ML20078C342
| ML20078C342 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 10/21/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078C332 | List: |
| References | |
| NUDOCS 9410310180 | |
| Download: ML20078C342 (5) | |
Text
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UNITED STATES g
g NUCLEAR REGULATORY COMMISSION
's WASHINGTON, D.C. 2055!HXci o
j 44....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.200 TO FACILITY OPERATING LICENSE NO. DPR-53 AND AMENDMENT NO. 177 TO FACILITY OPERATING LICENSE NO. DPR-69 BALTIMORE GAS AND ELECTRIC COMPANY f
CALVERT CLIFFS NUCi_AR POWER PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-317 AND 50-318
1.0 INTRODUCTION
By letter dated November 4,1993, Baltimore Gas t.nd Electric Company (the licensee /BG&E) submitted a license amendment request for the Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2, to revise the Updated Final Safety Analysis Report (UFSAR). The requested change would allow the removal of an orifice in the 4-inch containment vent / purge line resulting in greater flow.
The Unit I containment and the Unit 2 containment each have a separate but identical system.
Penetration room exhaust fans in the auxiliary building draw air through an in-containment moisture separator and an in-containment motor-operated valve (MOV).
The air is passed through the auxiliary building via the vent lines which have an outside containment MOV, flow reducing orifice, a flow monitoring system, a motor-operated butterfly valve, and a set high efficiency particulate air and two charcoal filters in parallel (the penetration room ventilation system filter bank).
The air is then discharged by the fans through the main plant vent. Vented air is replaced through a separate penetration.
The use of this system as a containment vent was approved by Technical Specification (TS) Amendment Nos. 115 and 98 for Unit Nos. I and 2, respectively, dated February 20, 1986. The maximum hypothetical accident doses in the UFSAR, Chapter 14.42, were revised to include venting of the containment at the initiation of an accident. The NRC staff's Safety Evaluation (SE) which supported TS Amendment Nos.115 and 98 also approved the higher calculated offsite dose than was currently described in the UFSAR at that time.
Subsequently, BG&E identified calculational errors in the offsite dose, which when corrected, indicate an offsite dose higher than that approved in the NRC staff's SE. An orifice plate with a 1-inch opening was installed in each of the vent lines in order to maintain the approved offsite dose levels.
2.0 EVALUATION Restoration of full-flow capability to the 4-inch vent / purge lines by removing the orifice plates will significantly reduce the time required to vent or 9410310180 941021 PDR ADOCK 05000317 P
. purge.
It now takes 7 times longer to vent a containment than it did with a 4-inch line (28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> versus 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />).
In addition, venting now occurs over three operating shifts instead of being completely contained within one shift.
Venting is a manually controlled operation, in that it requires operator attention (the operator opens and closes the valves from the control room).
Stretching the venting over three shifts introduces the possibility of additional human error into the venting process. Another consideration is that the probability of an accident occurring during venting decreases with decreased vent time.
Reducing the venting time will not increase the number of times BG&E needs to vent, because the starting and ending conditions for venting remain the same. Therefore, the total amount of time the containment vents would be open will be decreased.
Reanalyses have been performed to support the removal of the orifice plates which indicate that the offsite dose would be increased. Although the consequences of the maximum hypothetical accident would result in an increase in the fission product release, the total dose is well within the limits of 10 CFR Part 100.
Fission products would be released until the in-containment and outside containment isolation valves receive a safety injection actuation signal or a containment radiation signal which would close the valves isolating the vent line.
BG&E's reanalysis of the hypothetical loss-of-coolant accident (LOCA) indicate a dose of 118 rem to the thyroid and 10.6 rem to the whole body at the exclusion area boundary (EAB) and 39.3 rem to the thyroid and 2.7 rem t: the whole body at the low-population zone (LPZ) boundary.
The previously appcoved doses in the UFSAR, Chapter 14, are a dose of 124 rem to the thyroid and 3.0 rem to the whole body at the EAB and 33 rem to the thyroid and 0.8 rem to the whole body at the LPZ.
The reanalysis results show a slight dose decrease to the thyroid at the EAB and a slight dose increase to the thyroid at the LPZ. The whole-body doses are increased by approximately 3.5 times at the EAB and LPZ. The 10 CFR Part 100 limits are 300 rem to the thyroid and 25 rem to the whole body at both the EAB and LPZ. The increased doses to the whole body are approximately 40 percent at the EAB and 10 percent at the LPZ of the 25 rem limit provided in 10 CFR 100.11.
j The results of the reanalysis are roughly similar to the licensing basis evaluation contained in the Commission's Safety Evaluation Report (SER) dated August 28, 1972.
The SER results are 110 rem to the thyroid and 4 rem to the whole body at the EAB and 80 rem to the thyroid and 3.0 rem to the whole body, at the LPZ with no containment venting or purging assumed.
It should be noted that the dose estimates in the reanalysis represent an extreme upper bound because the release from the containment was assumed to contain fission products derived from a uniform mixing in the containment atmosphere of the iodines and noble gases specified in TID-14844.
Even though the percentage increase in offsite doses is not small, the actual total doses are a fraction of the limits of 10 CFR Part 100, as noted above.
In evaluating the impact of the increased doses, it is important to view these results in light of the low
. probability of the accident. This change does not significantly affect the risk of any dominant accident scenario and the effect on overall risk of accident at this facility is insignificant. With regard to normal environmental releases when venting during power operation with the orifice plates removed, the release limits are controlled by the previously approved TS for each of the Calvert Cliffs units. Therefore, the removal of the orifice plates and reestablishing full flow through the vent lines will result in no additional environmental impact for nonaccident releases.
in summary, the total doses based on the reanalysis are roughly similar to trose in the initial licensing basis SER dated August 28, 1972. The doses represent an extreme upper bound, and the doses are a fraction of the 10 CFR Part 100 limits.
In addition, as noted above, the removal of the orifice plates would reduce the required time to vent from 28 hours3.240741e-4 days <br />0.00778 hours <br />4.62963e-5 weeks <br />1.0654e-5 months <br /> to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and the probability of an accident occurring during venting decreases with a decreased vent time.
Therefore, based on the above, the NRC staff has concluded that the removal of the orifice plates in each of the Calvert Cliffs Nuclear Power Plant, Units 1 and 2, 4-inch containment vent / purge lines is acceptable.
The UFSAR shall be updated to reflect the removal of the orifice plates and the maximum hypothetical accident analysis revised to address the increased flow as the result of the removal of the orifice plates.
3.0 STATE CONSULTATION
In accordance with the Commission's regulati'ns, the Maryland State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental as:essment and finding of no significant impact has been prepared and was published in the Federal Reaister (59 FR 23239) on May 5,1994. Accordingly, based upon the environmental assessment, the NRC staff has determined that issuance of these amendments will not have a significant effect on the quality of the human environment.
i
5.0 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 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.
Principal Contributor: Daniel G. Mcdonald Date:
October 21, 1994 l
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DATED:
October 21, 1994 AMENDMENT NO. 200 TO FACILITY OPERATING LICENSE NO. DPR-53-CALVERT CLIFFS UNIT 1 AMENDMENT N0.177 TO FACILITY OPERATING LICENSE NO. DPR-69-CALVERT CLIFFS UNIT 2 Docket File PUBLIC PDI-l Reading S. Varga, 14/E/4 J. Zwolinski, 14/A/4 L. Marsh C. Vogan D. Mcdonald OGC D. Hagan, 3302 MNBB C. Liang, 8/E/23 G. Hill (4), PI-22 C. Grimes, ll/F/23 ACRS (10)
OPA OC/LFDCB PD plant-specific file C. Cowgill, Region I l
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Plant Service list l
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