ML20097C323
| ML20097C323 | |
| Person / Time | |
|---|---|
| Site: | Black Fox |
| Issue date: | 08/09/1984 |
| From: | Broadbent M FIELDS, GRIFFITH, HUBBARD & ASSOCIATES, INC., GLENCOE |
| To: | Whiston P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20097C312 | List: |
| References | |
| 76930, NUDOCS 8409170019 | |
| Download: ML20097C323 (4) | |
Text
____ __ __ _ __ _ _ __ _ __ _ __ _ __
'F dH Certified Radiat:on Physicists Fields Dnthtet HJbtwd -
Westem Regene Ottee Theoaore Fees M $ F ACR CHP and Associates. Inc-2483 Whwoormd -
8 Charies R Grdfan U S FACR Las Vegas NE 89121 Lmcoin 8 Hubbard Ph D.. MACR CHP 702 731-6446 h W 60022 Mchael V Broadbent PN D. MACR 3 t2 C35-4433 Frances E Gannon U S August 9, 1984 Patricia J. Whiston Materials Licensing Section U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Subject:
Control Number 76930
Dear Ms. Whiston:
In answer to the questions posed by your most recent letter and from the discussion held this morning the following information is submitted.
Beam Stops: The beam stops are mechanical. They will adjusted to stop the beam from coming to the on position whenever the beam exceeds 90 degrees to the east and west, or the beam will operate without the beam stop in place when the beam is perpendicular to the east and west walls.
It is estimated that the beam stop will be in place 98 percent of the time. With beam stop in place the unit can operate throughout 360 degrees.
Beam Stops:
Mr. Chalk furnished the following information in a phone conversation today, August 9,1984:
a.
Anticipated patient load per day:
16 Treatments per patient per week:
5 Assumed dose per patient per day:
200 From these assumptions the workload is calculated to be 10,240 R per week at one meter.
The maximum number of patients treated per hour would be 4.
And the maximum number of patients per week would be 30. These are the same number given in NCRP 49 with a workload of 40,000 R per week at one meter. These would represent a maximum.
Treatment time and on time "per hour" will depend on source activity and machine output. The maximum output per patient per day would not exceed 400 rads. If 400 rads per patient were being given then it would not be possible to treat 4 patients per hour since patients receiving this amount of radiation are generally very critical and they need extensive care and supervision in treating and setting up which would add to the time needed.
RECEIVED AUG 101984 8409170019 840822 REGION III letS LIC30 48-13109-01 PDR
i 1
j b.
Beam orientation.
The beam can jbe pointed in any direction.- The unit
-indicator is as follows; Direction Beam Pointed 0
Down 90 East wall barrier B 180 Up 270 West wall barrier A
~
The head of the unit is capable of rotating toward the North wall 90 degrees. Towards the South wall it can rotate 30 degrees.
The head motion will be mechanically restricted to the plane of rotation, i.e.
the beam will not point toward the north or south wall whatsoever. For the direction of North in relation to the room layout see Item 9a of 7/12/84 Maximum field sizN is 35 by 35 centimeters.
c.
The. distance to scattering' material is 80 cm.
The distance to the beam absorber is approximately 150 cm.
The beam stop intercepts an area of 70 degrees, 35 degrees from the center of the absorber in either direction in the place of rotation.
Scatter angle (worst case) is 30. degrees' Scatter Radiation (worst case) is CLOO60.
The is taken from NCRP 49 Table B-2, page 59.
In the calculations to follow the value of CLOO60 is used fbr the scattering ratio in' most cases. In some of the calculations the value of 0.0009 is used which is the value for 90 degree scatter, again from the same reference given above.
Barrier Distance in meters to Ab sorber ~
Area of Concern A
2.3
.4.4 B
- 2. 3 3.4 C'
D 5.3 6.1 r
E 3.35 4.0 F
- 2. 9 4.'O G
2.3 2.8 CEILING
- 2. 8 4.3 DOOR *8 6.7 6.7
'Ine distance to barrier C' is to the wall of the maze entering the room.
The area behind it is not occupied during any treatment.
- The distance to the door presents two scatters, one of 4.0 meters and the other of 2.7 meters.
The distances were derived from tpe blue prints which were drawn at a scale of 1/4 inch equals 1 rootr-(
d.
Leakage is assumed to be 0.1 percent of the primary radiation.
Leakage through the beam stop is 0.05 percent from the manufacturers specifications.
The use factors are those given in NCRP 49 Table 3 page.64. These arc 3
\\
/
N'
1/4 for the east and west walls and the ceiling and a use factor of 1 ll for the floor.
)
Only barriers E. F. and the ' Door enter restricted areas.
The rest are considered unrestricted.
The calculations are included in the following table.
It should be noted that the limits 10 CFR Part 20.105(b)(1)and (2) will not be exceeded in the changing of the units,.since the unit currently in place
'does not have a beam stop and the new unit will.
It is reported by the manufacturer that the beam stop will attenuate all but 0.05 percent of the primary beam.
In addition, for almost all treatments the beam stop will be in place. Therefore, without the calculations it can.be reasoned that the necessary limits will not be exceeded. Of course, with the completion of the installation the dose levels at the various locations with and without beam stop will be verified and the report will be furnished to the NRC as required. If there are further questions please contact me.
Sincerely yours, 0
r M. V. Broadbent, R1D, MACR
2 Barrier Distance Workload 1/d Use Scatter Transmissions mR/hr
~m R/ week - iTotals A Primary 4.4 40,000 5.2X10-2 1/4 5
2x10-6 4.0x10-5.1.6X10-3 6
6.4X10-5 Primary 1/4 (2X10-2) 6.2210 6 j,.6X10-6 1
Scatter 1
6X10-3 6.2X10-9x1o-3 '7,7xjo-2 Leakage 1
1X10-3 6.2x10-6 3.2X10-"
1.3X10-2 2.3X10-3hr 2
1.6x10-3. 9.2X10 wk B Primary 4.4 40,000 5.2x10-2 1/4 SX10-4 6.2X10-6 4.0x10 5 6.4x10-5 5
Primary-1/4 (2X10'2) 6.2X10-6 1.6X10-Scatter 1
6X10-3 6 1.9X10-3 7.7x10-2 -2.3X N:
Leakage 1
1X10-3.-
6.2X10 6 6.2X10-3.2X10-4 1.3X10-2 9.2X10-2wk-B1Pr$kary 4.4 40,000 5.2X10-2 jfg
- 5X10-4 1.8X10-4 1.2x10-3 s4.7X10-2 Primary 1/4 (2X10-2) 1.8X10-4 4.7X10-2 1.9 1
Scatter 1
6X10-3 1.8X10-"
5.6X10-2 2.2' Leakage 1
1X10-3 1.8X104 9.4X10-3 3.7X10-1 1.1X10-lhr 4.5 wk' D Scatter 6.1 40,000 2.7 x10-2 1
6X10-3 3.ox10-4 4.9X10 3,9 f
Leakage 1
1X10-3 3.cx10-4 8.1X10-3 3.2X10-1 5.7X10-2hr 2.2 wk.
E Scatter 4.0 40,000 6.2X10-2 1
9X10-N 2.8X10-6 1.6X10-4 6.3 Leakage 1
9.5X10-3 5.9X10-1 24 5.9X10-lbr 30.3 wk F Scat'ter 4.0 40,000 6.2X10-2 1
9X10-4 2.1X10-4 1.2X10-2 4.7X10-1 Leakage *'
1 1X10-3 2.1X10-4 1.3X10-2 5.2X10-1 2.5X10-2hr 9.9X10 wk-i G Scatter 2.8 4 0, rk' 1.3X10-1 1
9X10-4 9.6X10 4 2.4x10-2~ 4.59.6X10-1 1.3X10-lhr 4 1.1X10-1 1X10-3 9.6X10-Leakage 1
5.5 wk-Ceiling Pri 4.3 '
40,ux) 3.4X10-2 1/4 5x10-"
3.0X10-5 2.0X10-2 8.1X10-1 Scatter-1 6X10-3 3.0X10-5 9.7X10-3 3.9X10-1 Leakage 1
1X10-3 3.ox10-5 1.6X10-1 6.5X10-2 3,9xjo-1hr
- 1. 3 wk Door Scatter 4.0 40,000
- 6. 3X10-2 3-6.0X10-3 3.0X10-3 i
2.7 1.4X10-1 1
6.0X10-3 3.0X10-3 1.6X10-1 6.4-
~
Leakage 4.C 6.3X10-2 1
1X10-3 3.0X10-3 27 1.4X10-2 1
1X10-3 3.0X10-3 =2.6X10-2 1.1 1.9X10-lhr-
- 7. 5 wk
~
OShielding for the cut out portion in barrier B.
Beas stop items in parenthesis represent the 2 percent of the time the unit is used without the beam stop.