ML17332A212
| ML17332A212 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 07/07/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17332A211 | List: |
| References | |
| NUDOCS 9407140072 | |
| Download: ML17332A212 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSlON WASHINGTON> D.C. 28555-0001 I
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
TO FACILITY OPERATING LICENSE NO.
DPR-58 AND AMENDMENT N0.163 TO FACILITY OPERATING LICENSE NO.
DPR-74 INDIANA MICHIGAN POWER COMPANY DONALD C.
COOK NUCL'EAR PLANT UNIT NOS.
1 AND 2 DOCKET NOS.
50-315 AND 50-316
- 1. 0 INTRODUCTION By letter dated November 17,
- 1993, the Indiana Michigan Power Company (the licensee) requested amendments to the Technical Specifications (TS) appended to Facility Operating License Nos.
DPR-58 and DPR-74 for the Donald C.
Cook Nuclear Plant, Unit Nos.
1 and 2.
The proposed amendments would allow a portion of the Waste Gas Holdup Explosive Monitoring System to be inoperable (on a one time basis) for up to 160 days while the system is modified.
In
- addition, the surveillance requirement for the inoperable system would be suspended for the period of inoperability.
The modification involves replacing the existing analysis system (QC-370) used to continuously monitor oxygen in the gas decay tanks with a more reliable oxygen analysis system.
Another oxygen monitor (QC-31) would remain in s'ervice.
QC-31 would alert plant personnel to increasing oxygen levels at the "high" (2.5%)
and "high-high" (3%) levels.
At the upper limit setpoint (3%) plant personnel would be required to initiate a switching of the waste gas holdup tanks to prevent the oxygen level from reaching the point where it could ignite the hydrogen.
To further compensate for the oxygen monitor's inoperability, the licensee has proposed to collect and analyze grab samples every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> while QC-370 is out of service.
The proposed amendments would also make some editorial changes to increase clarity and eliminate confusion.
potentially combustible mixture of hydrogen and oxygen in the waste gas system.
During power operation, hydrogen gas is stripped from the reactor coolant and discharged to the CVCS [chemical and volume control system]
holdup tanks during boron dilution.
- However, the highest volume of hydrogen gas is generated during the process of plant shutdown when the reactor coolant system is degassed.
r 9407140072 940707 PDR ADOCK 05000315 P
PDR Since combustible concentrations
.of hydrogen are possible, during these evolutions, the waste gas system is designed to minimize oxygen concentrations.
This is accomplished by (1) using a nitrogen cover gas, (2) restricting components that discharge to the waste gas vent header'to those containing no air or no aerated fluids, and (3) maintaining'he vent header at a positive pressure to prevent in-leakage:
Despite the design consideration, oxygen ingress into the waste gas system is possible.
This could occur, for
- example, following a seal failure on the suction side of the waste gas compressor.
Thus, it is essential for operators to be promptly aware of oxygen concentrations that would support combustion of hydrogen.
The minimum concentration of oxygen and hydrogen required for combustion in a nitrogen environment is about 5% and 4%, respectively.
The licensee has stated that the hydrogen level will be assumed to be higher than the 4%
minimum flammable concentration during the oxygen monitor replaceme'nt.
Therefore, the limiting factor is the oxygen concentration at which hydrogen and oxygen become flammable.
While the unavailability of the QC-370 oxygen monitor during the replacement period does eliminate the redundancy in the capability to continuously monitor oxygen concentration, the prompt actions that would be required in response to oxygen in-leakage into the waste gas system would remain unchanged (i.e., the previously mentioned operator
- actions, Section 1.0). 'n addition, oxygen concentrations based on grab sample analysis would be available every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
The current D.C.
Cook TS action statement for the oxygen monitors allows operation of the waste gas holdup system for 30 days with one oxygen monitor inoperable with no compensatory requirement for obtaining grab samples.
Grab samples are only required if both oxygen monitors are inoperable.
- Thus, the licensee's proposal to take grab samples every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> (even when QC-31 is in service) constitutes a level of compensatory action equivalent to the existing TS.
If QC-31 were to become unavailable during the replacement
- period, the licensee would follow the exiting TS requirement (i.e., operation of the waste gas system would be discontinued if QC-31 could not be repaired or QC-370 could not be returned to service within 30 days).
The worst-case scenario involving the inoperability of the oxygen monitor would be that a highly explosive mixture of hydrogen and oxygen ignites and causes the failure of a gas decay storage tank.
Technical Specification 3/4. 11.2.6, "Gas Storage Tanks," for D.C. Cook, limits the radioactivity contained in each gas storage tank to 43,800 curies of noble gas (Xe-133 total body dose equivalent).
This limit ensures that in the event of an uncontrolled release of a gas storage tank's contents due to its failure, the resulting total body exposure to an individual at the nearest site boundary will not exceed 0.5 rem (see the BASES for TS 3/4. 11.2.6),
This is consistent with Branch Technical Position ETSB 11-5, "Postulated Radioactive Releases Due to a Waste Gas System Leak or Failure," for Standard Review Plan Section 11.3 "Gaseous Waste Management Systems."
As discussed
- above, the radiological consequences of the postulated failure of a storage tank would not be changed by the proposed modification.
The licensee's request for a 160-day period for replacement of QC-370 is based on the work involved and experience with the replacement of QC-31 in 1989.
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'I The replacement project requires cutting the gas lines to the panel, removal of the old panel, install'ation 'of the new panel',
welded connection of the gas
.lines to the new panel; and checkout'nd calibration of the new panel.
Since the new panel has two channels, to allow for cal'ibration of one while the.
other remains in service, the checkout and calibrati'on will have,to be done twice.
The licensee's prior replacement of gC-31 in 1989 took almost the entire 160 days allowed for that replacement.
Based on the work required and the previous experience, the staff considers the 160-day allowance reasonable.
Based on the above, the one-time, 160-day, inoperability and suspension of surveillances of an oxygen monitor to allow for replacement of the monitor is considered acceptable by the staff.
The licensee also requested that the tag number for the Automatic Gas.Analyzer (the other oxygen and hydrogen monitoring system) be changed from gC-31 to OC-1400..
This is proposed to eliminate confusion regarding spare parts for the new analyzer panel, This proposed change is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change the requirements with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change a surveillance requirement.
The 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 previously issued a
proposed finding that the amendments involve no significant hazards consideration and there has been no public comment on such finding (59 FR 4938).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
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.
5.0 CONCLUSION
The staff 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 Contributors:
J.
B. Hickman J.
G. Giitter Date:
duly 7, 1994
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