Description of occurrence (edited from investigation report) cont'd

Radiological Assessor Training

DOE-HDBK-1141-2001

Student's Guide

employees' respirators or respirator cartridges.

The actual incident began between the hours of

0130 and 0415 on August 23, 1991, at the PGDP

C-337-A Feed Vaporization Facility.

The operators routinely assigned to C-337-A for the

period of 1900 hours on August 22, 1991, through

0700 hours on August 23, 1991, were not available

due to the illness of one and an alternate work

assignment of the other at another facility (C-360).

Two operators who are not routinely assigned to the

area were then assigned to cover C-337-A. One

operator (No. 2) was qualified for operation of the

facility while the other (No. 1) was in training for

qualification. (This is in compliance with facility

Operational Safety Requirements.) Supervisor

interaction was minimal, with only one brief visit

around the middle of the shift.

The operations in process at the time of the incident

were the routine disconnection and removal of

emptied UF6 feed cylinders and subsequent

replacement with full cylinders. This operation

consists of disconnecting a short length of

connecting pipe between the cylinder and the

system piping that leads to the diffusion process

equipment. This pipe is called a pigtail; it has

threaded connections and gaskets on each end.

Since pigtails are routinely reused, each cylinder

change requires replacement of gaskets on pigtails

to minimize the possibility of UF6 releases during

heating and feeding of the UF6 into the diffusion

process. At times these gaskets can be difficult to

remove from the pigtail. A special tool is available to

assist in the removal of these gaskets; however,

difficulty can still be encountered. The pigtails used

that night had been used for several feeding cycles,

as is normally the case. The exact number of cycles

could not be determined.

Module 16 - 4