ML20137H217
Text
s
~f".181977 Docket No. 50-264,
Dow Chemical U.S.A.
ATIN: Dr. R. R. I.angner Radiation Safety Committee 1803 Building Midlande MI Gentlemen:
The enclosed circular No. 77-10 is forwarded to you for information. If there are any questione related to your under-standing of the actions required, please contact this office.
Sincerelye James G. Kappler Director fnclosurat IE Circular No. 77-10 cc w/encle Central Files Reproduction Unit URC 20b FDR NSIC TIC t
8508280225 850712 PDR FOIA KOHN05-256 PDR
.$bk--
.....s>
RIII,..
III.
e.... s >
Flore111/ b.
1e r...
7/18/77 v
..s*
Nac MRM lie (9 76) NRCM 0240 W u. s. eevenmuent Parav'ae
- Pries sete.eae4s4
F July 18, 1977 IE Circulai No. 77-10 VACUU:1 C0::D1T?.0 m nESUI1rI:C 1: D.'d:AG!: TO LIQUID PROCESS TA::KS Description of Circunctancen On January 31, 1977, at the Portland General Electric Company's Trojan Nuclear Station, a vacuuu va pulled on a Chenical and Volume Control System holdup tanh ubich caused tha tanh to buckle inuardly and crach at the junction of tuo buchied areas.
(LER 50-344/77-02)
Itadioactive cover con eccaped fron the tank to the fuel buildin:; c:: haunt ventilation und ultinately through the ue::111ary building ventilation stach to the environm.at.
Daring the period of January 31 through February 7,1977, (date of dincovery) appro::frately 62.5 curim of noble gasen vore relenecd to the environnant. 'ihe occurrtuce was cauned by malfunctions of loth the prin.ry (uaste cac decay inuh cellection headcr) and the bacl,up (af t regen preaurl::ction systcn) ccvar r.an nupply precaurc regu]atoto during punpout of the tank coatento.
The nallunctien of the pritary rerplator *.as due to noicture necut.ulation which led to the forra-tion of a water coluna on the discharce nide of the prersure regulater.
The regulator in the ba: hup nitrocen cer. ply rystcu nalfunctioned at the care Line, but the caurn han not been determined. 'lhere vere no ajatr.s or rcrotc indication for the holdup tank or the can control her. der to indicate abnornal prect.ure or to indice.tu the opcrr. ting ctatua of the nitrogen copply r.ynten.
A similar event occurred at the Sacrarento Municipal Utility D1ctrict's Itancho Seco nuclear cration wherein the T.uoctor Coolant Sycten Drain Tank partially collap:,cd ur. der vccuun conditienn and in doing no crurbed an in1<t lina attached to th4 tanh (ilk 50-312/77-03). The firnt indica-tion of the cond'tf en van dttccted by t he radiation r.onitor that r,ar.plen the ventilation c..haust in c.n nrea adjacent to the room in which the damaged Lan). ua:: Jocated.
1;adioactive tar.es were relecued threurh the failed line bcLucen Jaauary I? and rebruary 16, 1977.
Durinn thin period, appro::it atejy 9 curien of radioactive can were rolenceil. The cause of thin occurrence v.e, attributed to the tanh not heln3 ptoperly Vented by the operator durjun dischargo of itu liqujd contentn.
7 / M I LWM @
iO
^
A W m
/
IE Circular No. 77-10.luly 18, 1977 It in recot:nended that you examJnc the nyntens of your reactor '
facility (len) t!ut cent.ain leu prencore precenn or holdup tanha and annur.r that adequate tracured have been taken to protect crainst vacuna conditioan that could renu]t in tank invard buchling and failure uit.h subcequent release of radioactive nat erial or cause other detrinental ef fects uith regard to the overall scfety of p]nnt 'eperations.
It is also recome.:nded that you e:aimine your capability to detect and locate possible Itaks of radioactive caterini fron cuch tanha.
No uritten renpence to this Circular is requirtd.
If you desire additicnal infotuation re:'crdin;; thin tutter, coatnct the Director of the appropriat e.;RC liccicaal Of fice.
9 e
-.-_. _____ __ _ _ _ _ _., _ _ _ _ _, _ _ _ _ _ _ _ _ _ _ _ _ _ _ _