ML20245B345

Forwards Evaluation of Plant Control Room Emergency Air Cleaning Sys,Taking Into Account Identified Pathways for Unfiltered Inleakage of Airborne Radioactivity,To Meet Requirements of GDC 19,per 10CFR50,App A.Conclusions Listed

ML20245B345
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	06/04/1987
From:	Congel F Office of Nuclear Reactor Regulation
To:	Hind J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20235L610	List: ML20235L607 ML20235L612 ML20245B345
References
TAC-63135, TAC-63136, NUDOCS 8706100006
Download: ML20245B345 (5)

Text

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'. UNITED STATES

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! o NUCLEAR REGULATORY COMMISSION Y ' WASHINGTON. D. C. 20066 h

JUN 4 1987 ]

i PEMORANDUM FOR: Jack A. Hind, Director l Division of Radiation Safety and Safeguards Region II,1 FRON: Frank J. Congel, Director )

Division of Radiation Protection j and Emergency Preparedness j Office of Nuclear Reactor Regulation {

SUBJECT:

ABILIYY OF THE ZION CONTROL ROOM EMERGENCY AIR CLEANING SYSTEM TO MEET THE REQUIREMENTS OF 10 CFR 50 APPENDIX A, GDC-19 (TAC 63135/6)  !

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Your memorandum dated April 15, 1987 requested assistance in evaluating the adequacy of the Zion as-built control room air cleaning systems taking into account identified pathways for unfiltered inleakage of airborne radioactivity. i l Specifically, we were asked to evaluate the acceptability of the licensee's i so-called " realistic" evaluation and to determine the correct accident doses.

We have completed our evaluation and reached the following conclusions.

1. The so-called " realistic" analysis is not consistent with the Standard Review Plan and the deviations were not justified on a plant specific basis by the licensee so the analysis is unacceptable.

2. With the specified damper leakages, the thyroid dose in the control room would be about 380 rems using Train B and 270 rems using Train A. If the relief dampers were replaced with zero leakage dampers the thyroid dose would be 50 rems.

3. The Zion control room ventilation system does not meet GDC-19. One way this system could be made acceptable is by eliminating leakage through the relief dampers and modifying the " odor eaters" in the recirculation system so they could be relied upon to remove some of the radiciodine.

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Contact:

C. A. Willis, NRR 492-8340

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4 Jack A. Hind These matters are discussed in more detail in the enclosure. The technical contact is Charles Willis (492-8340). We consider our action on TAC 63135 and 63136 and on this TIA to be complete.

Original signed by F.J.Congol Frank J. Congel, Director Division of Radiation Protection and Emergency Preparedness Office of Nuclear Reactor Regulation

Enclosure:

As Stated Distribution:

RWStarostecki, NRR FJCongel, NRR LJCunningham, NRR DBMatthews, NRR RJBarrett, NRR ODLynch, NRR JEWigginton, NRR CAWillis, NRR DEMiller, RIII JWCraig, NRR E JANorris, NRR JJHayes, NRR CJPaperiello, RIII CENorelius, RIII JAGrobe, RIII MMHolzmer, RIII HJWong, ED0 T0 Martin, EDO Central Files Docket Files RPB R/F

• See Previous Concurrence

• RPB:DREP *RPB:DREP *AC:RPB:DREP 0:DREP:NRR J d b CAWillis:bt JEWigginton LJCunningham FJCengel b 06/02/87 06/02/87 06/02/87 06/ V /87 -

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ENCLOSURE I RADIATION DOSE IN THE ZION CONTROL ROOM DUE TO A LOSS OF COOLANT ACCIDENT Introduction By memorandum dated April 15, 1987, Region III asked NRR to evaluate potential doses in the Zion control room and to detemine whether the requirements of General Design Criterion 19 were being met. The requested study has been performed and our conclusions are discussed in the following paragraphs.

Background

By letter dated September 1,1981, Commonwealth Edison submitted a report on Zion control room habitability, contending that the requirements of GDC-19 and MUREG-0737 Item 111.D.3.4 would be met when certain specific modifications were .,

completed. The staff evaluated that submittal and in a letter dated June 24, 1 1982, stated that the submittal was acceptable and the control room habitabili- I ty systems would be adequate when the specified improvements were complete.

l An accident occurred on September 11, 1986 which led to the discovery that.

relief dampers allowed serious inleakage (154 cfm or 236 cfm respectively for the A or B train). Such inleakage suggested that the Zion control room did not l

meet GDC-19. Coninonwealth contended that a " realistic" calculation by Sargent

& Lundy.showed Zion to be in compliance with GDC-19 even with the high rate of inleakage. Then, by letter dated May 19, 1987, Commonwealth acknowledged that the Sargent & Lundy calculation included a seriously unconservative assumption. j In that same letter Commonwealth contended that (for unspecified reasons) they i still believed the Zion control room ret GDC-19. I

'l The " Realistic" Calculation j l This calculation was based on a series of assumptions which are neither consis-tent with the Standard Review Plan, conservative, nor justified on plant specific bases. Therefore, the assumptions and the resulting conclusions are ,

unacceptable.

The principal unacceptable assumptions are as follows:

1. The containment spray was assumed to deplete the organic iodine in 2 l hours; the current staff position is that credit is not allowed for removal of organic iodine by sprays.

2. The containment leak rate was assumed to be .035% per day for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and .0175% per day thereafter; the minimum acceptable values are 0.1% and 0.05%.

3. The assured control room occupancy factors were 1 for the first 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. O for the next 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />, .33 for the next 3 days , and 0.26 thereaf ter; the minimum acceptable values are 1 for the first day, .6 for the next 3 days and .4 thereafter.

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4. The activity released to containment was assumed to be the gap activity; 3 the minimum acceptable release to containment is 50% of the radiciodines  !

and 100% of the noble gases. ]

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5. The distance from containment to the air intake was assumed to be 80 m; the actual distance is 28 m (92 ft.).

6 ' The intake air was assumed to be further dilated by the flow through the buildings; this is not in accordance with the SRP and the non-safety grade

- ventilation systeem may be inoperable in an accident.

NRR Calculation of the Control Room Doses The calculation was. performed using data supplied by the licensee, assumptions from the standard review plan (including Murphy Campe), and the TACTS computer-code.

The results are: q l

l Inleakage,* cfm Thyroid Dose, Rems 1

10 50 164 270 246 380

• Inleakage includes 10 cfm to account for ingress / egress.

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