ML20010J586
| ML20010J586 | |
| Person / Time | |
|---|---|
| Issue date: | 09/02/1981 |
| From: | Catton I Advisory Committee on Reactor Safeguards |
| To: | Shewmon P Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1366, NUDOCS 8110050474 | |
| Download: ML20010J586 (4) | |
Text
_ _ _ _ _ _ _ _ _ _ _ _ _ - _ _
,0 ' ) t' F C, ' 4,.
j~;
t^
G7 /fgf
' \\.
p A vf g DQ $ a) y h
September 2, 1981 l
cy\\
.(p
/s E::E E:
p%.
%,4 g TO: Paul Shewmon FROM: Ivan Catton
SUBJECT:
Report of NRC Fuel Testing Task Forc2
. 3,;
- ,.y - ; 7.,q 15C. -' C C ;." T I E E ci
' " ? ~. 5/JE G;'..E;5 A number of licensing needs come to :nind when one postulates severe fuel damage (SFD). Recent studies of Zion and Indian Point, the TMI Action g
plan and certain rulemaking all require (or should require) some knowledge of the various phenomena governing SFD.
It was, therefore, disappointing to see. hat the task force did not include anyone from NRR.
Further, I found no reference to a user need letter for SFD research.
It could be that NRR believes that bounding estimates will suffice for the near future.
In that it will be a year or more before tLe proposed progrem could yield any substantive information, there is no need to rush into a hastily plan-ned, expensive program. Another cut is needed with input from a more balanced team.
The proposed research plan is composed of three major parts:
1.
A computer code - SCDAP Analysis and modeling of three core configurations will be the basis for a SFD code called SCDAP. The three core configura-tions are 1) essentially intact core, 2) loosely bcund rubble, and 3) cohesive debris. Radiation, chemistry, fluidization will be included.
It is not clear how the transient disruptive process will be modeled.
2.
Integral SFD tests - PBF A two pnase program is recomended. The first phase is scoping to supply direction to the ;rogram whereas the second la a more 8110050474 810902 ppg ACRS png CT-1366
>}
9',
H a-c
., reasoned. study to supply proof' tests for the code. Limited instru-cy y sc mentation results in PBF supplying primarily end-state data w
c h
through post' test, examination.
- 3.'.Phenomenological Separate-Ef f ects Experiments - ACRR 4
y A series-of small scale phenomenological experiments will be cen-ducted.in the ACRR. -These tests are to support the PBF studies.
i A principal objective is characterization of the core reconfigu-ration,, Visual observation will be the major diagnvatic tool for quantification of time dependent damage progression. Visual tech-niques can be very valuable but are lhaited for multiple pin tests.
In-pile dryout experiments are a part of this portdon of the pro-gram.
1 <
The various' processes that must be modeled (oxidation, melting, solidi-i-
fication,. fragmentation, fission product escape, etc.) are large in number and their dependencies on the state of the core (flow, temperature and 1
gecmetry) at any given time are so complex that a calculated progression of the. core degradation process will quickly lose meaning as the original
- fuel' geometry is lost.
It is my view that we will never have a complete answer and must use judgment. The computer code, LCDAP, seems like a reasonable approeth even though some of its parts appear to be somewhat overambitious.
It will require a great deal of empiricism and its results
- will always havJ to be viewed as approximate. The German code EXMEL is (maybe);further along in its development.and has a similar. purpose.
PBF is proposed as a proof test of the code as well as a source of someof the needed empiricism. For example, measuring pressure drop versus flow rate after the test is not sufficient.
It gives only one data point and does
~
it
/
.not.-allow phasa change or other processes to be factored into a model. W2 O~
1 4
= -*
r -
i b'-
' really need to know what is going -on during the core disruption period.
Fragmentation measurementsLafter the test only give an avera;e and do not allow intermediate stages'to be studied. Unfortunately PBF is not instru-mented well enough to give much information about the phenomena occuring during core recenfiguration. The possibility that the instrumentation on PBF could be improved should be considered.
In any case, the first few tests'should be' carried out as.they uppear to be scoping and will give us'an overview. Phase-II of the PBF test series appears to be similar to the planned SUPER-SARA tests and is most likely not.needed. We would be better of f becoming a partner in the European program.
~
.Thel ACRR Severe' Fuel Damage (SFD) and Core Quench (DCQ) Program is supposed to supply enough detail about the various phenomena that nodels can be developed for the computer code. The experiments are intended to
- complement -the PB1 experiments by supplying time dependent data.
The
}
. principal objective is to characterize core geometry reconfiguration. Time dependent evolution of hydrogen and fission products will be measured. The core reconfiguration will be followed visually. The type of detail needed for model confirmation does not seem to be available from these tests.
.The ACRR tests may. yield more detail than PBF tests but are still a long way from being. sufficient. The in-pile studies of core coolability limits are not'aecded.
Very little _out-of-pile experimental work is planned. Given that-we
. have a description of the reconfigured core, it is not clear that we could describe the subsequent..semica'. interactions, fluid flow and heat transfer.
Basic' processes such as quenching of a porous media do not require in-pile testing.' Another. process that needs study is hydrogen generation in a 4
- steam cooled steel rubble bed. This is best studied out-of-pile where a i
b:
y,;
z
[t large number of experiments can be conducted with ease. A review of SFD research programs is needed. The various phenomena need to be sorted out and the best method of obtaining information necessary to model it must i
be determined.
In my view this was not done by the Fuel Testing Task Force.
IC:pg cc: Dave Bessette 4