ML20205D375
| ML20205D375 | |
| Person / Time | |
|---|---|
| Site: | Cooper, Zion File:ZionSolutions icon.png |
| Issue date: | 10/08/1985 |
| From: | Gammill W Office of Nuclear Reactor Regulation |
| To: | Jacox J JACOX ASSOCIATES |
| References | |
| NUDOCS 8510110265 | |
| Download: ML20205D375 (2) | |
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Docket No.: 50-295/304 007 6 1985 Mr. Jack Jacox Jacox Associates 1445 Sunnit Street Columbus Ohio 43201
Dear Mr. Jacox:
SUBJECT:
USE OF SILICONE SEALANTS IN DUCTWORK in response to your request of October 7,1985 please find enclosed a co the guidance provided by the Office of Nuclear Reactor Regulation (NRR) py of to Region III on the acceptability of the use of silicone sealants in ductwork.
wisawa n.w u os4 stu w r. w u William P. Gamill, Chief Heteoralogy &' Effluent Treatment Branch Division of Systems Integration
Enclosure:
Memo to J. A. Hind from H. L. Thompson dtd Aug. 26, 1985 a
DISTR!GUTION DOCKET FILES 50 295/304
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August 26, 1985 HEMORANDUM FOR: John A. Hind Director Division of Radiation Safety and Safeguards,.RI!!- ----
FROM:
Hugh L. Thompson, Jr., Of rector Division of Licensing, NRR
SUBJECT:
ADEQUACY Of ZION CONTROL ROOM EMERGENCY AIR CLEANING SYSTEM MODIFICATION AND REPAIR (AITS T03018285)
This is in response to your request of April 9,1985 for technical assistance with respect to the use of temporary scalants in the modifications and repairs of the Control Room Air Cleaning System at the Zion facility, a practice that i
is contrary to etquiatory guidance (Regulatory Guide 1.52).
You also noted thd the Zion Station siay not be committed to, Regulatory Guide 1.52 due to its "*' '"~
earlier licensing timef rame'.* '
With respect to the question of applicability of Regulatory Guide 1.52 for the Zion Station, the licensee's submittal in risponse to item !!I.0.3.4 of NUREG-0737 references use of Regulatory Guide 1.52 with regard to iodine removal efficiencies.
Regulatory Guide 1.52 ' specifies iodine removal efficiencies for syctems designed in accordance with the regulatory guide. It is not clear that the licensee's reference constitutes a comitment that encompasses the exclusion of temporary scalants and patching materials from such systems. Nevertheless, it is clear that the intent of item III.O.3.4 was other things, an air cleaning system whose long-term integrity assured.
It is also clear that the need for long-tem integrity was a basis scalants in air cleaning systems.for the statement in Regulatory Guide 1 In the case of Zion Station, there are several factors which compound our concern about the use of temporary scalants and patching materials in the Control Room Emergency Air Cleaning System.
The system operates at a negative pressure, it is mostly located outside of the control room envelope, and there is little infonnation available on the characteristics or identity of the sealant material.
could result in the failure of the system to comply with GDC-19.It also app Experience with silicone sealants in general applications would indicate some degradation may exist today.
We presently have no assurance that the scalants have not degraded already, or will not degrade further in the future.
Thus, we conclude that the Itcensee's modifications and repairs at Zion Station are not presently acceptable and that there is a need for some fom of corrective action.
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2-August 26, 1985 ESF and non-ESF air cleaning systens and sugge n
actions.
Our staff is available for more detailed discussion on this subject should there be a need.
The NRR technical contacts on this matter is Jack liayes (FTS 497 7632)
Hugh L. Thompso,
rector
, Division of Licensing Office of Nuclear Reactor Regulation
Enclosure:
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1 ENCLOSURE I GENERAL GUIDANCE ON THE USE Of TEMPORARY SEALANTS AND PATCHING MATERIALS IN AIR CLEANING SYSTEMS It has recently become apparent that the use of sealants and tape to con leakage is a connen practice on ESF and non-ESF air cleaning system power plants.
This practice is contrary to guidance provided in Regulatory Guides 1.52 and 1.140.
Specifically, the Regulatory Guides state that "The use of silicone sealants or any other temporary patching naterial on filters, housing, mounting frames or ducts should not be used."A problem arises as a result of the licensees' classification of these materials as permanent rather than temporary.
While the quality of some of these sealants has improved, the NRR staff has not yet accepted such materials as being good for the life o e
plant.
Thus it is the staff's position that these materials can be expected to degrade over a period of years and may result in unacceptability high leakage in ductwork or filter housings.
The use of temporary sealants or patching materials in control room e air cleaning systeau is of particular concern to the staff since degradation o these raterials could lead to the inability of the system to meet General Design Criterion 19.
There is the additional concern over the ability of the
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9 system to adequately protect the operators from accidental releases of toxi These systems typically operate at a negative pressure resulting in t gases.
potential for inleakage of contaminated air which would subsequently be discharged into the control room without filtration.
Nominal leakage in sections of ductwork or filter housings located within the control room 3
envelope is usually of no concern to the staff.
However, those systers or
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sections of systems which operate at a negative pressure and are located outside of the control room envelope may fail to protect the control room operators from a radiological or toxic gas hazsFd.
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Such systems should be evaluated to determine the reed for corrective action.
5 Several alternatives are available in the event a need for co indicated.
Replacement of the system with all welded construction is an expensive action which may not be justified.
An exception nmy be where only a short section of duct is outside of the control room envelcpe.
Similarly, replacement of sealant with welded joints in the entire system may be impractical.
Frequently, the ductwork is of too small a gauge to permit welding and is not easily accessible.
However, replacement welding should be considered on problea areas of filter housings.
The most practical corrective action may be a leakage testing program which would establish the long-term integrity of the sealant or patching materials used and the total system Since rapid deterioration of the sealants would not be expected, a testin period on the order of 18 months should be adequate.
This approach will require a'n analysis to determine the rate of inleakage which could-be tolerated without exceeding the GDC-19 dose criteria, and taking into consideration
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I potential toxic gas hazard.
This number will be the basis for establishing an acceptance value for the periodic test, and the magnitude of the acceptance value will probably determine the method of leakage testing which should be used to demonstrate system integrity.
Other ESF and non-ESF air cleaning systems vary so much in design that little guidance can be provided with respect to use of temporary sealants. Leakage in most of these systems is not expected +to be as critical as for control room systems.
However, one should not jump to the conclusion that leakage in such systems is unimportant without first considering the likely magnitude of the leakage, whether the system operates at a negative or positive pressure or both, whether increased leakage has the potential for degrading the system to the point that it could not fulfill its intended air cleaning or ventilation functions, for creating a pathway for unmonitored releases, etc.
Therefore, such systems should be evaluated on a case-by-case basis.
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