ML20245L606
| ML20245L606 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 06/27/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20245L601 | List: |
| References | |
| NUDOCS 8907060009 | |
| Download: ML20245L606 (5) | |
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[d,* "%k UNITED STATES 3,
g NUCLEAR REGULATORY COMMISSION
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rn ij WASHINGTON. D. C. 20555 4
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i SAFETY EVALUATION BY.THE.0FFICE.0F NUCLEAR REACTOR. REGULATION RELATDdO_AMEhDNENT.NO.4/.TO.fAClLllY.0FERATINGLICENSE.WD..NPF-30
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i UNION. ELECTRIC. COMPANY j
CALLAkAY PUANT, UNIT 1 d
1 DOCKEI h0. 51N-50-483 1
1.0 INTRODUCTION
j By letter dated March 25, 1988, Union Electric Company (UE), the licensee for Callaway Plant Unit No.1, proposed a revision to Technical Specification (TS) 3/4.7.6, Control Room Emergency Ventilation Systeas (CREVS). The proposed l
changes were found to be necessary because of diffictIties identified when verifying the capability of the CREVS to comply with the flow tolerances and pressurization level incicated in the Final Safety Analysis Report (FSAR) and TS 3/4.7.6.
The proposed changes in TS 3/4.7.6 consist of:
1)increasingeachcontrol room pressurization system air handling unit flow rate from 2000 cfm 10%
to 2200 cfm with tolerances of 3000 cfm maxiraum and 1800 cfm minimura and increasing the corresponding pressurization filter unit flow rate from 500 cfm 10% to 500 cfm with tolerances of 1000 cfm maximum and 450 cfm minimum;
- 2) increasing each control rocci filtration system air handling unit flow rate from 2000 cfn 10% to 2000 cfm with tolerances of 2700 cfm maximum and 1800 cfm minimum, and 3) reducing the control room pressurization requirement from a positive pressure of greater than or equal to 1/4-inch water gauge (WG) re'ative to the outside atriosphere to a positive pressure of greater than or equal to 1/8-inch WG relative to the cutside atmosphere.
The licensee provided additional information 'n its submittals cated December 28, 1988 and March 31, 1989 in response to the staff's requests dated November 18, 1988 and February 2,1989.
2.0 B_ACKGROUND The proposed technical specification changes address the safety-related ventilation system associated with maintaining control room habitability.
The licensee has provided the following background information on the proposed changes.
TS 3/4.7.6 ensures a sufficient positive pressure envelope of t~11tered air in the control room to ensure habitable conditions under accident conditions. The sufficient positive pressure envelope is created by the pressurization system discharging outside filtered air into the portions of the control building which provide the suction for the control room filtration system which provides continual filtering of control room air. The centrol building end 8907060009 890627 FDR ADOCK 05000483 P
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the rooms containing filter adsorber units for the control room filtration system and control room air conditioning building, adjacent to the control room)g equipment (inside the auxiliary are serviced by the control roofo pressurization fans. These rooms are defined as part of the control room envelope as stated in FSAR Section 6.4.2.1.
A separate ventilation system is provided to maintain the auxiliary building at a negative pressure. The design of the control room pressurization system and the ability to maintain control room habitability are described in FSAR Sections 6.4 and 9.4.
The purpose of the CREVS is to protect the operators so they can achieve and/or maintain the bases accident (DBA) plant in a safe shutdown condition following a design The requested allowed decrease in control room pressurization level from 1/4-inch WG to 1/8-inch WG does not result in an increase in the unfiltered inleakage rate of potentially contaminated air during accident conditions and, therefore, does not adversely affect the control room habitability. The proposed changes to TS 3/4.7.6 have been evaluated for impact upon design bases associated with radiation exposure of control room personnel according to requirements of General Design Criteria (GDC) 19 of Appendix A to 10 CFR Part 50 and postulated hazardous chemical releares that could render the control room environment unsuitable for occupancy per GDC 19.
The control room dose calculations assume no unfiltered inleakage into the control room from control room ingress and egrest due to the utilization of a two-door vestibule configuration. However, 300 cfm of unfiltered inleakage is assumed by other paths into the control building.
Information is contained in FSAR Section 9.4.1.2.3 concerning a potential 80 cfm inleakage into the control room when the control room is isolated but not pressurized. This information was provided in a response to Atomic Energy Commission (AEC) question, Item 6.7, submitted in Revision 2 of the SNUPPS Preliminary Safety Analysis Report (PSAR), September 1974. The AEC question requested identification of potential leakage paths, contributions from each pathway and pressure differential estimates du to wind, temperature differences, barometric variations and ventilation units servicing spaces adjacent to the control room. To perform this analysis, in lieu of lack of guidance on pressure and criteria to be utilized in the AEC question, a positive pressure of 1/4-inch WG was selected based on consis^ency with the i
control room pressurization capability (not corresponding to the environmental conditions postulated to occur at the site). These conditions were not required to be postulated for analysis of control room habitability and thus were not a design basis or licensing basis for the Callaway Plant Unit 1.
Therefore, potential unfiltered inleakage under these hypothetical adverse external enviror. mental conditions do net need to be considered.
3.0 DISCUSSION The licensee stated the following in support of the pro' osed changes:
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, i FSAR Section 2.2 analysis is still valid for the postulated hazardous chemical releases.
It concludes that there are no onsite or offsite hazards which have an adverse effect on the plant structures or control room habitability
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at the Callaway Plant site.
The comparison of the design to Regulatory Guides (RGs) 1.78 and 1.95 as presented in FSAR Tables 6.4-1 and 6.4-2 is still valid. The flow variations under worst case conditions will increase the air exchange rate in the control room from 0.25 volume changes per hour to 0.336 volume changes per hour, and this increased rate has been evaluated and demonstrated to not
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have an adycrse effect on control room habitability. Also RG's 1.78 and 1.95 indicate that 1/8-inch WG positive pressure is sufficient to prevent unprocessed contaminants from entering the control room and Standard Review I
Plan (SRP) $ection 6.4, Revision 2, recommends at least 1/8-inch WG positive pressure relative to all surrounding air spaces. The proposed positive i
pressure differential of 1/8-inch WG inside control room complies with the above guidelines.
Calculations demonstrate that under worst case conditions, the control room doses are still bounded by those given in Table 15.6-8 of the FSAR, Revision OL-0. The method used for dose calculation does not require the control room to be pressurized to the full value of 1/4-inch WG above atmospheric pressure.
The method only assumed that the control room is maintained at a positive pressure allowing no inleakage. Pressurization to a value of 1/8-inch WG above atmospheric pressure, as recommended by the SRP, is sufficient to maintain control room habitability. This pressure differential is sufficient j
to counteract wino cifetia,, thermal column effects and barometric pressure i
changes under worst case conditions.
Charcoal from the pressurization and filtration system filter units is tested per the criteria of RG 1.52, Revision 2, March 1978, Position C.6.7 a.nd C.6.b for a methyl iodine penetration of less than 1%. The correspondirc assigned j
-fficiencier, per the aforementioned RG and Generic Letter No. 83-13, March 2, 1983, are 95%. Accident analysis assumes 90% charcoal efficiency for added conservatism. The revised flow rates for the pressurization system are within the filter unit design flow of 1000 cfm so the system complies with RG 1.52
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Position 31 of C.25 seconds residence time. The upper flow rate of 2700 cfm
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for the filtration system will comply with testing of residence time per ANSI j
510,1976 of 0.25 seconds 20%. The actual residence time will be 0.20
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secontis at 2700 cfm which is within the above acceptance criteria.
j The pressurization unit fans and associated ductwork are located in the control building and the filtration units are located in an area adjacent to the control room, but inside the auxiliary building. Both areas are serviced 1
by the control building pressurization fans. Since no change has been
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requested which would decrease the pressure in these areas during an emergency, there is no increosed potential for unfiltered air inleakage to the control room envelope due to leakage through dampers, seams, and housing access doors in ducts located upstream of pressurization unit fans and downstream of filtration units located outside the control room envelope.
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4 W ' No change'is requested which would change seal design inleakage limitations
. or increase seal degradation over the test interval. The control room isolation dampers are designed _for leak-tightness, in accordance with the existing FSAR Section 9.4.1.2.2.
The effects of errors in r.easving respective pressure differentials between the control room and the outsi.ie atmosphere will be minimized by administra-tively controlled Surveillance Procedure DSP-GK-0002, Control Building Pressure Test, which will incorporate limitations or correction factors fo.
wir.d s' peed and direction based on guidance from the ASHRAE 1985 Handbook of 03ndamentals, Chapter 14.
4.0 EVALUATION j
The staff has reviewed the above described change and supporting rationale and concurs with the licensee's conclusions. This review was conducted based on the guidelines of SRP Section 6.4.
However, due to the complexity
- of the lidensee's control room habitability system design compared to typical j
system design anticipated by the SRP and its referenses, a unique mathematical j
model of the iodine protection characteristics of this system was developed i
by thei straff, based on SRP principles, for use in this review. The staff performed an independent analysis of the licensee's control room habitability desigr, using this model. The analysis included the calculation of the degree of operator protection (iodine protection factor (IPF)) afforded by operation of the system, considering the entire range of component air flow rates and 4
control room pressures allowed by the proposed TS and various postulated
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single failures.. Based on this analysis, which involved consideration of 18 separate operational scenarios, a conservative IPF was arrived at by the staff for use in the staff radiological dose calculations for control room
.q personnel.
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The staff finds that the resulting value of the IPF is not decreased signifi-I cantly with the proposed increase in flow variations and lower control room pressurization in comparison to the IPF without these changes (the methodology andotherassumptionsinthecalculationwouldotherwisebeunchanged). The staff has calculated the potential radiation doses to control room operators followingadesignbasisaccident(DBA). The resultant doses (15 rem to the thyroid and 3.6 rem to the whole body) are within the acceptance criteria of GDC 19 and SRP Section 6.4 of 30 rem to the thyroid and 5 rem to the whole body.
Based on the above evaluation, the staff finds that the proposed changes to the TS are consistent with the Standard Technical Specifications and within the acceptance criteria of GDC 19 and SRP Section 6.4 and, therefore, are acceptable.
5.0 ENVIRONMENTAL CONSIDERATION
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Pursuant to 10 CFR 51.21, 51.32, and 51.35 an environmental assessment and finding of no significant impact has been prepared and published in the
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. Federal Register on June 27,1989(54FR27084)
Accordingly, based upon
.the environmental assessment, the Commission has determined that the L
issuance of this amendment will not have a significant effect on the L
. quality of the human environment.
6.0 CONCLUSION
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?The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner;.and (2) public such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
J. Raval, SPLB C. Nichols, SPLB Dated:
June 27, 1989 l
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