ML20237C975
| ML20237C975 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/10/1987 |
| From: | Silady J COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 3956K, NUDOCS 8712220291 | |
| Download: ML20237C975 (4) | |
Text
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[C s C:mm:nwrith Edison
/ One First National Plaza, Chicago, Illinois
,a\\' C ddress Reply to: Post Office Box 76T-
,PRIORJIY ROUtig
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Chicago, Illinois 60690 0767 December 10, 1987 R-+
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w-Mr. A. Bert Davis n
Regional Administrator 2$[
U.S. Nuclear Regulatory Commission
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l Region III u th, - -
l 799 Roosevelt Road Glen Ellyn, IL 60137
Subject:
Dresden Station Unit 1 Status of the Unit 1 Spent Fuel Pool NRC Docket No.50-10_
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Reference:
Letter from C. E. Norelius to Cordell Reed dated l
November 10, 1987 concerning allegation RIII-87-1-0138
Dear Mr. Davis:
The referenced letter requests commonwealth Edison to respond to an allegation concerning the Dresden 1 spent fuel pool. The concern pertained to potential degradation of the fuel racks or the concrete structure as a result of stagnant conditions in the pool. The attachment to this letter addresses these concerns as well as efforts to assure there is no impact on the spent fuel assemblies contained in the pool.
As indicated in the evaluation, prior to receipt of the allegation, j
the potential for microbial influenced corrosion (MIC) had been previously identified, an action plan had been developed, and a program was underway to address these concerns, Although Commonwealth Edison does not consider the safe storage of Dresden 1 spent fuel to have been compromised, the Company is actively pursuing resolution of these concerns as discussed in the attachment.
I When the results of post-cleaning examinations are available, a supplemental report will be provided which will identify any further corrective actions which may be planned at that time.
Please contact this office, should further information be required.
Very truly yours, gh J. A. Silady Nuclear Licensing Administrator Attachment d
cc:
M. Grotenhuis - NRR g
NRC Resident Inspector - Dresden I
C. E. Norelius - RIII f /
m22=ga mage P
t ATTACHMENT CECO EVALUATION OF ALLEGATION RI U-87-A-0138 The reference letter cites an allegation (RIII-C7-A-0138) regarding the Dresden Unit 1 spent fuel pool. The alleger was concerned that the pool had remained stagnant for over two years and that this might be having an effect on the integrity of the fuel racks and the concrete structure l
itself. Commonwealth Edison was asked to address procedures or practices in place to assure the integrity of the fuel racks in the Unit 1 fuel pool and the concrete structure itself.
BACKGROUND The Unit 1 fuel pool has been stagnant since December of 1983. At that time, the cooling and filtration system was taken out of service due to operational problems. Since the spent fuel in the Unit 1 pool had been discharged for a number of years and had therefore cooled down considerably, j
it did not generate enough decay heat to require operation of the fuel pool heat exchangers. The stagnant conditions in the fuel pool have since led to the growth of micro-organisms and the growth of these micro-organisms has led to the concern over microbial influenced corrosion (MIC) of pool structures and equipment. MIC is a relatively new issue within the nuclear industry. Dresden Station personnel were not aware of the MIC phenomenon at the time that the decision was made to take the cooling and filtration system out of service.
_ CORRECTIVE ACTIONS (IN PROGRESS AND PLANNED)
Once the potential of MIC was recognized, an effort was made to i
determine the extent of the problem and to obtain possible solutions.
Dr.
Daniel pope from Bioindustrial Technologies, Inc. was contracted to perform an on-site examination of the Unit 1 spent fuel pool on June 9, 1987.
Dr.
pope's results showed high levels of bacteria.
As a result of Dr. pope's examination, an action plan was developed to reduce the bacterial population using hydrogen peroxide as a biocide.
This method of treatment was successfully performed at the San Onofre Nuclear power plant. An initial 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> treatment of approximately a 100 ppm hydrogen peroxide was proposed. A residual level of about 10 ppm hydrogen peroxide concentration will then be maintained as needed after the initial treatment has been completed. Addition of hydrogen peroxide to the pool began on November 30, 1987.
Once the hydrogen peroxide has performed its function of microbial population reduction, there may be a residue of bacteria remnants in the pool that will have to be vacuumed out. Dresden is in the process of contracting the necessary services to vacuum the bottom of the pool following initial hydrogen peroxide treatment. To monitor any long l
term corrosion effects of hydrogen peroxide on the carbon steel storage racks, a coupon surveillance program is being implemented.
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_2-In addition, a program of visual surveillance of the fuel assemblies is being implemented to monitor any possible long term affects of hydrogen peroxide on the fuel assemblies. Visual examinations of selected fuel bundles will be performed one month, three months, six months and one year after initial treatment with hydrogen peroxide has been completed.
Annual inspections will then be made after the initial one year inspection program has been completed. Both General Electric and Advanced Nuclear Fuels believe that any long term effect on the fuel of such low level concentrations of hydrogen peroxide will be minimal.
An On-Site-Review of the hydrogen peroxide addition program has i
been performed. Also, procedures are in place for surveillance of the carbon steel coupons and the fuel assemblies.
The station will install a portable demineralizing system following the current cleaning program.
In addition, evaluation of several longer term options (such as a new, permanent demineralizing system) are in progress.
SAFETY SIGNIFICANCE Currently, there is no evidence of loss of integrity of the fuel assemblies, fuel rocks or concrete structures. This conclusion is based on the results of a visual examination, performed utilizing an underwater television camera, of a limited number of fuel assemblies and pool structures. A more detailed assessment of the structural integrity of these components will be performed following successful cleaning of the pool water and structural surfaces when examinations can be better conducted.
Following this detailed assessment, appropriate corrective actions will be taken if necessary. Long term monitoring of the fuel, fuel racks and concrete structures will be assured by the implementation of a new Dresden Administrative procedure, specifically addressing the maintenance and surveillance of Dresden Unit 1 in its non-operational status. This administrative procedure, which is currently in draft form, is being l
l developed as a part of the Unit I decommissioning effort.
As a result of a telephone discussion with peter Erickson (NRR i
reviewer of the Dresden Unit 1 possess-but-not-operate lice 7se amendment) in February of 1986, commonwealth Edison had an analysis performed to address the impact of a loss of cooling for the spent fuel pool. Additionally, it was decided to have other accident scenarios involving loss of inter-fuel assembly spacing analyzed (e.g. possible effects of a seismic event). NUS Corporation was contracted to perform these analyses of various spent fuel storage pool accident scenarios. The NUS study showed that the pool l
k-effectives would be below the NRC criteria specified for sp6nt fuel storage under accident conditions including wet, dry, and optimal moderation. The study further concluded that the dose at the site boundary would be below the epa's protective action guide under accident conditions.
Although the NUS studies were not undertaken to resolve potential problems resulting from microbial influenced corrosion, the accident scenarios studied do provide additional assurance of pool safety margins under a number of scenarios involving substantial changes in geometry and coolant conditions in the pool.
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? commonwealth Edison therefore believes that safe storage of the j
Dresden Unit 1 fuel is assured. Ceco further believes that any additional corrective actions, resulting from the post-cleaning examinations of the fuel and pool structures, could be implemented in a timely manner without compromising safe storage of the Dresden Unit 1 fuel, i
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