ML18102A473

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Calculation That Determines Doses Due to Airborne Radiation
ML18102A473
Person / Time
Site: Salem  PSEG icon.png
Issue date: 10/17/1996
From:
STONE & WEBSTER, INC.
To:
Shared Package
ML18102A471 List:
References
002-1, 2-1, NUDOCS 9610250079
Download: ML18102A473 (8)
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Text

-ONE & WEBSTER ENGINEERING CORP-TION

  • 5010.65 CALCULATION SHEET .

CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP- CALCULATION NO. OPTIONAL TASK CODE PAG,E 5 02560 UR(B) 002 - 1 NA 1.0 Objective The objective of this calculation is to determine the doses due to airborne radiation, at the Salem Generating Station EAB, LPZ and in the control room following a postulated Fuel Handling Accident in the Fuel Handling Bldg. The calculation assumes a simultaneous Loss of Offsite Power (LOOP) following the Control Room (CR) isolation signal generated by the CR intake radiation monitors, with the subsequent delay in switching from the* normal operation mode to the emergency operation mode of the control room ventilation system. The calculation considers two CR Emergency Ventilation operation scenarios:

~ The first scenario utilizes the automatic selection capability of the radiation monitors to select the less contaminated CR intake. In addition, it asswries that only one Unit's CR emergency ventilation systeiri. is available. 1

~ The second scenario assuffies that the CR emergency ventilation is already in operation at the time of an: accident. This sce.nario assumes two train operation.

---[_Additionally, the calculation considers two Fuel Building ventilation operation scenarios:

~ The first scenario assumes that the F~~l Bldg. ventilation ~xhaust is administratively aligned through the Fuel Bldg. filters prior to fuel movement (i.e., takes credit for the Fuel Bldg. Exhaust filters for the duration of the accident).

~ The second scenario assumes that the Fuel Bldg. Ventilation exhaust filters are bypassed for the dtiration of the accident. *

  • II

, I

--ONE & WEBSTER ENGINEERING COR.TION

  • 5010.65 CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE PAGE 8 02560 UR(B) 002 - 1 NA 3.0 Assumptions
1. Exhaust Lambda()..) for FHA in Fuel Bldg ........ 60 hr" 1 Ref.[1]

Design Lambda of the Fuel Pool Sweep Gas System.

2. Activity release Path Ref.[1]

FHA in Fuel Building Fuel gap activity is released to the fuel pool. Noble gas and unscrubbed iodine escape to the air space above the pool where they are exhausted by the fuel pool sweep gas system and released via the main Unit vent.

3. Fuel Building Exhaust Filter Efficiency Ref.[1]

90% Inorganic 70% Organic The actual fuel building filter efficiency for organic iodine is greater than that stated above, however, for conservatism, the filter efficiency value for organic iodine provided in Safety Guide 25 is followed in lieu of using the actual technical specification efficiency.

It is expected that the filter efficiency of inorganic iodine would be greater than the value presented above given that the filter is so effective in cleaning up organic iodine, however, for conservatism, the filter efficiency value for inorganic iodine provided in Safety Guide 25 is followed.

4. Delay time for the control room pressurization mode to be fully operational after receipt of the control room intake radiation monitor is : 48 seconds The normal intake damper closure time is assumed to be 20 seconds (Ref.[1]). The Loss Of Offsite Power (LOOP) is assumed to occur at the time the dampers are fully closed

.and the power to the EACS fans are lost. At the LOOP, the Diesel Generators start and it takes 13 seconds(Ref.[1]) for the DG's to become fully operational and the power is delivered to the EACS fans. The EACS fans are assumed to take 15 seconds (Ref. [ 1])

to gain full speed and the control room is considered fully pressurized at this time.

Therefore, the total delay time from the issuance of the control room radiation monitor signal until the control room is in emergency pressurized mode is the sum of normal intake damper closure time (20 sec), the Diesel Generator speedup time (13 sec), and the EACS fans speedup time (15 sec) for a total of 48 seconds.

5. The unfiltered inleakage after the control room is pressurized due to ingress/egress is assumed to be 10 cfm [Ref.l]. The Unfiltered inleakage after the control room is pressurized due to ductwork is assumed to be 50 cfm [Ref.1]. *
6. It is assumed that the control room can be maintained at (+)1/8" W.G. with a makeup flow of 2000 cfm.

-ONE & WEBSTER ENGINEERING COR.TION

  • 5010.65 CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP CAL CU LA TION NO. OPTIONAL TASK CODE PAGE 9 02560 UR(B) 002 - 1 NA 4.0 Data
1.
  • Total gap activity released to pool Ref.[1]
  • from the rods that failed {curie)

I-131 5.86E4 I-132 2.81E4 I-133 6.33E2 I-135 3.53E3 Xe-13 lm 8.895E2 Xe-133 8.096E4 Xe-133m 9.248E2 Xe-135 l.234EO Kr-85* 2.276E3 Values Based on:

Activity Values based on:

Thermal Power= 3600 Mwt Number of Damaged Assemblies= 1 Enrichment= 4.5%

Decay Time = l 68hr Radial peaking factor= 1.7 Fraction of core noble gas and iodine activity in gap:

I-131(12%); Kr-85(30%); All others (10%)

2. Pool Decontamination Factors Ref.[1]

Halogens Inorganic: 133 Organic : 1 Overall : 100 Noble Gas All :1 Values Based on:

Minimum ~ater depth for scrubbing = 23 ft

3. Iodine chemical form before scrubbing Ref.[1]

99.75% Inorganic 0.25% Organic

4. Offsite Breathing rate [Ref.I]

0- 8 hr 3.47E-4 m3/sec 8 - 24 hr l.75E-4 m 3/sec 24- 720 hr 2.32E-4 m 3/sec

-ONE & WEBSTER ENGINEERING CORP-TION

  • 5010.65 CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE PAGE 10 02560 UR(B) 002 - 1 NA
5. Control Room Breathing rate - 3.47E-4 m3/sec [Ref.1]
6. Control Room x/Qs (Atmospheric Dispersion Factors): Ref.[1]

Before Isolation (Unit I Main Vent, Unit I CR Intake) - s/m3 0-2 hr I .72E-3 2-8 hr I.22E-3 8-24 hr I .03E-3 I-4 day 7.13E-4 4-30day 4.I9E-4 After Isolation (Unit I Main Vent, Unit 2 CR Intake) - s/m3 0-2 hr 8.90E-4 2-8 hr 6.35E-4 8-24 hr 5.36E-4 1-4 day 3.72E-4 4-30day 2.20E-4

7. Offsite X/Q's (from all plant release points) [Ref. I]

EAB LPZ (s/m3) (s/m3) 0-2 hr l.30E-4 I .86E-5 2-8 hr 7.76E-6 8-24 hr 5.0IE-6 I-4 day 1.94E-6 4-30day 4.96E-7

8. CONTROL ROOM PARAMETERS - Modified design [Ref. I]
  • Control room pressure envelope volume:

8 I ,420 ft 3

  • Control Room Normal Operation & EACS Vent System margin:

. IO%

  • Normal unfiltered air intake rate:

design value: I200 cfm with margin: 1320 cfm

  • Filtered emergency makeup flow:
  • design value: 2000 cfm with margin: 2200 cfm
  • Total unfiltered inleakage- 60 cfm (10 cfm from ingress/egress; 50 cfm from ductwork leakage)
  • Filtered recirculation flow rate

- one EACS fan operation design value: total EACS flow = 8000 cfm design value: recirc = 8000-2000 = 6000 cfm with margin: total EACS flow = 7200 cfm with margin: recirc = 7200-2200 = 5000 cfm

- two EACS fans operation + i'

-ONE & WEBSTER ENGINEERING COR~ATION

  • 5010.65
  • CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE PAGE 11 02560 UR(B) 002 - 1 NA design value: total EACS flow = 16000 cfm design value: recirc = 16000-2000 = 14000 cfm with margin: total EACS flow = 14400 cfm with margin: recirc = 14400-2200 = 12200 cfm
  • Intake and recirculating filter efficiencies:

Elemental iodine - 95%

Organic iodine - 95%

Particulate - 95%

  • Control room occupancy factors:
  • Time from Start Occupancy of Accident Factors 0 to 8 hrs 1.0 8 to 24 hrs 1.0 I to 4 days 0.6 4 to 30 days 0.4
9. Data for Control Room Intake Monitors [Ref. I]
  • Monitor response time - Table 6-1 of Ref.[3] [Ref.3]

The Salem control room monitors are Sorrento Electronic in-duct monitor RD-25A with micro-Processor RM-2000. The monitor response time in Table 6-I ofRef.[3] is for filter constant (FC) equal to 6. FC=6 is the SE recommended value (Ref.[I]).

  • Noise reject delay time= 5 x 600 msec

= 3 sec [Ref.I]

The noise reject time count of 5 is recommended by SE (Ref.[1]). 600 msec is the RM-2000 shift register time segment.

  • Detector Response - Xe133: 6.2IE7 cpm/(µCi/cc) [Ref.4]

Kr85: 2.58E8 cpm/(µCi/cc)

++ ONE FA,.; PE.R E'Ac S FIL 'f'R.A-r-JoAJ 7RAlfl/,

-ONE & WEBSTER ENGINEERING COR-ATION

  • 5010.65 CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.O.OR W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE PAGE 21 02560 UR(B) 002 - 1 NA 8.0 Results I Conclusions The calculated doses (rem) at the Salem Generating Station EAB, LPZ and control room from a postulated Fuel Handing Accident in the Fuel Building are:

EAB Thyroid Whole Body Filtered Release 4.31 0.16 Unfiltered Release 28.73 0.19 LPZ Thyroid Whole Body Filtered Release 0.62 0.03 Unfiltered Release 4.11 0.034 The exposure guidelines at the EAB and LPZ set forth in 10CFRlOO are 300 rem thyroid and 25 rem whole body. The calculated doses at the EAB and LPZ, assuming (credit)/(ho credit) for a filtered release, are well within the 10CFRl00 exposure guidelines.

CONTROL ROOM Thyroid Whole Body Beta CASE 1: Selection of Favorable IntakeO Filtered Release 6.66 0.18 2.14

: Unfiltered Release 44.4 0.18 2.15 CASE 2: Pre-Existing Emergency Modee Filtered Release 0.7 0.32 3.86 Unfiltered Release 4.04 0.26 3.14 0 Values reflect automatic selection of the control room favorable intake with only one unit EACS operating.

8 Assumes worst case control room intake but that the CR EACS for both units are operational The exposure guideline in the control room set forth in 10CFR50 General Design Criteria 19 is 5 rem to the Whole body or its organ dose equivalent (accepted as 30 rem to the thyroid from inhalation and 30 rem beta from submersion). The calculated doses in the control room, assuming the releases from the Fuel Building are filtered, are well within the 10CFRSO exposure guidelines. However, if the Fuel Bldg. releases are not filtered the calculated dose to the thyroid exceeds the 10CFR50 GDC 19 exposure guidelines.

-ONE & WEBSTER ENGINEERING COR.TION

  • 5010.65 CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.0.0R W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE APP- A( 1 of 2) 02560 UR(B) 002 - 1 N/A APPENDIX A CALCULATION OF INTAKE MONITOR RESPONSE TIME TO A FUEL HANDLING ACCIDENT IN THE FUEL BUILDING Control Room Intake Monitor Response Time The intake monitor response time is determined by the final count rate at the detector (Cr), the monitor setpoint (C 5 ), the background courit rate (C 0 ) ; and the time constant of the micro-processor (RC). The new Salem control room intake monitors consists of Sorrento Electronic beta sensitive inline detectors and RM-2000 micro-processor. The smoothing algorithm of RM-2000 will generate an effective time constant for a step change of the detector count rate. The effective time constant depends on the initial count rate, the final cotint rate, and the smoothing filter constant (fc). The time constant corresponding to the 95% observation time (i.e. 3RC) given in Table 6.1 of reference[3]

if for fc=6 and will be used to determine the monitor response time.

The detector response function (cpm per µCi/cc) for Xe-133 and Kr-85 are listed below (see Assumptions Section):

Xe-133 - 6.21 E7 cpm/(µci/cc)

Kr-85 - 2.58E8 cpm/(µci/cc)

The process safety setting for the intake monitors is determined in Ref.[5] to be 4E-5

µci/cc (Xe-133). 1bis value will be conservatively used as the monitor alarm setpoint for response time calculation.

C, = 4E-5 µci/cc x 6.21E7 cpm/(µci/cc) = 2484 cpm The initial Xe-133 and Kr-85 concentrations at the control room intake for the FHA are calculated as follows:

Cone= (gap activity)( bldg leak rate)(X/Q)

Cx = (60 hr 1 ) (hr/3600sec)(l.72E-3 s/m3)

= 2.867E-05 m-3 Cone xc- 133 = 2.867E-05 m*3 x 8.096E4 Ci = 2.32 Ci/m3 Cone Kf. 85 = 2.867E-05 m*3 x 2.276E3 Ci = 0.0653 Ci/m 3 Count Rate xc- 133 =2.32 µC/ce x 6.21E7 cpm/µCi/cc = l.44E8 cpm Count RateKr-ss =0.0653 µC/cc x 2.58E8 cpm/µCi/cc = l.69E7 cpm

-ONE & WEBSTER ENGINEERING CORP-TION

  • 5010.65 . CALCULATION SHEET CALCULATION IDENTIFICATION NUMBER J.0.0R W.O.NO. DIVISION & GROUP CALCULATION NO. OPTIONAL TASK CODE APP- A( 2 of 2) 02560 UR(B) 002 - , N/A The step increase of the instantaneous detector raw count rate at the arrival of the contaminated air is:

Cr - C0 =1.44E8 + 1.69E7 = l.61E8 cpm The monitor is saturated, however, per the control room intake radiation monitor specification, Ref. [6), the monitor will actuate even if the monitor saturates.

It is clear that the control room intake monitor will instantaneously reach it's high high alarm following an FHA in the fuel building. To demonstrate this assume that the count rate is one one-hundredth (1/100) of the calculated count rate then:

From Table 6.1 of ref.[3]. the three times time constant of the monitor response for a step increase of 1E+6 cpm is 0.36 min, Therefore, the effective time constant (RC) for a step increase of 1.61 E6 cpm will be less than 0.36/3 = 0.12 min. The monitor response time, t*, is determined by:

2484/1.61 E6 = l-e*1*ro.u t* =0.00019 min =0.011 sec To avoid spurious alarm due to noise count rate, RM-2000 features a noise rejection algorithm.

The noise rejection response time is equal to the reject time count (5, recommended by SE) multiplied by the shift register time segment (600 msec). Therefore, noise rejection response time = 5 x 600 msec = 3 sec

*The over-all monitor response time= 3 + 0.011=3.01 sec Four (4) seconds will be used as the monitor response time for the Fuel Handling accident in the Fuel Building. The monitor response time will be assumed to be one (1) second plus the three (3) second spurious alarm delay or four (4) seconds.
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