Next: 5.1.2.2 Radiation Gates
Previous: Oxygen Deficiency Hazard
TJNAF's high intensity, high energy electron beam is a potentially
lethal radiation source and hence many redundant measures aimed at
preventing accidental exposure of personnel to the beam are in place.
This is the purpose of the Personnel Safety System.
The current status of Hall A is displayed in the Hall A counting house
on a sign with green lighted letters. The possible conditions are:
- Beam Permit
- There is potentially beam in the hall.
- Power Permit
- In this mode all devices which normally prevent
beam transport to Hall may be removed or energized. This is one level
below that required for beam delivery. No personnel are allowed in the
hall when it is at this level.
- Sweep
- The machine safety officers are securing the hall. No
access is permitted during this process.
- Controlled Access
- Access is permitted only by using the keyed
interlock system (A procedure for this type of entry is listed below).
- Restricted Access
- The entry gate to the hall is open and
trained personnel with appropriate dosimetry may enter.
If the hall is in either Beam Permit or Power Permit states it is
impossible for personnel to enter. If a situation arises that requires
a hall entry then the shift leader will call the Machine Control Center
(MCC) and request an entry. The state of Hall A will then be lowered to
controlled access and a limited number of trained personnel can enter
the hall via the two door entry gate from the labyrinth. It is required
that personnel entering have a TJNAF Radiation Dosimeter and they must
have completed the radiation worker safety training course at TJNAF or
another DOE laboratory and TJNAF specific Radiation Worker Training.
Access to Hall A is allowed under a General Radiation Work
Permit (GRWP). The GRWP specifies access requirements for areas within
the Hall. For instance, access to the detector huts or spectrometer
carriage may be allowed before a general area radiation survey is
completed but access to the target chamber platform may not e allowed
without a radiation dose rate survey and contamination control survey.
- 1.
- Access to Hall A is allowed under a General Radiation Work Permit
(GRWP). The GRWP specifies access requirements for areas within the
Hall. For instance, access to the detector huts or spectrometer carriage
may be allowed before a general area radiation survey is completed but
access to the target chamber platform may not be allowed without a
radiation dose rate survey and contamination control survey.
- 2.
- The hall status sign in the counting house must read "controlled
access". If not the shift leader must call the MCC and they will send a
radiation survey team over to check the radiation levels in the hall.
- 3.
- Proceed downstairs to the two door entry gate to the hall and call
the MCC at 7050 before touching the door. Inform the MCC crew
chief of your name and the names of those accompanying you and request
that they open the outer door.
- 4.
- Hang up the phone and enter the two door gate. The last person in
should close the outer door after entering the gate area.
- 5.
- Each person entering must take a key from the key bank and inform
the MCC via the phone or intercom which key they have taken. The keys
form a personnel accounting system and all the keys must be in the bank
for the hall to be returned to a beam permit state. Therefore one
should NEVER leave the downstairs with a key. In addition to the
individual keys there is a master key which must be removed from the key
bank and placed in the master lock. This is normally done by radiation
officials who survey the hall.
- 6.
- The MCC will need to see that all personnel entering have a TJNAF
radiation dosimeter. They verify this visually with a TV camera in the
gate area. Do not open the inner, hall side, gate door at this time and
it is never permissable for both gate doors to be open
simultaneously.
- 7.
- After everyone has a key the inner door will be opened allowing
entry into the tunnel leading to Hall A. The inner door must be
shut behind the last person entering.
- 8.
- When the work in the hall is complete you must either push the
buzzer button by the inner door or call the MCC to get back into the
gate area. The keys should be returned to the bank and the last person
leaving must remove the master key from the master lock and replace it
in the first position of the bank (This key is normally placed in the
master position by the individual who first surveys the hall when it is
opened for a controlled access.).
While downstairs the status of the beam is visible on the yellow
run-safe boxes. The lights should either be green or yellow. If
the run-safe box in an area where you are working has a red light lit
you should hit the scram button immediately.
If the hall status reads restricted access then there is free access for
trained personnel.
Figure 2.1.2.1:
Location of Run Safe boxes in Experimental Area
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Figure 2.1.2.2:
Location of Run Safe boxes in Hall A (elevation view)
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Figure 2.1.2.3:
Location of Run Safe boxes in Hall A (plan view)
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Figure 2.1.2.1 is the Run Safe locatgion for all of the end stations.
Hall A is included in that layout, specfically the attached figures
2.1.2.3 and 2.1.2.2 for Hall A, shows a total of fifteen (15) run safe
boxes. These include six (6) around the periphery of the hall, one in
each of the detectors huts and in the spectrometer upper level (4) and
one on each of the gantry platforms (2), one (1) in the truck ramp, one
(1) in the tunnel and one (1) near the entry gate door. Access to the
dump, a high radiation area, is restricted by a locked gate. This would
not be part of the sweep as one does with the accelerator dumps.
Next: 5.1.2.2 Radiation Gates
Previous: Oxygen Deficiency Hazard
10/13/1997