ML19270G475

Forwards LER 79-010/03L-0

ML19270G475
Person / Time
Site:	Cooper
Issue date:	05/23/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19270G476	List: ML19270G475 ML19270G478
References
CNSS790240, NUDOCS 7906080309
Download: ML19270G475 (2)

Text

• *

• .e t-COOPER NUCLEA R ST ATioN Nebraska Public Power District " ' * * "A"e"3"J %'; ""s"".":':"

-] =. -- - _ - . = - = = = = = - - - = = = . -. ==---,---=.==;-

CNSS790240 May 23, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Co= mission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrenc,e that was discovered on April 24, 1979. A licensee event report form is also enclosed.

Report No.: 50-298-79-10 Report Date: May 23, 1979 Occurrence Date: April 24, 1979 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Condition leading to operation in a degraded made permitted by a limiting condition for operation as delineated in Section 3.6.G of the Technical Specifications.

Conditions Prior to Occurrence:

Reactor shutdown for scheduled ref:eling.

Description of Occurrence:

During performance of scheduled inservice inspection, a surface linear indication was noted in weld RAS-CF-13.

Designation of Apparent Cause of Occurrence: -

The apparent cause of the linear indication in weld RAS-CF-13 is lack of fusion near the weld t urface in the original weld.

Analysis of Occurrence:

This defect did not prevent continued operation of the associated systems. The associated systems are the steam condensing mode of the RHR System and the High Pressure Coolant Injection pump turbine.

a,?] 93, u- )/ L l [)

Y

r i je 7 906 08 0J(;h

. . ~r Mr. K. V. Seyfrit May 23, 1979 Page 2.

The indication originated in the weld and extended from the toe of the weld and runs 3/4" perpendicular to the weld. The indication was found by liquid penetrant technique and ultrasonics. Review of the original radiograph showed no relevant indication. The weld was radiographed, concentrating the direction of the source along the plane of the weld bevel. This technique showed an area of lack of fusion near the surface at the location of the defect.

The weld is located in the main steam supply to the "A" Residual Heat Removal (RHR) heat exchanger. The piping is 8" schedule 100 with a minimum wall of .440". The wall thickness in the area of the repair was .560". The weld is in the Class II portion down-stream of main steam isolation valves for the "A" and "B" RER heat exchangers and high pressure coolant injection pump turbine and upstream of the pressure control valves for the steam s2pply to the "A" RHR heat exchanger.

In the event the indication propagated into a through wall defect, steam line break detection temperature switches would have notified the control room of the condition. This portion of the main ateam line is isolatable and the reactor could be shut down safely.

This occurrence presented no adverse consequences from the stand-point of public health and safety.

Corrective Action:

In accordance with approved station procedurcs the defect was removed. The depth of the excavation did not exceed the minimal wall thickness of the pipe. Upon completion of the repair the area was reexamined in accordance with the Inservice Inspection Program and was found to be satisfactory.

Sincerely, q,,

dJd? llf 86 L. C. Lessor Station Superintendent _

~

Cooper Nuclear Station LCL:cg Attach.