ML20140E569

Responds to NRC 841120 Request to Reevaluate Main Steam Line Break Using Differential Assumptions,Per NUREG-0737, Item III.D.3.4 & Generic Ltr 82-33 Re Control Room Habitability.Results of Listed Methodologies Provided

ML20140E569
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	12/31/1984
From:	Linder F DAIRYLAND POWER COOPERATIVE
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM GL-82-33, LAC-10488, NUDOCS 8501110140
Download: ML20140E569 (6)

Text

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- g i;W O DA/RYLAND COOPERA T/VE *' P.O. BOX 817

• 2615 EAST AV SOUTH = LA CROSSE. WISCONSIN 54601 - )

, (608) 788-4000 December 31, 1984 In reply, please refer to LAC-10488 JOCKET NO. 50-409 U. S. Nuclear Regulatory Comm'.ssion Atta: ?Mr. Darrell G. Eisenhut, Director

Division of Licensing 0ffice of Nuclear Reactor Regulation Division of Operating Reactors Washington, DC( 20555

SUBJECT:

DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LACBWR)

- PROVISIONAL OPERATING LICENSE NO. DPR-45 POST.TMI REQUIREMENTS, ITEM ~III.D.3.4 AND REQUIREMENTS FOR EMERGENCY RESPONSE CAPABILITY, SUPPLEMENT TO NUREG-0737 (GENERIC LETTER 82-33)

CONTROL ROOM /TSC HABITABILITY

Reference:

(1) DPC Letter, LAC-10286, Linder to Eisenhut dated October 25, 19S4 (2) NES Document 81A0013, Rev. 1, " Additional.Information Requested by USAEC on Pipe Breaks Outside Containment" dated December 4, 1974.

Dear Mr. Eisenhut:

Reference 1 provided information on Control Room and Technical Support Center

(TSC) doses following postulated accidents other than a Maximum Credible Accident.~ One of the postulated accidents covered in Reference 1 was a main

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steam line break outside the Containment Building. The NRC has requested

'(telecom, November 20, 1984, Dudley etc. (NRC) to Goodman (DPC)) that the main steam line break be re-evaluated using some different assumptions. DPC, while-not accepting the revised methodology as more valid, has agreed to perform the evaluation.- This letter contains the results of that evaluation.

' The basic difference between the two methodologies is that in the first, the release was arsumed to be an almost instantaneous, explosive release. The environmental release point was assumed to be at a weakest Turbine Building panel. In the second case, all the wall and roof-' panels with the same design-pressure, are assumed to fail, leaving'an open Turbine Building at the roof-and upper walls. The subsequent-cloud, consisting of the steam, expanded to L atmospheric pressure and diluted in the initial Turbine Building atmosphere, is assumed to travel at 1 meter /second. Other assumptions, such as primary

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l- coolant' activity and release duration remain the same.

WP6.24.  ;- p i

Mr.'Darrell G. Eisenhut, Director

. December 31, 1984 Division of Licensing LAC-10488 During the event, it is assumed the main steam line breaks in the turbine building. fMain steam line pressure decreases to 1000 psig in 4 seconds at which. time the Reactor Building Main Steam Isolation Valve (MSIV) starts 'to

'close'. -The MSIV closes within 10 seconds (Technical Specification closure time limit). Therefore,-the release terminates 14 seconds after the break

- with a total of 17,000 lb, of steam released to the Turbine Building (Reference 2).

^ An evaluation was performed in Reference 2 of the pressure which would be reached in'the turbine buiding if the ventilation flow through the turbine building'to the stack was neglected. The turbine building is normally maintained at a negative pressure by the stack fans. Per Reference 2, the pressure in the turbine building (neglecting the stack discharge flow) would increase above'the turbine building design pressure within 1 second. The turbine wall or roof panels will blow out when their design pressure is exceeded.

For this Control Room / Technical Support Center (TSC) dose evaluation, the conservative assumption of Reference 2, the neglecting of the stack discharge flow, is made. Any stack discharge would result in negligible control room

' dose. The Control Room and TSC are separated by one door each from the Turbine Building open areas and are served by separate ventilation systems.

Other assumptions include:

1) The primary coolant is at the spike Technical Specification limit for Dose Equivalent I-131 of 4 .ci/g. Based on the expected ratio of iodine to noble gas concentration,-the noble gas. activity is assumed to be at 200

.Ci/g.

2) The activity concentration in the steam is conservatively assumed to be the same as in the primary coolante

3) A release duration of 14 seconds.

4) The environmental release point is at the walls and roof of_the main floor

~of the Turbine Building.

=5) When the steam is released from the main steam line, it expands due to the increase in its specific volume to 26.8 f t 3/lb, at atmospheric pressure.

6) For conservatism, plateout and condensation in the Turbine Building are neglected.

- The free air space in the connected areas of the Turbine Building is approximately 356,000 ft3 (Reference 2). The volume occupied by the released steam at atmospheric pressure is:

17,000 lb,x 26.8 ft 3/lb,= 456,000 ft . 3 If the cloud of material released is assumed to be equivalent in volume to the WP6.24 .

1 .

Mr. Darrell G. Eisenhut, Director December 31, 1984 Division of Licensing LAC-10488 Turbine Building free air space plus the volume of the steam at atmospheric pressure, its volume will be 812,000 f t3 . If the steam / air cloud is assumed to form a hemispherical shape, the diameter of the hemisphere would be approximately 146 ft, or 44.5 meters. If the cloud was traveling at 1 meter /second with respect to the ground, it would take 44.5 seconds for it to pass over any point.

1/2 4 ar3 = 812,000 ft 3 3

.r = 72.9 ft, 2r = 146 ft.

The dose equivalent I-131 concentration in the cloud, prior to any dispersion, would be:-

4 pCi/g x 454 g/lb. x 17,000 lb. = 1.34 x 10-3 pCi/cc 812,000 ft3 x (12in)J x 2.54 cm)J lft 1 in >

No dispersion will be assumed prior to the cloud passing by the control Room

-or TSC ventilation intakes.

The Control Room ventilation system air handling unit is designed for approximately 1000 ft 3/ min inlet air and 5500 ft3 / min recirculation air. The air volume serviced by the unit is about 35,000 ft3 During the 45 see the puff moves past the air intake, approximately 750 ft3 of contaminated air is taken into the ventilation system.

45 see x 1 min /60 see x 1000 ft3 / min = 750 ft3 If the accident occurred at a time when the outside air damper was mostly closed, e.g. winter, less contaminated air would enter the ventilation system.

The incoming air' mixes with the recirculating air. If xt is the concentration in the plume, the peak concentration in the Control Room is:

.750 ft3 _ 4t= 0.021 xt 35,000 ft J During each minute following the puff passage, 1000 ft3 of clean air enters

-the Control Room and dilutes the activity concentration, while 1000 ft3 og existing air'is lost.

After 10 minutes,'the D.E.I-131 activity concentration is approximately:

(9.25)(1000 ft3)(0 pCi/cc) + (35,000-9,250 f t3)(.021 xi) = 0.016 X1 35,000 ft 3 Af ter 20 minutes, the D.E.1-131 activity concentration is approximately:

(10)(1000 ft3)(0) + (35,000-10,000 f 3t )(0.016 xi) - 0.011 xt 35,000 ft J WP6.24 -

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Mr. Darrell G.' Eisenhut, Director December. 31, 1984 Division'of Licensing . LAC-10488 After.30 minutes:

(10)(1000 ft3 )(0) + (35.000-10.000 f 3t )(,ott x,) . o,0079 X1

-35,000 ft J After 40 minutes:

'(10)(1000'ft3)(0) + (35,000-10.000 ft3)(.0079 xi, = 0.0056 X1 35,000 ftJ After 50 minutes = 0.gD40 x1 After. 60 minutes = 0.v029 X1 Af terl 70 minutes = 0g7021 X1 After 80 minutes = 0.0017) xi Af ter . 90 minutes. = 0.0010 xi Af ter 100 minutes' = 0.0007 xt Af ter 110 minutes = 0.0005 xt-

. Af ter 120. minutes = 0.0004 xi The thyroid dose would.be:

D=4 kAtt, where k is the conversion factor of 9.5 x 105 Rem /hr/C1/m3 ,

7 t=0 which takes into account the breathing rate.

3 D = (9.5 x'10 5. Rem /hr/Ci/m

) i X t=0(10-0 min) + X =10 t min (20-10 min) +

60 min /hr At=20 min (30-20 min) + X t=30 min (40-30 ~ min) + Xt =40 min (50-40 min) +

Xt =50 min (60-50 min) + Xt=60 min (70-60 min) + Xt=70 min (80-70 min) +

At=80 min (90-80 min) + Xt=90 min (100-90 min) + X t=100 min (110-100 min) +

At=110 min (120-110 min) + X t=120 min (130-120. min) . . . }

3 D= (9.5 x 105 Rem /hr/Ci/m ) [(0.021 X1)(10 min) + (0.016 X1)(10 min) +

60 min /hr *

-(0.011 41)(10 min) + (0.0079:xt)(10 min) +.(0.00567 xt)(10 min) +

-(0.0040 x't)(10 min) + (0.0029 xt)(10 min) + (0.0021 X1)(10 min) +

(0.0015 41)(10 min) + (0.0010 xt)(10 min) + (0.0007 X1)(10 min) +

-(0.0005 ri)(10 min) + (0.0004 x1)(10 min) ...]

41 = 1.34 x 10-3 Ci/m3

/ D.= 16 Res thyroid WP6.24 ,

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, p.

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Mr. Darrell G. Eisenhut, Director December 31, 1984

. Division of Licensing LAC-10488 The whole body immersion dose is calculated similarly, based on the noble gas concentration. The noble gas concentration in the cloud is as follows:

200 uCi/g x 454 g/lb._x 17,000 lb._ = 0.067 pCi/cc = 0.067 Ci/m3 812,000 ftJ x (12 in)J x 2.54 cm)J

\ ft) in }

The dose would be:

D= kAt t, where k is 3.1 x 105 mrem /hr/Ci/m3 t=0 Using the same methodology as in calculating the thyroid dose, the whole body dose would be 260 mrem. The beta skin dose due to airborne radioactivity can be conservatively estimated by multiplying the whole body penetrating dose by a factor of 1.68, based upon beta air dose factors from a semi-infinite cloud of noble gases with relative concentrations expected during normal operation

(

Reference:

Reg. Guide 1.109).

260 mrem x 1.68 = 430 mrem beta skin dose.

Similar doses would be calculated for the TSC, since its ventilation _ system is similar, though not identical, in size.

These calculated doses of 16 Rem to the thyroid, 260 mrem whole body and 430 mrem skin (beta) are well within the recommended limits of 10 CFR 50, Appendix A, GDC 19. Since both these doses and the doses calculated in Reference 1 are within the recommended limits, it can be concluded that the guidelines of GDC 19 are met for a main steam line break outside the Containment Building.

Actual doses expected during this postulated event would be less than these conservatively calculated values.

If there are any further questions, please contact us.

Sincerely, DAIRYLAND POWER OPERATIVE Frank Linder, General Manager FL:LSG:ska Enclosure cc: Ron Paul, NRC, R-III J. G. Keppler, Regional Administrator NRC-DRO III Richard Dudley, LACBWR Project Manager NRC Resident Inspector WP6.24 mens ,

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