ML20141N741

Forwards Response to 850318 Request to Hl Thompson Re Acceptability of Loop Seals,Increased HVAC Filtration Capacity & Silicone Sealants.Use of Sealants & Filtration Approved Provided Util Commits to Encl Recommendations

ML20141N741
Person / Time
Site:	Clinton
Issue date:	03/10/1986
From:	Bernero R Office of Nuclear Reactor Regulation
To:	Hind J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
NUDOCS 8603180045
Download: ML20141N741 (9)

Text

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Docket No. 50-461 DISTRIBUTION BAR 101996 JN 2 PDR PD#4 Reading MEMORANDUM FOR: J. A. Hind, Director IPC (F. Spangenberg)

Division of Radiation Safety BSiegel and Safeguards EHylton Region III FROM: Robert Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation

SUBJECT:

RESPONSE TO REQUEST FOR TECHNICAL ASSISTANCE RELATED TOAIRCLEANINGSYSTEMSATCLINTON(TIA85-70)

By memorandum dated March 18, 1985 to H. L. Thompson, Jr., Director, Division of Licensing, you requested the NRR staff to provide you guidance concerning the acceptability of: 1) the use of loop seals on filter housing drain lines;

2) HVAC filtration train capacity above the maximum allowable; and 3) the use

.of silicone scalants on ducts and housings at Clinton Power Station. Our eval-uation in response to your technical assistance request, contained in Enclosure 1, concludes that the use of loop seals, silicone sealants, and an HVAC filtration capacity above 30,000 cfm for a single cleanup train is acceptable at Clinton provided the applicant commits to the staff recommendations contained in the evaluation.

Enclosure 2, provided for your information, is a copy of a document prepared by the former Meteorology and Effluent Treatment Branch titled " General Guidance on the Use of Temporary Sealants and Patching Materials" which contains i our position with regard to the use of temporary sealants and patching materials on filters, housings, mountings frames or ducts.

The NRR staff has incorporated informal comments received from C. Gill of your staff into this evaluation. Both Mr. Gill and the applicant have been informed of the rewmmendations contained in this evaluation and the applicant has agreed to adopt the staff's recommendations, and has proposed approprate provisions for the Technical Specifications. This com lete ouryeviJwonthis l issue and TIA 85-7C will be closed, ortsamal DFs gggwfwb l

l p astenu. M 8603180045 860310 C PDR ADOCK 05000461 A PDR Robert Bernero Director Division of BWR Licensing l Office of Nuclear Reactor Regulation

Enclosures:

As stated cc: R. Gre er, Region III l C. Gil , Region !!!

l J. Lee P. Gwynn, Resident Inspector l G. Lainas PD#4)

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W Ist n 7 ne 03/6 . 03/g/86 03//o /86 03/}/86

Docket No. 50-461 DISTRIBUTION MAR 10 g Docket File PDR PD#4 Reading MEMORANDUM FOR: J. A. Hind, Director IPC(F.Spangenberg)

Division of Radiation Safety BSiegel and Safeguards EHylton Region III FROM: Robert Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation

SUBJECT:

RESPONSE TO REQUEST FOR TECHNICAL ASSISTANCE RELATED TO AIR CLEANING SYSTEMS AT CLINTON (TIA 85-70)

By memorandum dated March 18, 1985 to H. L. Thompson, Jr., Director, Division of Licensing, you requested the NRR staff to provide you guidance concerning l the acceptability of: 1) the use of loop seals on filter housing drain lines; i

2) HVAC filtration train capacity above the uoximum allowable; and 3) the use I of silicone sealants on ducts and housings at Clinton Power Station. Our eval-l uation in response to your technical assistance request, contained in Enclosure 1, concludes that the use of loop seals, silicone sealants, and an HVAC filtration capacity above 30,000 cfm for a single cleanup train is acceptable at.Clinton provided the applicant commits to the staff recommendations contained in the evaluation.

Enclosure 2, provided for your information, is a copy of a document prepared by the former Meteorology and Effluent Treatment Branch titled " General Guidance on the Use of Temporary Sealants and Patching Materials" which contains our position with regard to the use of temporary sealants and patching materials on filters, housings, mountings frames or ducts.

The NRR staff has incorporated informal comments received from C. Gill of your staff into this evaluation. Both Mr. Gill and the applicant have been informed of the recommendations contained in this evaluation and the applicant has agreed to adopt the staff's recommendations, and has proposed approprate provisions for the Technical Specifications. vi issue and TIA 85-70 will be closed. This com letes erssamm1 8F8our/nW:uubfe,,9w on this anwrt & Desmoes Robert Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation

Enclosures:

As stated cc: R. Greger, Region III C. Gill, Region !!!

J. Lee P. Gwynn, Resident Inspector G. Lainas PD#4 PD#4/D' D BSi b WButler W st n ne 03/ 03/g/86 03//o /86 03/}/86

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~g UNITEE) STATES

! o NUCLEAR REGULATORY COMMISSION h  : WASHINGTON, D. C. 20555

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Docket No. 50-461 MAR 10126 MEMORANDUM FOR: J. A. Hind Director Division of Radiation Safety and Safeguards Region III FROM: Robert Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation

SUBJECT:

RESPONSE TO REQUEST FOR TECHNICAL ASSISTANCE RELATED TO AIR CLEANING SYSTEMS AT CLINTON (TIA 85-70)

By memorandum dated March 18, 1985 to H. L. Thompson, Jr., Director, Division of Licensing, you requested the NRR staff to provide you guidance concerning the acceptability of: 1) the use of loop seals on filter housing drain lines;

2) HVAC filtration train capacity above the maximum allowable; and 3) the use of silicone sealants on ducts and housings at Clinton Power Station. 0ur eval-uation in response to your technical assistance request, contained in Enclosure 1, concludes that the use of loop seals, silicone sealants, and an HVAC filtration capacity above 30,000 cfm for a single cleanup train is acceptable at Clinton provided the applicant commits to the staff recomendations contained in the evaluation.

Enclosure 2, provided for your information, is a copy of a document prepared by the former Meteorology ar.d Effluent Treatment Branch titled " General Guidance on the Use of Temporary Scalants and Patching Materials" which contains our position with regard to the use of terrporary sealants and patching materials on filters, housings, mountings frames or ducts.

The NRR staff has incorporated informal comments received from C. Gill of your staff into this evaluation. Both Mr. Gill and the applicant have been informed of the recommendations contained in this evaluation and the applicant has agreed to adopt the staff's recommendations, and has proposed approprate provisions for the Technical Specifications. This completes our review on this issue and TIA 85-70 will be closed.

v  %

bort Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation

Enclosures:

As stated cc: R. Greger, Region III C. Gill, Region !!!

J. Lee P. Gwynn, Resident Inspector G. Lainas

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l ENCLOSURE 1 l RESPONSE TO REGION III TECHNICAL ASSISTANCE REQUEST REGARDING CLINTON AIR CLEANING SYSTEMS

1.0 INTRODUCTION

The March 18, 1985 memorandum from J. A. Hind, Director, Division of Radiation Safety and Safeguards, R:III, to H. L. Thompson, Jr., Director, <

Division of Licensing, NRR, requested guidance concerning (1) the use .

l of silicone sealants in the Clinton ESF (Control Room) and non-ESF  ;

l (Radwaste Exhaust and Drywell Purge) HVAC systems, (2) the use of loop  ;

seals on filter housing drain lines, and (3) filtration train capacity above the maximum allowable. ,

! 2.0 EVALUATION 2.1 The Use Of Silicone Sealant Regulatory Guides 1.52 (Revision 2 (March 1978)) and 1.140 (Revision 0 (March 1978)) state in Regulatory Positions 5.C that the use of silicone l sealants or any other temporary patching material on ESF and non-ESF filters, housing, mounting frames, or ducts should not be allowed.

The Clinton FSAR, Table 6.5-3 states that silicone sealants will not  ;

be used in ESF filtration systems. Also in the Clinton FSAR, Section 1.8, the applicant did not take exception to Regulatory Guide 1.140 for non-ESF filtration systems in regard to use of silicone sealant.

Contrary to the above, Region III inspectors noticed the limited use l

of silicone sealants in ESF and non-ESF filtration systems at Clinton  ;

j Power Station. Subsequently, the applicant acknowledged the limited I

use of silicone sealants in their letter dated June 4, 1985. [

l There are two engineered safety features (ESF) filtration systens 4 at the Clinton Power Station, the Standby Gas Treatment System (SGTS) and the Main Control Room Habitability System (MCRHS). The applicant ,

stated in their letter dated June 11,1985 that (1) use of the silicone

, scalant to seal mechanical lock longitudinal seams is limited to the control room recirculation and makeup air filtration ductwork in the MCRHS, and (2) the SGTS does not use the silicone sealant, since it consists of piping rather than ductwork. Both ESF system filter housings are welded stcol plate construction and no silicone sealant has been used.

l A part of the MCRHS ductwork operates at a negative pressure and l a significant portion of the ductwork is located outside of the '

l control room habitability boundary envelope. Any potential inleakage l

! of contaminated air into the negative pressure ductwork will be l filtered b adsorber)ory the either the makeup recirculation airair filter filter unit unit (2 (4 inch inch charcoal charcoal l adsorber) prior to returning it to the control room envelope. There is, however, a bypass damper in the recirculation filter housing. i In addition, there are three isolation dampers in each train interfacing with the negative pressure ductwork located outside of the control room habitability boundary. ,

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The applicant has determined that the maximum inleakage of unfiltered contaminated air, during and following a design basis accident which could be tolerated without exceeding the GDC 19 dose criteria, would be approximately 646 cfm. The applicant stated in its letter dated October 8,1985, that this determination was based on (1) 99 percent for all forms of iodine by the makeup air filter removal adsorber charcoal efficiency (3000 cfm), (2) 70 percent removal efficiency for all forms of iodine by the recirculation air filter charcoal adsorber (59.500 cfm), (3) 2 percent bypass damper leakage (1200 cfm) around the recirculation air filter charcoal adsorber unit, (4) the control room operator thyroid dose of 27 rem (90 percent of the dose guideline specified in SRP Section 6.4), and (5) 10 cfm of unfiltered inleakage.

On the basis of recent measurements by the staff of control room inleakage at several operating plants, particularly leakage through isolation dampers, the staff concludes that the applicant's calculated leak rate will be difficult to achieve and maintain. However, the staff also concludes that the applicant's calculated value of 646 cfm of tolerable inleakage is unnecessarily conservative. The staff's computed value is approximately 1000 cfm.

Since we presently have no assurance that the silicone sealant used at Clinton will not degrade in the future, we believe there is a need for some form of corrective action. We therefore made the following recom-mendations to the applicant which have since been incorporated into the draft Clinton Technical Specifications:

(A) the applicant should provide an acceptable method of leakage testing for the portions of ductwork which are located outside of the control room boundary operating at a negative pressure. The leakage test boundary should include all isolation dampers interfacing with these negative pressure portions of ductwork.

(B) the leak rate test should be performed prior to fpel loading and every 18 months thereafter.

(C) the maximum allowable inleakage for the ductwork under negative pressure outside of the MCRHS should not exceed 650 cfm.

(D) the testing requirements fcr the recirculation filter housing bypass damper (1200 cfm) be specified in the Clinton Technical Specification Section4.7.2(c).

(E) the testing of the recirculation filter housing and its flexible con-nection to the fan should be performed in accordance with ANSI N-510 prior to initial system operation. Subsequent testing, other than visual survelliance of the filter housing flexible connection to the fan, is not required. Visual inspection should be perfonned every 18 months or more frequently if deemed necessary, m ____ _.

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For non-ESF systems at Clinton, all the filter housings are of welded construction. However, the silicone sealant was used in the transition (consisting of a sheet metal duct piece) between the filter housings and the exhaust fan. Although these sheet metal transition pieces are upstream of the exhaust fans at a negative pressure, any inleakage through the duct pieces would be from areas with relatively low levels of radioactivity.

Therefore, we find the use of silicone sealant in the transition duct pieces in combination with the testing guidance to be acceptable.

2.2 HVAC Filter housing Drain Line Loop Seal The statemt.nt " loop seals shall not be used" in Section 5.6 of ANSI N-509-1976 has been deleted in the same section of ANSI N-509-1980.

The loo) seals installed at Clinton HVAC systems should be considered accepta)le only if the loop seals are provided with devices and operating procedures so that the intended functional requirements of the loop seals are verifiable by the plant operator.

2.3 Engineered Safety Featuro HVAC Filter Train Capacity The exception to the volumetric air flow rate exceeding 30,000 cfm for a single cleanup train (59,500 cfm for the Clinton control room air ventilation recirculation system) taken by the applicant is acceptable since high capacity DOP generators for the in-place DOP testing of HEPA filters are not available. The applicant has since revised Table 6.5-3 of the Clinton FSAR in Amendment 36 to state this exception.

3.0 CONCLUSION

All of the foregoing recommendations (A through E) in Section 2.1 above have been incorporated in the Clinton Technical Specifications. The use of loop seals is acceptable provided the conditions stated in Section 2.2 ara satisfied. The increased filter train capacity is also acceptable as stated in Section 2.3 and the FSAR has been revised to include this exception. In addition, the NRR staff will observe forthcoming ESF filtration system startup and air balancing tests, and control room pressurization (habitability) test at Clinton Power Station to assure the Clinton ESF filtration systems are tested in accordance withANSIN-510(1980).

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ENCLOSURE 2 GENERAL GUIDANCE ON THE USE OF TEMPORARY SEALANTS AND PATCHING MATERIALS IN AIR CLEANING SYSTEMS ,

It has recently become apparent that the use of scalants and tape to control leakage is a common practice on ESF and non-ESF air cleaning systees in nuclear 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 material on filters, tousing, 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 sealar:ts has improved, the I

NRR staff has not yet accepted such materials as being good for the life of the 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. 1 t

The use of temporary sealants or patching materials in control room emergency air cleaning systems is of particular concern to the staff since degradation of i these meterials could lead to the inability of the system to meet General Design Criterion Ig. There is the additionel concern over the ability of the l l

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system to adequately protect the operators from accidental releases of toxic gases. These systems typically operate at a negative pressum resulting in the potential for inleakage of contaminated air which would subse<;uently be discharged into the control room without filtration. Nominal leakage in

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sections of ductwork or filter housings located within the control room envelope is usually of no ' concern to the staff. However, those systems or sections of systems which operate at a negative pressure and are located -

outsfde of the control room envelope may fail to protect the control rcos operators from a radiological or toxic gas hazard. Such systems should be '

evaluated to determine the need for corrective action.

1 Several alternatives are available in the event a need for corrective action is indicated. Replacement of the system with all welded construction is an expensive action which may not be justified. An exception may be where only a '

short section of duct is outsia'e of the control room envelope. Similarly, replacement of sealant with welded joints in the entire system may be impractical. Trequently, the ductwork is of too small a gauge to permit teelding and is not easily accessible. However, replacement welding should be considered on problem areas of filter housings. The most practical corrective action may be a leakage testing program which would establish the long-teru integrity of the sealant or patching materials used and the total systen. '

1 Since rapid deterioration of t5c sealants would not be expected, a testing period on the order of 18 months should be adequata. This approach will require an analysis to determine the rate of inleakage which could be tolerated without exceeding the GDC-19 dose criteria, and taking into consideration any I

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! potential toxic gas hazard. This number will be the basis for establishing an  ;

J acceptance value for the periodic test, and the sagnitude of the acceptance i

I value will probably detemine the method of leakage testing which should be  ;

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vsed to demonstrate system integrity. .

i Other ESF and non-ESF air cleaning systems very so much in design that little i j guidance can be provided with respect to use of temporary sealants. Leakage in .

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most of these systems is not espected to be as critical as for control mes

} systems. However, one should not jump to the conclusion' that leakage in such  !

4 j systees is unimportant without first considering the likely magnitude of the 1

j leatage, whether the system operates at a negative or positive pressure or 3 (

both, whether increased leakage has the potential for degrading the system to l t

j the point that it could not fulfill its intended air cleaning or ventilation  !

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{ functions, for creating a pathway for unmonitored releases, etc. Therefore. I such systems should k evaluated on a case-by-case basis.  :

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