A

4

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of 1000 dme 100 cm2. ?Decontamination?efforts have reduced the remainder of

the area to normal contamination levels.

6 . Stack Ef?uent Activity

 

Radioactivity routed to the stack from thegaseous storage tanks passes
through absolute filters and is then diluted with 25,000 of outside air. Ex-
haust from the high bay area is not vented to the stack but rather to a separate
outlet located on top of the high bay area. The high bay exhaust is passed
through CWS filters only when potentially hazardous operations are in progress
within the reactor building, e. g. during reactor operation or fuel handling.

.The original design of the gaseous waste handling system incorporated radiation?
level?actuated by-pass valves in the line leading from each source of gaseous
activity to the storage tanks. In this way, automatically and depending on the
activity level, the gas would be vented either to the stack or to the storage tanks.
This system was later modified, because of malfunction, and a manually oper-

ated bypass was placed in the reactor control room.

Prior to run 14, there had been no indication that activity concentrations
in the stack ef?uent had exceeded'allo?able values. On several occasions, the
stack monitor had indicated the presence of high activity levels, but the cause
could always be traced to either instrument malfunction or the fact that the in-
strument was responding to direct radiation (usually resultant from radiation

beams existing at the same time in the high bay area).

Two instances in which the stack monitor readings indicated activity con-
centrations in excess of allowable values were noted during run 14. The first
of these occurred on July 12 at 1700, at which time the stack activity rose
sharply to a value of 1.5 This instance of apparent high activity
levels occurred simultaneously with the high radiation levels which were detect-
ed above core channel number 7 and, as a result, the stack monitor was re?
sponding to this direct radiation. The activity level returned to normal by 2200
on the same day. The. second instance Jul if; 31%; this,
time the sharply to 7 10-5 Ec/cm . The activitv level

Mm

continued intermittently high until about 1100 alluly  No explanation can

 

be offered for this second occurrence unless it is assumed that the storage tank
I u-?I 
bypass switch_l_1_?d inadvertently b?enplaced in the bypass osition. If this were

NFC-24