ML20029A298

LER 91-001-00:on 910109,determined That Containment Tendon Surveillances Performed in 1981 & 1985 Did Not Reflect Guidance in Tech Specs.Caused by Inadequate Administrative Controls.Testing Program Plan implemented.W/910208 Ltr

ML20029A298
Person / Time
Site:	Fort Calhoun
Issue date:	02/08/1991
From:	Gates W, Voss K OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-001, LER-91-1, LIC-91-008L, LIC-91-8L, NUDOCS 9102120030
Download: ML20029A298 (5)

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Omaha Public Power District 444 South 16th Street Mall Omaha, Nebraska 68102-2247 402/636-2000 l

February 8, 1991 LIC-91-0008L V. S. Nuclear Regulatory Commission Attn Document Control Desk Mail Station P1-137 Washing'.an, DC 20555

Reference:

Docket No. 50-285 Gentlemen: I

Subject:

Licensee Event Report 91-01 for the Fort Calhoun Station l Please find attached Licensee Event Report 91-01 dated February 8, 1991. This I

report is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B).

If you should have any questions, please contact me.

Sincerely, i

A&. $. $s&r W. G. Gates Division Manager l_

Nuclear Operations WGG/djm Attachent c: .R. D. Martin, NRC Regional Administrator W. C. Walker, NRC Project Manager R. P. Mullikin, NRC Senior Resident Inspector INP0 Records Center l

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-On January 9, 1991, with the reactor-in Mode 1 at approximately 26% power, it was -

c determined that prior to the performance of the containment tendon surveillances l in~1981 and 1985, the test procedures were changed to reflect the guidance of L Revision 3 to Regulatory Guide 1.35. Tecanical Specification 3.5(7)a, which j incorporates the guidance in Revision 1 af Regulatory Guide 1.35, is more-restrictive relative to detensioning of tendons. By using guidance not reflected l

in the Technical Specifications, both these tests failed to completely detension all the required tendons. This violation of the Technical Specification is reportablepursuantto10CFR50.73(a)(2)(i)(B).

l The root cause for this event was inadequate administrative control of the tendon I, surveillance program, with inappropriate actions by personnel as a contributing factor.

Corrective actions include: enhancement of station en implementation of a Containment Testing Program Plan;gineering improvements insupport, the safety including evaluation process for procedure changes; and submittal of a proposed license amendment to incorporate appropriate Regulatory Guide 1.35, Revision 3 guidance into the Technical Specifications.

l NRC Form 354 L6491

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t The containment structure at Fort Calhoun Station Unit No. 1 is a ' reinforced concrete pressure vessel that includes ungrouted prestressing tendons in the domed roof and the walls. These tendons are stressed to keep the containment concrete in compression. The compressive. forces are of sufficient ma internalforces(i.e.,anincreaseincontainmentpressure)gnitudesuchthattheintroduced b basis accident will be offset by the containment prestressing. This will result in an essentially stress-free containment building during the event. Tnere are 210 dome tendons and 616 helical wall tendons in the containment structure. The idome tendons are divided into three layers that are mutually inclined at 120 degrees. The wall tendons consist of four layers arranged in a 45 degree helical-3attern-in two directions,--i.e., two right-handed helical and two left-handed 1elical layers. Each orientation is considered to be a group.

NuclearRegulatoryCommission(NRC)RegulatoryGuide1.35,"InserviceInspection of Ungrouted Tendons =in Prestressed Concrete Containments, Revision 1", dated June

.1974, specified that a tendon liftoff test should include an unloading cycle going

'down-to essentially complete detensioning of the tendon to identify broken or.

damaged wires or strands. It also stated that for. containments that differ from the typical, the model program. described should serve as a basis for a com) arable inservice inspection program. The Fort Calhoun containment differs from tie

, typical model.due to the use of the helical wall tendons.

InAugust1974,OmahaPublicPowerDistrict(0 PPD)submittedaFacilityLicense i Change to the NRC to in' corporate the guidance provided.by Regulatory Guide 1.35, Revision 1, into the Fort Calhoun Technical Specifications. In August 1975, the requirement for comp btely detensioning each selected tendon was incorporated into the Technical Specifications by License Amendment No. 6. The 1976 tendon testing.

was completed to this specification.

Technical Specification 3.5(7)a requires that periodic inspections be performed on three dome-tendons, one from each layer, and on three wall tendons of each orientation. The surveillance requirements for each tendon selected include

, taking of lift-off readings,. complete.detensioning, and examination for broken l wires and for any evidence of damage or deterioration of anchor hardware.

.-Additionally, the Specification requires the removal of one wire from each of three-helical tendons and one from.a dome tendon for inspection and testing. This is accomplished after fully detensioning the selected tendons. Following the

-surveillance, each detensioned tendon-is fully retensioned to at least the average wire stress indicated by the last liftoff reading for that tendon.

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. o .a - unc w, am ,mn In April 1979, the NRC issued for comment Revision 3 of Regulatory Guide 1.35.

This revision proposed the requirement to detension all sample tendons be relaxed to detensin just one tendon per group. The value and im)act section noted that detensioning all the surveillance tendons to look for broien wires "is quite marginal and the cost is high." Revision 3 of Regulatory Guide 1.35 was approved and issued in July 1990.

1 On January 9, 1991, with the reactor in Mode 1 at approximately 26% power, a nonconformance in the tendon surveillance testing program was identified by the Special Services Engineer in charge of the Containment Tendon Testing Program. It was found that prior to the performance of the tendon surveillance in 1981, the

_ test procedure was changed to reflect the guidance of the proposed Revision 3 of Regulatory Guide 1.35 without having an approved corresponding change incorporated into Technical Specification 3.5(7). The 1985 test was also performed usir.g the guidance in Regulatory Guide 1.35, Revision 3. By using guidance not reflected in the Technical Specifications, both these tests failed to completely therequiredtendonsasrequiredbyTechnicalSpecification3.5(7)ai). This (detension all violation of the Technical Specification is reportable pursuant to 10 CFR 50.73(a)(2)(1)(B).

An operability evaluation was subsequently aerformed by Station Engineering. This I evaluation confirmed that, although the Tec1nical S)ecification requirement to detension all selected tendons was not fulfilled, tie operability of the tendons and the containment structure was not compromised.

Investigation revealed that the engineers assigned to coordinate the 1981 and 1985 surveillances apparently did not realize that Fort Calhoun Station was committed to Revision 1 of Regulatory Guido 1.35 by License Amendment No. 6. A procedure change to the surveillance test prior to the performance of the 1981 test revised the test to ref'a t the guidance in Revision 3 of the Regulatory Guide. Prior to l the performance of the 1985 test another 3rocedure change was made to incorporate the guidance of a vendor procedure into t1e test procedure. The vendor procedure stated that it satisfied the requirements of Revision 3 of Regulatory Guide 1.35.

Both these procedures changes were approved by the Plant Review Committee.

The root cause for this event was inadequate administrative control of the tendon surveillanco program, with inappropriate actions by personnel as a contributing factor. Inexperienced engineers were assigned to coordinate the tendon surveillance tests in 1981 and 1985, and they initiated did not fully comply with the Technical Specifications. procedure There was changes poor turnover which of information between the test engineers. Inadequate review by management, including the Plant Review Committee, allowed approval of changes to the test procedures such that the tests did not meet all the requirements of the Technical Specifications.

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The results of the tendon testing indicate that the containment prestressing system is not degraded by the failure to detension all the surveillance tendons in the 1981 and 1985 surveillance tests. Detensioning of tendons is not required to to inspect for degraded wires or anchor hardware. Since this examination was adequately performed during the performance of the liftoff portion of the surveillance and no problems were found, the operability of the containment prestressing system was never compromised. The surveillance methods used met the guidelines of Regulatory Guide 1.35, Revision 3 which has been approved by the NRC. It is concluded that there is no safety significance associated with this event.

The following corrective actions have been completed:

(1) Anoperabilityevaluation(PED-SSE-91-0032, Revision 1 dated January 16, 1991) and root cause analysis were performed by the Special Services Engineer in charge of the Containment Tendon Testing Program.

(2) The OPPD program for generation and review of nuclear safety evaluations associated with procedure changes has been improved in recent years. This will assure compliance with regulatory guidance.

(3) Station engineering support has been enhanced with additional personnel and administrative controls. A Programs Development Project was initiated to establish program plans which insure quality, regulatory compliance, and continuity for infrequent tests such as tendon surveillance. The Technical-Specification noncompliance noted in this report was identified during the preparation of the Containment Tendon Testing program plan by the Program-

! Engineer.

l l The following corrective actions will be completed:

e

! (1) A Facility License Change will be submitted to incorporate ap3ropriate guidance provided by Regulatory Guide 1.35, Revision 3 into t1e Technical

' Specifications. This change will be submitted by June 30, 1991.

(2) The Containment Testing Program Plan and Basis Document will be completed and issued prior to performance of the next scheduled tendon surveillance.

Therehavebeen-4additionalLER's(87-10,87-37,88-08,and89-02)dealingwith surveillance tests-that did not meet the r"uirements of the Technical Specifications.

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