ML19296C867
| ML19296C867 | |
| Person / Time | |
|---|---|
| Issue date: | 02/15/1980 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| References | |
| REF-10CFR9.7 NUDOCS 8002290004 | |
| Download: ML19296C867 (40) | |
Text
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U NIT E D STATES N UCLE AR REG UL ATORY COMMISSION In the matter of:
BRIEFING ON COMPARISON OF RISKS OF PLANT OPERATION AT LOW POWER VERSUS s.
FULL POWER PIaee:
Washington, D. C.
Date:
February is, 1980 Pages: 1 - 28 INTERNATIONAL VERBATIM REPORTERS. INC.
499 SOUTH CAPITOL STREET. S. W. SUITE 107 WASHINGTON, D. C. 20002 202 484-3550 a
800229000y
paGE N C.
s I
UNITED STATES OF AMERICA I
I NUCLEAR REGULATORY COMMISSION l
_____________________________x 1
4 In the Matter of:
BRIEFING ON COMPARISON l
3 OF RISKS OF PLANT OPERATION AT LOW POWER VERSUS l
l I
FULL POWER 3
X l
s to li l
1 "*
Commissioners' Conference Room 1717 H Street N.W.
f IU Washington, D.C.
l 14 Friday, February 15, 1980 l
Id The Commission met, pursuant to notice, for 17 presentation of the above-entitled matter, at 2:35 p.m.,
!S Victor Gilinsky, presiding as Chairman.
19 BEFORE:
20 VICTOR GILINSKY, Commissioner
- ]
RICHARD T.
KENNEDY, Commissioner PETER A.
BRADFORD, Commissioner I
JOSEPH HENDRIE, Commissioner I
24 I
15
.' r s e jrs 1
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I
_P _R _O _C _E _E _D _I _N _G _S l
I COMMISSIONER GILINSKY:
Harold, we are all ears.
I I
2 MR. DENTON:
All right.
Are we in session?
l l
1 COMMISSIONER GILINSKY:
We are in session.
f MR. DENTON:
You've requested a discussion of the l
l 6
relative risk of the proposed fuel low power testing program 7
for the near-term OL's versus the risk of full power long term g
operation.
I Dick Denise, who is with me, has some slides and a
- g presentation to compare the risk for the various types of l
accidents that might occur.
COMMISSIONER GILINSKY:
Fine.
MR. DENTON:
In general, we'll give you a bottom punch line if you think the relative risk is less than the I
factor of 100.
l 13 i
MR. DENISE:
Okay; Norm, the first slide?
16 i
This is the basic conclusion that we have reached 17 that the public risk doe to the fuel load and low power test 18 programming is less than the public risk for full power long 19 term operation by a factor of 40' to 4000.
And, we'll proceed 20 to demonstrate to you how we arrived at that number.
21 g
COMMISSIONER GILINSKY:
Well, this is per unit time
~,
or what?
I f
2.
MR. DENISE:
It's in instantaneous risk or the inte-24 grated risk, either one.
i e
i
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pacz sc.
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I COMMISSIONER GILINSKY:
Well, the integrated risk has got to be less --
l I
MR. DENISE:
Even less than that.
l 4
COMMISSIONER GILINSKY:
Because, I'm sitting here thinking of a short period of time from the low power phase and i
6 a rather longer period of commercial operation.
7 MR. DENISE:
This is n. ore correctly the instantaneous l
I 3
risk, although I did factor in 6 months versus 4 years.
That would be another factor certainly.
9 COMMISSIONER GILINSKY:
Good enough.
g MR. DENISE:
Next slide.
11 These are the major factors which contribute to the j
1,s first one is a reduced fission product build I reduced risk.
The 1"i up in the inventory, which is due to the restricted power level,
l.L and the intermittent nature of the operation; I'llgomoreintol IS j
detail o.. that later.
16 t
I COMMISSIONER GILINSFY:
Could you give quantitative 17 I
on that?
18 MR. DENISE:
Well, the value that we are thinking 19 about in terms of maximum power is 5 percent.
20 COMMISSIONER GILINSKY:
Yes.
l 21 l
MR. DENISE:
The value which is most probable is i
3 percent, 3 to 4 percent.
COMMISSIONER GILINSKY:
Oh, I see.
l 1
's MR. DENISE:
We'll have some charts later on which 3
l
, _ _ - ~. -
"0 PAGE NC.
l I
will show that.
COMMISSIONER GILINSKY:
As a maximum or as an average i
or what?
l l
A MR. DENISE:
It probably will be an average over i
i some 1-day or 2-day period.
But, the maximum would apply when l
6 you take it over that 1-or 2-day period and it would be, prob-l ably, 2 to 3 percent.
t 7
MR. DENTON:
What Dick is saying is that not all of 3
the low power tests are run at 5 percent, and there are periods 9
i of time when a reactor isn't run at all in low power testing g
programs.
COMMISSIONER GILINSKY:
Right.
MR. DENTON:
You make certain assumptions for your code calculations --
14 i
MR. DENISE:
Right, and I'll show you the graph that 1.5 l
i shows you the kinds of assumptions that we made, j
14 i
COMMISSIONER GILINSKY:
Fine.
17 MR. DENISE:
Another factor is the elimination or 18 the lowered probability of some transients and accident, and b
I'll mention those, for example, if you are operating at low 20 power and the turbine is not on and you are not generating Il steam, you are going to void things like turbine trip from full power and its cascading effect should void a loss of heat i
23 i
water flow and its effects because these systems are not t
b operating.
I i
1 f prTYppeancreak '/EMaaned 4W TU.1 ' aC
irs e irs 5
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I going te focus on when we talk about fuel load and low power i
l testing programs.
There is fresh fuel in the reactor.
There's 2
a clean coolant; now, this becomes very important in some l
l 4
accidents.
For example, when we analyze accidents at full powerj we assume that there is 60 microcuires per gram of ioding 131 3
circulating in the coolant.
Under this phase of operation, we
+
7 expect essentially none.
3 There is the low power limit, as I mentioned before, l
5 percent, and the interrittent operation at low power; we 9
exp t about 2 weeks at 2 to 3 percent power range in this 2 to 10 3 weeks to be accomplished in about 1 month.
And, that's what we are told is to be expected in a low power testing phase; which is when the core is at antisignificant power.
I COMMISSIONER KENNEDY:
And, Dick, you are taking a 14 l
6 month pursuant period; is that right?
13 MR. DENISE:
Yes, correct.
I6 i
t There will be low decay heat levels which are much 17 less than the 5 percent equilibrium level, if you assume that 18 it was at equilibrium.
19 COMMISSIONER GILINSKY:
You will tell us how fast it 20 l
takes to approach that level.
21 l
MR. DENISE:
That level?
I don't have a viewgraph i
-4 on it that will tell you.
j COMMISSIONER GILINSKY:
Okay.
- 4 MR. DENISE:
We start out with low fuel temperatures,,
15 3
jrs e jrs 6
1 sacg sc.
1 for example, the fuel temperature, the average fuel temperature 2
in the core at the 5 percent power would be about 580 degrees, and that's only about 30 to 40 degrees above the coolant l
A temperature compared to about 1150 degrees when the plant it l
i 3
at full power.
f i
6 COMMISSIONER GILINSKY:
Which temperature is this now?;.
l 7
l MR. DENISE:
The average fuel temperature.
I COMMISSIONER GILINSKY:
I sec.
And, what is the g
center temperature?
9 MR. DENISE:
I would say no more than 5 degrees above 10 that.
11 COMMISSIONER GILINSKY:
as little as that?
12 MR. DENISE:
Yes, at 5 percent power.
13 I
COMMISSIONER GILINSKY:
Five degrees above the 580 i
14 l
degrees?
13 MR. DENISE:
Well, I gave you core average temperature.
16 Now, if I went to the center line of it, that average pin 17 would be just a few degrees, say about 5.
j COMMISSIONER GILINSKY:
What is it in normal operation'?
19 MR. DENISE:
1150 degrees, core average.
20 COMMISSIONER GILINSKY:
Yes, but what is this, the Il center of the fuel pin?
i MR. DENISE:
I don't have the numbers with me.
l
-n COMMISSIONER GILINSKY: Isn't it way above that?
i f
MR. DENISE:
Oh, yes.
Well, I'm sorry -- you mean the i
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hot pin or the center of the average pin?
I 2
COMMISSIONER GILINSKY:
No, the center of an average l
j pin.
i 4
MR. DENISE:
The center of an average pin would be f
I J
about -- I'd say 500 degrees above that core average.
6 The reason I'm giving you this number is because it 7
is indicative of the amount of store energy --
g COMMISSIONER GILINSKY:
No, I understand that it's a 9
very important point.
But, I'm just trying to get the numbers right.
0 I
What is the temperature at the center of a pin, an
- )
average pin in normal cperation; what is it?
l i.
MR. DENISE:
I don't know what it is for this typical 1
plant, maybe the man behind the viewgraphs looked it up for me; he gave me this temperature.
Norm?
MR. LAUBEN:
1480 degrees.
I 17 MR. DENISE:
There he is, thanks.
la MR. LAUBEN:
You wanted the normal center line 19 temperature of the average --
20 COMMISSIONER GILINSKY:
Yes.
21 MR. LAUBEN:
About 1480.
f l
4 MR. DENTON:
And, what's the cooresponding temperature',
22 I
Norm, for 5 percent power?
24 I
MR. LAUBEN:
About 590.
i 3
I
irs irs 8
i pacz sc.
i I
MR. DENISE:
And as already mentioned, the turbines 2
not running, no electrical power being generated, and will I
2 reduce plant configurations.
l 1
4 I wanted to make a few points about the reduced f
I 3
decay heat level.
Just by way of example; it takes 2 days j
i 6
to dry up the steam generators if you isolate them and are at l
7 decay power; that is if you SCRAM the reactor and you take 3
ut decay heat only through steam generators.
And, about 5 l
9 gallons per minute will make up that boil off rate.
s The natural heat losses through the system, that is g
through the insulation around the piping which are passive
- )
systems, are about 7 megawatts.
And, the decay heat level in i
the core would reach that about 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> after shutdown.
So, i
13 i
even just heat losses would take care of that.
14 The total heat losses when the plant isrunningwouldj IJ i
i be about 3 megawatts, but that would inc_ude coolant around j
16 I
the control rod drives and other systems, so that's about 3 17 megawatts compared to the 7/10's of a megawatt, which are la just strictly passive heat losses.
19 COMMISSIONER KENNEDY:
7/10's of a megawatt?
20
. tR. DENISE:
7/10's of a megawatt is passive.
- Now, Il as I say, the 7/10 's of a megawatt is about what you would have '
22 in the core 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> after shutdown.
The shutdown decay heat w
l rate is about 2 megawatts when you shutdown, and just contrast '
A ing that to another number, the pump heat; that is the heat If f wTvereAtosas VDeceTTim RE7*:rtfUtf. I'*C
9 j
jrs jrs nacz so.
l 1
i input
,m one pump running, that's about 4 megawatts.
I'm l
trying tr build for you a picture of how low a level of heat j
3 w'
c dealing with.
l 1
4 COMMISSIONER GILINSKY:
This is after what sort of l
3 operation?
6 MR. DENISE:
About 6 months of operation.
7 COMMISSIONER GILINSKY:
So, this is at the end of i
i 3
that operating period.
j i
9 MR. DE*ilSE :
Yes, if you operate it straight up
- o for 6 months.
COMMISSIONER GILINSKY:
At the start of that period, j;
it would be zero, presumably.
MR. DENISE:
Oh, yes.
COMMISSIONER KENNEDY:
But, you are not implying or 14 leading to a build up to that point?
1.5 I,
MR. DENISE:
No.
I'm saying step up and operate at I
that point.
Just to give you a feel for abounding numbers of 17 the decay heat being only half the heat that's put into the 18 s-l stem by one pump running, and there are four pumps.
19 And, the-fact that you can 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> after shutdown, 20 the system looses the decay heat' through in insulation around 21 the system.
O i
The next slide, Norm.
This slide is intended to 22 illustrate to you the kind of heat up that you would have or
- 1 the kind of build up of fission products that you would have.
i
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i l
jrc jrs 10 3
nacz sc.
I i
I The figure at the bottom shows a scenario wherein you would go 2
up to 5 percent power for a day and then back down and up to 3
5 percent power and back'down; this is, I believe, based on 4
the information that we have much more restrictive or much I
5 l
more power operation then they anticipate at all, as they say 5
they anticipate a couple weeks at 2 to 3 percent power witnin 7
one month.
3 Now, that kind of numbers that I've given up there i
9 l
on the chart show the iodine 131 build up.
Now, the iodine 131 '
I plotted because iodines constitute about 50 percent of the 10 radiological risk; telluriums I haven't plotted, they are about 25 percent; ruthenium, 10 percent; cesiums, 5 percent; strontium),
..,u 5 percent; and itrium (?) about 5 percent of the risk if you go to a coremelt accident as described in the WASH-1400.
i This shows that the iodine 131 build up which is
- 5 j
1 indicative of all the iodines, goes at a very slow rate if l
!4 you are considering operation for a day or for half a day and i
17 then it would decay of f somewhat.
In fact, what I've shown 18 here is rather stylized, the up and down operation where it i
19 says, iodine 131 intermittent at 5 percent.
But, the end l
20 3
point at 40 days, is about 2 percent of full power.
Now, that 21 means that if I operate in an intermittent mode like this, C
l that the iodine concentration is about of what I calculate l
22 l
I for steauy operation.
A I
So, I have steady operation at 5 percent which reduces 2
i
. =
4 jrs 3 jrs 11 nacz so.
the inventory and then I say on top of that, there is another
~
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factor to considering the intermittent operation.
I i
3 As you can see, the cesium takes a long time to l
4 build up, even after all of the test program is conducted you would expect to be well less than 1 percent of the full power e
inventory.
The strontium, you would expect to be well less 6
than 5 percent.
7 COMMISSIONER KENNEDY:
Is it coincidence that the steady state operation at 5 percent would generate 5 percent of the full power inventory of iodine?
10 i
1 MR. DENISE:
Well, it's not a coincidence; it is 11 a derived fact.
12 MR. DENTON:
If the half-life of the isotope is i
short compared to a period of operation, you tend to equalize.
So, that shows that after 5 or 6 half-lives, iodine 131 does 13 stablize that percentage that you would expect.
16 MR. DENISE:
It's an 8 day half-life, so if you go 17 up to that point, it would steady --
13 COMMISSIONER KENNEDY:
It would steady out at any 19 percentage of operation with essentially that percentage of total inventory.
21 MR. DENISE:
Correct.
If you operate at 2 percent, it would steady out in about 40 days at 2 percent.
I MR. DENTON:
What it does show, too, is many of the i
'd long -- many of the more hazardous isotopes has long half-lives
'5 l
I f
a
l irs:
irs 12 asaz so.
i t
and it takes them a long time and you're not getting any i
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where near the percentage of power from extended operation.
l 2
MR. DENISE:
Okay, next slide.
I This slide is --
MR. DENTON:
It shows that itwouldbeaconsiderablel 5
f safety advantage in requiring fresh cores at the end of 30 7
days.
I 3
MR. DENISE:
This slide shows the accident we normally 9
analyze and report --
10 COMMISSIONER KENNEDY:
If you'd reprocess all that 11 fuel, you could probably do it.
);
MR. DENISE:
The accidents which we normally analyze
- 3 and report in the Safety Evaluation Reports, and I've shown l
9 here the full power calculated doses; those doses are in g
rem to the thyroid and the numbers I'm giving as an example l
are for Sequoyah and the Sequoyah exclusion area.
l
,6 Now, the point of this slide is to show that there ire a variety of accidents which make up the preponderance of the risk.
And, there are two which stand out, at least in a 19 way we conservatively analyze them posing the greatest po-20 tential for radiological dose; that is, loss of coolant and 21 steam generator tube rupture.
i C
I t
I will later on go through each of these accidents to:
22 l
show you why it is that there is so much less severe than 5
{
percent for a factor of 20 we tend to show you.
l me i
irs irs 13
,,c; ye, I
The next slide.
This deals with a loss of coolant I
2 accident and let me say first of all, this is with a very severely degraded ECCS system.
If the ECCS worked, we would nott t
l be talking about temperatures which melted CLAD or failed to j
A CLAD or let any of that out.
So, we run a number of cases with a degraded ECCS 3
7 and I've only noted a couple of them here to give you some 3
perspective.
The first one is that low steam flow cools the low 9
p w r core without any CLAD rupture or metal water interaction.
10 That is about 5 pounds per second of steam flowing through
,l i
the whole core would keep that core cooled and keep it below CLAD failure point.
The boiloff of the reactor vessel water; now this 14 is what occurs after the reactor vessel fills from the accum-13 ulators, boiloff would not occur ur.til about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> later 14 versus 33 minutes for full power core.
And, at that point, l
17 you would reach where -- the point where we calculate CLAD 18 melt.
19 New, there are many calculations that you can do and 20 I
show that given a day after the core is uncovered, if you hung 21 it in air, it might be coolable.
It's probably even a more restrictive excmple than that, because we have the core 22 essentially blocked at the bottom with some coolant or the
- 4 sub assemblies are, and there's only a little bit of steam flow 2
i n TTD4944DCM &b YN D Ad NNRM 87.C
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through that.
People will tell you that if you hang the sub I
assembly in the air, you could probably cool it; and I suspect f
2 2
you could come pretty close to that.
l l
4 l
COMMISSIONER GILINSKY:
This is at the end of a 6 5
month period?
6 MR. DENISE:
Yes, these are at the end of 6 months.
7 These do not take into account the intermittent operation.
3 COMMISSIONER KENNEDY:
This is a steady, 5 percent 9
operation?
i MR. DENISE:
Yes, sir.
10 COMMISSIONER GILINSKY:
For 6 months or 3 months?
- )
Y MR. DENISE:
Well, it's for 6 months, yes, sir, i
I i
l COMMISSIONER KENNEDY:
So, that is really the upper 1
bound.
14 MR. DENISE:
Certainly, it's the upper bound even IS l
bounded.
l 16 i
COMMISSIONER KENNEDY:
Which is well beyond anything
?
17 l
l that they contemplate or we'd expect from them.
MR. DENISE:
Right.
And, we could cool that core by 19 and cool it -- I mean, cool it and keep it before below CLAD, 20 below metal water reaction point by merely pumping an 8 gallons 21 per minute which is well within the capacity of one other 22 reciprocating charging pump, so we have no low pressure / high j
22 pressure problem at all.
24 MR. DENTON:
I think that this is a good point to l
15 t
a 15 pacz sc.
- s. tart rcp I
emphasize:
why we don't see 5 percent power as presenting any problem with regard to the hydrogen and the ice condenser.
1 l
Now, these Westinghouse plants have about half, I 4
i guess, the zirconium that reactors have; and even though it's in' i
I a small Wescinghouse containment, it's a couple of times larger i
5 than the smallest GE plant.
j I
i And so, in terms of the metal water reaction required 3
to get into a problem with the ice condenser, the Westinghouse 9
plant is four or five times the amount of metal water reaction 10 of a GE plant.
So it's -- the ice condenser is kind of in a class between big dry -- and GE plants.
11 Five-percent power operation, we see metal problems i
l r3 we don't -- with these kind of times it's inconceivable that i
- 4 you'd end the metal water reactions in the --
- c COMMISSIONER GILINSKY
Well, what you're saying is, g
that the likelihood of such a reaction is, is very much reduced;,
I and even if you got it, the amount of fission products would be very much reduced.
MR. DENTON:
That's correct.
19 COMMISSIONER GILINKSY:
That could be released.
MR. DENISE:
But it does have less capability than a Il dry containment.
We will address that before full-power l
22 i
1 operation in the report that will be to you within a week.
22 I
COMMISSIONER GILINSKY:
Okay.
l MR. DENTON:
Now the risk-reduction bases which I've,'
2-l
16 l
0 sacz sc.
l I
listed are the source term, that is, the fission product i
e inventories.
And I've taken what I feel is conservatively to l
f be a factor of 40.
That's factor 20 from, from the 5 percent L
I and a factor of 2 for the intermittent operation.
i The lower containment pressure is not so straight-6 forward.
But an ice-condenser plant such as Sequoyah has a 7
lower peak pressure by at least a factor of 2 than it would at 3
full power because of the decay heat which is dumped into the l
9 containment being much lower.
Ar:d the leakage was_ reduced by 10 at least a factor of 2; some people say a factor of 4.
6 11 l
And the mitigation actions which I've mentioned, 12 turning on the charging pumps and so forth, we believe can t
I 13 easily provide a factor of 5 to 10 risk reduction.
i 14 COMMISSIONER GILINSKY:
Now, where does that come i
- c from? the, the additional time.
l
\\
16 MR. DENTON:
The additional time to take action.
l
)
77, MR. DENISE:
And the low volumes required.
MR. DENTON:
So on that particular accident we end up 73 with an overall f actor of somewhere between 400 and 800.
The next slide shows a fuel-handling accident.
We 0
4 had a, we had a relatively low dose consequence.
But since we are not dealing with handling irradiated fuel during this l
1 period of time, there's an infinite risk-reduction factor.
I 20 The steam-line break is affected by very low 14 circulating activity: as I mentioned earlier, there's at least e
me l
17 I
pacz sc.
s t
a factor of 100 from the full-power tech spec conservative I
l calculation we normally do.
The steam system is not really usedl, 2
i and that would almost make that an infinite factor if it weren't!
A force from steam dump to condenser.
I i
And there's a low fuel failure rate from, from such ad accident.
In fact, we calculate that there's no fuel failure.
7
{
But for, for conservatism we don't say it's point zero.
But I
thic overall factor is a thousand to 10,000, depending on those I
numbers.
10 Steam generator 2 ruptured.
Again, what happens j
11 there is, you dump primarily radioactive coolant from the 12 primary system into the secondary system and out to the l
1:3 atmosphere.
Since you are way reduced in primary-system i
14 circulating activity, it's a f actor of hundred below; and the l
1.1 will delay at least another factcc of 10 and wabh it out, 14 rather than a straight shot as we normally assume.
And that's 17 about a factor of a thousand.
ja Those last three I mentioned aren't -- well, the 79 steam-generated feedback, if you'll recall, is a serious con-sequence as we calculate it.
20 Control-ride-objective accident is, is a subclass of 1
l 6
the loss of coolant accident.
f Next slide.
(Pause.)
24 i
That reduces the activity release, release by a (6ADCptAL YC'fSADM N
'M
o 18 i
ancz sc.
l I
factor of a hundred.
The low fuel failure and the low gap i
I activity together should give us another factor of 200, a facto of 20 on the gap activity and a factor of 10 on the fuel 4
failure.
And low leakage out through the system, particularly I
the containment system, should give us a factor of 1,000 to 6
2,000.
I COMMISSIONER GILINSKY:
Now, where is that, where do 3
you get that factor of 10?
9 MR. DENISE:
The low leakage from the pr,imary, fron 10 l
the primary system -- I'm sorry -- from the secondary system 11 and from the containment system.
I 12 COMMISSIONER GILINSKY:
That comes from what?
13 MR. DENISE:
And comes from the reduced pressures in i
14 the containment.
l 15 (Pause.)
l l
16 MR. DENISE:
And that's an overall factor of a l
- 7 thousand to 2,000.
You can't multiply all these numbers together, because some of the dose comes from the circulating jg activity, and some of the dose comes from the fuel failure and g
the gap activity.
,0 We've also looked at the, at the anticipated transi-l ents without SCRAM and find that most of them are eliminated, due to the nature of operation.
As I've already mentioned, a
there's no turbine trip.
There's not loss of any significant 24 loss of feedwater flow without turbine trip cs a serious thing.,
a un a
w e
0 19 l
nacs sc.
i I
And the one thing that we did look at, that we think 2
l is still operative, is the, was the rod-withdrawal transient j
from low power.
The fuel failures from that should be essential :
nil.
We also understand that TVA intends to operate the reactor, so with the, with the high boron concentration auring 6
this test program, so that all rods will essentially be with-drawn.
3 In that case, it's almost impossible to have a rod-l 9
withdrawal accident of any serious nature, because,they're all,'
10 almost all withdrawn anyway.
So we, I just stuck a conservative 11 estimate factor of a thousand on that.
It's not calculated to 12 result in any significant dose, even during normal operation.
13 (Pause.)
14 MR. DENISE:
Next slide.
is These are the conclusions.
The first one I stated is l
- 4 that, for the most important accidents, the loss of the
}
17 coolant and steam generator tube rupture, the risk is reduced g
by a factor of --
COMMISSIONER GILINSKY:
Could you just go back to g
that steam generator tube rupture, there was a steam system
,0 i
4 i
delay and factor 10?
I didn't fully understand that.
l
,1 4
MR. DENISE:
Yes.
Okay.
The, our normal assumption l on this is that -- let me turn back to it.
Norn, can you go back to that one?
It's about two slides back.
Yes.
2
- - ne.w vm n-notes. -
l
e 20 I
pacz sc.
l l
I Our normal assumption on this is that the relief I
valves will lift on ste,i generators and discharge the coolant.
We don't think in this case, because of the low power, that it l 4
would -- and the nonsteaming nature of the steam generators i
today would.
But even if they did it would not progress 6
rapidly through the system.
It would rather be washed out and 7
absorbed in that.
And that's the kind of estimate we've made i
3 for that reduction factor.
I 9
We don't expect any without the relief valves lifting.-
jg j
(Pause.)
i MR. DENISE:
Go back to the other slide.
Other way.
Flip it.
Flip it over, Norm.
13 There we go.
i We looked at the most important accidents from a dose I
consequence.
They, those were the accidents which resulted in 15 I
the 200-rem range of dose.
They're reduced by a factor of l
16 between 400 and 1,000.
We don't believe that there's any 17 significant loss of coolant accident which would give you even 18 those releases, because of the time to achieve operator correc-19 tions.
And therefore, we believe, considering all the accidents, 20 at an estimate between and 4,000 -- I mean between 400 and 4,00(
21 is a, a reasonable estimate for the dose reduction factor.
Harold wanted me to say something --
l Do you want me to say anything more about the hydroge.!
?
2A Or have covered that sufficiently?
l c.
I t
8 m
O PAGE NC.
21 i
l COMMISSIONER GILINSKY:
I think it answers my l
questions reasonably, unless you have something --
l l
MR. DENTON:
No, I think what the, the study was j
4' useful and that, that Dick quantified the differences other I
than power level -- power level giving you a factor of 20.
And 6
I everyone understood that there's something in the upper l
i l
7 inventory.
The factor really doesn't build up fission products,!
3 and then lastly the fact that it buys time.
9 So it's a, I think it confirms the kind of numbers we 10 were discussing --
i 11 (Pause.)
12 (Laughter.)
l g3 COMMISSIONER GILINSKY:
We'regettinganembarrassmenh g4 of Commissioners, i
ge MR. DENTON:
Leave the conclusion up --
g (Pause.)
t g.
COMMISSIONER GILINSKY:
Why don't we let Joe and Peter scan the slide charts that they have.
If they -- to see if there's something new and to raise, to raise --
I found this very interesting.
(Paase.)
21 COMMISSIONER GILINSKY:
So most of the systems are l
22 1
running on off-site power.
The reactor itself isn't generating I
e i
anything.
04 i
MR. DENISE:
Correct.
c me
o 22 l
pacz sc.
1 In fact, it should all be running on off-site power.
l i
(Pause.)
l l
COMMISSIONER GILINSKY:
You're satisfied, Joe?
l 4
COMMISSIONER HENDRIE:
My only comment is that the risk reduction is probably closer to the 4,000 end of the range s
than the 400, factor of 400; and I find no disagreement with f
7 the thrust of the comments.
3 COMMISSIONER BRADFORD:
Did the 400 relate to a 9
particular sequence?
Or are you saying that the rough --
7o l
whatever it is, it's roughly --
MR. DENTON:
Well, Dick, Dick looked at a half dozen j;
.ypical accident scenarios and took into account an effective I.s
.ow power and short-term operation on that.
And the 400 was g
which accident?
COMMISSIONER BRADFORD:
It's a particular sequence.
COMMISSIONER GILINSKY:
Well, I looked at a number of I
sequences.
17 MR. DENISE:
If you look at the sixth vugraph that 18 you have there --
19 Further oi down.
20 COMMISSIONEh GILINSKYi Maybe --
21 MR. DENISE:
It starts at the top.
It's called 22 l
" Design Basis Accidents."
l 22 COMMISSIONER HENDRIE:
Maybe we could back up the
- 4 i
screen display.
l 15 larTTRNAfiCMas. VD' EAT 1M PF.AftPt 1==C
c PAGE N o.
23 t
I MR. DENISE:
Sure to any -- do you want to start 2
over?
3 COM31ISSIONER HENDRIE:
Well, no, no.
L To where you were going.
3 MR. DENISE:
Norm --
6 COMMISSIONER HENDRIE:
That's the one.
7 I
MR. DENISE:
Correct.
Godd.
3 In order to arrive at this number, what I've done is, t
9 I
is to look at these six events.
This slide is intended to show 10 what are major contributors to dose.
And I've used Sequoyah, 11 the Sequoyah SER calculated doses for two hours at the 12 exclusionary boundary, in order to illustrate the point.
I 13 i
There are two accidents there which are much larger 14 than others, though control rod ejection is close.
These are j l ~'
calculated doses in rem; that's one thing that should be on i
16 the slide that's not on the slide -- within two hours and 556 II meters; I believe that's the exclusionary boundary.
I8 Now, what, what I then did was to go through a series I9 of explanations of why those doses would be much lower at i
20 5-percent power and why those doses would be lower by more Il than the factor of 20 that you get by ratio in 100 to 5 percent 22 power.
22 COMMISSIONER BRADFORD:
- Yes, I,
I, I don't want to 24 put Dick and Victor through the whole briefing.
I U
MR. DENISE:
And it's composite.
But if you'll go i
imo. was vmunu noenro s. I,.c.
24 l
pacz m, to the next one, only the next slide, I'll illustrate what we l
went into.
This was, this was the slide for loss of coolant i
i accident, which is about a 200-rem dose calculated at, at full power.
6 Now, the first thing that I said was ths' the very i
i 7
low flow of steam will cool that core without any clad rupture 3
or without any metal water reaction.
That low flow is about l
9 5 pounds per second of steam.
You could almost cool it in air 10 if you hung it up in air.
11 I also said that it took 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to boil that coolant g7 out of the reactor vessel when this accident started.
I'm l
- 3 sorry.
Not when it started.
After the accumulators have
~
- 4 dumped water in, versus something like 30 minutes of full power,l 15 therefore allowinr_, some time for mitigative actions.
l t
6 Mitigativeactionscanincludeturningononecharging!
I pump which can meet full pressure requirements, and that delivers 8 gallons per minute, and that's more than sufficient to cool it.
19 So the factors I came up with were a dose reduction i
20 I
i term -- source term reduction, a factor of 40, which is composed!
Il l
of a factor of 20, due to 5 percent power and an additional j
e.
factor of 2 because of the intermittent nature and short-term f
nature of the actual test program operation; a factor of 2, due j 2A to lower containment pressure, because pressure is reduced by at; I
r,n,,,..n m v o.o n % n n : c
0 25 l
ancz sc.
l I
l least of factor of 2 at low power, because the decay heat does l
2 not hold it up to this high pressure as full-power decay would; j 2
i and a factor of 5 to 10 for mitigative actions.
I i
4 Now, if you multiply the 40 times the 2 times the 5, I
e I
you get 400.
And if you multiply the 40 times the 2 times the i
10, you get 800.
That was the range for that particular acci-7 dent.
3 No, it's not 800.
f 9
COMMISSIONER BRADFORD:
Yes.
10 MR. DENISE:
Yes, 800.
Right.
j i
l 11 COMMISSIONER GILINSKY:
This was at the end of six 12 months of such operations.
t 13 MR. DENISE:
Yes, six months.
i 14 Well, I can't say that, that that's at the end of six i
1,c months steady, because --
{
l 16 COMMISSIONER GILINSKY:
No, no, no.
That's right.
I
- 7 MR. DENISE
The factor of 2 are intermittent.
So
- g within a factor of 2, you could reach the same conclusion for j
six months at 5-percent power.
- 9 One of the, one of the earlier ones perhaps was intended to show how fission products built up with time, rather than being instantaneously available.
And you might 9
find that interesting; and if you wish, I couldrunthroughit.j i
I'd be very happy to do it if you wished.
24 COMMISSIONER BRADFORD:
I tell you, I think it's l
i i
INTT7P* EAT 1Cre AL '/C*SA79he 4 I
pacz sc.
?6 l
c I
probably easier for everyone else in the room if I just read the; i
transcript-I take it you already did run through it.
I I
MR. DENISE:
Yes, sir, I did.
l l
COMMISSIONER GILINSKY:
Oh, no.
We can just leave, f
A l
3 and you can continue.
I 5
(Laughter.)
I I
7 COMMISSIONER GILINSKY:
Happy to do that.
3 COMMISSIONER BRADFORD:
Why don't I read the tran-9 script : hich will be available before we have to actually vote to on Sequayah anyway.
t If I have further questions, I can call.
g MR. DENISE:
Commissioner Bradford, in answer to your, isacomposi.elookat,I question, that 4,000, that 400 to 4,000, l,a I
at the variety of accidents; and one thing it's important to 14 i
i bear in mind is that the coolant at the very low, if any, circu I
lated activity during this period -- and there are two accidents
,d j
which release primary coolant activity which are very signifi-i cant.
And they just go away, essentially. because there isn't 18 that high concentration that you get from steady-state opera-19 tion, fuel, and so forth.
It's just very clean -- clean coolant is what I cal'. it.
11 COMMISSIONER GILINSKY:
Harold proposed requiring l
'2 I
J fresh quarters every 30 days.
l 22 i
MR. DENTON:
And I suggest that we don't do that if l
24 we can reprocess it.
~$
l twfntfeanevea '/ UPPA M M r.
o 27 sact Nc.
1 I
COMMISSIONER IIENDRIE:
Wewouldprobablyrequiremixedl i
I stock s'de to --
l 3
MR. DENTON:
Right.
Exactly.
i a
COMMISSIONER GILINSKY:
We're using it all the time.
I J
COMMISSIONER HENDRIE:
As I commented the other day, Ij i
i 5
think the real -- you've dealt here with the range of design l
7 basis accidents.
And the real, to me the real essential of the 3
l five-power operation is a really quite low-risk sort of opera-9 tion is in the very greatly reduced potential for more extreme i
jo events.
That is, if one -- if the accidents that occur are l
design-basis accidents and are within the framework of design-
- 7 basis accidents, so that minimum safeguards work, then the eff-'
i e
side effects are not, not very severe at full power and equilibrium fission products and are that much less by substan.
tial factors indicated here if you're c.t 5-percent power.
But the overall hazard to the oublic also has an 17 another element to it, and that is elements beyond the design basis or other than the design-basis accidents.
And the 19 possibility of getting into any sort of significant fission-20 product release from a 5-percent power operation points, are 21 really very, very much reduced for that whole class of O
possibilities.
l l
- e.,.
j It's there that I, that I find my principal comfort 24 I
in the benign nature of 5-percent-max operation.
15 I
f m
D f
$ ' uyL 28 i
pact sc.
i l
t COMMISSIONER GILINSKY:
Well, there's a lower power 2
level and lower fission-product inventory.
i t
I COMMISSIONER HENDRIE:
And very much lower driving j
forces for dire events.
Your, your cooling needs are very much a
~
less.
And you probably keep a 5-percent equilibrium core from 6
melting with -- like, judging from the Three Mile experience, 7
with relatively ittle steam flow, apparently.
I 3
COMMISSIONER GILINSKY:
Well, that was the point that 9
Dick was making.
10 (Pause.)
11 l
COMMISSIONER GILINSKY:
Well, thank you very much.
I, 1
12 I found it very useful; and I thank you very much for it.
13 (Whereupon, the Commission adjourned at 3:30 i
14 o' clock p.m.)
l t,e I
u 17 13 19
- o 21 22 l
l 2
i
- 1 l
2 l
1 a t*
A '/ m rt ae 4 t
a RELATIVE RISK FUEL LOAD AND LOW POWER TESTING VERSUS FULL POWER LONG TERM OPERATION e'
k I
[
[
h
BASIC CONCLUSION PUBLIC RISK DUE TO FUEL LOAD AND LOW POWER TEST PROGPAM IS LESS THAN PUBLIC RISK DUE TO FULL POWER LONG TERM OPERATION BY A FACTOR OF 400-4000.
I
EAJOR FACTORS CONTRIBUTING TO REDUCED RISK REDUCED FISSION PRODUCT BUILDUP AND INVENTORY ELIMINATION OR LOWERED PROBABILITY OF TRANSIENTS AND ACCIDENTS EXTENDED TIME TO EFFECTIVELY DEAL WITH ACCIDENTS REDUCED SEVERITY AND CONSEQUENCES OF ACCIDENTS
CONDITIONS OF FUEL LOAD AND LOW POWER TESTING FRESH FUEL CLEAN COOLANT LOW POWER LIMIT INTERMITTi OPERATION AT LOW POWER LOW DECAY HEAT LEVELS LOW FUEL TEMPERATURES TUPSINE NOT RUNNING, NO ELECTRICAL POWER BEING GENERATED.
Fraction of Full Power Inventory I
(steady 50
.05 -
.04 _
y Sr 9 (steady 5%)
.03 -
/
1131 (intermittent 5%)
7
/
.02 -
7'/
.01 -
/
Csl37 (steady 5%)
/
' ~ ~
~
.00 I
i i
i 0
20 40 60 80 100 days Percent
\\
of Full Power i
I 5.0 2.5 0.0 j
i 0
1 2
3 4
5 days r
G
DESIGN BASIS ACCIDENTS FULL POWER
- CALCULATED DOSE LOSS OF COOLANT 194 FUEL HANDLING 20 STEAM LINE BREAK 26 STEAM GENERATOR TUBE RUPTURE 214 CONTROL R0D EJECTION 97 ATWS
- NUMERICAL EXAMPLE IS FOR 2 HOUR THYROID DOSE AT SEQUOYAH EXCLUSION AREA.
O LOSS OF COOLANT ACCIDENT MITIGATION LOW STEAM FLOW COOLS LOW POWER CORE WITHOUT CLAD RUPTURE OR METAL WATER REACTION BOILOFF 0F RV WATER CAUSES CLAD MELT AT 12 HOURS FOR LOW POWER VERSUS 30 MINUTES AT FULL POWER.
DOSE AND RISK REDUCTION BASES FACTOR SOURCE TERM (LIMITED POWER AND 40 INTERMITTENT OPERATI0t0 LOWER CONTAINMENT PRESSURE 2
filTIGATION ACTIONS 5 - 10 OVERALL FACTOR 400 - 800 t:
o FUEL HANDLING ACCIDENT FACTOR NO IRRADIATED FUEL HANDLING ANTICIPATED P,ISK REDUCTION FACTOR INFINITE STEAM LINE BREAK ACCIDENT VERY LOW CIRCULATING ACTIVITY 100 STEAM SYSTEf1 NOT USED LOW FUEL FAILURE 10 OVERALL FACTOR 1000 - 10000 STEAM GENERATOR TUBE RUPTURE LOW PRIMARY COOLANT CIRCULATING 100 ACTIVITY STEAM SYSTEf1 DELAY 10 OVERALL FACTOR
'1000
4 CONTROL R0D EJECTION FACT 0P, LOW CIRCULATING ACTIVITY 100 LOW FUEL FAILURE AND 200 GAP ACTIVITY-LOW LEAKAGE 10 OVERALL FACTOR 1000 - 2000 AIES MOST TRANSIENTS ARE ELIMINATED DUE TO NATURE OF OPERATIONS FUEL FAILURE FOR R0D WITHDRAWAL TRANSIENT VERY SMALL OVERALL FACTOR 1000
s CONCLUSIONS RISK FROM MOST IMPORTANT ACCIDENTS, LOSS OF COOLANT AND STEAM GENERATOR TUBE RUPTllRE REDUCED BY FACTOR OF 400 - 1000.
LOSS OF COOLANT ACCIDENT RESULTING IN SIGNIFICANT ACTIVITY RELEASE EVEN LESS LIKELY THAN ASSUMED DUE TO ABILITY TO COOL CORE WITH MINIMUM ACTIONS.
OVERALL RISK REDUCTION FACIOR IS ESTIMATED TO BE 400 - 4000.