ML20147E520
| ML20147E520 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/29/1988 |
| From: | SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML20147E485 | List: |
| References | |
| NUDOCS 8803070090 | |
| Download: ML20147E520 (18) | |
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RANCHO SECO NUCLEAR GENERATING STATION CONTROL ROOM / TECHNICAL SUPPORT CENTER (TSC) HABITABILITY STUDY Radiological Dose Assessment i
i February 1988 i
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Table of Contents
- 1. Introduction and Summary 1
1.1. Introduction
.............................1 1.2. Summary of Results 1
- 2. Direct Radiation Doses 2
2.1. Containment Shine..........................
2 2.2. Contaminated Systems Shine
....................3 2.3. Containment Penetration Dose....................
3 2.4.HVAC Filter Shine
..........................4 l
- 3. Doses from Airborne Radioactive Materials 4
3.1. Radioactive Sources.........................
5 3.1.1. Containment Leakage....................
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3.1.2 Recirculation Loop Leakage.................
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3.1.3. Containment Minipurge
...................7 3.2. Atmospheric Dispersion Factors...................
7 3.3. Plume Shine 7
3.4. Control Room HVAC Model
.....................8
- 4. References 9
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List of Tables Table 1 Assumptions and Parameters Used for Calculation of Control Room Operator Doses,,.......
10 Table 2 Calculated Control Room Operator Radiation Exposure from all Sources Using USAR Assumptions...........
13 Table 3 Calculated Control Room Operator Radiation Exposure from all Sources Using Regualtory Guide 1.4 Assumptions...
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- 1. Introduction and Summary 1.1.
Introduction This report discusses the methodology and results of the radiological analysis used to demonstrate the habitability of the Rancho Seco Nuclear Generating Station Unit 1 Control Room (CR) and Technical Support Center (TSC) from a postulated design basis accident. Detailed descrip-tion of the basis for the atmospheric dispersion factors used in the analysis is presented, along with the description of the radiation sources considered in the evaluation.
This report supplements the information previously provided in Reference 4.1 and amplified in Reference 4.2.
1.2.
Summary of Results The radiation exposures to the Control Room operators from both direet and airborne contributors have been evaluated. A detailed description of the evaluation is presented in the following sections. The resultant exposures were found to be acceptable.
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- 2. Direct Radiation Doses De direct radiation exposure to Control Room operators originates from six sources:
A. Direct gamma dose from the reactor building attenuated by the containment wall and Control Room shielding, B. Direct gamma dose from the plume resulting from containment
- leakage, C. Internal and external doses from airborne radioactive materials which may reach the Control Room with the emergency HVAC pressurization air, D. Direct exposure from systems required to process primary reac-tor coolant after an accident, E. Direct gamma dose through containment penetrations, and F. Direct gamma dose from activity deposited in the Control Room IIVAC and Auxiliary Building HVAC filters attenuated by the Control Room shielding.
De resultant doses from source C are discussed in section 3.4. The shine dose from the plume (source B) is presented in section 3.3 All of the other direct radiation sources are discussed in the following sections.
2.1. Containment Shine The whole body dose rate contributions due to direct shine from the ac-tivity inside the Containment Building through the Auxiliary Building roof were calculated at three different locations inside the Control Room /TSC envelope.Dese locations are at the Control Room panels, at the computer room and at the TSC. The maximum dose rates at these locations were calculated to be 0.63 mR/hr,1.4 mR/hr, and 1 mR/hr, respectively. The resultant 30 day whole body dose from containment shine in the Control Room is calculated to be less than 4.4 mR.
2.2. Contaminated Systems Shine Area dose rates for source D were evaluated in Reference 4.3 and reported in Reference 4.1. De time integrated dose to the Control Room operators using source D is presented below. The evaluation of direct exposure from systems required to process primary coolant after an accident, presented in Reference 4.3, resulted in post accident radia-tion zone maps and curves of normalized dose rate versus time. The radiation zone map at the turbine deck (el. 40'-0") shows the Control Room console area and entryway is in radiation zone A (less than 15 mr/hr), and the adjoining support instrumentation area is in zone B (15 to 100 mr/hr). The Control Room kitchen, bathroom, conference room and supervisor's office are also in 7.one A.
A realistic estimate of the maximum operator 30 day integrated dose would include consideration of operator occupancy fac' ors in zones A and B. In this evaluation, the conservative assumption was used that the operator stays in zone B and that the dose rate is the upper limit within the zone of 100 mr/hr. The integrated operator dose using the conser-vative source C (of reference 4.3) is less than 1.4 rem. An operator spending half of his Control Room time at the console, conference room, or supervisors office would receive a maximum dose of 0.81 rem from source D.
2.3.
Containment Penetration Dose 7
The contributions to the total whole body dose from containment penetration shine was also included in the analysis. Contributions from mechanical and electrical penetrations were considered. Mechanical penetrations considered included the 66" purge valve penetration and i
the personnel lock. Electrical penetrations considered consisted of three types, type 1-1 penetrations (24" diameter penetration with 5" steel shielding), nozzle or spare penetrations (12" diameter with 8" steel shieIding), and all othe r pcnetrations (12" diame te r with 4.5" steel shield-ing). The resultant 30 day doses from the mechanical and electrical penetrations are 3.5 mR and 0.48 mR, respectively.
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2.4.
HVAC Filter Shine Contributions to the whole body dose from shine of contaminated char-coal filters was included in the analysis. Three filter units were con-sidered: the Auxiliary Building filter, Essential CR/TSC HVAC train A filter and Essential CR/fSC HVAC train B filter. The resultant 30 day whole body dose to the Control Room personnel is less than 20 mR.
- 3. Doses from Airborne Radioactive Materials In addition to direct radiation exposure from activity contained in the Reactor Building or in systems containing primary coolant, exposures from radioactive materials released to the environment were considered.
Exposures to the Control Room personnel consists of two types, shine from the cloud outside of the Control Room through the roof and walls of the Auxiliary Building and external and internal exposure from air-borne radioactive materials which may reach the Control Room with the emergency HVAC pressurization air.
The analysis considered three release pathways of radioactive materials:
- 1. Leakage of airborne radioactive materials from the containment.
2 Leakage of contaminated water from ESF systems in the Auxiliary Building, and
- 3. Releases from the containment minipurge systems prior to isola-tion.
Two types of analyses were performed, one following the assumptions l
presented in the Rancho Seco USAR Section 14.3, and one following the assumptions of Regulatory Guide 1.4. The assumptions and parameters for both analyses are presented in Table 1. The resultant doses are presented in Table 2 for the USARanelysk and Table 3 for the R. G.1.4 analysis.
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3.1.
Radioactive Sources 3.1.1.
Containment Leakage De containment leakage source term is calculated using the following assumptions and parameters, summarized in Table 1:
- 2. De fraction of the core radioactive inventory instantaneously released and uniformly mixed in the containment consists of 100% of the noble gas inventory and 25% of the iodine inventory.
The iodine species fractions are presented inTable 1 for both the USAR and R. G.1.4 analyses.
- 3. The containment spray system is actuated by a 30 psig Reactor Building pressure signal with a 5 minute delay. The Reactor Building pressure reaches 30 psig approximately 6 seconds after the LOCA.
- 4. The containment sprays cover approximately 67.6% of the con-tainment volume.
- 5. The containment sprays are assumed to remove only the elemen-tal iodine species.De elemental iodine removal rate is 19.5 hrs'l.
- 6. One containment filtered cooler recirculation fan is a'sumed to operate. A flow rate of 40,000 cfm is initiated 36 c.econds after the accident. De charcoal filter efficiency for iodine removal is assumed to be 85%.
- 7. De containment is assumed to leak at 0.1%/ day throughout the accident in the USAR analysis, and 0.1%/ 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 0.05%/ day thereafter in the R. G.1.4 analysis.
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Recirculation Loop Leakage ne recirculation loop leakage source term is calculated using the fol-lowing assumptions and parameters, summarized in Table 1:
- 2. 50% of the core iodine source term is assumed to be instan-taneously released and mixed in the recirculation loop volume.
- 3. He recirculation loop volume is composed of two contributing volumes: the reactor coolant volume and the emergency cooling water volume. The total volume is 1.710 x 10' cm3
- 4. Contaminated recirculation loop leakage is assumed to begin 30 minutes after the start of the LOCA, since for the first 30 to 40 minutes clean water from the borated water storage tanks leak i
through this pathway.
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- 5. A constant recirculation loop leakage of 2,400 cm /hr is assumed for the duration of the accident.
- 6. Of the iodine laden water leaked from the recirculation loop, 10% becomes airborne as a result of evaporation.
- 7. De recirculation loop leakage is directed to sumps in the two decay heat pump rooms. The free air volume of these rooms is r
3 15,000 ft.
- 8. He decay heat pump rooms are served by the Auxiliary Building HVAC. De filtered exhaust flow rate of these rooms is 4,000 cfm. De iodine removal efficiency of the charcoal filters is as-sumed to be 90%.
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3.1.3.
Containment Minipurge ne LOCA coincident with containment minipurge release is calculated using the following assumptions and parameters, summarized in Table 1:
- 1. Reactor coolant inventory spiked to 60 Ci/gm I-131 equivalent
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is assumed to exists prior to the LOCA.
- 2. A 12" diameter purge valve is assumed to be open prior to the LOCA.
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- 3. Conservatively, other valves equivalent to a 10' diameter open-ing are assumed to be also open prior to the LOCA.
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- 4. All valves are assumed to be closed 35 seconds after the start of F
the LOCA.
3.2. Atmospheric Dispersion Factors ne radioactive materials released from the pathways described above F
will be mixed and diluted prior to entering the Control Room through the essential HVAC air intakes or producing doses from shine of the E
cloud above the Auxiliary Building. De atmospheric dispersion factors used describing this mixing and dilution are presented in Table 1 Sec-tion IV.
7 3.3.
Plume Shine
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The whole body dose contribution from shine of the airborne plume F
above the Auxiliary Building was considered in the analysis. De activity released was assumed to be mixed uniformly and diluted by the Control Room X/O in a 300' x 300' x 100 volume above the Auxiliary Building.
ne Control Room was assumed to be shielded by a l' thick roof slab, l' thick south wall and a l'-3" thick west wall. He north and east walls, which are inside the Auxiliary Building were not modeled since shine
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must penetrate the roof then the walls, for a shielding thickness greater than 2 feet. An HVAC penetration through the ceiling of the computer room was model as a poetration leading directly to the outside cloud.
De resultant 30 day whole body is 038 rem.
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3.4. Control Room HVAC Model Radioactive materials released to the emironment can enter the Con-trol Room through the normal HVAC system prior to isolation, then through the essential HVAC system or leak unfiltered through doors or HVAC ducts. The analysis assumed four separate HVAC flow condi-tions:
- 1. Normal HVAC flow until the radiation monitors isolate the nor-mal HVAC system. It is assumed that the normal Control Room HVAC system continues to operate for 5 seconds after the radia-tion monitor isolation setpoint has been reached.
- 2. Maximum air flow through both essential HVAC units until flow stabilization is achieved. Once the normal HVAC system has been isolated, an additional eight minutes is required to complete flow stabilization.
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- 3. Stabilized air flow through both essential IIVAC units until operator action isolates one of the two units. Once the high radia-tion alarm has sounded in the Control Room, it is assumed that the operators willisolated one of the two essential HVAC trains within 15 minutes.
- 4. Stabilized air flow through one essential HVACunit until the end of the accident.
Once isolation of the normal Control Room HVAC system has been achieved, the Control Room is pressurized with filtered air. Conserva-tively, to cover potential unfiltered inleakage form door openings and HVAC ducts,60 cfm is assumed to enter the control room unCltered.
He flow rates associated with each of these different conditions are presented inTable 1 Seetion V.
De internal and external doses to Control Room operators from all release sources are presented in Table 2 for the USAR analysis and in i
Table 3 for the R. G.1.4 analysis.
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- 4. References
,j 4.1 Letter from G. C. Andognini to F. J. Miraglia, USNRC, "Control Room /rechnical Support Center (TSC) Habitability Report, Rev.
5," July 22,1987.
4.2 Letter from J. F. Firlit to F. J. Miraglia, USNRC, "Control Room Habitability Request for Addi;tional Information,"January 13,1988.
43 Letter from J. J. Matimore to R. W. Reid, USNRC, April 11,1980.
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Table 1
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ASSUMPTIONS AND PARAMETERS USED FOR CALCULATION OF COi4 TROL. HOOM OPERATOR DOSES S
Parameter USAR R.G.1.4 I Coritainri.$nt Leakige Centribution A. InitialCoreInventory............... USAR Tsble 14D.1 B. Noble Gas Airborne
.100.%.......... 100.%
4 C. Wh Airborne....
. 25.%.......... 25.%
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Elerae. tal.................. 25.%.......... 91.%
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Organic.........
.... 10.%........... 4.%
Particulate
...... 5.%........... 5.%
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D.
Mntainment Volume (ftD............ 1.98 x 106........ 1.98 x 106
- 12. Containment Spr.vj Parameters y
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- i. Sprayed Reghn
........... 67.6%......... 67.6%
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ii. T.emoval Ratra (hrs'I) h, Elemental................ 19.5.......... 19.5 Orgaric
..................0.............0.
Partienlate................ 0.
............0, iii. Decontamination F6am ) i
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Elfmental....
...... 100........ ; 3... 100.
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i Organic......., '......... N/A
\\,....N/A Particulati '.....
N/A... '........ N/A iv. Spray initiation..
. 5 mia &sec..,.... 'S min 6 sec v.
Cooler Mixing Flow (cfm)
.... 40,000.......... 40,000.
vi Cavaler Fijter Rtmoval Efficiency.... 85%.......... 85 %
F. Containment Leakage Rad (CVday)
O to l day... '.......
... 0.( q. (. i. g... 0.1 7
l to 30 days
.'...M1
........... 0.05
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Table 1 (Cont.)
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Parameter Value
, s ll Recirculation LMp Leakage Contribution "A. haklCoreInventory...................... USAR Table 14.D-1 it Edine Released to Recire Loop Volume.................. 50.%
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- C. Recaredation Loop Volume (cm )....................... 1.71 x 10' 3
D. Recirculation Loop Leakage (cm /hr)................... 2,400.
E. Iodme Decontamination Factor........................ 10.
3 F.
Decay Heat Pump Room Volume (ft ).................. 15,000.
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G. AuxiliaryBuildingHVACSystem Flow Rate (cfm)............................. 4,000.
h Charcoal Filter Efficiency......................... 90.%
lll Containment Minipurge A. IodineSourceTerm.............................. 60. Ci/gm I.131 B. Vahes Considered...............................
12.' dia. purge valve 10.' dia eqiv. other valves h5 C. Ct.vure Time.................................. 35.sec
-jV_Coritrol Room Atmospheric Dispersion Factors (X/O) in sec/m
o O to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.................................... 3.61 x 10'3 4
s 8 to 2 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.................................... 2.55 x 10'3 1 to f days..................................... 1.43 x 10'3 a
,.a' 1 to 30 days.................................... 5.85 x 10 4
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L, Table 1 (Cont.)
Parameter Value V Control Room Parameters -
3 A. Free Air Volume (ft )........................... 90,800.
B. HVAC System Flow Rates (cfm) 1.
Unaltered Flow /Inleakage O to 5 sec............................... 1,978.
S sec to 30 days............................60.
ii. Fdtered Pressurization Intake O to 5 sec................................. 0.
S sec to 8 min 5 sec......................... 4,553.
8 min 5 sec to 15 min 5 sec.................... 3,520.
15 min 5 see to 30 days....................... 1,760.
iii Filtered Recirculation Flow O t o 5 sec................................. 0.
5 see to 8 min 5 sec......................... 2,987.
8 min 5 see to 15 min 5 sec..................... 2,240.
15 min 5 see to 30 days....................... 1,120.
C. Charcoal Filter Efficiency........................... 99.%
l D. Control Room Occupancy Factors O t o l day.................................. 100.% -
I to 4 days
.................................60.%
4 to 30 days................................. 40.%
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Table 2 CALCULATED CONTROL ROOM OPERATOR RADIATION EXPOSURE FROM ALL SOURCES USING USAR ASSUMPTIONS Source Thyroid Whole Body Beta Skin A.
Direct containment shine 0.004 B.
Plume shine 038 C.
CR cloud exposure 38.6 1.56 373 D.
Contaminated systems shine 1.4 E.
Containment penetration shine 0.004 F.
HVAC filter shine 0.02 Total 38.6 3.4 373 10CFR50, App. A.G.D.C.19 Guidelines and SRP 6.4 Sec. II.6 30.
5.
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I Guideline is 75 reon if protective actions are taken.
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Table 3 CALCULATED CONTROL ROOM OPERATOR RADIATION EXPOSURE FROM ALL SOURCES USING REGULATORY GUIDE 1.4 ASSUMPTIONS Source Thyroid Whole Body Beta Skin A.
Direct containment shine 0.004 B.
Plume shine 038 C.
CR cloud exposure 353 1.47 35.0 D.
Contammated systems shine 1.4 E.
Containment penetration shine 0.004 F.
HVAC filter shine 0.02 Total 35.3 33 35.0 10CFR50, App. A. G.D.C.19 Guidelines and SRP 6.4 Sec. II.6 30.
5.
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- Guideline is 75 rem if protective actions are taken. _ _ - - - -
a ATTACHNENT 4 Toxic Gas Analysis
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