PNO-II-79-001C, on 791005,completed Investigation Into Cause of Overpressurization of Vol Control Tank & Release of Radioactive Gases Into Bldg.Caused by High Influx of Water from Primary Sys

PNO-II-79-001C:on 791005,completed Investigation Into Cause of Overpressurization of Vol Control Tank & Release of Radioactive Gases Into Bldg.Caused by High Influx of Water from Primary Sys

ML20197E428
Person / Time
Site:	North Anna
Issue date:	10/10/1979
From:	Alderson C, Kellogg P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-79-001C, PNO-II-79-1C, NUDOCS 7912190751
Download: ML20197E428 (1)

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PRELTHINAkY NOTIFICATION Octc 10, 1979 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II/79-IC This safety preliminary or public notification constitutes EARLY notice of an event of POSSIBLE interest significance.

The information presented is as initially I IE staff as of this date. received without verification or evaluat'on and is basically -: all that is known FACILITY: Virginia Electric and Power Company North Anna Unit 1 Docket No. 50-338 r'fineral, Virginia ..

SUBJECT:

REACTOR TRIP AND SAFET7 INJECTION ~

This supplements information previous,1y submittet in PNO-II/79-1B.

Region II (Atlanta) has completed its investigation into the cause of the over-pressurization of the Voluna Control Tahk (VET) and subsequent release of radio-cctive gases into the Auxiliary Building.

• The investigation determined that the control evitch for the VCT level control

• system was not defeated at the time of the incident. Overpressurization of the VCT was caused by lifting of the letdown line pressure relief valve, which discharges to the VCT, when letdown flow was automatically blocked due to a high level in the Baron Recovery System gas stripper. The high water level in the gas stripper was due to the high influx of water from the primary system when  ;

letdown flow was reestablished. The investigation also determined that due. to [

volume of gas involved a'nd the design of the radioactive waste h cantly lessened by proper connection of the vent line from the high level waste tanks.

• It appears that two items of noncompliance occurred, both relating to system modifications without safety evaluations required by 10 CFR 50.59. These modifications involve the periodic defeating of the VCT level control valve during operation and,the vent line instatiR ion. "

cf defeating other contcol switches was identified.In the former case, no evidence '

k ing addressed in IE Circulars currently being prepared.Both of these matters are Continued media interest is expected. n release; however, the investigation report is receiving priority attention. Region II doe The Comonwealth of Virginia is being kept informed of developments.

Region II (Atlanta) concluded its investigation at 5:00 p.m. on October 5,1979.

Contact:

C. Alderson, RII 242-5507; P. J. Kellogg, RII 242-5649 Distribution:

i Chairman Hendrie Transmitted H. St. D 4 Commissioner Kennedy Commissioner Bradford S. J. Chilk, SECY Commissioner Gilinsky Commissioner Ahearne C. C. Kamerer, CA ACRS (For Distribution)

Transmitted: hNBB 9.*/g L. V. Gossick, EDO P. Bldg. g* i IE,:X00S2l.38 (IE:HQ Dist.)

R. L. Ornstein, ED3 E. R. Denton, NRR

.Y. J. Fouchard, PA R. C. DeYoung, NRR

% M. Haller, MPA R. J. Mattson, NRR Landow 9,'o/

. G. Ryan, OSP D. Vassallo, NRR J. J. Cummings, OIA (6 min./page)p\

. K. Shapar, ELD D. Eisenhut, NRR 6g SS Bldg. 14.3 OtherRegionalOffices2/53 P. J. Dircks, NMSS HAIL R. Minogue, SD h S. Levine,'RES Ch

'IE:XOOS k f.[-

ELIt!INARY NOTIFICATION _ _ _ _ _ _ _ __ - - - - - - - - - - - - - - - - - - -- -