ML20236D899
| ML20236D899 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/17/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-89069, NUDOCS 8903230341 | |
| Download: ML20236D899 (3) | |
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C 906.5 901'8 TUELECTRIC W. J. Cahm March 17, 1989 nuu,= ve, r,,,u,,,,
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 REQUEST FOR ADDITIONAL INFORMATION PERTAINING TO SPLB FSAR 6.5 AND 1A(B) REVIEW I
REF:
1.
.NRC Letter from C. I. Grimes to W. G. Counsil dated I
(
November 16, 1988.
2.
TV Electric letter TXX-88858, dated December 28, 1988 from W. G. Counsil to V. S. NRC.
Gentlemen:
Your letter dated November 16, 1988, requested additional information with respect to the SPLB FSAR review.
A response to the question regarding FSAR l
Section 6.5 and 1A(B) was submitted by TV Electric letter TXX-88855, dated December 21, 1988.
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I In recent discussions the NRC staff requested additional information regarding FSAR Section 6.5 and 1A(B).
The following additional information is provided in the response to that request:
IN-PLACE TESTING OF HEPA AND CHARC0AL FILTERS (FOLLOWING PAINTING, FIRE OR A
[CIfCHFC~AL RCT[All):
The CPSES filter testing program assures that the assigned decontamination efficiencies for radioiodine (from Regulatory Guide 1.52, Table 2) remain valid, because the practice of identifying degraded carbon through in-place and laboratory testing, and replacing charcoal filters as needed, ensures that the carbon adsorption ef ficiency remains at or above Regulatory Guide values.
Following painting, fire or a chemical release in a ventilation zone communicating with the ventilation system in such a manner that the charcoal adsorbers could become contaminated from the furoes, chemicals or foreign materials, TV Electric performs laboratory tests to determine adsorber acceptability.
The CPSES testing program does not require in-placc testing cf the charcoal filters and HEPA filters following painting, a fire, or a chemical release, because such testing cannot reveal changes in carbon adsorption efficiency due to chemical contamination.
In-place testing will only identify mechanical defects that cause leaks, such as mechanical defects in filter frames or improper carbon compaction.
However, because the program of laboratory testing and replacing carbon when test results are 8903230341 890317 PDR ADOCK 05000445
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TXX-89069 March 17,1989
, Page 2 of 3 unsatisfactory ensures that carbon adsorption efficiency remains at or above Regulatory Guide values, the testing program assures the continuing validity of the assigned decontamination efficiencies for radiciodine.
In the unlikely event that painting, fire, or a chemical release occurred at CPSES in a manner that loaded the HEPA filters to a failure point, the failure would be detected by the differential pressure gages which are monitored twice a shift and the high pressure indicator which is alarmed in the Control Room to indicate possible filter problems.
A fire or chemical release which is significant enough to defeat CPSES monitoring or alarming would be of such magnitude that CPSES would be inspecting and repairing a whole host of equipment, including the filtration systems.
1 The CPSES exhaust system design is somewhat " unique", because it exhausts air from nearly the entire Auxiliary, Fuel Handling and Safeguards Buildings.
This system also exhausts from the Hot Machine Shop where painting, fire (welding) and chemical release (cleaning solvents) may occur to a minor extent l
l every day.
These conditions would not warrant continual filter testing.
I l
IN-PLACE TESTING OF HEPA FILTERS:
The CPSES filter testing program does not perform in-place testing of the downstream HEPA filters.
The Regulatory Guide suggests considering that the filtration units have downstream HEPA filters to capture charcoal fines, and supposedly to be redundant to the upstream HEPA filter. The upstream HEPA filter is designed to capture particulate contamination before it gets to the i
charcoal adsorber.
The charcoal adsorber function is to capture the gaseous ef fluent.
If the upstream HEPA does not filter the particulate then the charcoal adsorber gets filled with particulate making it difficult to adsorb the gaseous effluent.
The downstream HEPA is not redundant, based on its location, to either the upstream HEPA filter or the charcoal filter.
Sufficient redundancy is provided for each ESF filter unit by the redundant l
safety train.
The design of the CPSES filtration units differs from the filtration units that were predominant at the time of the origination of the Regulatory Guide.
The old charcoal adsorber frames generally were riveted into place, whereas the CPSES charcoal adsorber frames are welded into place.
This welded design minimizes the vibration, which would potentially generate charcoal fines.
CPSES has a plant specific maintenance procedure for changing the charcoal that prevents significant generation of charcoal fines. When new charcoal is installed, roughing filters are installed in place of the downstream HEPA filters and the units are run to initially blow the charcoal fines out of the system.
These roughing filters are then replaced with the HEPA filters which were removed.
If the HEPA filters are near their dust loading capacity, as determined by the differential pressure gage reading, then they are left in place during the blowdown of the new charcoal adsorber and then replaced with new HEPA filters.
Another factor involved in minimizing charcoal fines is the restriction of the charcoal particle size and the hardness of the charcoal. Once the initial fines are purged from the system, as described above, the charcoal hardness and the stiffness of the welded frames will reduce the production of fines during operation.
1 J
' March 17, 1989 Paje 3 of 3-Based'on the location and function of the downstream HEPA filter, the_ improved filter. design, the characteristics of the charcoal used and the process followed when replacing.the charcoal, the downstream HEPA filters at CPSES do not require in-place testing to satisfy the intent of the Regulatory Gnide.
1 CONCLUSION:
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The combination of.the CPSES filter testing program, CPSES maintenance procedures, CPSES monitoring program, CPSES filter unit design, and the s)ecific plant layout of the CPSES exhaust duct system provides a total design w1ich meets or exceeds the filtration efficiencies defined in the Regulatory Guide and meets the overall intent of the Regulatory Guide to provide particulate filtration and radiciodine adsorbtion to. reduce the quantities of radionuclides in gaseous effluents released from the plant.
Sincerely,
/
M William J. Cahill, Jr.
l MCP/ddm c - Mr. R. D. Martin, Region IV Resident Inspectors, CPSES (3) i i
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