ML20098F745
| ML20098F745 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 09/26/1984 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737 9226N, NUDOCS 8410030328 | |
| Download: ML20098F745 (6) | |
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) one First Nati'nal PI:29, Chic'ge.' ilknois
,k C 7 Address Reply to: Post Offics Box 767
\\ j' Chicago, Illinois 60690 -
September 26, 1984
-Mr. Harold R. Denton,' Director Of fice of Nuclear Reactor Regulation '
U.S. Nuclear' Regulatory Commission
~
Washington, DC 20555
Subject:
Byron Generating Station Units 1 and.2 Braidwood Generating Station Units 1 and 2 Iodine Sampling of Stack Effluent NRC' Docket Nos. 50-454/455 and 50-456/457
Dear Mr. Denton:
This is to provide additional information regarding the design basis for the shielding associated with iodine sampling of the Byron /
Braidwood-vent stack effluent under post-accident conditicos.
NRR review
.and acceptance of this aspect of design is necessary to close open items identified during I&E inspections at Byron Station.
Table II.F.1-2 of NUREG-0737 indicates that an iodine source term of 100 'pCi/cc :and a. sample time of 30 minutes are to be used as the
' design basis shield ~ envelope for post-accident grab sampling of vent stack effluent.
These criteria are unnecessarily conservative.
We have verified that the existing equipment and procedures can be used to keep personnel exposures during sampling well within the limits imposed by General Design Criteria 19 (5 rem whole body and 75 rem extremity) assuming release of 1.5% of the core iodine inventory.
Details of our calculations are provided in Attachments 1 through 4'to this letter.
Appendix E of the FSAR will be revised to
- document the iodine source term and sample time used in this evaluation of.the(shielding.
These changes will be incorporated into the FSAR at the earliest opportunity.
Please address further questions regarding this matter to this office.
^
One. signed original and fifteen copies of this letter and the attachments are-provided for NRC review.
e Very truly yours,
- TrM, h
b T. R. Tramm Nuclear Licensing Admininstrator im
{2 cc:
Byron Resident Inspector 8
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' ATTACHMENT 1: Calculation'of-Iodine Source Term The following iodine source term calculation is based on a loss of
-all AC power scenario (details of-this scenario are available from
- 13. T. Klopp, Project Engineering Department).
100% of the noble gas
. core. inventory and 1.5% of the iodine core inventory is released 33
- hours after.the event occurs. The duration of.the release is 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
At the time of the-release.-it is assumed that one Auxiliary Building
1.
Iodine Core Inventory'(Byron FSAR, Table 15.0-8)
I-131 8.8E7 curies Decayed 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br />
- 5.14E6 curies I-132 1.34E8 curies 5.30E3 curies I-133~
1.97E8 curies 6.38E7 curies 1-134 2.31E8 curies 8.01E-4 curies I-135 1.79E8 curies 5.84E6 curies Total 7.49E7 curies
.
- Release occurs 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> after event.
2.
Total Fraction of Iodines Peleased =.015 7.49E7 Ci x.015 = 1.12E6 Ci released
~ 3.
Fraction of Iodines Released Per Minute
.015 1 hr
.6.25E-5/ minute x 7.49E7Ci -= 4680 C1/ min x
4 hrs.
60 min-4
- 4. ' Assume One Auxiliary Building Fan On.
4680 Ci i 159000 ft3 2.94E-2 C1/
1.04E 0 uCi/cc ft3
=
=
min min
- 5.. Assume Charcoal is 10% Efficient for Iodines..
1.04E-0 uCi/cc i 10 1.04E-1 uCi/cc Iodine Source Term
=
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2 ATTACHMENT 2:
Dose Rate froa Iodine Filter Assembly The following is a calculation of the dose rate from the General Atomic Wide Range Gas Monitor grab sample assembly. A one-minute grab sample is obtained. The monitor flowrate is 0.06 cfm.
1.
Contact Dose Rate 1.04E-1 uCi/cc x.06 ft / min x 28320 cc/ft3 3
x 1 min 177 uCi
=
on assembly 5.6E3 x 1.77E-4 Ci x.5May = 4.95-1 R/hr
= 495 mR/hr at I cm 2.
Dose Rate at One Foot (495) (1)2
.533 mR/hr at 1 ft.
=
(30.48)4
ATTACHMENT 3:
TIE MOTION STUDY The following sununarizes the dose accumulated in the process of going to the General Atomic Wide Range Gas Monitor, obtaining the grab sample, and transporting the samples back to the laboratory for analysis.
The purpose of this sununary is to verify Byron can meet criteria of GDC 19 (5-rem whole body and 75-rem extremity).
The dose rate specified at the monitor includes dose rates from the sample lines ar.d from the two high range continuously sampling filter assc211es. Dose rates along the path to and from the monitor are based on values specified in the Postaccident Radiation Zone Maps found in Appendix E of the Eyron FSAR (for a major line break accident in containment).
Area Time spent in Area Dose Rate in Area Dose Accum:14ted in Area OSC to 451' Aux. Bldg.
3 minutes IR/hr 50 mR 451' to 426' Aux. Bldg.
I minute 15 mR/hr
.25 mR 426' to 451' Aux. Bldg.
.5 minute 10 R/hr 83.5 mR 451' to 477' Aux. Bldg.
1.5 minutes 10 R/hr 250 mR At moettor
- 4 minutes 60 mR/hr 4 mR 477' to 451' Aux. B1dg.
1.5 minutes 10 R/hr 250 mR 451' to !.ab 1 minute 15 mR/hr
.25 mA Total 638 mR
- Includes contact dose rate from grab sample filter assembly.
Two individu&ls will be needed to perform this task, thus the total dose is multiplied by 2 to get a TOTAL dose for this task of 1.276 R whole body. The extremity dose to the sample collectors is not ex-pected to exceed 2 R.
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ATTACHMENT 4: Dose Rates from Sample Lines, Sample Casks The following calculations document additional dose rates due to sample lines on the Wide Range Gas Monitor and the two continuous sampling filter assembly cask units. Sample line dose rates are based on noble gas activity in the lines.
Specific values reported are obtained from " Analysis of Radiation Detectable from Stack Vent Sample Line Under Design Basis Accident Conditions - CECO contract 37844", prepared by Catalytic, Inc. (November,1980).
1.
Noble Gas Core Inventory (Byron FSAR, Table 15.0-8)
Kr 83 m 1.64E7 Cf Decayed 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br />
- 7.50E 1 Ci Kr 85 9.'99E5 Ci 9.99E 5 Ci Kr 85 m 3.95E7 Ci
- 2. IGE 5 Ci Kr 87 7.59E7 Ci 1.09E 0 Ci Kr 88 1.08E8 Ci 3.06E 4 Ci Kr 89 1.40E8 Ci 0
Ci Xe 131 m 6.68E5 Ci 6.16E 5 Ci Xe 133 2.03E8 C1 1.69E 8 Ci Xe 133 m 5.16E6 Ci 3.38E 6 Ci Xe 135 5.55E7 Ci 4.55E 6 Ci Xe 135 m 5.46E7 Ci 0
Ci Xe 138 1.79E8 Ci O
Cf
.1.79E 8 C1
- Release occurs 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> after event.
2.
100% of noble gases released.
Fraction released per minute:
1 x I hr 4.17E-3/ min x 1.79ES Ci 7.46ES Ci/ min
=
4 hr 60 min 3.
Assume One Auxiliary Building Fan On 7.46E5 C1/ min 3
159000 ft / min = 4.69 C1/ft3 = 166 uCi/cc 4.
Sample Line Dose Rates Dose rates are reported for (a) 2 foot section of 1-inch diameter sample line at 6 inches from the line and (b) 2 foot section of 3/8 inch diameter sample line at 6 inches from the line.
This results in a conservative dose rate as the sample collector will actually be approximately 2 to 3 feet from the sample lines and actual sample lines are 3/4-inch and 1/8-inch in diameter.
I a.
Dose rate from 1-inch diameter line at 6 inches
.17 mrem /hr 166 uCi/cc 1.4*. 39.5 mrem /hr x
x uCi/cc
- Dose rate for 2 foot line section is 40% greater than foi the.17 mrem /hr/uCf /cc value for a 1 foot line section.
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ATTACHMENT:41 Continued p
b.
Dose rate.from 3/8-inch diameter line at 6 inches
.015 mrem /hr 166 uC1/cc 1.4 x
x 3.5 mrem /hr
=
uC1/cc.
- 5.. Sampling Cask Dose ~ Rates
- Dose rates from the.two continuous sampling filter assemblies are based on the-iodine source term of 1.04E-01 uCi/cc and a sample time of 30 minutes. The lead casks are 2 inches thick.
.1.04E-luci/cc x 28320 cc/ft3 3
x.06 ft / min x 30 min = 5300 uCi on filter assembly 5.6E3 x.5 Mev x 5.3E-3 Ci = 14840 mR/hr at I cm
= 575 mR/hr at 5.08 cm unshielded I= Ige-ux
= - 575e -(1.82)(5.08cm)
=.05 mR/hr at surface of cask s
4..
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