ML20128N952

Forwards Comments Re Quest Study of Surry Tmlb Scenario. Clarification Needed Re Where Data Obtained for Solid Triangle (Sascha) Data Points in Figure A-3

ML20128N952
Person / Time
Site:	Surry, 05000000
Issue date:	04/30/1984
From:	Reynolds A VIRGINIA, UNIV. OF, CHARLOTTESVILLE, VA
To:	Jankowski M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20127B155	List: ML20127B150 ML20128M845 ML20128N097 ML20128N476 ML20128N493 ML20128N545 ML20128N599 ML20128N657 ML20128N663 ML20128N743 ML20128N952 ML20128P693
References
FOIA-85-110 NUDOCS 8507130176
Download: ML20128N952 (6)

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UNIVERSITY OF VIRGINIA P mAm DEPARTMENT OF NUCLEAR ENGINEERING AND ENGINEERING PHYSICS NUCLEAR REACTOR FACILITY l k ) SCHOOL OF ENGINEERING AND APPLIED SCIENCE

, P u 2 CHARLOTTESVILLE. VA 22901 April 30, 1984 Telephone: 841 924 7136 Michael W. Jankowski Accident Source Term Program Office Office of Nuclear Regulatory Research U. S. Nuclear Regulatory Comission Washington, D. C. 20555

Dear Mike:

I am enclosing a copy of my coments en the QUEST study of the Surry TMLB' scanario. I am sorry that I have not had time to do justice to this review. It is very difficult to assess the QUEST study due to its complexity. -

Sincerely, ,

A. B. Reyno s. Professor Dept. of Nuclear Engineering and Engineering Physics ABR:ph Encl.

8507130176 850425 PDR FOIA l ALVARE285-110 PDR

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Pr'eliminary Comments on the QUEST Study A. B. Reynolds I as still unprepared to make significant comments on the QUEST study. I think a meeting of the revis.v committee would be needed to perfo m an adequate review of the material. There is so much material in the DILB' report that was sent to us that I as having trouble focussing on the really significant uncertainties. The combined.

insights of the peer and observer groups might shed the necessary light and provide thA perspective required to assess the QUEST results.

A proper assessment of the QUEgT' study is important. The vide variations in possible results suggested by the Q0EST study cast greater doubt on the value of the BMI 2104 results than I think is warranted, but I cannot argue this working alone.. On the other hand, if the review committee comes to a consensus that the results are as uncertain as QUr.ST indicates, then little definition can be said about the source term unless the containment failure working group demonstrates that early failure is not credible.

Despite my lack of time to assimilate auch of the extensive work reported by SANDIA, I would offer a few specific comments, as noted below.-

l Specific Co u nts Tellurium Release The first point to note is that I as perplexed as to where the data was obtained for the solid triangle (SASCHA) data points in Figure A-3.

I have plotted the tellurium data points from the SASCHA tests, as noted 1

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in red (open A,D , and o's) on,the next page, and they are totally

different from the data in Fig. A-3. Also I believe there was a factor 4

of 10 error in the plotting of the.HI-2 datus. My understanding of the correct placement of this point is also shown on the next page. The Ku w 772 curve for Te appears to be close to the upper limit of the

) release rates for the data as I have plotted them.

j In Appendix A, and elsewhere, tellurium is included with iodine and cesium as a volatile fission product, and it is argued that the volatile 1 .

fission products likely are released from the fuel early. Yet I see a factor of three variation in Te releases in Fig. 6-27, from - 30%

l release in most cases to 901 in the late high case. This is nearly as

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I wide variation as Barium (except for the late low case), Technetium, and total mass aerosolized (Figures 6-28, 6-28, and 6-29).

Moreover, the effect of the presence of oxidized versus unoxidized

! zirconium on tellurium release was ignored, even though this effect has i been reasonably well established experimentally.

The suspended To for the late high case for code-input uncertainty (6 ) reaches 7 or 8 kg for about an hour period, while only - 1 kg is c

suspended for the base case. (These numbers compare to the total Te ,

inventory of 25 kg.) One notes that 11% of the Te is released to the I

environment in the Surry, Volume V calculation for the TMLB'-6, accident

, (Table 7.16. Vol. V). This is a high release so that Te may be important for the TMLB' accident. Hence, treatment of uncertainties in Te release data may have important consequences. Does ais-plotting the data on Figure A-3 of the QUEST study have auch significance? I find it disturbing if either mis-plotting the data or ignoring the effect of i

zirconium on Te release has little effect on the final release to the a environment.

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Next, I note the effect of 6 uncertainties on Te release. The p

uncertainties in temperature histories in the 6 uncertainty section p

lead to Te release uncertainties similar to antimony, barium, and molybdenum releases (compare Figures 7-3, 7-4, 7-6, and 7-7). Hence Te acts like a low volatility element, not like the high volatility iodine i and cesium. These results later propagate to potentially large Te releases relative to the base case (Figure 7-30). Again I question the effect of errors in the basic Te release data (either the mis-plotting or the ignoring of the effect of Zr) on these QUEST results.

Overall Results . .

I note that the end result of QUEST is not the ,same as in the BMI study. The BMI analysis concludes with fraction of fission products released from the containment. QUEST does not present this. Based on the QUEST results of fission products suspended versus time, perhaps that ratio can be related to the fission priwiucts released.

I note that most of the QUEST results fall below the BMI base case, which is encouraging. However, some of the early failure cases fall auch above the EMI case, and some of the high late cases fall somewhat above the EMI case.

i Bence, it is difficult to assess the proper source term, especially l l if early containment failure is possible, without more understanding of l l

the complex QUEST analysis than I now have. l Effect of Natural Convection velocities The presence of large natural convection velocities relative to

, forced-flow steam velocities identified in the QUEST study may be i

important. This appears to create significant differences from the BNI 3

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analysis.

n{e problem is so complex, however, as discussed in Appendix B, affecting condensation. of fission products on urosols and solaero~

settling in the' core versus the upper plenue in aadition to temperatur e distributions, that I catsot tell yet how important all of this is It .

appears to be quite important-somewhat like the whole problem of resuspension and remayoration that was also neglected in the BMI base - '

i case analysis. '

In the time availt.ble to me so far, without a meeting of the entire peer review couaittee. I have difficulty assessing a probina of this kind. /

• J*

Uncertainty in Steel and Zirconium Melt $'ractions in the Melt Uncertainties awa=faed in CORCON-VANESSA in both ste and zirconium melt fraction in ths, melt are large (4000 to 70 000 kg for steel; O to 80% for Zr-Table 4-2). ,

I, realize that' examining such large "

uncertainties in one code does not necessarily imply that the MA2 e 3 cod actually leads to such large uncertainties in these parameters

, though I ,

am concerned that some may look at Table 4-2 and wonder that , if our uncertainty range has to be this large, then diive have any cohfidence at all in what MARG is telling us? \

I Therefore I looked at the MARG uncertainty analysis to see if I J l

could gain any information on the segel and zirconium salt fraction in \

the melt. +

results.

So far I have not/ been able to determine this from the N ACH 1 I do note that there is not a large variation in'hydrogeIn

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generation from the MARG results.

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This wo dd indicate that there is a

not a l'rge variation in the amount of zirconium that reacts with steam .

i Hence there should not be the tremendous variation in zirconium available in the melt. ,

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