ML20086B221

AO 50-267/74-19A:in Response to Dro Bulletin 74-3,insp of Class I Support Structures Indicated Design Problems on 24 Structures.Addl Structural Steel Bracing & Reinforcement Added & Review Initiated

ML20086B221
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/05/1974
From:	Reader J, Swart F DUKE POWER CO., PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20086B210	List: ML20086B207 ML20086B221 ML20086B234 ML20086B242
References
50-267-74-19A, AO-50-267-74-19, ROB-74-3, NUDOCS 8311170102
Download: ML20086B221 (3)

Text

._.

O REPORT DATE: November 5, 1974 e

ABNORMAL OCCURRENCE

' FORT ST. VRAIN NUCLEAR GENERATING STATION

• PUBLIC SERVICE COMPANY OF COLORADO P. O. BOK 361 PLATTEVILLE. COLORADO 80651 REPORT NO. 50-267/74/19A FINAL IDEITTIFICATION OF OCCL'RRENCE:

As requested in AEC DRO BULLETIN NO. 74-3, Public Service Company of Colorado and General Atomic Company have conducted on inspection of the Class I support structure at Fort St. Vrain.

The results of the inspcetion program indicated that design problems existed -

on 24 of the'238' Class I support structures at Fort St. Vrain. f This condition is considered reportable under Paragraph B-3 of AEC DRO Bulletin No. 74-3.

CONDITIONS PRIOR TO 00CL'RRENCE: Steady State Power Routine Shutdown Hot Shutdown Routine Load Change

. I Cold Shutdown Other (specify) l Refueling Shutdown Routine Startup The major plant, para =cters at the time of the ew:nt were as follows:

Power PTR, O MWth ELECT, O MWe Secondary Coolant Pressure N/A psig

}

Temperature N/A *F 8311170102 741114 PDR ADOCK 05000267 Flow 0 #/hr.

S PDR Primary Coolant Pressure O psig Temperature 100 *F Corc. Slet 100 *F Core Atiet

Elow 0 f/hr.

O o. v. 2 DESCRIPTION OF

' OCCURRENCE:

~

. The results of the inspection program of the Class I support structures indicated that a prob 1cm existed regarding the seismic design of some Class I support structures. The problem related to the support structure natural vibrational frequency and the design carthquake vibrational frequency on 24 Class I support structures.

The specific types of support structures found to have problems were:

! 1.) Heat Exchanger Support Structures 2.) Filter Support Structures 3.) Varicus Tank Support Structures APPARANT CAUSE OF OCCURRENCE: X Design Unusual Service Cond.

Including Environ.

Manufacture Component Failure Installation /

Construction Other (specify)

Operator Procedure ANALYSIS OF OCCURRENCE:

! The analysis of this problem consisted of a visual inspection of CJ cs: I support structures by General Atomic Company engineers to verify that the field configurcticn was accurately reflected in the seismic calculations; and where incorrect assu=ptions were made, further analysis cnd structural additions were specified.

General Atomic Company elected to'have the Sargent & Lundy Structural Engineering Department perform the additional analysis where required.

CORRECTIVE

-ACTION:

, Additioncl. structural:. steel. bracing .and reinforcement has been added to those structures (24 in all) found to have scis=ic design problems. The physical work has been co:pleted and scismic calculations have been forwarded to Public Service Company for review.

Public St vice Company is currently in the process of performing an in-dependent review of all calculations and "as-built" configuration for those l structures requiring additional reinforcement. ,

i

_ _ _ _ _ .. ~

s . . -( . .. . O o Page 3 During Public Service Company's review of the scismic calculations submitted by General Atomic Company an error was found on one (1) structure calculation regarding an assu=ption made in the General Atomic /Sargent &

General Atomic Company concurred that the error existed, Lundy calculations.

and the additional structural steel bracing indicated has been installed ,

on this support structure.

FAILURE DATA /SIMILIAR REPORTED OCCURRE';CES:

None of the Class I support structures have evidenced any sign of actual failure. Also, there has not been any similiar reported occurrences at Tort St. Vrain.

-PROGRA301ATIC IMPACT:

None CODE IMPACT:

None ,

Approved by:

Prepared by:

OS-ELt

. /)/ '~ ~

/ J1 >

Fr'ederic E. Swart N

J II.' Reader SherintendentNuclearProduction Resident Engince.

- Fort St. Vrain Nuclear Generating Station