05000298/LER-1982-012, Forwards LER 82-012/03L-0.Detailed Event Analysis Submitted

Forwards LER 82-012/03L-0.Detailed Event Analysis Submitted

ML20054K497
Person / Time
Site:	Cooper
Issue date:	06/21/1982
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20054K498	List: 05000298/LER-1982-012, Forwards LER 82-012/03L-0.Detailed Event Analysis Submitted
References
CNSS820377, NUDOCS 8207020256
Download: ML20054K497 (2)

LER-2082-012, Forwards LER 82-012/03L-0.Detailed Event Analysis Submitted

Event date:
Report date:
2982082012R00 - NRC Website

text

_ _ - _ _ - _ - __

7 ,

cooper NUCLEAR ST ATioN Nebraska Public Power District "A"E" a"MM;L""^i" ^ " ' ' '

CNSS820377 June 21, 1982 j I

~

"hh f,  !

Mr. John T. Collins, Regional Administrator {l M2gg I U.S. Nuclear Regulatory Commission  ;

Region IV l'

611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.3 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on May 22, 1982. A licensee event report form is also enclosed.

Report No.: 50-298-82-12 Report Date: June 21, 1982 Occurrence Date: May 22, 1982 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Observed inadequacies in the implementation of administrative or procedural controls.

Conditions Prior to Occurrence:

The reactor was in cold shutdown for a maintenance refueling outage.

Description of Occurrence:

The reactor vessel head studs were not detensioned in accordance with Maintenance Procedure 7.4.4, Reactor Vessel Head Removal -

Installation.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence was personnel error in that the procedure was not followed.

Analysis of Occurrence:

The reactor head closure contains 52 studs. During the deten-sioning process, four studs are detensioned simultaneously (one per quadrant). Maintenance Procedure 7.4.4 requires a two pass de-tensioning process. During this occurrence, the first 48 of 52

~

8207020256 Fl20621 PDR S ADOCK 05000298 pyg

Mr. John T. Collins June 21, 1982 i Page 2. i studs were detensioned in one pass. This caused the tension to increase to a higher value in the last four studs. As a result, the last four studs could not be detensioned. The other 48 studs were tensioned to an intermediate value and all 52 studs were then detensioned.

A quantitative analysis was performed by the vessel vendor. The yield stress of the four studs in question was not exceeded. A qualitative analysis of the studs, stud nuts, and closure head flange was conducted under the direction of the vessel vendor.

This included measurement of critical areas, penetrant testing, ultrasonic testing, and visual examination. No damage was found.

This occurrence presented no adverse effects to the health and safety of the public. A NRC Region IV, I&E Inspector has reviewed the incident on site.

Corrective Action:

Immediately the remaining 48 studs were tensioned to an inter-mediate value, then all 52 studs were detensioned per the proce-dure. Prior to further use of Maintenance Procedure 7.4.4 for head detensioning, this incident will be further reviewed and the proce-dure checklist revised in an effort to prevent recurrence. This occurrence has been discussed with appropriate personnel.

Sincerely, L. C. Lessor l

Station Superintendent Cooper Nuclear Station LCL:cg Attach.

l l