ML18045A287

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Forwards Evaluation of Opened Bypass Lines in Containment Based on Licensee Accident Assumptions.Licensees DBA Represents Realistic Accident Consequences
ML18045A287
Person / Time
Site: Palisades Entergy icon.png
Issue date: 11/07/1979
From: Bland J
NRC
To:
NRC
References
NUDOCS 8007010289
Download: ML18045A287 (6)
v • d • e


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  • DO NOT use this form as a RECORD of approvals. concurrences. cfispo1 clearances, and 5imilar actions Room No.-Bldl

$041-lOI l>U.S. G.P.O. 1977*241*530/3090 OPTIONAL FORM 41 (Rev. 7-'.

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THIS DOCUMENT CONTAINS POOR QUAtlTY PAGES I

1.

Opened By-Pass Lines in Containment at Pfllisades Accident Evaluation

-v In the Licensee Event Report 79-037 update. the licensee presented the Probable Consequences (accident doses) of the open valves -~s-su-~ing a 42" line break r _____

accident.

The findings were that if the charcoal absorbers are assumed to be 90% efficient for iodines, the Design Basis Accident doses would be less than the 10 CFR 100 limits (i~e., less than 300 rem, thyroid).

But if no

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credit is assumed due to the uestionable efficienc of charcoal in a steam

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e.!U'"ichm:n~. the DB$' thyroid dose would be 1.4 times 10 CFR 100.

(Total body doses were 1 ess than 10% of 10 CFR" 100 for b°i>th cases.)

However. in additional internal correspondence/calculations received from the licensee, the licensee has calculated a Maximum Hypothetical Accident dose. ~hich is roughly equivalent to what th~ NRC calls the Design Basis Accident/loss of Coolant Accident.

These calculated doses were more than two ------

orders_Ef magnitude greater than 10 CFR 100 for both the thyroid and total body.

lhe--e-t-t-a*eh~:-ent is an excerpt from the 1 i censee correspondence and presents an overview of the dose calculations.

The following is a discussion of the calculaticns.

y licensee Evaluation Considering the open valves, the licensee has evaluated two separate accident conditions:

L.

The Maxi.mum Hypothetical Accident (MHA) - The licensee's MHA assumed typical NRC Design Basis Accident/loss of Coolant Accident conditions, i.e., 2 hr dose at site boundary, Reg. Guide 1.4 type source term

{100% noble gases and 2si iodines)~ Crtdit is taken for the effective-ness of the containment spray system for additional idoine removal.

In determining the doses, the 1 icensee has ca 1 cul ated radi onucl ude (mass)

T~akage for the by-pass line~ being"open and simply ratioed the FSAR doses, which were calculated using the0J%/~ay containment leakage.

2.

The Design Basis Accident (OBA) - The OBA like the MHA assumes a 42 11

  • Hne break but credit is taken for ECCS operation.

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A 93% clad perfora-tion (FSAR) was assumed.

To arrive at doses, the licensee has rationed the Midland FSAR OBA doses since the Palisades FSAR did not calculate OBA doses.

NRC Evaluation A typical NRC type accident evaluation would be similar to the licensee's MHA evaluation.

The~type calculation is used to demonstrate compliance with mo the 10 CFR1siting criteria. This MHA corresponds to the NRC Design Basis

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  • Accident/loss of Coolant Accident except that containment is assumed to be isolated with o.1ffi l*~akage per day, not an opened valv~ as e~isted. at
  • Palisades and assumed in the licensees MHA calculation. This type *accident dose calculation is the one of importance in determining compliance with the regulations (10 CFR 100).

The licensee's OBA presents more realistic accident consequences, i.e., assumes ECCS operation.

However, this type dose is not referenced in any.regulations. Appendix K to 10 CFR 50 addresses ECCS operation*

but does not address accident doses

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}~r&scti.c 2-hr MHA Dose 10CFRlOO lOCFF To!nl Body (Skin)

Rem 2,200

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Thyroid (Rem)

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19L,ooo i.11

{0% charcoal efficiency) (~ charcoal efficiency) 19,1'00 lal. 7 (90% charcoal efficiency)

(90~ charcoal efficiency MHA AJlALYSJS Total Body MHA skin dose -

2 hr given:

10.3% mass loss in 2 hr throush 3" line given:

FSAR Sec. l~ - 0.1% ~ass/de¥ =(~~lJ {2) = 0.0083~/2hr ratio or ioss = o.~~8~3 = i,236

  • given:

FSAR Fig lL.22.7 2 hr dose= 1.8 rem /f>-Y

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25 300.

300 ll,236) (1.8 re~) = 2,200 re~

Thyroid MHA dose ~ 2 hr given:

1 min 38 se.c delay prior to hydrazine addition (VNWL 35-77) vith_~urrent tank pressurization given: Table 3 {RAE 58~77) can be modified to represent 1.63 min time delay vs 5.0 min or table:

0.01 l.. 39 o.1L Ti:ce Interval (min)

Core Iodine Leaked e 0.1'/./aay Mass Fractions Lee.Y.ed Ratio Core loci~

0 - l.63 1.63 - 16.3 16.3 - 60 60 - 120

(%.x 10-5) 2.8 11.l lli.3 12.1 i.0.9 3" Purae 0.1~/day*

(% x 10-5)

(~ x 10-5) 16 1000 11.3 150,000 lOlt.

350,000 303.

530,000..

1t17.

1.i.2 x 103 l.Lla x io3 1.16 x 103 1.27 x 103

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0.16 0.17 0.)6 0.53

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. from \\.he ubcve, rntio of 1.hp*oid do~es for O. l'/./~ey cu:c to 'lhc 3" Pl:: Ge y~~vc cosc iz; 0.53/~0.9 x lO~s* = 1.30 ~ 103 Dose vas previously o.nalysed as ih9 Rem from containment lenkaac (lli9 Rem) (1. 30 X 103) =

  • 191',000. R~m :

Becnuse purge line lesY.ase i.s through the hydrogen purge charcoal filter, dose could.be.up to a,factor of 10 loYer; than this, or 19,hOO Rem.

Hovever, steam'..

condensation vi.thin the filter could limit efficiency to an linknovn desree.

LOCA Analysis -

DBA 1'2" break per FSAR l~.17.5

&iven:

Accident analysed in Midland FSAR {Sec 15.6.5 and Table 15.6-10)

@ 100% fuel clad perforation.

This is conservative in relo.tion to Palisades FSAR Table. lh.17-1', vhich indicates vorst case 93~ per-

!oration:

Also includes primary coolant.

Midland Total Body Skin Doses =

(2 hr)

O. 00183 rel!? {"Derf)

-4 8.0 x 10 ratio

2. 29 rem (l*lRA, melt) 0.213 rem (t1er1')

_Hid.land Thyroid Doses = 98_9 rem {HH.A, melt) =

{2 hr) 2.15 x 10-3 ratio Palisades Skin of Total Body = (2.200). (8.*. 0 x io-2') = l. 76 rem

__ P~lisadcs Thyroid = (191' 1000) *(2.15 x 10-3 ) = 1,17 rem Palisades thyroid vit"b 90% et":ficiency charcoal= (19 11'00).(2.15 x l0-3) = 1'1. 7 rem

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