ML20117J474
| ML20117J474 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/09/1985 |
| From: | Schnell D UNION ELECTRIC CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-1092, NUDOCS 8505150114 | |
| Download: ML20117J474 (4) | |
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UNION ELECTRIC COM PANY lect GRATIOT STREET ST. Louis, MISSOURI May 9, 1985
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oO~,eo m.cu~cce ST. Louis, MessOURB S3,Se weC s puestoa.et Mr. Harold R. Denton, Director Office of Nuclear. Reactor Regulation U.S. Nuclear Regulatory Commission
-Washington, D.C.
20555 ULNRC-1092
Dear Mr. Denton:
DOCKET NUMBER 50-483 CALLAWAY PLANT, UNIT 1 INDUCTION OF EXHAUST GASES INTO THE CONTROL ROOM
References:
- 1. NRC letter dated 4/2/85
- 2. ULNRC-1001 12/21/84
- 3. BLSE-13,391 3/21/84 This is in response to the request for additional infor-mation on the subject issue contained in Mr. Youngblood's letter
.(reference 1) dated April 2, 1985.
In the initial evaluation of the incident by our A/E (reference 3), the infiltration of SO2 was concluded to represent no threat to operator performance.
Also, as indicated previously in reference 2, the normal air supply to the Control Room HVAC is isolated by operator action upon indication of CO, CO2, or the presence of a malodor, i.e.,
exhaust fumes.
With this action the makeup air is provided by the pressurization system.
The makeup air intake for the pressurization system is located considerably more distant from the auxiliary boiler. exhaust stack and has a different relative orientation than the normal Control Room HVAC intake.
Taking into account this location and orientation, it has been conservatively estimated that the concentration of exhaust gases at the pressurization system intake is a factor of 10 less than that at the normal air intake (reference 3,
-Table 1).
Assuming the Control Room isolation is due to the CO/CO2. alarm, the SO2 level is estimated to be 3.33 ppm; however, once' isolation is initiated, the Control Room will reach an SO2 equilibrium concentration of approximately 2 ppm which is well below the Regulatory Guide 1.78 limit (10 ppm) and the concentration which results in nose, throat, and eye irritation (20 ppm).
The previous assessment (reference 3) did indicate an equilibrium concentration of SO2 equal to 20 ppm; however, this assumed that control room isolation was not initiated.
Therefore, long term protection is provided with this operator action and provisions of the existing design.
It should be stressed once again that the auxiliary boiler is not normally running while the plant is operating.
Operation will occur during unit outages and infrequent testing.
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8505150114 850509 7
ew 3
'Mr.. Harold R. Denton May 9,.1985 Page~Two
.Therefore, in view o'f the the very low equilibrium SO2 concentration that could be. reached in the-Control Room, we do not believe that an estimate of the frequency and duration of boiler operation, an assessment of the effect of SCBA on operator performance,'or an evaluation of the feasibility of periodic
. drills is necessary to conclude that additional occurrences of the subject incident will'not interfere with or preclude operators
-from performing their safety functions.
We trust this information
.will conclude your review of this subject.
Very truly yours, n
Donald F.
Schnell RPW/JJS/JJM/sla
STATE OF' MISSOURI )
)
Donald F. Schnell, of lawful age, being first duly sworn upon' oath says that he is Vice President-Nuclear and an officer of Union Electric Company; that he has read the foregoing document and knows-the content thereof; that he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.
By Donald F.'Sc'hnell Vice President Nuclear SUBSCRIBED and sworn to before me this f!h day of 19857 1/Q BARBAM prAF NOTARY PUCUC, STAfg 0F !.flS$004 MY COMMtsioff GNRIS APRtL 22,193g ST. LCul3 Coutry
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cc:
Gerald Charnoff, Esq.
Shaw, Pittman, Potts & Trowbridge 1800 M. Street, N.W.
Washington, D.C.
20036 Nicholas A. Petrick Executive Director SNUPPS 5 Choke Cherry Road Rockville, Maryland 20850 John H. Neisler Callaway Resident Office U.S. Nuclear Regulatory Commission RR$1 Steedman, Missouri 65077 William Forney Division of Projects and Resident Programs, Chief, Section lA U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137 Bruce Little Callaway Resident Of fice U.S. Nuclear Regulatory Commission RR91 Steedman, Missouri 65077 Jan Stevens, Callaway Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop P-316 7920 Norfolk Avenue Bethesda, MD 20014 1
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