ML20137F775
| ML20137F775 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 03/27/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20137F758 | List: |
| References | |
| NUDOCS 9704010205 | |
| Download: ML20137F775 (8) | |
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5L UNITED STATES s
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 175 TO FACILITY OPERATING LICENSE NO. DPR-29 AND AMENDMENT NO. 171 TO FACILITY OPERATING LICENSE NO. DPR-30 COMMONWEALTH EDISON COMPANY MD MIDAMERICAN ENERGY COMPANY OVAD CITIES NUCLEAR POWER STATION. UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265 i
1.0 INTRODUCTION
By letter dated March 26, 1997, as supplemented March 27, 1997, Commonwealth Edison Company (Comed, the licensee) submitted an application for an emergency i
license amendment requesting review and approval to allow a decrease in the methyl iodide penetration for standby gas treatment (SBGT) charcoal from 10 percent to 2.5 percent in Technical Specification (TS) Sections 4.7.P.2.b and 4.7.P.3 to compensate for a reduction in calculated secondary containment volume. The licensee's submittal also contained a revised evaluation of the dose consequences to a control room operator resulting from a loss-of-coolant accident (LOCA). This evaluation was submitted as a result of the identification of an error in the secondary containment free air volume.
In addition, the licensee also proposed to change Specification 5.2.C to reflect the new calculated minimum free volume for the secondary containment.
As a result of this discrepancy, the licensee performed a 10 CFR 50.59 evaluation and found that the error in the secondary containment volume resulted in a Unreviewed Safety Question (USQ).
In accordance with 10 CFR 50.59 and pursuant to 10 CFR 50.90, the licensee requested a license amendment 2
to evaluate the USQ and approve associated TS changes.
2.0 BACKGROUND
The licensee recently identified an error in the assumption for the free air volume of secondary containment. The licensee utilized the volume of the secondary containment in the calculation of mixing for releases from the secondary containment to the environment. The licensee found that the free air volume of the secondary containment was actually 18 percent less than the value previously assumed. Because the error was foimd to be a decrease in secondary containment volume, this decrease would result in an increase in the control room operator thyroid dose since the licensee had taken credit for 50 percent mixing in the secondary containment. Because the doses had 9704010205 970327 PDR ADOCK 05000254 P
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increased and the licensee was unable to expand the volume of secondary containment to return the plant to its original design, the licensee determined that this represented a USQ. Consequently, the licensee revised
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their. LOCA analysis of the control room operator dose and submitted this USQ to the staff for review and approval.
In the licensee's revised analysis they j
enacted some compensatory actions to offset the decrease in secondary
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containment volume. The licensee's revised evaluation assumed a removal j
efficiency for the SBGT charcoal of 95 percent for the elemental and organic forms of radiciodine. This was an increase from the licensee's previous analysis whi:h had assumed an efficiency of 90 percent. With this increase'in l
SBGT adsorber efficiency and the decrease in secondary containment volume, the J
l licensee calculated the thyroid dose to the control room operator to be 21.88 rem.
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To ensure that the charcoal was actually capabic of performing at the 95 percent level, the licensee proposed to change the acceptance criteria of surveillance requirement 4.7.P.2.b and 4.7.P.3 to an allowable penetration of I
i the methyl form of radioiodine to <2.5 percent. The licensee also proposed to change TS 5.2.C to provide the correct volume for secondary containment.
i The licensee evaluated the consequences of the decrease in secondary
. containment on the offsite doses.
Because the secondary containment volume was not utilized by the licensee in the calculation of offsite doses, the licensee concluded that the change in volume would have no effect upon the offsite doses.
The licensee evaluated the effect the reduction in the secondary containment free air volume would have on the Environmental Qualification (EQ) pressure / temperature analysis-during a Reactor Water Cleanup (RWCU) line break j
in the RWCU heat exchanger room. The licensee determined that the pressure j
rise in the secondary containment is a function of the release path through j
the building and is not sensitive to the building total air volume for breaks i
of this size comaared to the secondary containment volume. The licensee concluded that t1e reduction in the secondary containment free air volume does not adversely affect the EQ pressure / temperature analysis during a RWCU line i
break.
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The licensee evaluated the effect the reduction in the secondary containment free air volume would have on the pressure and temperature of the secondary containment during a 1-inch instrument line break accident. The licensee determined.that the decrease in the secondary containment free air volume would not adversely affect the calculated response to this line break because, as stated in the UFSAR, " Building pressure would adjust to a value such that the volumetric inflow of steam would be approximately equal to the combined volume extraction rates of the SBGT fan, leakage, and steam condensation."
The licensee concluded that the reduction in the secondary containment free volume does not adversely affect the pressure and temperature of the secondary containment during a 1-inch instrument line break accident.
, The licensee evaluated the effect the reduction in the secondary containment free air volume would have on the normal reactor building ventilation system.
The licensee determined that the commitment to provide at least one free air volume change per hour in the reactor building is still provided. The licensee determined that the air flow rates, design basis temperatures, emergency isolation function, and the process radiation monitoring trip signal are not adversely affected. The. licensee concluded that the reduction in the stcondary containment free volume does not adversely affect the normal reactor i
building ventilation system.
3.0 EVALUATION Evaluation of the US0 The proposed amendment requested review of the USQ to take credit for a decrease in the allowed methyl iodide penetration for the SBGT charcoal adsorbers and reduction in the secondary containment free volume and would revise the TS.
Credit for Decrease Allowed Charcoal Adsorber Penetration The staff has evaluated the proposed TS change by the licensee and the revised control room operator dose from a LOCA.
Inspection Report 50-254/91019 (DRSS) and 50-265/91015 (DRSS) contained an evaluation performed by the staff on the adequacy of the Dresden and Quad Cities control room emergency air cleaning systems to meet General Design Criterion (GDC) 19. This evaluation was in response to a request from NRC Region III to NRR. The evaluation performed by NRR contains several tables which present the control room operator dose as a function of (1) time to begin pressurization flow, (2) SBGT adsorber efficiency, and (3) control room emergency filter system (CREFS). Table 5 of the NRR evaluation assumes that pressurization flow starts 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after the accident.
In addition, the NRR evaluation uses International Committee on Radiation Protection (ICRP) 30 dose conversion factors and a retention factor for iodine in the suppression pool of one.
Based upon a SBGT adsorber efficiency of 95 percent and a CREFS efficiency of 90 percent, the staff projected the control room operator dose to be 21 rem thyroid.
If those l
calculations are corrected to account for the 18 percent decrease in reactor building volume, then the revised dose would be an increase from the previously calculated dose by 22 percent, resulting in a dose of 25.6 rem.
This is below the acceptance limit of 30 rem thyroid for GDC 19 and, therefore, acceptable.
It should be noted that the licensee's analysis assumed pressurization started 110 minutes following the accident rather than at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> as the staff had assumed. The staff determined that this 10 minute difference in pressurization times would not result in the doses increasing to a point where GDC 19 would not be met.
The staff has evaluated the licensee's proposed change to the acceptance criteria for the laboratory test of the SBGT charcoal which is contained in 4
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. surveillance requirements 4.7.P.2.b and 4.7.P.3 to <2.5 percent penetration.
The staff has concluded reduction in the allowable penetration from the present value of <10 percent to <2.5 percent would provide adequate justification for assuming that the SBGT charcoal will perform at least at a level of 95 percent if called upon to mitigate the consequences of an accident. The proposed acceptance criteria of 2.5 percent includes a safety factor of two which provides the staff a degree of assurance that, at the end of the operating cycle, the charcoal will be capable of performing at a level at least as good as that assumed in the staff evaluation. Because the SBGT charcoal has a depth of 2 inches, an allowable adsorber efficiency of i
95 percent can be assumed.
In addition, the licensee presently performs the laboratory test using the American Society for Testing and Materials (ASTM) l D3803-1989 protocol with the test temperature being at 30 degress Celsius and the relative humidity at 70 percent. Therefore, the test method is considered adequate.
Based upon the above, the staff concludes that the licensee can assume an adsorber efficiency of 95 percent for the SBGT charcoal and the proposed change in surveillance requirements 4.7.P.2.b and 4.7.P.3 for allowable penetration for the laboratory test of charcoal is acceptable, i
With respect to the consequences on offsite doses as a result of the decrease in secondary containment volume, the staff is in agreement with the licensee that the offsite consequences are not impacted since the' licensee took no credit for mixing in the secondary containment.
j With respect to the effect the reduction in the secondary containment free air volume would have on the EQ pressure / temperature analysis during a RWCU line break, the staff concurs with the licensee's conclusions that the EQ pressure / temperature analysis is not adversely affected.
With respect to the effect the reduction in the secondary containment free air volume would have on the pressure and temperature of the secondary containment during a 1-inch instrument line break accident, the staff concludes that the pressure and temperature of the secondary containment is not adversely affected since the smaller air volume enables the SBGT to draw down the pressure faster in the secondary containment and, thus, offsetting the slight increase in pressure due to the 1 inch steam break.
With respect to the effect the reduction in the secondary containment free air volume would have on the normal reactor building ventilation system, the staff concludes that the normal reactor building ventilation system is not adversely affected since the smaller air volume will increase the number of free air
- volume changes per hour and cause the isolation trips to occur sooner.
The staff finds the licensee's proposed change to TS 5.2.C to reflect the correct secondary containment volume acceptable.
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i 4.0 EMERGENCY CIRCUMSTANCES In its March 26, 1997, application, as supplemented March 27, 1997, the licensee requested that this amendment be treated as an emergency amendment.
In accordance with 10 CFR 50.91(a)(5), the licensee provided the following information regarding why this emergency situation occurred and how it could not have been avoided.
The licensee was reviewing the ISI inspection results at the Dresden Station and identified that the value for secondary containment free volume stated in the UFSAR was higher than the actual volume.
Quad Cities determined on l
March 24, 1997, that there existed a potential USQ, therefore, they initiated an immediate 10 CFR 50.59 evaluation. This discrepancy in the volume results in a calculated increase in dose to the operators in the control room during i
an accident. On March 26, 1997, the licensee completed the evaluation and determined that a USQ did exist due to a reduction in the margin to safety and an increase in the consequences of an accident.
1 The staff concludes that an emergency condition exists in that failure to act i
in a timely way would result in prevention of resumption of operation of Quad Cities Nuclear Power Station, Unit 1.
In addition, the staff has assessed the licensee's reasons for failing to file an application sufficiently in advance i
to preclude an emergency and concluded that the licensee identified the i
deficiency in the UFSAR and TS, notified the staff of the deficiency, and promptly proposed this amendment to remedy the situation. Thus, the staff concludes that the licensee has not abused the emergency provisions by failing i
to make timely application for the amendment. Thus, conditions needed to satisfy 10 CFR 50.91(a)(5) exist, and the amendment is being processed on an 4
l emergency basis.
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5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission's regulations in 10 CFR 50.92(c) state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in accordance with the amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated, or (2) create the possibility of a new or different kind of accident from any previously evaluated, or (3) involve a significant reduction in a margin of safety.
(1)
Involve a significant increase in the probability or consequences of an accident previously evaluated because of the following:
The consequences of previously analyzed accidents are not significantly affected by this proposed License Amendment.
It was determined that the only impact of the Secondary Containment free volume discrepancy was a small increase in Control Room operator dose; however, by decreasing the allowed methyl iodide penetration for SBGT charcoal from 10 percent to 2.5 percent, calculated operator dose levels are lower than the value previously calculated. Calculated offsite dose levels are not impacted by this issue.
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. The proposed License Amendment will not result in the reactor having the potential for operating in a different condition such that it may adversely affect the initial conditions assumed in any design basis accident analysis.
The associated systems related to this proposed amendment are not affected in a way that could impact the initiation of any accident sequence for Quad Cities Station; therefore, the probability of any accident previously evaluated is not increased by the proposed amendment. No modes of operation are introduced by the proposed changes such that adverse consequences are 4
observed for Quad Station.
(2)
Create the possibility of a new or different kind of accident from any accident previously evaluated because:
The proposed license amendment for Quad Cities does not create the possibility of a new or different kind of accident previously evaluated for Quad Station.
No new modes of operation are introduced by the proposed changes. This change increases the SBGT efficiency in accordance with generic industry guidance.
This increase in SBGT charcoal efficiency is required to compeasate for the discrepancy in Secondary Containment free volume. As such, the proposed changes do not create the possibility of a new or different kind of accident.
(3)
Involve a significant reduction in the margin of safety because:
The proposed license amendment does not significantly affect existing plant safety margins or the reliability of the equipt,ent assumed to operate in the saftty analysis. The proposed changes ensure that Control Room operator doses are lower than the value previously calculated considering the impact of the Secondary Containment free volume discrepancy and the increase in SBGT charcoal filter efficiency.
In addition, the proposed license amendment for i
Quad Cities Station will not reduce the availability of systems required to mitigate accident conditions; therefore, the proposed changes do not involve a significant reduction in the margin of safety.
6.0 ENVIRONMENTAL CONSIDERATION
The amendments change surveillance requirements. 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 released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has made a final no significant hazards finding with respect to this amendment.
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.
7.0 CONCLUSION
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
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1 activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
j Principal Contributor:
J. Hayes 4
J. Segala R. Pulsifer Date:
March 27, 1997 4
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I. Johnson A copy of the related Safety Evaluation is also enclosed. The Notice of Issuance of Amendments to Facility Operating Licenses and Final Determination of No Significant Hazards Consideration and Opportunity for a Hearing will be included in the Commission's biweekly Federal Reaister notice.
Sincerely, 4
ORIGINAL SIGNED BY:
Robert M. Pulsifer, Project Manager Project Directorate III-2 l
Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-254 and 50-265 i
Enclosures:
1.
Amendment No. 175 to DPR-29 2.
Amendment No. 171 to DPR-30 3.
Safety Evaluation cc w/ encl:
see next page DISTRIBUTION:
Docket File PUBLIC PDIII-2 r/f J. Roe, JWR E. Adensam P. Hiland, RIII R. Capra C. Moore R. Pulsifer OGC, 015B18 G. Hill (4), T5C3 C. Grimes, 013H15 ACRS, T2E26 DOCUMENT NAME: G:\\CMNTJR\\ QUAD \\QC98227.AMD
- SEE PREVIOUS CONCURRENCE Ta noelva z copy of tido document, Indicate in the box: "C" = Copy without enclosures *E* = Copy with enclosures *N* = No copy 0FFICE PM:PD3-2 f,. 1 LAtRR3-2 l Rs PERB l SPLB l EELB l
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'03 /r7 /97 0FFICIAL RECORD COPY