ML20083D354

Application for Amends to Licenses DPR-29 & DPR-30,changing Tech Spec 4.8.H.2.b(2) to Define Differential Temp Criteria for Control Room Emergency Filtration Sys Header

ML20083D354
Person / Time
Site:	Quad Cities
Issue date:	09/24/1991
From:	Schrage J COMMONWEALTH EDISON CO.
To:	Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
Shared Package
ML20083D355	List: ML20083D354 ML20083D356
References
NUDOCS 9109300216
Download: ML20083D354 (7)

Text

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Osmm:nwealth Edisen

- 7 s) 1400 Opus Place  ;

. . Downers Grove, Illinois 60515 September 24,1991 Dr. Thomar, E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk

Subject:

Quad Glties Station Units 1 and 2 Application for Amendment to Facility 03erating Licenses DPR-29 and DPR-30 N 30_DocketBos,.50:25 Land.50:265

Dear Dr,

Murley:

Pursuant to 10 CFR 50.90, Commonwealth Edison (CECO) proposes to amend Appendix A, Technical Specifications, of Facility Operating Licenses DPR-29 and DPR-30. The proposed amendment requests a change to Technical Specification 4.8 H.2.b(2), which defines a differential temperature criteria for the Control Room Emergency Filtration System heater. The proposed change estabilshes a A T requirement based upon flow, consistent with the design basis of the system. The revision will provide a more technically correct criteria to evaluate the ability of the heater to satisfy the design basis Commonwealth Edison appreciates your staff's efforts to review this proposed amendment in a time frame which will allow for the use of the revised criteria during future surveillances.

This proposed amendment request is subdiviaed as follows:

1. Attachment A gives a description and safety analysis of the proposed changes in this amendment.

2. Attachment B includes the marked-up Technical Specification pages with the requested changes indicated.

3. Attachment C describes CECO's evaluation performed in accordance with 10 CFR 50.92 (c), which confirms that no significant hazards consideration is involved.

4. Attachment D provides the Environmental Assessment.

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p Dr. Thomas E. Murley September 24,1991 This proposed amendment has been reviewed and approved by CECO On-site and Off-site review in accordance with Commonwealth Edison procedures.

To the best of my knowledge and belief, the statements contained above are true and correct. In some res Sect these statements are not based on my personal knowledge, but obtained information ' urnished by other Commonwealth Edison employees, contractor employees, and consultants. Such information has been reviewed in accordance with company practice, and I believe it to be reliable.

Commonwealth Edison is notifying the State of Illinois of this application for amendment by transmitting a copy of the proposed amendment to the designated state Official.

If you have any further comments or questions regarding this i tier please contact J. Schrage at (708) 515-7283.

Sincerely,

/hgdu

/

John L. Schrage Nuclear Licensing Administrator Attachments:

A. Description of Safety Analysis of the Proposed Changes B. Marked-up Technical Specification Pages and Summary of Changes C. Evaluation of Significant Hazards Consideration D. Environmental Assessment cc: A. Bert Davis, Regional Administrator - Rlli L.N. Olshan, Project Manager - NRR T,E. Taylor, Senior Resident inspector - Quad Cities Office of Nuclear Facility Services - IDNS State of E county of It o$$$a01.*e"?!Y " ' { ?E5) 3

.w~mm Notary Pubne, / ,  ; . .

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ATTACHMENT A DESCRIPTION AND SAFETY ANALYSIS OF PROPOSED CHANGE TO APPENDIX A, TECHNICAL SPECIFICATIONS OF FACILITY OPERATING LICENSES DPR-29 AND DPR-30.

1) INTRODUCTION The proposed amendment requests the following ch1nge to the Quad Cities Station Technical Specifications: Revision of the Control Room Emergency Filtration (CREF)

System heater operability criteria. The revised criteria incorporates a A T requirement based uaon system flow, consistent with the ability of the heater to ensure that the relative lumidity at the inlet to the charcoal adsorbers is maintained at less than 70%.

2) DESCRIPTION AND BASES FOR THE CURRENT REQUIREMENT X

The current Technical Specification requirement for Section 4.8.H.2.b(2) requires the demonstration of a 15* heater A T in order to demonstrate heater operability. This a T ensures that the relative humidity at the inlet to the charcoal adsorbers is less than 70%

and therefore the charcoal adsorbers satisfy the safety objective of the system.

The safety objective of the CREF System is to assure that operators are adequately protected from the effects of an accidental release of toxic and radioactive gases and that the nuclear plant can be safely operated or shutdown under design basis accident conditions as specified in General Design Criteria (GDC) 19. This function is accomplished by pressurizing the control room emergency zone with filtered outdoor air no later than one hour after a design basis accident has occurred. Procedural guidance has been established to ensure the initiation of the system within one hour of a design basis accident.

The CREF System consists of a roughing filter, an electric heater, a pre-HEPA filter, a charcoal adsorber, a post-HEP A filter, two 100% capacity booster f ans in parallel, a fire suppression valve, and inlet and outlet dampers.

The air filtration unit induces unfiltered outdoor air to the roughing filter. This filter removes atmospheric dust and particulates with an efficiency rating of 80 to 85%. The booster fans also provide 100% capability to draw outside air through the filtering media at a flow between 1800 and 2200 scfm and discharge it to the "B" control room HVAC system, and thus into the control room. Fire suppression capability is provided in the event that the adsorber outlet temperature reaches 350 F. Dampers are provided for isolation of the idle booster fan.

After the roughing filter, the air passes through a resistance heater which maintains incoming air relative humidity to the charcoal adsorber below 70%. Following the heater, the air passes through a pre-HEPA filter, the charcoal adsorber, and a post-HEPA filter.

Together, these filters remove radioactive iodine and methyl iodide from the air stream.

The removal efficiency for methyl iodide is dependent on the relative humidity of the air passing through the filters.

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At a relative humidity of less than 70%, the air filtration unit will function to limit !

dose to personnel in the control room during a design basis accident to less than i GDC 19 limits. 1 l

Technical Specification surveillance 4.8.H.2.b currently requires: "At least once per I operating cycle, but not to exceed 18 months, the following conditions shall be )

demonstrated: 1) Pressure drop across the filters is less than 6 inches of water at '

2000 cfm (+_10%) flow rate; and 2) Operability of inlet heater demonstrates heater A T of 15 F".

Design basis calculations indicate that the Technical Specification A T limit is based upon the A T necessary to maintain relative humidity at the adsorber intet to less than 70%, assuming an outside wet-bulb temperature of 95 F. As such, the two key parameters for the heater design A T are (1) the worst-case cond!tions for the intake air wet-bulb temperature and (2) the allowable system flow. The design specification for the CREF system defines the maximum wet-bulb temperature for the intake air as  !

l 95 F. At this inlet condition a A T of 12*F is required to maintain relative humidity less  !

l than 70%. The Technical Specification requirement of a 15' F A T supports the design  !

bases. The requirement ensures that a A T of 12 F will be achieved at the maximum flow (2200 cfm) if a A T of 15 F is achieved at the minimum flow (1800 cfm). This in turn ensures that the relative humidity of the intet air to the charcoal adsorbers will be <

less than 70% relative humidity at all flows under worst case environmental conditions. )

3) DESCRIPT10N OF THE NEED AND BASES FOR THE PROPOSED AMENDMENT The proposed amendment requests that the criteria for heater operability be revised to establish a A T rec oirement based upon flow, consistent with the ability to maintain relative humidity to ess than 70%. The need for this change is based upon i

information obtained during the September 1991 monthly surveillance.

l l On September 4,1991 Quad Cities Station performed the monthly operability i surveillance lor the CREF system pursuant to Technical Specification 4.8.H.1. This specification requires that "At least once per month, initiate 2000 cfm (+10%) flow through the control room emergency filtration system for at least 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> with the i heaters operable". The Otation surveillance procedure (OOS 5750-2) which implements the Technical Specification, also requires that less than 6 inches of water differential pressure across the combined filters be demonstrated at a flow of 2000 cfm

(+10%), and that the differential temperature of the heater be demonstrated to be at least 15#F. The Technical Specification requires the demonstration of a differential pressure and differential temperature for the system on an 18-month basis; however, i the Station included the parameters in the monthly surveillance as further assurance of system operability and performance.

On September 4,1991, the surveillance could not be successfully performed. At a flow of 1975 scfm, the indicated dP was 6 inches of water and the indicated A T was 11 F. The system was declared inoperable at 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> on September 4,1991 and the Station entered limiting Condition for Operation 3.8.H.1.a, which allows continued I operation for the succeeding fourteen days. The Station initiated an investigation to determine the cause of the inability of the system to meet dP and A T requirements.

The Station investigation revealed that the inability of the system to maintain less

' than 6 inches dP was caused by a f aulty pressure indicator. As such, the failure was not related to system performance. A new pressure indicator was installed and pressure indication was restored.

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As part of the investigation for the heaters, the Station verified various parameters using more sensitive test equipment to determine the cause of the apparent heater deficiency. The parameters which were verified included differential pressure, flow, heater current, heater voltage and, inlet and outlet temperatures. The Station oersonnel utilized a digital multimmer to measure the resistance at the inlet and outlet Resistance Temperature Detectors (RTD). During the investigation ~connel identified that there was a discrepancy between temperatures whers . osured by the installed instrumentation versus the digital multimeter. Further testing and investigation revealed that the differential temperature requirement could be met at the lower end of the acceptable range of flows using the installed instrumentation (15.5" A T at 1925 cfm) but the differential temperature requirement could not be met when utilizing the more sensitive instrumentation (12.53"F A T at 1917 cfm).

A historical review of surveillances revealed that, overall, the heater successfully met the surveillance requirements. The review revealed that the heater could not maintain the required A T on two occasions (4/17/89 and 6/12/90). In review of the historical data, some deterioration of the heater may have occurred; however, this was not previously investigated since the monthly surveillances were acceptable.

Subsequently, the station installed a new 12 KW heater, which provides approximately 35% more heating capacity to tha system. On September 18,1991, the Station successfully demonstrated a A T of 15.3* F at a flow of 2000 cfm. Although both the current and proposed Technical Specification requirements were mot, the use of more sensitive instrumentation has created the need for the revised differential temperature criteria during future surveillances An analysis of the design information revealed that the Technical S aecification requirement of 15"F A T ensures that 12"F A T is maintained under all f ow conditions up to the maximum flow (i.e.,2200 cfm). This requirement is unnecessarily conservative when the system is successfully tested at flows greater than 1800 cim.

Commonwealth Edison has determined that a A T ranging from 15"F at 1800 cfm to 12"F at 2200 cfm will maintain relative humidity at less than 70%. This analysis is detailed in Enclosure 1 to this attachment. This analysis concludes that since A T is a linear function of flow between 1800 cfm and 2200 cfm, (assuming a constant heater output at different flows), the A T limit is then detemiined by the following formula:

A T > 28.5 - (0.0075F);

where A T is the required differential temperature ("F) and F is the flow (cfm) at which the system is operated or tested.

Since the analysis demonstrates that the range of A Ts and associated flows defined by the above formula will mc.intain relative humidity at the inlet to the charcoal adsorbers to less than 70%, the proposed change does not affect the ability of the charcoal adsorbers to limit dose to control room personnel under design basis accident conditions. Therefore, the requested change to the A T requirement has minimal safety consequences.

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ENCLOSURE ANALYTICAL BASES FOR A FLOW BASED A T REQUIREMENT The design specification for the CREF System states: "The Air Filter Unit shall be designed for incoming saturated air at a design temperature of 95*F to - 10*F".

At the inlet condition of 95*F wet-bulb temperature, the ASHRAE Psychometric Chart from the ASHRAE Handbook of Fundamentals defines a required A T of 12'F in order to maintain relative humidity at the inlet to the charcoal adsorbers to less than 70%

Where Oj - HEATER OUTPUT AT 2200 cfm (BTU /hr)

O2- HEATER OUTPUT AT 1800 cfm (BTU /hr)

Given this, the following relationship is valid M3 C pAT j = M2 Cp AT2 Where fA$ = Mass flow rate at 2200 cfm (Ib!hr)

M2 - Mass flow rate at 1800 cfm (Ib/hr)

Cp - Specific heat (STUllb- F)

Ai j = Differential temperature at 2200 cfm ( F)

AT2= Differential temperature at 1800 cfm (*F)

Solving for AT2 fA1 AT 2 g (AT ) 3 Since the mass flow rates are proportional to volumetric flow, the relationship becomes 2200 AT2" g (AT ) -$ 1.22 AT 3 Therefore, tho AT observed at 1800 cfm (AT2) should be 122% of the AT observed at 2200 cfm (AT3 ).

This relationship describes the behavior of A T as flow is increased from the initial flow where A T was established. This relationship is presented graphically in Figure 1. The formula defining the curve is described below:

AT = 28.5 - (0.0075F)

Therefore the analysis demonstrates that if a AT is established consistent with this formula, a minimum AT of 12'F will be achieved at the highest flow (2200 cfm). This in turn ensures that the heaters will maintain relative humidity at the inlet to the charcoal adr.,orbers to less than 70% at all flows greater than the initial flow.

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6 FIGURE 1 MINIMUM DELTA T CURVE -

DELTA T 17 16 -

1.5 14 -

N.\

.x 13 N

s,.

12 -

N 't

, 11 --

L l i 10 L_ i i 2_ l

.1800 1900 2000 210 0 2200 AIRFLOW-- (cf m)

The curre represents the minimum delta T necessary to ensure that 12 degrees F is maintained at the maximum flow.

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