ML20206J600

Advises That NUREG-0956 Support Calculations Using ORNL Trends Code to Evaluate Influence of Containment Chemistry or Retention of Hi Can Also Provide Useful Info for General NUREG-1150 Issue Paper,Per Telcon Discussion

ML20206J600
Person / Time
Site:	Surry, 05000000
Issue date:	08/08/1986
From:	Kress T OAK RIDGE NATIONAL LABORATORY
To:	Chan L NRC
Shared Package
ML20204G644	List: ML20206C066 ML20206E142 ML20206F071 ML20206F086 ML20206F182 ML20206F313 ML20206G821 ML20206G928 ML20206H081 ML20206H113 ML20206H144 ML20206J252 ML20206J270 ML20206J368 ML20206J403 ML20206J600
References
RTR-NUREG-0956, RTR-NUREG-1150, RTR-NUREG-956 NUDOCS 8704160132
Download: ML20206J600 (5)

Text

.. , Jo $ M Sh./S$

O TO: L. Chan FROM: T. S. Kress, Manager of ORNL Source Term Progress

SUBJECT:

Utilisation of TRINDS Results for Cuidance en the NUREC-Il50 lesue Paper on Iodine Chemical Form As we discussed over the telephone, the recent NUREC-0956 support calculations using the ORNL TRENDS code to evaluate the influence of containment chemistry or retention of HI can also provide useful in-formation for the general WREG-1150 issue paper on todine chemical form. In particular, the calculations evaluated the retention of ,II within the SURRY containment for a TMLB'-6 sequence and in the Peach Bottom reactor building (RB) for a TC-6 sequence. These results can be used to evalusta the fraction of the HI that enters containment or I3 that eventually leaks out (F00NV for surry and DF,g for Peach Bottom in NURIC-1150).

As outlined in our earlier letter (E. C. Desha to L. K. Chani May ,

22, 1986) TRENDS was used to calculate three variations of the Surry THLB' sequence designed to parametrically evaluate the consequences of different levels of conversion of CsI to HI within the reactor coolant system (RCS): Case 1 assumed no conversion to HI and wee conducted as a repeat of the Source Term Code Package (8TCP) original calculations but to include any possible chemical effects when the release is all as l CsI. Case 2 assumed that the iodine that had been calculated by the STCP to have been retained as Cet in the RCS was fully raleased as HI.

This was accompanied by a Cal release into containment given by the  ;

l original Cs1 release calculated by the $7CP. Case 3 assumed all iodine 8704160132 870408 l PDR NUREG 1 50 C PDR

1 l

calculated by the STCP to have been released from the fuel entered the containment as HI.

You any also recall that the TRENDS calculations reported in the May 22 letter used STCP calculated containment thermal hydraulice that 1

included the "wanhout" effect due to what is now believed to be $

erroneously predicted massive early condensation of moisture onto the aerosol particles. The TILENDS Cases 1, 2, and 3 above were therefore, rerun with new STCP thermal hydraulic behavior that suppressed this washout effect. The results of the new TREND 8 Surry THL5'=6 calcula-tions are summarised in Table 1, below Table 1. Summary of TRENDS results for iodine releasa Surry 1ML8" early containment failure Case II

1 2 3 Total iodina released into 6.2 26 5 26 3 containment, kg

• Total HI released into 0 20.0 26.5 containment, kg Total iodina released from 5.7 14.3 13.5 cont ainment , kg Total RI released from 0 8.6 12.5 containment, kg For the most worst case (Case 3), the total HI released from containment is 12.5 kg and the FCONV valve for HI ist rCONv,1 - M .03 l

l A number of run variations were also made for the Peach Botton TC-6 sequence to evaluate the influence of the conversion enount as well as the influence of the Stand-By Gas Treatment System (SGT$). Pbr the

l

~ '

. 1

. i i

I case of complete conversion to HI and no operation of the OCTS, the TRENDS results for the dispositions of HI is summariasd in Table 2 below:

Table 2. Summary of TRENDS results for the reactor building retention of HI for Peach Bottom TC-4 sequence (results at termination of calculation)

Geseous iodine still airborne in RB, kg 0.01 Iodine deposited on RB ourfaces, hg 35 Iodine released from RB as HI gaseous. 06 kg Iodine released from RB as HI adsorbed 1.0 onto aerosols, kg From the results summarised in Table 2. the total HI that entered the RB is given by Total RI into RB = 0.01 + 3.5 + 0.6 + 1 0 = 5.1 ng The total released from the RB is given by Total HI released = 0.6 + 1.0 = 1.6 kg ,

l Therefore the RB decontamination f actor for HI is nominally 01,1 .M.3.2 l This corresponds to the NUREC-1150 base case for which the equivalent DF '

for aerosols was estimated from the STCP results to be only ~1.5. This illustrates that a reactive ses that reacts with both aerosol surfaces and building surf aces can be retained more effectively than aerosols.  !

The SAARP values and degrees-of-belief for aerosol retention in the RB are:

DF e (aerosols) 15 3 1.5 1 {

Degree-of-belief 0.17 0.37 0.34 0 11 l

i l

1 l

1 A

., - l From Table 2, it is seen that in the TRgNDS calculations some portion of the released HI is directly as gaseous HI but that an additional amount 26 released as adsorbed HI onto aerosol particles. Therefore an overall W for HI can be defined as heal HI into O Dr(HI) a Gaseous HI released + adsorbed EI release 3

,_ 51 .

(o,,) J1.0) 15 __

DF(aerosols)

Therefore if it is assumed that there is 3 uncertalaty associated with the gaseous fraction of the release, then the DF valves for RI that would correspond to the 3AAAP values above would be.

Case 1 2 3 4 DF (aerosol) 15 3 1.5 1 DF (RI) 7.5 4.7 3.2 2.4 Degree-of-belief 0 37

0. ~ 0.34 0.11 hwever, it is more reasonable to expect that there is considerable un-certainty associated with the calculated gaseous release as well as the aerosol ralesse.

As no detailed uncertainty analyses have been made for the

'$ IDS models there is no firm basis for establishing the uncer-y contribution associated with the gaseous re'er.se cal culation.

If

.a e t akes the view that the airborne aerosol / gaseous stature has a rela =

tively constant partition coefficient (i.e. ratio of tha amount of HI airborne as gaseous HI to the snount of HI adsorbed onto airborne aerosol particles, one car. define separate decontamination factors for both gaseous HI and aercools:

A 8

+A DF, = 3 1=[A. +1 l

I I

l

^

\

1 l - . l l

and A, + A, A, D F, =

e = 3 e- + 1 where the A valves are coefficient in the assumed concentration equation 1 4C i g * ~~ A C De t g and 1 is for surface deposition of gaseous species, A, is for aerosol is!!out, and 1, is the leakage contribution.

The overall decontamination factor, DF g ,, for RI mast include the quantity leaked as gas plus the quantity leaked as absorbed onto aero-s ole.

If it is assumed that the entire uncertainty in both DF, and DFg is due entirely to uncertainty in A, (i.e. as a result of uncertainties in the leakage flow resulting from uncertainties in the He burning cal =

eulation), then (while not entirely rigorous) a good approximation tot he overall DFgo for RI can be had by using a constant correction factor to the DF, that is given by tta base case ratio 3 2/1.5 = 2.1. There-fore the recomunended reactor building DF's for MI and Degrees-of-Belief are:

DF gr Deg(ree}-of-belief 35 63 32 1 0.17 0.37 0.34 0 11 cc: R. Andaraan E. Seahm A. Dhlinauskas C. Weber S. Wisboy i

t

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