown material could not be intro-duced to the core.
Only a few of the control and orificing assemblies exhibited excessive bleed-off time.
The other assemblies successfully passed the test, and in fact a test
~
was run on one assembly in which the rupture disc was actually broken and the reserve shutdown material released into a bag to simulate actual energization of the reserve shutdown system.
This latter test was conducted with no apparent problems.
It is evident then that the reported deficiency did not manifest itself in all the control and orificing assemblies; however, we recognize that the orifice could be loosened from its design position sometime in the future unless remedial action is taken for all the control and orificing assemblies.
Due to the testing schedule and the overall plant start-up schedule only two of the assemblies were inspected.
The remaining 35 assemblies were not inspected at this time.
In view of the schedular effects and due to the fact that the control and orificing assemblies must be removed again for fuel loading, the decision was made to-inspect and modify all the control and orificing assemblies after the hot flow test and prior to fuel loading.
Corrective Action 1
Upon completion of the hot flow test the control and orificing.
assemblies will be removed.
Each assembly will be inspected and a_ shim will be installed to maintain the orifice position.
2.
The reserve shutdown pressuriza' tion system for each assembly will be tested upon completion of the shim installation per the original requirements of POT 12-01.
3 Continued testing of the pressurization system for the reserve shutdown system will be done every three months, and other surveillance checks will be made per Technical Specification SR 5.1.2 4
Engineering drawings will be modified to include the-shim.
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1 DEPTCTENCY REPORT
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10 CPR 50 PART-50.55 Pacility:
Fort. Saint Vrain Nuclear Generating Station
Subject:
Control and Orificing Assemblies Report Date: February 15, 1973 Incident:
Excessive bleed-off time of helium pressure from the rupture disc of the reserve shutdown hoppers during tests.
2 General Description i
The control and orificing assemblies were installed in their respective refueling penetrations.
The PCRV cavity was at atmospheric conditions, and the Preliminary Operating Test (POT 12-01) was being conducted for the control and orificing a'ssemblies as a part of the overall plant testing program.
At the time the deficiency was discovered that portion-of POT 12-01 concerning' testing of the reserve (shutdown ^ system was being conducted.
The POT calls for pressurizing -the reserve shutdown hoppers with helium to test the capability of the system to pressurize the hopper and the relative integrity of the rupture disc.- With reference to'the attached drawing, SLR 1201-100, helium for the reserve shutdown system is intro-duced into the hopper via the reserve shutdown line.
The hopper is vented back to the normal helium purge line via an orifice as shown in Detail A.
.The purpose of the orifice is to permit pressure equalization across the rupture-disc in
~
the reserve shutdown hopper-during normal-operation, and yet provide sufficient flow restriction to permit ' pressurization; of the hopper,. and' hence bursting of the rupture-disc, when the reserve shutdown helium pressurization system ~ is energized.
The POT called for pressurizing the hopper to. some predetermined-1 pressure (well below the rupture disc burst pressure) and
~
measuring the rate of pressure bleed-cff: via the-orifice.
In-a few instances it was noted that the1 bleed-off time was excessively short and considerably below1the predetermined limits.
Cause Determination and Immediate Action Taken-It was subsequently determined by.:3,nvestigation of-two--of the f
suspect control-and ori icing assemblieszthat the orifice-had slipped from.its design:positiontinto,the:counterbored area provided Tfor-the : threaded ? connector (see Deta311 A). 'As a result helium ' flow was. bypassing thel orifice ' causing excessively f ast; pressure bleed-off Ltime.-
InspectionJrevealed that due-to a-combination? of. tolerances'on~ the orifice, Lthe' depth of: the counterbere,nand theKdepth tolwh'ich the threaded' connector.
was screwed into thesassemblyiresulted in clearanceibetween..
the~end ofEthe' connector 1and the counterbore., This:clearancei
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Pcgo 2 D2ficiency R rt Control & Ori 2cing Ass mblica was such to allow the orifice to slip from its position into the counterbored area.
A temporary washer / shim was inserted in the counterbored area between the orifice and the threaded connector on two of the assemblies.
Subsequent tests on these two assemblies were successful.
Evaluation of Consequences Although the actual testing during the Por does not provide conclusive evidence that the reported deficiency could have resulted in f ailure of the reserve shutdown system, it is possible that the orifice could slip from its design postion into a position that could result in sufficient bypass flow such that the hoppers could not be pressurized.
Under these conditions the reserve shutdown material could not be intro-duced to the core.
Only a few of the control and orificing assemblies exhibited excessive bleed-off time.
The other a'ssemblies successfull y passed the test, and in fact a test was run on one assembly in which the rupture disc was actually broken and the reserve shutdown material released into a bag to simulate actual energization of the reserve shutdown system.
This latter test was conducted with no apparent problems.
It is evident then that the reported deficiency did not manifest itself in all the control and orificing assemblies; however, we recognize that the orifice could be loosened from its design position sometime in the future unless remedial action is taken for all the control and ori ficing assemblies.
Due to the testing schedule and the overall plant start-up schedule only two of the assemblies were inspected.
The remaining 35 assemblies were not inspected at this time.
In view of the schedular effects and due to the fact that the control and orificing assemblies must be removed again for fuel loading, the decision was made to inspect and modify all the control and orificing assemblies after the hot flow test and prior to fuel loading.
Corrective Action 1.
Upon completion of the hot flow test the control and orificing assemblies will be removed.
Each assembly will be inspected and a shim will be installed to maintain the orifice position.
2.
The reserve shutdown pressuriza' tion system for each assembly will be tested upon completion of the shim installation per the original requirements of POT 12-01 l
3 Continued testing of the pressurization system for the reserve shutdown system will be donc every three months, and other surveillance checks will be made per Technical Specification SR 5.1.2 l
4 Engineering drawings wilJ be modified to include the shim.
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DEFICTENCY REPORT:
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10 CFR 50 PART 50.55 I
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Detail of Orifice and Pressurization Piping l
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DEFICTENCY REPORT 10 CFR 50 PART 50.55 Pacility:
Fort. Saint Vrain Nuclear Generating Station
Subject:
Centrol and Orificing Assemblies Report Date: February 15, 1973 Incident :
Excessive bleed-off time of helium pressure from the rupture disc of the reserve shutdown hoppers during tests.
General De sc ri pt ion The control and orificing assemblies were installed in their respective refueling penetrations.
The PCRV cavity was at atmospheric conditions, and the Preliminary Operating Test (POT 12-01) was being conducted for the control and orificing a'ssemblies as a part of the overall plant testing program.
At the time the deficiency was discovered that portion of POT 4
12-01 concerning testing of the reserve shutdown system was being conducted.
The POT calls for pressurizing the reserve i
shutdown hoppers with helium to test the capability of the i
system to pressurize the hopper and,the relative integrity of the rupture disc.
With reference to the attached drawing, j
SLR 1201-100, helium for the reserve shutdowa system is intro-4 duced into the hopper via the reserve shutdown line.
The hopper is vented back to the normal helium purge line via an orifice as shown in Detail A.
The purpose of the orifice is to permit pressure equalization across the rupture disc in the reserve shutdown hopper during normal operation, and yet provide sufficient flow restriction to permit pressurization of the hopper, and hence bursting of the rupture disc, when the reserve shutdown helium pressurization system is energized.-
The POT called for pressurizing the hopper-to_some predetermined pressure (well below the rupture disc burst pressure) and measuring the rate of pressure bleed-cff via the orifice.
In a few instances it was noted that the bleed-off time was excessively short and considerably-below the-predet. ermined limits.
Couse Determination and Immediate Action Taken It was subsequently determined by investigation of two of the suspect control and orificing assemblies that the orifice had slipped from its design position into the counterbored area provided for the threaded connector (see. Detail A).
As a result helium' flow was bypassing the orifice causing excessively f ast pressure bleed-off time.
Inspection revealed that:due_to~a combination of tolerances on the orifice, the depth-of_the counterbore, and the depth to which the. threaded connector was screwed into the assembly'. resulted in clearance between the end ' of the connector and the counterbore.
This clearance.
~
T
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()
Page 2 Control & OritTcing Ass:mblies i
was sucn to allow the orifice to slip from its position into the counterbored area.
A temporary washer / shim was inserted in the counterbored area between the orifice and the threaded connector on two of the assemblies.
Subsequent tests on these two assemblies were successful.
Evaluation of Consequences Although the actual testing during the PUT does not provide conclusive evidence that the reported deficiency could have resulted in failure of the reserve shutdown system, it is possible that the orifice could slip from its design postion into a position that could result in sufficient bypass flow such that the hoppers could not be pressurized.
Under these conditions the reserve shutdown material could not be intro-duced to the core.
Only a few of the control and orificing assemblies exhibited excessive bleed-off time.
The other assemblies successfully passed the test, and in fact a test
~
was run on one assembly in which the rupture disc was actually broken and the reserve shutdown material released into a b'ag to simulate actual energization of the reserve shutdown system.
This latter test was conducted with no apparent problems.
It is evident then that the reported deficiency did not manifest itself in all the control and orificing assemblies; however, we recognize that the orifice could be loosened from its design position sometime in the future unless remedial action is taken for all the control and orificing assemblies.
Due to the testing schedule and the overall plant start-up schedule only two of the assemblies were inspected.
The remaining 35 assemblies were not inspected at this time.
In view of the schedular effects and due to the fact that the control and orificing assemblies must be removed again for fuel loading, the decision was made to inspect and modify all the control and orificing assemblies after the hot flow test and prior to fuel loading.
Corrective Action 1.
Upon completion of the hot flow test the control and orificing assemblies will be removed.
Each assembly will be inspected and a shim will be installed to maintain the orifice position.
2.
The reserve shutdown pressuriza' tion system for each assembly will be tested upon completion of the shim installation per the original requirements of POT 12-01 3
Continued testing of the pressurization system for the reserve shutdown system will be done every three _ months, and other surveillance checks will be made per Technical Specification.
SR 5.1.2 4.
Engineering drawings will be modified to include the shim.
O O
,i DEFICTENCY REPORT:
10 CFR 50 PART 50.55
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