ML20041A624

First Interim Deficiency Rept Re Unevaluated Missile Source,Initially Reported on 820108.Probability of Fly Wheel Failure Under Investigation.Deficiency Will Be Reviewed for Possible Generic Applications

ML20041A624
Person / Time
Site:	Yellow Creek
Issue date:	02/05/1982
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8202220348
Download: ML20041A624 (2)

Text

. _ - - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ .

. ,k .

TENNESSEE VALLEY AUTHORi{Y .

CH ATTANOOGA, TENNESSEE 374ol '*,. ._

~~

400 Chestnut Street Tower II February 5,5318RIs 10 Ill! . O J YCRD-50-566/82-04  !

YCRD-50-567/82-04 t- O .h W/

9) \

U.S. Nuclear Regulatory Commission Q i

Region II -,-j g,,, .cq7., 1 l ' 1 # '" ~

Attn: Mr. James P. O'Reilly, Regional Administrator 3 101 Marietta Street, Suite 3100 tA C ', . . .

Atlanta, Georgia 30303 \, M

./

\ , e

Dear Mr. O'Reilly:

y ,

~ '

~

YELLOW CREEK NUCLEAR PLANT UNITS 1 AND 2 - UNEVALUATED MISSILE SOURCE -

YCRD-50-566/82-04, YCRD-50-567/82 FIRST INTERIM REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. V. Crlenjak on January 8,1982 in accordance with 10 CFR 50.55(e) as NCR YCN NES 8103 Enclosed is our first interim report. We expect to submit our next report by August 18, 1982.

If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.

Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Man ger Nuclear Regulation and Safety Enclosure cc: Mr. Richard C. DeYoung, Director (Enclosure)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555

, -. q ; if COPY 8202220349 820205 s"" ^" '" M ____

^yy 7 ~~~ A h7 ,

. ).

ENCLOSURE YELLOW CREEK NUCLEAR PLANT UNITS 1 AND 2 UNEVALUATED MISSILE SOURCE YCRD-50-566/82-04, YCRD-50-567/82-04

~~

10 CFR 50.55(e) ~~ ~ ~

FIRST INTERIM REPORT Description of Deficiency During an evaluation of the Yellow Creek Nuclear Plant's Control Building missile protection requirements, it was determined that four 845-pound flywheels, if they should fail, could possibly generate missiles whose energy would exceed the design parameters of the present protection barriers. These flywheels are coupled to two control rod drive motor- I generator sets (two flywheels per each m-g set) which are located at the 490' level. Directly above and below this area, separated by type A barriers, are the Auxiliary Control Room, elevation 508, and the Vital Battery Area, elevation 465, which house safety-related equipment.

In determining reportability, the probability of the flywheels failing was considered the key item. While it is believed to be so small as to be considered incredible, sufficient data is currently unavailable to support belief. On the one hand, the flywheel is a simple structure driven by a motor which cannot exceed 1800 rpm, its synchronous speed. On the other hand, the control rod drive motor-generator sets are not considered safety related, so the extent of the QA program used during the manufacture of the flywheels is not known at this time.

The cause of this deficiency is a failure to recognize that such an energetic missile source existed within the Control Building. Separation barrier requirements for the Control Building, being structural in nature, were developed early in the plant design. They were considered to be l conservatively specified (100 pounds at 150 ft/s) to accommodate all internally generated missiles except those originating from high energy pipe breaks (high energy piping is excluded from this portion of the Control Building). No other missile sources of this magnitude have been discovered in the Control Building; and because of the nature of the equipment located in the electrical complex, it is not considered credible that another such device exists. However, this deficiency is being l reviewed for possible generic implications at other TVA plants.

Interim Progress TVA is investigating the probability of failure of these flywheels and will report on our intent to provide assurance that failure is incredible or to develop an acceptable method of mitigating the failure.

As the problem may be generic in nature, TVA is in the process of notifying all 1ts project managers of this deficiency.

As