ML20199J706

Summary of 971212 Meeting W/Gpu Re Control Room Habitability Evaluation Concerning CR Operator Thyroid Dose from Fission Product Release During Postulated Design Basis Accident at Plant

ML20199J706
Person / Time
Site:	Three Mile Island
Issue date:	02/02/1998
From:	Colburn T NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
References
NUDOCS 9802060017
Download: ML20199J706 (41)

Text

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. .g .%:, ;, ,- , , , , [f%;2h^f Q j' UNITED STATES L 4 c L NUCLEAR REGULATORY COMMISSION -

WASHINGT001, D.C.'segaMeet 1 February'.2, 1998 LICENSEE: _GPU Nuclear Corporation

' FACILITY:- Three Mile Island Unit No. 1 (TMI-1)

SUBJECT:

MEETING

SUMMARY

On December 12, 1997, GPU Nuclear Corporation (GPU or the licensee) representatives met with members of the NRC staff to discuss the licensee's Control 1 Room Habitability evaluation related to control room operator thyroid dose from-fission product releases during a postulated design b6 sis accident

at THI 1. The meeting was requested by the staff in a September-24,1997,

' letter to the licensee. The letter acknowledged that by previous agreement with the NRC staff, as documented __in an August 14, 1986 letter and '

supplemental Safety Evaluation Report, the licensee was only required-to-address-whole body and beta skin doses in its response.to NUREG 0737 Item Ill.D.3.4, Control. Room Habitability. Consideration of thyroid doses from -

iodine releases was to be deferred until a source term reevaluation effort by-the. staff was completed. As the staff has yet to complete its. implementation plan on the use of revised accident source terms for operating plants, the licensee was- requested to provide the results of its evaluation of the thyroid doses within six months of the September 24, 1997, letter. The purpose of the-December 12 meeting was for the-staff to review the licensee's progress and igain a c'atter understanding of the design and operation of the THI-1 control building-ventilation system (CBVS). Also in-attendance as an observer was a representative from Nucleonics Week.

The licensee provided the staff with a discussion of the CBVS layout and control. room-building arrangement. The licensee.also provided details of the CBVS design features, automatic initiation features.and potential failure-modes. The licensee also.provided operational details of the system _and assumptions'being made in the thyroid dose calculation including modeling itechniques/Jsed. X/Q values assimed,1and accidents considered. The licensee indicated 1it was- still'on-schedule for a March 24. 1998, submittal.

.:The lipensee broached the concept.of using a' total effective dose equivalent'

- L(TEDE) foFthe thyroid in lieu of the thyroid dose limit.: but the staff indicated that it. may be premature to consider that argument in Regulatory; space and that current regulatory requirements would_ need to be addressed such  !

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as are contained in General Design Criterion (GDC) 19. The staff also commented on the licensee's proposed use of probabilistic risk assessment consideration, indicating that such considerations were not normally credited in design basis accident analyses. The licensea also discussed use of the new source term limit and credit for offsite power restoration and restoration of the non-class 1E auxiliary building ventilation system, but the staff indicated that these were not normally given credit on the front end analysis.

The licensee indicated it used NUREG-1228 for iodine reduction factors and plate out assumptions and used the same assumptions as in its Chapter 14 FSAR accident analysis, The staff acknowledged that there may be conservatism in the licensee's single failure assumptions described in its analysis.

Enclosure 1 is a list of attendees; and Enclosure 2 contains the licensee's l

slides. Original signed by-Timothy G: Colburn, Senior Project Manager ProjectDirectorateI-3 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation Docket No, 50-289

Enclosures:

1. List of Attendees

2. Slides cc w/ enclosures: See next page HARD COPY E-MAIL Nv SCollins/FMiraglia (SJC1/FJM)

PUBLIC RZimmerman_(RPZ)

POI-3 Rdg. BBoger (BAB2)

OGC REaton (RBE1)

ACRS TColburn (TGC)

TMartin (e mail to SLM)

BBuckley (BCB)

JLee (JYL1)

CMiller (CLH1)

REmch (RLE)

LBrown (LAB 2)

DOCUMENT NAME: G:\THI1212.mtg- TClark (TLC 1)

• PREVIOUS CONCURRENCE To receive a copy of this document, indicate in the box: "C" - Copy without

-attachment /enclcsure' "E" = Copy with attachment / enclosure "N" - No copy -

0FFICE POI 3/aN Wj, l P0l*3/LA

• l AD/P01 3 N /l PfR8* PDI-3/D l NAME TColburn (" TClark REston V CMitter 8. EMC44 f% A #f "Dra m a G---

DATE Ql4 2 /96 01/14/% 01 /Stf \ 01/29/98 f/ 7 /QA 0FFICIAL RECORD CDPY

e.

6; e -*

Three Mile Island Nuclear Station. Unit No. I cc:

Michael-Ross

' Director. O&M. THI Wayne L. Schmidt GPU Nuclear Corporation Senior Resident inspector (TMI-1)

P.O. Box 480 U.S. Nuclear Regulatory Commission Middletown. PA 17057 P.O. Box 311 Middletown. PA 17057 John C. Fornicola Director.-Planning and Regional-Administrator Regulatory Affairs Region I GPU Nuclear Corporation U.S. Nuclear Regulatory Commission

' 100 Interpace Parkway 475 Allendale Road Parsippany NJ 07054 King of Prussia. PA 19406

[ Jack S. Wetmore

. Manager. THI Regulatory Affairs Robert B. Borsum B&W Nuclear Technologies GPU Nuclear Corporation Suite 525 P.O.-Box 480 1700-Rockville Pike Middletown. PA 17057 Rockville. MD 20852 ,

Ernest L. Blake. Jr. Esquire William Dornsife. Acting Director Shaw. Pittman. Potts & Trowbridge Bureau of Radiation Protection 2300 N Street NW. Pennsylvania Department of Washingtur. DC 20037 Environmental Resources P.O. Box 2063 Chairman Harrisburg, PA 17120 Board of County Commissioners of Dcuphin County Dr. Judith Johnsrud Dauphin County Courthouse- National Energy Committee Harrisburg, PA 17120 Sierra Club 433 Orlando Avenue Chairman State College. PA 16803 Board of Supervisors {

-of Londonderry Township Peter W. Eselgroth. Region I R.D. #1. Geyers Church Road U.S. Nuclear Regulatory Commission Middletown. PA 17057 475 Aller. dale Road King of Prussia PA 19406.

Mr. James W. Langenbach. Vice President' and Director GPU Nuclear Corporation P.O. Box 480 Middletown. PA 17056 g

December 12, 1997 HEETING WITH GPU NUCLE /.R CORPORATION CONTROL R00H HABITABILITY STL'DY ATTENDEES HAmg Affiliation T. Colburn NRC/NRR/DRPE/PD1-3 B. Buckley NRC/NRR/DRPE J. Lee NRC/NRR/ DRPH /PERB C. Miller NRC/NRR/ DRPH /PERB R. Emch NRC/NRR/ DRPH /PERB L. Brown NRC/NRR/ DRPH /PE98 K. Boughton GPU Nuclear / Engineering

8. Parfitt THI/ Radiological Engineering T. Y. Byoun GPU Nuclear / Nuclear Fuels P. Bennett TNI/HVAC System Engineer J. Fornicola GPU Nuclear / Director Nuclear Safety Assessment K. Woodard PLG Consulting A. Irani GPU Nuclear / Safety Analysis C. Hartman GPU Nuclear / System Engineering TMI D. Distel GPU Nuclear / Licensing B. Williamson Nucleonics Week Enclosure 1 e _ _ _ - - _ - _ _ _ - - _ _ _ - _ - _ . - _ -

I GPU NUCLEAR CORPORATION CONTROL ROOM HABITABILITY STUDY DECEMBER 12,1997 HANDOU1 .ATERIAL USED AT THE MEETING Enclosure 2-

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GPU NUCLEAR /NRC MEETING December 12.1997 TMI-1 CONTROL ROOM HABITABILITY EVALUATION

1. Control Building Envelope (CBE) and Control Building Ventilation System (CBVS)

Site Building Layout CBE Arrangement

- CBVS Arrangement II. Control Building Ventilation System

- Design Features

- System Diagram

- Potential Failure Modes III. Control Room Evaluation Analysis

- Modeling TMI-l Control Room Doses

- X/Q Values for Control Room Habitability Analysis

' - Accidents Considered

- TEDE Dose Criteria IV. Control Room Habitability Submittal

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CONTROL BUILDING ENVELOPE (CBE) &

CONTROL BUILDING VENTILATION SYSTEM (CBVS) s

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PARTIAL SITE PLAN FOR TMI-1 l 4

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CONTROL BUILDING VENTILATION ZONES Definitions: Control Room (CR)- Elevation 355' of Control Building excluding stairwell and Control Building Hallway (Patio).

Control Building Envelope (CBE)-

Elevations 355' (CR),338' and 322' of the Control Building, excluding stairwell and Control Building Hallway (Patio).

Control Building Hallway (Patio)-

Adjacent to west wall of Control Building Envelope, and elevation 380' of the Control Building.

Controlled Access Area (CAA)-

Elevation 306' of the Control Building, excluding the Hot Tool room area.

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To Aux /FH Bido Exhaust TMl-1 CONTROL BUILDING VENTILATION SYSTEM

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• 4 CONTROL BUILDING & VENT. SYS. FEATURES l

. Control Building Separate Concrete Structure- Protection from Direct Streaming '!

• Penetrations Between Floors Saaled - Minimizes Transfer Air

. Ventilation Ductwork-Welded Construction

. Redundant Emergency Powered Fans with Filter Banks

. Redundant Emergency Powered Control Air System for Dampers & Controls

. Diverse Operation initiation Features for Control Building Ventilation System Emergency Mode of  ;

. Positive Pressure Maintained in Control Room As Demonstrated By Test for Various '

Failures

. Procedural Action to Maintain Pressurized Envelope by Admission of Outside Air

• Breathing Apparatus and Potassium lodide Available

. Single Doors Between CBE and Patio Area

. Positive Pressure Not Maintained in Lower Elevations During Various Failures 1

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1 PATHWAYS ANALYSIS (CONSISTENT WITH PREVIOUS HABITABILITY ANALYSIS)  ;

External (Atmospheric Transport)

Damper 28 Failure (Open)

Positive Pressure All Elevations of CBE e No Internal Paths Modeled

. ESF Leakage Assumed External e

X/Q 's Determined for Yard Intake (300' from containment)

Gradual Position Switch Failure (AH-D-39 & AH-D-37 Closed, AH-D-36 Open)

• Positive Pressure Control Room l e Two Intake Pathways (Yard Intake & Vent. Exhaust Leakage)

• ESF Leakage included L

• Two conditions of X/Q's

• No internal transport assumed Internal Transport e

Gradual Position Switch Failure (AH-D-39 & AH-D-37 Closed, AH-D-36 Open)

Two credible pathways developed (South Int. Bldg. & Aux /FH Bldg No External Contribution Assumed e l

.Non - emergency powered ventilation systems off e l Transport by Diffusion

• Infiltration to CBE based on previous DP test & analysis . I

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MODELING TMI CONTROL H00M DOSES

• Use PLG's MCD (Multi-Compartment Dose) computer program.

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• Assumes well mixed isotopic concentration in each volume.

• Dynamic model using 1-minute time scale.

• Accounts for varying isotopic input to, and transfer from, each volume.

• Doses are accumulated for up to 30 days in each volume.

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MCD PROCESSING

• Reads input source term comprised of 13 noble gas and 5 iodine isotopes.

• Computes concentration in each room including effects of radioactive decay.

• Concentrations and doses are printed for each volume as I a function of time.

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• Dilution between the containment surface and leakage into a compartment is accaunted for.

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MCD METHODOLOGY

• A differential equation is set up for each compartment volume.

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• These equations are solved simultaneously for concentration every minute using a numerical algorithm.

referred to as the Runge-Kutta method.

• The removal mechanisms for radioactive material include air flow, isotopic decay, and filtration of iodines. -

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i EXTERNAL DOSE MODEL i l External dose is adjusted using a finite volume correction j factor such that the walls, floor, ar;d ceiling limit the j receptor dose. The reduction factor (F.) applied to the external dose is of the form:

i Fe = (I c'")-(p -p.) Re'"

l where: p and p are attenuation factors for air and R is i

the radius of a hemisphere with volume equivalent to that .

! of the Control Room p

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TMI-I x/Q-Values for Control Room liabitability Analysis f-METHODOLOGY; 5

• In accordance with the Murphy & Campe Guidelines e-Source-Receptor configuratfor, o Diffused Source and Point Receptor *

• Meteorological Data o 1996 Joint Frequency Data i e

Effecthe X /Q-Valuest

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XQ =

1/ [U (no, o, + a /(K + 2))] ' D

• S

• O K =

3 /(s /d )"

Long term adjustment Getors included are:

(1) Wind Direction Factors (D)

(2) Wind Speed Factors (S)

(3) Occupancy Factors (0)

(Nomenclatures to be referred to the Il' Air Clearing Conference Proceedings)

, KEY DATAt e MHA Source Receptor Distance (s*) =

300 A o 91 meters e MSLB Source Receptor Distance (s""8) =

370 A o 112 meters -

e =

Reactor Containment Diameter (d) 140 A o 42 meten e Containment Projected Area (a) = 1985 m' >

e - 5% Wind SpeeJ (U) =

0.67 m/see (1,5 mph = 4.94%)

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TMI 1 Control Room Habitability x/Q Analysis (Source Receptor Configuration) ,

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Maximum Hypothetical Accident l Reactor Building Leakage Assumptions  !

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2568 MWt Core Inventory i

Increased by 10% for conservatism l

l TID-14844 release Containment leak rate

0.1% / day for first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 0.05%/ day for remaining 29 days l

Two compartment containment model

67.1% sprayed 32.9% unsprayed 100,000 efm flow between volumes

- _ , .. - _ - - _ . . , ~. _ .~ , , ., , - - - - - . - - - - , . .- _ - ,. . _ - - ,

. Maximum Hypothetical Accident Reactor Building Leakage Assumptions Spray Removal Coefficients based on one spray pump operation Elemental 7.39 hr-1 Particulate 3.03 hrl Organic 0.0072 hr-1 Decontamination Factors Elemental 100 Particulate 100 .

Organic 1.04

l .

Maximum Hypothetical Accident ES Lea cage to the Auxiliary Builcing Total lea c rate to the Auxiliary Building is I 18 gpa  ;

l 50% of core iodine inventory in water being recirculated - 0.0477 Ci/ml DEI 1.25% of coolant flashes to steam for the

first two hours of the accic ent - no l

partitioning  ;

, 1 l

Remaining coolant released as liquid -

partition factor of 0.009

! Maximum Hypothetical Accident ES Leakage to the Auxiliary Builting 50% of airborne iodine plates out in Auxiliary Builcing prior to release No credit taken for filtration by the ,

Auxiliary Bui:Lding ventilation system

) No credit taken for decay during hold up in the Auxi:.iary Building l

1

l Maximum Hypothetical Accident

ES Leakage to the BWST Leak rates to the BWST are: l 0-1hr 3 gpm 1-24 hrs 1.6 gpm l l-30 days 0.5 gpm l 50% of core iodine inventory in water being recirculated - 0.0477 Ci/ml DEI Partition factor of 0.009 between liquid and gas spaces of tank Release rate from the tank equal to air displaced by water leaking in No credit taken for plateout in the tank .

Main Steam Line Break RCS Dose Equivalent Iodine prior to accident is 1 uCi/g l

When accident occurs, iodine release rates l from the fuel rods increase by a factor of 500 The total primary-to-secondary leakage during the duration of the accident is 9960 gallons (hot)

Reduction factors in the secondary side:

0.5 for the first 10 minutes 0.25 after 10 minutes .

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l l Dose Equivalent Iodine-131 l Releasec.

Maximum Hypothetical Accident 9u,u,vnturies l

Main Steam Line Break l

, 1070 Curies l

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i GDC 19 Acceptable Dose l

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The requirement of General Design Criterion

(GDC) 19 in Appendix A of10CFR50 states

I "A control room shall be provided from which actions can be taken to operate the

nuclear power unit safely under normal

! conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents.

Adequate radiation protection shall be .

provided to permit access and occupancy of the control room under accident conditions

without personnel receiving radiation i exposure in excess of 5 Rem whole body, or its equivalent to any part of the body, i for the duration of the accident."

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i GDC 19 Acceptable Dose

, 1 Key words - or its equivalent to any part of the body -- 5 Rem Total Effective Dose Equivalent (TEDE).

TEDE, CEDE, and DDE are defmed in 10CFR50.2 (Amended 12/96).

The Standard Review Plan (NUREG 0800)

, in Section 6.4.II.c states that the system design is acceptable if the requirements of GDC 19 are met.

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GDC 19 Acceptable Dose i

i SRP interprets the acceptable dose of GDC 19 as 5 Rem whole body ganuna,30 Rem l to t:1e thyroid, and 30 Rem to the skin.

Consistent with the annual dose limits j specified by ICRP 2 - 10CFR20 at the i

time.

When the SRP was written, there were no NRC regulations describing method.s for the determination of "5 Rem whole body or, or its equivaient to any part of the bocy".

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GDC 19 Acceptable Dose l

January 1,1994, - a new revision to 10CFR20 was required to be used by

licensee's for radiation protection - based on ICRP 26 New 10CFR20 requires (and provides a method for) licensee's to sum the external whole body dose with the internal whole

body equivalent dose to other parts of the

aody as the method for controlling occupational radiation exposure.

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i GDC 19 Acceptable Dose Tae criteria for habitability specified in GDC 19 is solely based on operators not receiving more than 5 Rem TEDE dose l during the accident.

There is no need for a separate thyroid dose

! limit. It is automatically accountec for in l TEDE concept.

i Control room operators during an accident receive occupational dose. Current regulations for measuring occupational dose conform to the language in GDC 19.

Calculation of TEDE occupational dose can be performed for any source term assumed. .

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CONTROL ROOM HABITABILITY SUBMITTAL i

Submittal to NRC by March 24,1998 Description of CBE and CBVS Description of Analytical Model  ;

• Basis for X/Q Values Utilized <. escoN es)

Accidents Analyzed - MHA Bounding ( L oc M Comparison of Results with GDC-19 TEDE Limits Discuss Compensating Factors New Accident Source Terms More Realistic X/Q Models Credit for Offsite Power Restoration to Aux. -

. and FHB Ventilation System.

Scenario Based on PRA Insights ,

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