ML18033B355

Forwards Response to 891219 Request for Addl Info on Hazardous Chemicals Re Control Room Habitability

ML18033B355
Person / Time
Site:	Browns Ferry
Issue date:	05/31/1990
From:	Wallace E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-00155, TAC-00156, TAC-00157, TAC-155, TAC-156, TAC-157, NUDOCS 9006080203
Download: ML18033B355 (9)

Text

bCCELERATED DIQHUBUTION DEMONSTION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9006080203 DOC.DATE: 90/05/31 NOTARIZED:

NO DOCKET FACIL:50-259 Browns Ferry Nuclear Power Station, Unit 1, Tennessee 05000259 50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 AUTH.NAME AUTHOR AFFILIATION WALLACE,E.G.

Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards response to 891219 request for addi info on hazardous chemicals re control room habitability.

DISTRIBUTION CODE: C001D COPIES RECEIVED:LTR ENCL SIZE: TITLE: Licensing Submittal:

EnvirOnmental Rept mdt&elated Correspondence D NOTES:1 Copy each to: B.Wilson,D.M.Crutchfield,B.D.Liaw,S.Black R.Pierson, 1 Copy each to: S.Black,D.M.Crutchfield,B.D.Liaw, R.Pierson,B.Wilson 1 Copy each to: S.Black,D.M.Crutchfield,B.D.Liaw, R.Pierson,B.Wilson 05000259 A 05000260 D 05000296 D RECIPIENT ID CODE/NAME LA ROSS,T.COPIES LTTR ENCL 3 3 1 1 RECIPIENT ID CODE/NAME PD COPIES LTTR ENCL 1 1 INTERNAL: ACRS NRR/DET/ESGB 8D OGC/HDS2 RGN2 DRSS/RPB EXTERNAL EG&G S IMPSON g F NRC PDR NOTES 6 6 AEOD/DSP/TPAB 1 1 O~CLg@B 0 EG FIL Ol 1 1 2 2 , LPDR 1 1 NSIC 5 5 1 1 1 0 1 1 1 1 1 1 D NOTE TO ALL"RIDS" RECIPIENTS:

D D PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.20079)TO EL/MINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!TOTAL NUMBER OF COPIES REQUIRED: 'LTTR 27 ENCL 25!

TENNESSEE VALLEY AUTHORITY CHATTANOOGA.

TENNESSEE 37401 SN 157B Lookout Place MAY 9l1990 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.20555 Gentlemen:

In the Matter of Tennessee Valley Authority Docket Nos.50-259 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN)-CONTROL ROOM HABITABILITY

-HAZARDOUS CHEMICALS (TAC NOS.00155, 00156, AND 00157)This letter is in response to the NRC's December 19, 1989 request for additional information on control room habitability

-hazardous chemicals.

TVA letter to NRC, dated February 20, 1990, committed to provide a response to this NRC request by May 31, 1990.Enclosed is an updated list of chemicals barged past BFN and an evaluation of the release of chlorine and other hazardous chemicals from a potential barge accident for control room habitability..

There are no commitments contained in this letter.If you have any questions, please telephone Patrick P.Carier, Manager of Site Licensing, at (205)729-3570.Very truly yours, TENNESSEE VALLEY AUTHORITY Enclosure cc: See page 2/E.G.Wallace, Manager Nuclear Licensing and Regulatory Affairs 9006080203 90053i PDR ADOCK 0500025'r' PDC An Equal Opportunity Employer

~r)g<'4r'I U.S.Nuclear Regulatory Commission cc (Enclosures):

Ms.S.C.Black, Assistant Director for Projects TVA Projects Division U.S.Nuclear Regulatory Commission One Hhite Flint, North 11555 Rockville Pike Rockville, Maryland 20852 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35609-2000 Mr.B.A.Hi lson, Assistant Director for Inspection Programs TVA Projects Division U.S.Nuclear Regulatory Commission Region II 101 Marietta Street, NH, Suite 2900 Atlanta, Georgia 30323 ENCLOSURE BRONNS FERRY NUCLEAR PLANT (BFN)CHENICAI S BARGED PAST THE BFN SITE-.-Chemical Acrylonitrile Caustic Soda Chemical Fertilizers (Potash and Urea)Chlorine Creosote Fertilizers Creosote Crude Coal Tar Ethanol Fuel Oil No.6 Aromatics (Benzene, Ethyl Benzene&Toluene)Nitrogen Solution Phosphate Residual Fuel Oil Sulphate Potash Vegetable Oil Vinyl Acetate and Styrene Shipment Frequency (er Year)14 30 12 30 44 104 12 Heights (Per Shi ment)4,000 Tons 1,500 Tons 1,500 Tons 1,200 Tons 1,500 Tons Not Available Not Available 1,500 Tons 2 Barges per Tow 1,500 Tons per Barge 2 and 3 Barges per Tow 1,500 Tons per Barge 2,400 Tons 1,500 Tons 1,500 Tons 2,000 Tons 3,500 Tons 1,500 Tons 4,000 Tons (2,000 Tons of Each Chemical)Xylene 36 4 Barges per Tow 1,500 Tons per Barge Page 2 of 5 By letter dated December 19, 1989, NRC requested that TVA evaluate the release of chlorine and other hazardous chemicals from a potentjal barge-accident for impact on control room habitability.

This letter also stated"that the intent of Regulatory Guide 1.78, Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release, is to require specific accident evaluations of all hazardous chemicals if total hazardous chemical barge shipments, as opposed to shipments of specific chemicals, exceed 50 per year.In order to be responsive to the Staff's concerns, TVA has performed the analysis as summarized bel'ow.TVA has performed a review of previous Staff guidance'nd other dockets correspondence on this issue.This review does not support the latest Staff interpretation of the frequency criteria of Regulatory Guide 1.78.The current Staff position is in conflict with the guidance provided in NUREG/CR-2650, Allowable Shipment Frequencies for the Transport of Toxic Gases Near Nuclear Power Plants, October 1982 and NUREG/CR-5042, Evaluation of External Hazards to Nuclear Power Plants in the United States, December 1987.Accordingly, this submittal does not endorse the Staff's interpretation of Regulatory Guide 1.78.Hlthout prejudice to its position, TVA has performed a control room habitability evaluation in accordance with the guidance of Regulatory Guides 1.78 and 1.95 Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release.Maximum concentration and maximum concentration-duration accidents were postulated.

The results of the evaluation are summarized below: Acrylonitrile-The maximum acryloni tri le concentration at the control room air intake is 7584 ppm.The value exceeds the toxicity limit of 40 ppm.The odor threshold of acrylonitrile is 21.4 ppm.The worst case accident toxicity limit in the control room is reached in slightly less than three minutes after the odor threshold is reached.Further discussion of this chemical is provided at the end of this section.Benzene-The maximum benzene concentration at the control room air intake is 2169 ppm.This concentration exceeds the toxicity limit of 50 ppm.The odor threshold of benzene is 4.68 ppm.The worst case accident toxicity limit in the control room is reached more than 12 minutes after the odor threshold is reached.Further discussion of this chemical is provided at the end of this section.Chlorine-The toxicity limit of chlorine is 15 ppm for two minutes.The habitability analysis showed that the toxicity limit is exceeded within fifteen seconds after the arrival of the chlorine puff.Further discussion of this chemical is provided at the end of this section.Ethyl Benzene-A toxicity limit is not provided in Regulatory Guide 1.78 for this chemical, however it has been found that a concentration of 1,000 ppm causes eye irritation and a concentration of 2,000 ppm causes extreme irritation and dizziness.

The maximum concentration at the control room air intake is 252 ppm.Therefore, a barge accident involving ethyl benzene does not cause any adverse effects on control room habitability.

Page 3 of 5 Nitrogen-The main concern for nitrogen is asphyxiation effects due.to displacement of oxygen.The maximum nitrogen concentration of 4,829 ppm is significantly less than the one third air volume displacement which could lead to asphyxiation.

Therefore, a nitrogen barge accident does not cause any adverse effects on control room habitability.

Styrene-A toxicity limit is not provided in Regulatory Guide 1.78 for this chemical, however OSHA provides a threshold limit value (TLV)of 100 ppm for an eight hour weighted average.The TLV is defined as the concentration of a substance in air that can be breathed for five consecutive eight hour workdays by most people without adverse effects.This is above the 74 ppm maximum concentration at the control room air intake.Therefore, a barge accident involving styrene does not cause any adverse effects on control room habitability.

Toluene-A toxicity limit is not provided in Regulatory Guide 1.78 for this chemical.OSHA provides a TLV of 200 ppm for an eight hour weighted average.The maximum concentration at the control room air intake is 759 ppm.The odor threshold for this chemical is 0.17 ppm which can be immediately detected.The concentration in the control room after two minutes is only 4.4 ppm.Further discussion of this chemical is provided at the end of this section.Vinyl Acetate:-A toxicity limit is not provided in Regulatory Guide 1.78 for this chemical.The maximum concentration in the control room is 57 ppm.OSHA provides a TLV of 10 ppm for an eight hour weighted average.The odor threshold value for vinyl acetate is 0.12 ppm and can be immediately detected.The concentration in the control room two minutes after detection is 13 ppm.Further discussion of this chemical is provided at the end of this section.Xylene-The toxicity limit for xylene is 400 ppm.The maximum concentration at the control room air intake is 195 ppm after a xylene barge accident.Therefore, a xylene barge accident does not cause any adverse effects on control room habitability.

Caustic soda, chemical fertilizers (potash and urea), creosote fertilizers, creosote, crude coal tar, ethanol, fuel o'il, phosphate, residual fuel oil, sulphate potash, and vegetable oil are all sufficiently non-toxic such that further analysis is not required.In order to evaluate the likelihood of a chlorine barge accident, a probabilistic risk assessment (PRA)was performed.

The assessment was performed using the following parameters:

Regulatory Guide 1.78,-Section C.2, references HASH-1238, Environmental Survey of Transportation of Radioactive Materials to and from Nuclear Power Plants, December 1972, as the basis for the definition of frequently shipped hazardous chemicals.

This reference was developed to estimate the probability of an accident while transporting radioactive materials.

The barge accident data is based upon Department of Transportation data, but due to the stated purpose of Page 4 of 5 the report, data regarding the probability of a..release involving a barge shipment containing hazardous chemicals is not provided.Therefore, the probability of a barge accident releasing hazardous chemicals was evaluated using the HASH-,1238 total probability of a minor, moderate, severe, extra severe and extreme barge accident (1.8 x 10'er shipmen't mile).A conditional probability of 2.3 x 10'eleases per accident was developed using barge accident and release data specific to the Tennessee River.This results in a probability of 4.1 x 10'eleases per shipment mile.The frequency of chlorine shipments is 30 per year~The range at which a postulated chlorine barge accident produces toxic concentrations in the control room within two minutes of the release being detected by the odor of the chlorine-is wi thin 5.5 kilometers (3.3 miles)from the site.The river is relatively straight in the vicinity of BFN.There are 11.8 kilometers (7.1 miles)of barge navigational channel on the river within this radius.The effective-probability of the wind blowing in the direction which would produce toxic concentrations of chlorine in the control room is 9.1 x 10'.It was conservatively assumed that all wind stability classes produced toxic concentrations in the control room.Therefore, a conservative estimate of the total probability of a postulated chlorine barge accident incapacitating the control room operators before protective breathing apparatus could be donned is 8.0 x 10'vents per year.As stated in NUREG/CR-3786, A Review of Regulatory Requirements Governing Control Room Habitability Systems, August 1984: "Even in the remote event that a chlorine release led to complete incapacitation of all personnel at the site, the probability of any danger to the health and safety of the public would still be minimal because the reactor could operate unmanned for several hours under most circumstance." The probability of a radioactive release in the event that site personnel were incapacitated and operator intervention could not be assumed for several hours, can be qualitatively bounded within an acceptable degree of uncertainty.

The draft BFN PRA, which has been selectively audited by the Staff, shows the probability of the occurrence of an initiating event is on the order of 10 per year (or 10'er day).NUREG-0800, Standard Review Plan (SRP), defines design basis events external to the nuclear plant as those accidents that have a probability of occurrence on the order of about 10'er year or greater and have potential consequences serious enough to affect the safety of the plant to the extent that Part 100 guidelines could be exceeded.Because of the difficulty of assigning accurate numerical values to the expected rate of unprecedented potential hazards generally considered in the SRP section, judgment must be used as to the acceptability of the overall risk presented.

In addition, because of the low probabilities of the events under consideration, data are often not available to permit accurate calculation of probabilities.

Accordingly, the expected rate of occurrence of potential exposures in excess of the 10 CFR 100 guidelines of approximately 10'er year is acceptable if, when combined with reasonable qualitative arguments, the realistic probability can be shown to be lower.

f~t 1 Page 5 of 5 lhe probability of a postulated chlorine barge accident incapacitating the control room operators before protective breathing apparatus.:could be"'donned is 8.0 x 10'vents per year, which is below the SRP criteria for design basis events.The total probability of a postulated chlorine barge accident occurring in the vicinity of BFN simultaneously with detrimental wind conditions, resulting in incapacitation of the operators, when combined with the probability of an initiating event requiring reactor trip and operator action occurring wi thin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the barge accident is beneath regulatory concern.Since chlorine produces significantly more severe toxic effects than the other chemicals barged past BFN, this estimate conservatively bounds the probability of a acrylonitrile, benzene, toluene or vinyl acetate barge accident degrading control room habitability.

Therefore, the above evaluation confirms that TVA's and the Staff's previous conclusion that the closure of NUREG-0737, Item III.D.3.4, Control Room Habitability Requirements, is still valid and no additional modifications are necessary.

One stated objective of Generic Letter 88-20 is to determine if modifications to hardware and procedures are necessary to reduce the frequency of severe accidents or to mitigate their consequences.

It is TVA's understanding that the additional analysis of external events, which is discussed in the Staff's January 12, 1990 letter to TVA, will request the reevaluation of the release of hazardous chemicals transported in the vicinity of the plant.This Staff request is scheduled to be issued as a supplement to Generic Letter 88-20 on June 30, 1990.TVA wi 11 further assess this i.ssue in accordance with the upcoming Staff guidance for Individual Plant Examinations for External Events.