ML20086C772
| ML20086C772 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 11/18/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20086C771 | List: |
| References | |
| NUDOCS 9111250078 | |
| Download: ML20086C772 (3) | |
Text
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UNITED STATES E\\g# '(
NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR RE.
OR REGULATION RELATED TO AMENDMENT NO.133 TO FACILITY OPERATING LICENSE NO. DPR-29 AND AMENDMENT NO. 178 TO FACILITY OPERATING LICENSE NO. DPR-30 COMMONWEALTH EDISON COMPANY AND IOWA-ILLINOIS GAS AND ELECTRIC COMPANY, QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265
1.0 INTRODUCTION
By submittal dated September 24, 1991, Commonwealth Edisun Company (the licensee) proposed c Technical Specification (TS) change for Quad Cities Nuclear Power Station, Units 1 and 2.
Specifically, the licensee requested to change TS 4.8.H.2.b(2), which defines a differential temperature criteria for the control room emergency filtration system (CREFS) heater's operability requirement.
The licensee is requ.: sting a variable differential temperature criteria that is a function of the air flow rate as opposed to a constant differential temperature criteria that is presently being used.
2.0 EVALUATION The CREFS safety function is to ensure that the operators are adequately protected from the effects of an accidental release of toxic and radioactive gases and that the nuclear power plant can be operated safe'ly or shut down under design basis accident conditions as required by General Design Criteria (GDC) 19.
The CREFS consists of a coughing filter, an electrical heater, a pre-HEPA filter, a charcoal adsorber, 6 post-HEPA filter, two 100% booster fans, a fire suppression v ' 'e, and inlet and outlet dampers The.CREFS l
heater is required to ensure that air at the inlet of the charcoal adsorber L
has a relative humidity (RH) of less than 70%.
This is necessary so that the l
maximum removal efficiency of radioactive iodine is-achieved by the charcoal adsorber.
Current TS 4.8.H.2.b(2) requires that the heater produce a change in air temperature (AT) of 15*F in order to demonstrate that the heater is operable.
The AT of 15 F ensures that the RH of the air at the inlet of the charcoal adsorber is less than 70%.
The TS AT requirement of 15 F is independent of the air flow rate.
The licensee has proposed a TS change which requires the differential temperature change to be dependent upon air ilow rate.
The proposed TS change -is based upon the AT necessary to maintain a RH of less l
9111250070 911118 PDR ADOCK 05000254 t
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2-than 70% at a given flow rate.
The licensee has determined a AT ranging from 15 F to 12 F, depending upon the flow rate, that will ensure a RH of less than 70%.
In its rationale for the proposed TS change, the licensee stated that AT is a linear function between 1800 cubic feet per minute (cfm) and 2200 cfm (assuming a constant heater output at different flows).
Therefore, the AT limit can be determined by the following formula:
AT 2 28.5 - (0.0075F) where F is the air flow rate (in cfm) and AT is expressed in *F.
The design basis criteria for the CREFS heater is to ensure the RH at the inlet of the charcoal adsorber is less than 70%.
The proposed TS change considers the most limiting climatic conditions of 95 F wet bulb (95"F and RH 100%) to establish the AT boundary.
With an air flow rate of 2200 cfm at 95 F wet bulb, a AT of 12 F is necessary to change the RH from 100% to 70%.
At 1800 cfm, a AT of 15*F is needed to demonstrate that the heater is producing the same power needed to change a flow of 2200 cfm from 100% to 70%.
However, when climatic conditions are less severe, a AT of 12 F at 2200 cfm will reduce the RH to some value less than 70%.
For example a wet bulb temperature of 78 F requires a AT of approximately 10.8'r to change the RH frem 100% to 70% at 2200 cfm, a AT of 12 F would yield a RH nf approximately 67%.
Published _ climatic conditions contained in the ASHRAE Handbook of Fundamentais indicate that the wet bulb i
temperature in the Quad Cities area is below 78 F approximately 99% of the time.
Specifically, during 1990, the wet bulb temperature at Quad Cities airport was greater than 78 F approximately 1.7f; of the time.
The maximum l
wet bulb temperature during 1990 was 82 F and this occurred approximately 0.14%
of the time.
From the weather data and the bounding conditions used it is evident that a sufficient margin to ensure a RH cf less than 70% is built into the proposed TS change.
In order to ensure that the RH at the inlet of the charcoal adsorber is less j
than 70%, with worst case conditions, the heater must deliver at least 8.14 kW l
under full range conditions (1800 cfm to 2200 cfm).
However, in order to meet TS requirements un' der all inlet conditions (-10 F to 95 F) the heater must deliver 10.1 kW.
The heater must deliver more power at lower temperatures to j
heat the cold, dense air to the required AT, however the RH is much lower than
[
70% when the required AT is reached.
At the nominal voltage of 480V AC, the 12 kW heater provides approximately 50%
margin-to design basis requirement (RH less than 70%) and a 20% margin to the TS requirement.
To-ensure the heater can produce the necessary output.to meet the TS requirements the licensee has analyzed the effects of degraded voltage l
on the heater's performance.
Under worst-case conditions which include a loss-l of-coolant accident (LOCA), loss _of off-site power on Unit 2, with all auxiliary power on Unit 1 and emergency loads on Unit 2 fed from the Unit 1 auxiliary transformer, without emergency power supplied from the emergency diesel generators and assuming maximum summer thermal loads will cause the 480V AC bus to degrade to 381.6V AC.
The resultant heater output at this voltage (381.6V AC) would be 7.58 kW, which would result in a Rn af 72% at worst
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, case conditions and a flow of 2200 cfm.
At 95 F the heater output would produce-a AT of 12 F and RH of 70% for approximately 93% of the flow condi-tions.
The licensee has stated that, based upon calculations that indicated the charcoal adsorber efficiency is not impacted until the RH reaches 90%, a slight increase in RH due to the pnstulated degraded voltage conditions would have a negligible impact upon the c-harcoal adsorber's efficiency.
Therefore, the heate should be able to provide the output necessary to achieve the TS AT requirements.
Since the proposed TS change _still ensures a RH of less than 70% at the inlet of'the charcoal adsorber, it allows the CREF system to achieve its safety objective.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the_ installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be re: eased offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (56 FR 51937).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51,22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
- 5. 0 CONCLUSION Based upon ti e above findings, the staff concludes that the lictisee's l~
proposed changes to Quad Cities, Units 1 and 2, TS 4.8.H.2.b(2) dealing with the differential temperature criteria for the control room emergency filtration system heater-are acceptable and, the -fore,.should be granted.
The Commission has concluded, based on the considerations discussed above,
.that: -(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activitnes will be conducted in compliance with the Commission's regulations,
- and (3; the_ issuance of the amendments will not be inimical ta the common defense and security or to tne health and safety of the public.
Principal Contributor:
S. Flanders Date: November 18, 1991
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