ML20141D879
| ML20141D879 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 04/01/1986 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1500K, NUDOCS 8604080301 | |
| Download: ML20141D879 (4) | |
Text
r'N Commonwealth Edison r
,/
- ) One Forst Nationxl Plaza Chicago. Ilhnoes l
O "J Address Reply to. Post Office Box 767 j Chicago, Illinois 60690 April 1, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC. 20555
Subject:
Post-Accident Control Room Habitability Analysis for Braidwood Station NRC Docket Nos. 50-456/50-457
Dear Mr. Denton:
In late 1984, the NRC conducted a re-review of Byron's control room HVAC system (VC).
The NRC did not allow credit for
" dual" inlets.
Without an upgraded recirculation system, the post-accident radiological dose criteria of GDC-19, Appendix A to 10CFR50 could not be met with the " single" inlet configuration; therefore the design was unacceptable.
We committed to upgrading the recirculation system and making other improvements to the VC system: Section 6.4 of the FSAR was amended to reflect the changes.
The radiological dose assessment results included in revised FSAR Table 6.4-la and b for the Byron station (which will be submitted in Amendment 47) show that post-accident doses meet GDC-19 criteria with the reconfigured HVAC system.
The radiological dose assessment for the Braidwood station i
has now been completed.
The results are given in the attached Braidwood FSAR Table 6.4-la and b.
Of mild concern is the beta skin dose of 32.2 rem which exceeds the 30 rem GDC-19 limit.
(Thyroid and whole body doses are 16.4 and 2.8 rem, respectively, and within limits of 30 and 5 rem, respectively.)
We submit this assessment for your review and acceptance.
We believe that when one considers the conservatisms included in the analysis, the beta skin dose meets the Standerd Review Plan (Section i
6.4) beta skin dose objective of 30 rem.
Some of the conservative assumptions include the following:
Noble gases (100%) are immediately released to the containment 8
8604080301 860401 PDR ADOCK 05000456 A
PDR I
i l 7
L
. The containment begins to leak at its technical specification rate immediately Distance of travel is a 100-foot straight line, " plan view" path from the containment surface to the air intake (In reality a more tortuous path is likely.)
Murphy-Campe X/O formulae Murphy-Campe occupancy factors Further, our calculations show that the beta skin dose objective of 30 rem is calculated to be exceeded approximately 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> after the initiation of the accident.
We will have adequate time to monitor personnel exposure and ensure that GDC-19 dose limits are not exceeded.
Adequate time is available to restore the assumed inoperable "best-inlet" HVAC filter train to operable condition and/or implement use of beta-shielding protective clothing and eyeware as a final protective back-up measure.
In summary, we believe the results of this radiological dose assessment demonstrates that the control room ventilation system at the Braidwood Station will perform to ensure that the requirements of 10 CPR50, Appendix A, Criterion 19 are met.
Please direct any questions you may have regarding this matter to this office.
One signed original and fifteen copies of this letter and enclosure are provided for your review.
Very truly yours, l
is -
A. D.
iosi Nuclear Licensing Administrator
/klj 1500K
m e
e BRAIDWOOD-FSAR TABLE 6.4-1 g
EXPECTED DOSE TO CCNTROL ROCM PERSONNEL AT BRAIDWOOD STATION FOLLCWING A LOSS-OF-COOLANT ACCIDENT (LOCA)
CCNCRITE SHIELD ACCUMULATED 30 DAY DOSE, REM THICKNESS BETWEEN SOURCE AND CONTROL Y
ROOM, INCHES WHOLE BODY SKIN TRYROID Direct Dose From Airborne Radioactivity in the containment Sidewall - 102 0.023 Ceiling -- 68 Dose From Post-LOCA Plume Surrounding Control Room 24 0.003 Dose From Radioactivity Accumulated on Control Room Makeup Air Filters 8
0.013 l
Doses From Air Drawn into the Control Room From Containment Leakage N/A 2.81 32.20*
16.40 From ESF Equipment Leakage N/A 7.72 x 10'0 4.70 x 10' O.195 10 CFR 50, Appendix A, Criterion 19 limits 5
30 30 Principal assumptions are listed in Table 6.4-la.
Considering the conservatisms and error bands in the analysis, the beta skin dose meets the Standard Review Plan, Section 6.4, beta skin dose objective to 30 rem.
Cons'ervative assumptions include:
a) Noble gases (1004) are immediately released to the containment; b) The containment begins to leak at its technical specification rate immediately; c) Distance of travel is a 100-foot straight line, " plan view" path from the containment surface to the air intake (In reality a more tortuous path is likely.);
d) Murphy-Campe X/Q formulae; and e) Murphy-Campe occupancy factors.
6.4-9 l'
EhMK5 WOOD-FSAR s
TABLE 6.4-la PRINCIPAL ASSUMPTIONS USED IN CONTROL ROOM HABITABILITY CALCULATIONS Core thermal power 3565 MW(t)
Containment volume:
sprayed volume 2.55 x 10 6 unsprayed volume 2.130 x 10 ft 5
3 Flow rate, sprayed to unsprayed volume 5
1.80 x 10 ft / min Containment spray coefficients:
elemental iodine 29.9/hr particulate and organic lodine O
Containment leak rate 0-24 hr 0.1%/ day ECCS leak rate 1-30 day 0.05%/ day Auxiliary bldg filter efficiency 1 gal /hr.
90%
Control room habitability methodology:
Murphy /Campe 13th Air Cleaning Conference paper Single inlet configuration is assumed at a distance of 100 feet from the containment surface.
x/0 (maximum 0-8 hour)
-3 3
6 39 x 10 sec/m in a direction 262' in
=
a clockwise sense from the North directed line of the North containment.
y/O REDUCTION FACTOR WIND TOTAL y/Q WINDSPEED FACTOR OCCUPANCY REDUCTION TIME PERIOD FACTOR DIRECTION FACTOR FACTOR 0-8 hr 1.0 1.0 1.0 1.0 8-24 hr 0.651 0.820 1.0 0.534 24-96 hr 0.384 0.641 0.6 0.148 96-720 hr 0.212 0.282 O.4 0.024 Control room HVAC envelope volume 405,164 ft Actual control room volume used for finite cloud correction 3
230,837 ft Control room air intake filter efficiency 99%
~
Control room recirc. filter efficiency 90%
Control room flow rates (see Figures 6.4-6 and 6.4-7 Total unfiltered inleakage rate into th control room pressure boundary 3
25 ft / min.
=
6.4-10 l
-