ML20127H357
| ML20127H357 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/19/1993 |
| From: | Antony D NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9301220297 | |
| Download: ML20127H357 (5) | |
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g Northern States Power Company 414 Nicollet Mau Menneapohs Minnesota 55401 Telephone (612) 330 5500 January 19, 1993 10 CFR Part ?
Section 2.201 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PIANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Response to Notice of Violation Insnectinn Reports No. 50-282/92022(DRP) and 50-306/92022(DRP)
Reference:
Letter from T H Parker, Northern States Power Company, to U S Nuclear Regulatory Commission dated December.21,1992 titled
" Reply to a Request for Information on the Station Blackout / Electrical Safeguards Upgrade Project" In response to your letter of Decem1er 18, 1992, which transmitted Inspection Reports No. 282/92022 and 306/92022, the following information is offered.
Violation 10 CFR 50, Appendix A, Criterion II, states, in part, that structures, systems and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes without loss of capability to perform their safet.y function.
10 CFR 50, Appendix B, Criterion III states, in part, that measures shall be established to assure that the design basis is correctly translated into spec i fications, drawings, procedures and instructions.
DS/D6 Building and Building Support Systems Design Criteria, Revision 2, dated February 28, 1991, paragraph 7.2.2.1.6, states "the DS/D6 Building and its foundation are physically separated from existing plant structures."
Fluor Daniel Final Report on D5/06 Building "G Row" Wall Construction Problems, dated October 23,~ 1991, Section 2.0, states, "A 1/2 inch compressible board was used between the turbine flood wall (up to elevation 705') and the "G" row wall of the D5/D6 building to maintain the design separation between the two walls."
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Nodhem States Pever Company USNRC January 19, 1993 Page 2 The Station Blackout / Electrical Safeguards Upgrade Project Design Report dated November 27, 1990, Section 4.3.2.2.1.f, states that the building and its foundation are physically separated from the existing plant and the gap filled with compressible material between the D5/D6 building and adjacent structures.
Contrary to_the above, the licensee failed to adequately translate design requirements into applicable drawings.
This resulted in the compressible board not being installed between the walls and the subsequent degradation of the seismic independence of the safety related D5/D6 generator building.
This is a Severity Level IV Violation (Supplement I.D.3).
Response
The design intent was to maintain the physical independence'of the new D5/D6 Building from the existing plant structures so that the motion of each' building would not be restricted by another building during a seismic event.
The physical independence between the DS/D6 Building and the Turbine Building was to be established by maintaining a specified gap between the two buildings.
There are two problems regarding the gap between the stairwell wall of the D5/D6 Building and the flood wall of the Turbine Building.
The most significant problem is the failure to maintain the physical independence of the two buildings as originally designed. Also, we stated in the Design Report that there would be compressible material in this gap but we did not construct the new wall in that manner.
Background:
For this project, the basic design requirements were defined in Design Criteria Documents. generated by Fluor Daniel (the project architect / engineering firm) with Northern States Power concurrence.
The design requirements contained in the Design Criteria Documents for the project were-translated into specifications, drawings, procedures and instructions.
The Station Blackout / Electrical Safeguards Upgrade Project Design Report which was written to provide a design description of the project for NRC review, was developed.by summarizing the Design Criteria Documents.
Explanation of the failure to maintain the physical independence of the.
structures:
The Design Criteria Document requirement of the physical independence of the buildings was translated into the drawing requirement ofr an isolation gap between the stairwell wall of the D5/D6 Building and the flood wall of the Turbine Building.
During construction, the DS/D6 wall was built without_the specified gap being maintained uniformly.
The design requirement of the
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Northem States Power Company January 19, 1993 Page 3 physical independence of the buildings gap was-not satisfied due to-the mis-use of a forming method by the civil contractor.
The contractor used " Stay-Forms" which are forms that remain in place on one side of_the concrete after:
construction is complete. They are intended for an application where a wall is being poured next to another wall or structure.
The." Stay-Form" is-partially made of expanded metal which is not impervious and. therefore, actually did not maintain the required gap because'some cement mortar had oozed through the " Stay-Forms" into-the gap. Use of " Stay Forms" without' anything linin 6 the inside of the expanded metal form can allow this oozing of mortar.
The contractor initially was using the " Stay-Forms"-without any-liner.
Later, after the wall in question had already been built, use-of-polyethylene sheetin$ was specified and the " Stay-Forms" were thereaf ter used effectively; the " Stay-Forms", by themselves, were not appropriate to maintain the required gap.
Explanation of the lack of compressible material between the subject walls as discussed in the Design Report.
The Design Criteria Document for the diesel generator building states that "the D5/D6 Building and its foundation are physically separated from existing plant structures" but it does not specify the method of maintaining the physical separation.
The drawings specified maintenance of a gap between the-walls but also did not specify the method-.
The Design Report erroneously-stated that the gap would be filled with compressible material.
The original draft of the Design Report did not dis,uss the-use of-
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compressible material.
During the period of time when Revision:0 of the-Design Report was being developed, the method of maintaining the-separation between walls was being determined. Use of compressible material; between the steps of the-foundations was planned and knowledge of this prompted the inadvertent inclusion of the subject statement in the Design Report. The Design Report statement is inaccurate, not in discussing compressible material filling the gap, but in implying that the gap is to be maintained by.
compressible material everywhere,' rather than just at the. foundation level and between the D5/D6 Building and Auxiliary Building walls.
The statement is partially true and this contributed to its being overlooked during the completion of the review phase leading up to the~ submittal of Revision 0 of the Design Report to the NRC in November 1990.
Since the Design Criteria Documents and the drawings never referred to compressible material between' the walls, there was never a need to revise those documents when the contractor chose not to use any board between the walls.
Because those documents were-not revised.-there was nothing to prompt a re-examination of the Design Report.
Corrective Steos Taken and Results Achieved The failure to maintain a gap between the two walls was analyzed by Fluor Daniel for the effects on the structural integrity of the D5/D6 Building.
The
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-USNRC-January 19, 1993 Page 4 conclusions of the analysis are that the overall seismic responses of the Turbine'and D5/D6 Buildings are-not affected by the lack of gap between the walls; and the stairvell wall and the flood wall are capable of carrying the conservatively evaluated seismic forces without exceeding _ their code allowable -
stresses. This analysis was provided to the NRC by letter dated December 21, 1992 (Reference).
This analysis is under review by the Structural and i
Geosciences Branch, The draft Design Report was developed from the Fluor Daniel Design Criteria Documents as described earlier. The November 27, 1990 version differed from:
the draft because of the inclusion of numerous comments during the development stage.
The incorrect statement regarding the use of the compressible material was incorporated during this process.
Because of this, we decided to review-all of the changes made to the draft Design Report during-this development stage in order to determine whether there was any other discrepant design information incorporated into the Desi n Report during this stage, This 6
review revealed no other discrepancies.
Corrective Steps to Avoid Further Violations It is believed that the review process works adequately, that this was an unusual-exception. However, to ensure that this experience is educational, we -
will include this matter in Engineering and Technical Staff Work Package Training scheduled for the first quarter 1993.
Date When Full Compliance will be Achieved Full compliance has been achieved.
i Related Issue Another inaccuracy occurred. in a statement in Section 2.0.of the Fluor Daniel Final Report on D5/D6 Building "C-Row" Wall Construction Problems,; dated October-23.-1991.
This statement, also quoted in the. Notice of Violation, "A 1/2' inch compressible board was used between the turbine flood wall (up to elevation 705') and the "G" row wall of the D5/D6 building to maintain the-design separation between the two walls,"" was not' based on a design requirement of either a Design Criteria Document or other desi n document but 6
was based on the civil contractor's assertion that compressible board was used. During' Fluor's evaluation of another "C" row wall concrete placement problem'(discussed in Inspection Reports Nos. 50-282/92019(DRS) and 306/92019(DRS)), they were mis-informed by the civil contractor during a-
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telephone conversation that they had used the board between the walls, We believe that there was no intent to misrepresent the situation but rather honest confusion because of the use of. compressible material in some locations.
In addition, the gap area between the two walls; at a -doorway -
' between the two buildings did show compressible board around the door -
perimeter, substantiating the contractor's assertion, However, later, it was determined that the board at this location was only a limited use.
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Northern States Power Company USNRC.
January 19, 1993 Page 5 In summary, we believe these problems were isolated events and not representative of the way we perform and document modifications. The referenced completed analysis demonstrates that the safety of the buildings-has been maintained. We have made a commitment to include this matter in-Engineering and Technical Staff Work Package Training scheduled for the first quarter of 1993.
Please contact Jack Leveille (612-3881121, Ext, 4662) if you have any questions related to our response to the subject inspection reports, fO
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Douglas D Antony b
Vice President Nuclear Ceneration c: Regional Administrator III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg