ML20045C928
| ML20045C928 | |
| Person / Time | |
|---|---|
| Site: | Zion, Kewaunee File:ZionSolutions icon.png |
| Issue date: | 06/21/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045C918 | List: |
| References | |
| NUDOCS 9306250116 | |
| Download: ML20045C928 (4) | |
Text
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f1 2*i UNITED STATES E'
E NUCLEAR REGULATORY COMMISSION WASHINGTON, D,C. 20506-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ~
j ON-SITE DIESEL FUEL STORAGE RE0VIREMENTS COMMONWEALTH EDIS0N COMPANY ZION STATION. UNIT NOS. 1 AND 2 DOCKET NOS. 50-295 AND 50-304 l.0 INTRODUCTION During an Electrical Distribution System Functional Inspection (EDSFI), the team identified inconsistencies between the Technical Specification (TS) j requirements and the Updated Final Safety Analysis Report (UFSAR) with regard to on-site diesel fuel oil storage volume.
Technical Specification Limiting Condition for Operation (LC0) 3.15.3 requires that a minimum of 40,000 gallons-of diesel fuel be maintained on site for each emergency diesel generator (EDG). According to the TS basis, this quantity of diesel fuel.is sufficient.
for seven days of diesel operation at rated power (4000 KW).
Conflicting with r
the TS basis, Section 8.4.3.1 of the Zion UFSAR states that the diesel'fcal consumption over a seven day period is 45,360 gallons-based on a consumption 1
rate of 270 gallons per hour (gph). This issue was carried as an unresolved item in the inspection report (295/92003-05 and 304/92003-05)'pending NRC-review.
The licensee provided its response to this unresolved item in a letter dated April 15, 1992.
2.0 BACKGROUND
INFORMATION In its response to the unresolved item, the licensee indicated that UFSAR t
Section 8.4.3.1 was correct and that the TS bases statement pertaining to the diesel fuel oil storage volume requirement was in error since 40,000 gallons of fuel oil is not sufficient to power a Zion EDG at rated load for seven i
days.
Based on a recent load study that was completed, the licensee dctermined that the wor.st-case EDG fuel consumption rate was 'about 283.5 gph (assumes that the EDG is operating at rated load using the worst-case heating value fuel that is allowed to be purchased for the EDGs at Zion).
For.the EDG loading conditions that actually exist at Zion during a design basis accident with loss of off-site power, the licensee determined that 34,627 gallons of diesel fuel would be required for seven days of continuous EDG. operation. As a result of the load study, the licensee also determined that each fuel oil storage tank contains an unusable fuel oil-volume of about 5134 gallons, so o
that 39,761 gallons of diesel fuel must actually be available to support seven days of continuous EDG operation during an accident condition.
The. licensee has committed to confirm that the maximum EDG fuel consumption at rated load is less than 284 gph and to revise the UFSAR description and the TS basis to 9306250116 930621 DR ADOCK 0500 5
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be consistent with the results of the load study that was completed. The licensee also committed to raise the diesel fuel oil storage tank low level alarms to 43,300 gallons and to continue its standard practice of ordering more fuel whenever the volume in either EDG fuel oil storage tank drops to 44,000 gallons.
The staff's review criteria (Standard Review Plan Section 9.5.4, " Emergency Diesel Engine Fuel Oil Storage and Transfer System") requires that a minimum on-site inventory of fuel oil be available for each redundant diesel generator system to enable the diesel generators to power required engineered safety features for a period of seven days following any design basis' accident and loss of off-site power event. The Standard Review Plan makes reference to ANSI-N195, " Fuel Oil Systems for Standby Diesel Generators," which provides a methodology for calculating the minimum required on-site diesel fuel storage volume.
For the case where the required storage volume is calculated based on time-dependent loading conditions, the minimum required fuel storage volume is equal to the amount of fuel consumed by the diesel for the postulated loading conditions over a seven day period, plus the amount of fuel required for periodic testing, plus an additional ten percent to account for uncertainties.
Therefore, based on this criteria, the minimum amount of diesel fuel required by the TS to be available on-site should be equal to the postulated seven-day diesel fuel consumption plus an additional ten percent.
For Zion,'this equates to 43,224 gallons (includes 5134 gallons to account for the unusable-storage tank volume), which is 3224 gallons more than the current TS requirement.
3.0 EVAtVATION The Zion construction permit safety evaluation report (SER) was issued on August 21, 1968, and the licensing SER for Zion was issued on October 6, 1972.
Since ANSI-N195 was not issued until April 12, 1976, it is not applicable to the Zion station and further, the licensee has not committed to the provisions of this standard.
Therefore, the licensee is not obligated to implement the measures stated by ANSI-N195.
The basis that was established for the 40,000 gallon diesel-fuel storage requirement that is listed in the Zion TSs is to "... allow continuous rated load operation for a minimum of 7 days."
It is the staff's view that the basis that was stated for the TS requirement is in fact correct, but that the 40,000 gallon requirement is in error.
Based on the information that was i
available at the time of Zion licensing, the minimum required amount of diesel fuel should have been listed as 46,000 gallons.
The actions being taken by the licensee to establish a licensing basis for EDG fuel storage based on time-dependent loading of the EDGs is acceptable to the staff.
Actions that were taken to quantify the usable volume in the fuel oil storage tanks, to establish time-dependent loads on the EDGs, and to determine fuel consumption rates based on the lowest grade fuel allowed for EDG application at Zion provide a high level of confidence that the 40,000 gallons of diesel fuel required by the TS is sufficient to support at least.seven days of continuous EDG operation following a design basis accident concurrent with
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- ij a loss of off-site power.
Also, actions that are planned to raise the diesel fuel oil storage tank low level alarms and to order additional diesel fuel well in advance of reaching the TS limit.will help to ensure.that sufficient fuel inventory will be available on-site at all times.
However, to fully resolve this issue, Ceco should confirm that the emergency diesel generator (EDG) fuel consumption rates which were calculated.in its load study are conservative compared to the actual fuel consumption rate (corrected to account for the lowest quality diesel fuel allowed for EDG application) over the entire load range that is anticipated following an event, not just for the rated load condition.
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4.0 CONCLUSION
S The licensee's actions are responsive to the concerns that were identified.
during the EDSFI and will help to ensure that sufficient fuel inventory will be available on-site at all times to provide at least seven days of continuous EDG operation following a design basis accident condition concurrent with a loss of off-site power.
However, to fully resolve this issue, CECO should confirm that the emergency diesel generator (EDG) fuel. consumption rates which were calculated in its load study are conservative compared to the actual fuel consumption rate (corrected to account for the lowest quality diesel fuel allowed for EDG application) over the entire load range.that is anticipated following an event, not just for the rated load condition.
Principal Contributor:
James Tatum Date:
June 21, 1993 4
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Mr. D. L. Farrar change acceptable. The revised page is enclosed with this letter and should be used to replace the current page.
Sincerely, orgindSigned4 Clyde Y. Shiraki, Senior Project Manager Project Directorate III-2 Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation
Enclosure:
Revised Bases page 273 to Zion Station, Units I and 2, Technical Specifications j
cc w/ enclosure:
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