ML20127A656
| ML20127A656 | |
| Person / Time | |
|---|---|
| Site: | 05000447 |
| Issue date: | 06/16/1983 |
| From: | Houston R Office of Nuclear Reactor Regulation |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20127A304 | List: |
| References | |
| FOIA-84-175, FOIA-84-A-66 NUDOCS 8306240146 | |
| Download: ML20127A656 (17) | |
Text
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BHardin WButler gg I 6 1963 FE1tawila LHulman JMitchell BSheron d!5 8d D JM FOR:
Ashok C.'Thadani, Chief Reliability and Risk Assessment Branch, DST FRDM:
R. Wayne Houston, Assistant Director for Reactor Safety, DSI SUSJECT:
GESSAR-II PPA Q-2 SU3MITTAL FRDM DSI.
Enclosed are questions on the GESSAR-II PRA that have been developed by DSI contractors and staff members from the Containment Systems, Accident Evaluation and Reactor Systems Branches.The questions result from our continuing review of the PRA and from GE's responses to our Q-1s, many of which were incomplete. Questions from RSB and CSB were provided informally to David Yue of your branch on May 26.
Please contact B. Hardin (X28507) of RSB if you have any questions.
Please note that inforcation contained in pages 14 and 15 of the enclosed questions has been judged to be proprie.tarv by General Electric.
Ungina1 S:gned By R. W3?ne. Houston R. Wayne Houston, Assistant Director for Reactor Safety, DSI
Enclosure:
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r EECLOSURE 1 Q-2s FOR GESSAR - 11 pRA 720.102 List. all of the possible pathways through which the suppression pool could be bypassed during a severe accident. Provide a discussion of any pathways not included in the.. questions following (Questions 720.103-720.105). The discussion should include a description of the syste=s involved, the accident conditions necessary to cause the bypass, the expected impact of the bypass on plant risk,
. and any design or procedural changes that have.been considered by General Electric to prevent or mitigate the effects of the bypass.
-720.103 Referrir.g to the response to Question 720.23, have calculations been performed to,specifically determi.ne the temperatures that might be expected at the ISIVs during a severe accident? If so,'what were the results of these calculations and how were they performed ?(i.e., describe
.the simplifying assumptions that were made and the solution methods)
Also, if credit is taken for the ISIVs remaining fully functional under such an environment, provide justification for taking such credit. The response should include a discussion of data for. ISIV leakage rate taken duri_ng surveillance testing of these valves in operating BWRs. If credit is taken for the ISIV positive leakage control system, justify taking such credit at the expected temperatures and range of leakage flow rates.
Also, in the ouestion response, it is stated that there would be significant radionuclide removal in the ISIVs due to tortuous paths and the source aerosol cenposition. provide further support forthisstatknentaccountingfor the range of leakage flow rates erperienced in past MSIV testing and including or referring to experimental data. Discuss any design or procedural changes that have been considered by General Electric to mitigate the effects of. MSIV leakage er failure. If your response assu=es credit for additional valves other than the MSIVs, identify these valves and discuss the operating environment expected during a severe accident, the valve servica qualifications for the environ =ent, and the. planned =aintenance progran.
720.104 In Appendix D.l.7 (Refer to Table D.l.7-2 on page 15.D.3-387.), it is-stated that two vacuum breakers..in_s_erjes, one. mechanical.and one, power
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a.. Further justification cf these probabilitie2 is needed. In particular, address the effect of the hydrogen phenomena (local or global detona-tions or severe burns) described in Appendix I of the pRA on the probability of the vacuum breakers to stick open.
- b.. Provide the nurrber, location, and potential flow area of these breakers should they remain stuck open due either to mechanical failure or because of debris entrained in the atmosphere following a LOCA or ves s el. mel t-through.
.m
e -
'720.104 cont.
'c. -Provide a discussion of the potential for significant leakage through the vacuum breakers under severe accident conditions, Include reference to available leak rate test data.
- d. Discuss any design or procedural changes that have been considered by General Electric to
. mitigate the effects of vacuum breaker f ailure or leakage.
720.105 Discu s the probability that any of the following ' lines become a bypass path.
-c. drywell purge lines Discuss any design or procedural changes that have been considered by General Electric to citigate the effects of bypass through these lines.
720.106 Justify the following assumptions made with regard to the MARCH model used for predicting the quantity of hydrogen produced during in-vessel-core heat-up and slumping:
(a) The input values used for parameters ISTM and IMWA in NLBOIL, which appear to have been selected to minimize H2 production during core
. heat-up prior to slumping.
(b) The core debris fragments into particles 1.0 cm in diameter.
(c) The debris is assumed to be an intimate mixture of UO, Zr02 and 2
Zr metal.
These modeling assumptions minimize the metal-water reaction during core heat-up and virtually eliminate it during the core slumping phase.
720.107 Question 720.106 above requires that GE justify certain modeling assu=ptions used in their MARCH analysis. Minor changes in input assumptions can signifi-cantly influence the predicted generation of hydrogen during the in-vessel heat-up and slumping of the reactor core. How would the probabilities of the various hydrogen phenomena discussed in the GE response to Question 720.40 be; influenced by uncertainties regarding MARCH modeling of hydrogen generation during in-vessel core heat-up and slu= ping?
A 4
720.105 The GE. response to question 720.35 has not addressed our basic concern, namely that H2 phenomena other than the four assumed categories may The probabilistic relationship between these sequences may be occur.
significantly different than those outlined in the PRA.
In addition, combinations of burns and detonations may well produce pressures and temperatures in excess of those predicted by considering the four cate-
~
gories separately.
GE should further discuss the potential for these integrated. phenomena and assess how they may influence the probabilities in the containment event trees.
~'
720.109 With reference to GE r the expression for pea,esponses to question 720.37 and' 720.39. Although k pressure in an Hp detonation occurring in a closed system may be verified, it probably does not take into considera-tion the presence oof complex geometries which may result in reflective
. and focusing phenomena.
Peak local pressures due to sucn-phenomena may exceed those predicted by the simple relationship used in Appendix I of the PRA. Supply a reference which would justify application of this ex-pression to the GESSAR containment system geometry.
720.110 In the Third Technology Update Meeting, the CORRAL volume model was de-scribed. Unfortunately, this description does.not exactly correspond to the sample CORRAL problem provided by GE.
Please provide a more de-tailed description of the actual. CORRAL model used.
In addition, also provide a description of how the thermodynamic input was determined for those volumes modeled in CORRAL but not in the MARCH code.
720.111 The response -to question 720.40 and the containment event tree quantiff-cation given in Appendix 0.1.7 are of great help when attempting to un-derstand the containment event trees in Appendix C.15.
However, further discussion is needed on the derivation of the event tree probabilities.
Spec (fically, provide more information on the following:
Referring to Table D.1.7-2:
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- a. Justify the!
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b ' '_.,.u 1
~ (Refer to P' on page T5.~D;3:3847) p
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- b. Explain why; i
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- c. Justify the failure probabilities for.
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on page 15.D.3-3SS).
-720.111 cont.
Referring to the response to Question 720.40:
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- a. Justify the value assumed for the r-
- b. Explain the inconsistency appearing between the event trees for Cases 3,5 and 6 and the conditional probabilities in Table I.4-1.
720.112 Fcr certain sequences, water will be present in the pedestal cavity and the potential for an ex-vessel' steam explosion would exist (refer to Ap-pendix H.8 of the GESSAR-Il PRA).
Wnile these steam explosions will probably _not directly f ail containment, they could result in enhanced Please dis-oxidation of Ruthenium and Tellurium for these sequences.
cuss this possibility and its potential effect.
720.113 Augmented decay heat removal may be helpful in reducing severe accident risk. The - @rmans are considering separate dedicated s0poression pool g
heat removal systems. Provide a discussion of the potential use of such
(
systems in the GESSAR-II design including descriptions of the systems that have been considered by GE and the expected impact of these systems on plant rf'sk. Also include a discussion of the potential that augmented heat removal systems may have for removing the limitations of core retention devices discussed in your response to Part 3 of Question 720.83.
720.114
-From an inspection of NUREG-0772, it is clear that there is no experi-mental data for fission product release beyond 2800C.
What release rate constants were used to compute fission product release from core mate-rial at temperatures nigher than 2800C?
720.115 The total quantity of fission products released during the so-called
" MELT" release phase is presumably a function of the time at which the core 'is assumed to slump into the bottom of the reactor vessel.
Have any sensitivity studies been performed related to the assumed point of core slumping.
If so, what is the impact en the predicted release f ractions ?
/20.116 In-the CESSAR-II PRA, up to '
of the fission products are predicted to be held up1in the primary sisTem. What is the potential for re-emission cd of these fission products? In prticular, address the possibility of these fission products being released from the primary system af.ter vessel failure to the drywell and subsequently from the drywell via a breach in in the drywell wall such that the suppression pool is bypassed. Include in your assessment the role of decay heat from the fission products in the re-emission process.
720.117 The release of fission products during in-vessel core heat-up is a strong functica of the temperature history in soace and time of the reacter core, which is predictec by tr.e MARCH code.
Tne temperature history can be strongly influenied by MARCH input parameters (refer to question 106). Justify your choice of KARCH input parameters con-trolling core heat-up.
In addition,.please describe any sensitivity studies performed related to core heat-up and fission product release.
720.113 Please provide a mechanistic description of the in-vessel vaporization release postulated to occur when the core debris is in the bottom of the reactor vessel.
This' response should be consistent with the response related to the potential for H2 production during this phase of the core meltdown (refer to question 106)Jinally, the CORRAL sample problem provided by GE does not appear to include this release.
Pisase explain this apparent discrepancy.
720.119 Question 720.43 (Scaling of Tests) asked how the pool scrubbing tests were scaled with respect to the prototype.
The response does not fully resolve the question.
Among the unresolved areas are the following.
- 1. Geometric similarity was not entirely maintained.
This is a first requirement in conducting tests that can be scaled to the prototype.
A specific example of dimensions not scaled is inlet submergence.
A second example is bubble size.
- 2. The size of large bubbles formed prior to detachment was apparently not correlated with all relevant physical parameters.
If the large bubbles break up in N1 diameter, as GE suggests, the breakup distance would vary with initial bubble size.
Available information does not allow a sufficiently confident prediction of effective scrubbing height to be made for all Cases.
- 3. The rise velocity of bubble swarms is probably a function of swarm size, which in turn would vary with medel size.
Specific information which addresses the effect of size scale on swarm rise velocity has not been provided.
- s..
720.119 cent.
- 4. Interactions between multiple discharge pathways may not be negligible.
No information on such interactions has been presented.
- 5. The justification for the applicability of Froude scaling has not-been presented.
Discuss these specific points, and provide the bases for relevent assumptions.
720.120 Question 720.44 (Effect of lodine Form on DF) asked the effect on predicted DF if some elemental iodine or organic iodide is assumed.
Also, the potential for formation of organic iodides in the drywell was questioned.
A first response is that the DF for elemental iodine would be comparable to that for iodide. A GE document (NEDO-22216) is referenced to support this statement.
Neither the cited document nor supporting technical discussions are provided, and the response cannot be accepted because:
o for particles, DF depends critically on particle size, o for 1, DF would depend importantly on the partition coefficient, 2
which in turn would depend on water chemistry.
Thus, the DF for the two assumed forms might be equal for a given set of conditions, but it is highly unlikely that a general parity would exist.
The existing data bse on pool scrubbing of I,; supports the view that a substantial DF wot.id be achieved if the form Ts I. Anal required to estimate numerical values for specifi$ cases.yses would be A second GE response is that 0.03% of core iodine is assumed to pass through the pool in every sequence, limiting DF to 3333.
It is agreed that conditions within the RCS do not favor organic iodide formation, and for sequences where the pathway to the pool is through the quenqhers, little organic iodide could be present in inlet gas.
The third GE response suggests that conditions in the drywell (steam / hydrogen, low residence time) do not favor organic iodides, but that the 0.03% cited in NUREG-077 is assumed. Two comments are offered.
1.
The absence of oxygen in the drywell atmosphere may favor radiolytic formation of organic iodides because oxygen is a radical scavenger that competes with iodine.
It is not clear that drywell conditions would
^ limit organic iodides to extremely low values.
2.
The 0.03% formation fraction cited in NUREG-0772 has a questionable technical basis and falls far below many experirental measurements of organic iodide fractions.
While it is agreed that organic iodides will always L
0._
720.120 cent.
represent a small fractioil of total icifide (<1%) it is not ev'ident that the 0.03% value is a realistic estimate, especially when it is the effective limit of iodine emission from the plant, in GE's analysis.
Provide justification for the value used and state how organic iodine is used in the CRAC analyses.
720.121 Question 720.45 (Particle Shape Factors for Eu 0 ) asked what shape 73 factors apply to the Eu 0, test particles.
The fesoonse is that the 2
shape fac ors are unity because electron microcraphs (which are provided with ques.icn 720.47) indicate the powder to be dispersed was rounded grains. The larger particles shown are indeed rounded grains, for which shape factors close to unity would apply.
Smaller particles appear to be agglomerates and, hence, could have shape factors different from unity. The conditions under which the sample were taken are not given.
What is needed is a sample of particles as they are injected into the pool.
The experimental set-up used by GE involved a deposition /re-entrainment processes, and it is expected that smaller particles would be agglomerated by this process. Therefore, the photographs shown may or may not depict the particles entering the pool.
!!are information on where and how the samples were collected is necessary to help resolve questions of how well the pictures shown re-
~
present the aerosol that actually entered the pool.
Provide the information requested.
For inertial deposition and sedimentation, shape factor is not an important issue in interpreting the experiments because, in principle, the cascade impactors give aerodynamic sizes which can be put into the model directly.
However, for diffusional deposition one needs to know the effective density in order to estimate the actual size.
Uncertainties in shape factors for smaller particles introduce uncertainty into predictions of diffusional capture.
Provide a discussion, and bases therefor, of the effective density and uncertainties in shape factors.
720.122 Question 720.46 (Particle Size) asked for clarification of which of several. stated particle sizes was used by GE in the theoretical predictions.
GE's reply clarified the picture by stating that none of the ranges or averages was used, but that impactor data were used for each experiment. Unfortunately the impactor data are not given.
It is necessary in assessing the models and experiments to obtain the cascade impactor data.
Data needed are:
(1) Impactor flow conditions, (2)
Calibration procedure, (3) mass of material on each stage.
Since a specific size is input to the analysis of each experiment, provide the requested information for each experiment.
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720.123 Question 720.48_(Deposition and Reentrainment) was directed at particle deposition and reentrainment within the recirculating flow system used to keep Eu 0, particles airborne. The GE response deals with processes 2
inside the pdol; the question apparently was not understood by GE. The crux of the question deals with the possibility that the particles entering the pool were larger than measured either by deposition or agglomeration of small particles,,ydownstream of the sampling point. The question is important because pai ticle size is a critical parameter in scrubbing efficiencies.
Relattyely small errors in particle size could lead to erronecus interpretations of scrubbing efficiency.
Provide a cis:ession of how the upstream 3ampling methodology realistically accour.ted for potential particle, agglomeration by deposition /reentrainment processes.
720.124 Question 720.49 (Diluter Function) dealt with the use of diluters to obtain impactor samples.
The GE explanation for the outlet sample is adequate. However, the diluter used for the input impactor is not adequately described.
Specifically, provide a description of how was the flow rate of dilution air measured and controlled to maintain isokinetic flow in the sampler tube. A schematic diagram with a narrative that describes the experimental procedure would be helpful.
This issue is important because isokinetic sampling conditions would be
-required to obtain a representative sample of inlet aerosol. The single sentence descHbing the input isokinetic sampler, to the extent that we may have misinterpreted what was actually done, describes a procedure which would be unlikely to produce accurate results.
From the description in the response, we infer that the input sampler is not isokinetic.
720.125 Question 720.50(SamplingLineDimensions)addressedparticledeposition in sampling lines.
The issue is important because such deposition is size dependent with larger particles being more effectively deposited.
Such depositicn would tend to make the impactor rich in small particles, which would in turn lead to erroneous interpretations of the scrubbing efficiency.
Deposition in the. outlet sample was measured by GE to be less than 1%, a satisfactory answer. This result is not unexpected because only the most penetrating particles would escape from the pool.
Unfortunately losses in the inlet tube were neither measured nor theoretically analyzed.
Inlet particles would be larger than those in the outlet and, therefore, susceptible to sampling line loss.
The lack of data on inlet line losses introouces uncertainty into the particle size measurements; a technical analysis to quantify this uncertainty is requested.
-g-720.126
' Question 720.52 '(Recycle Flow) asked about flow in the recycle stream.
'The GE answer.is adequate and points out that an insignificant amount of material remained in the loop after 10 experiments.
The GE finding of little residu'al material supports the postulate that particles were deposited and reentrained in the loop. Such processes usually cause particle agglomeration which must be quantified if the size of particles entering the pool is to be accurately known.
Information supplied by GE has not directly addressed the question of agglomeration in the aerosol
- circuit.
The recycle ficw cor.plicates intercretation of the cercsol size effect of the'ynamics.
however,.it would be prcductive to analyze the cistribution d loop and its pump on the aerosol size distribution.
Provide such an analysis.
720.127 Question 720.53 (Cascade I'mpactor Calibration) asked for a definition of data columns of Tables 1-1 and 1-2.
The GE answer adequately describes the listed particle diameters as calculated cut diameters for each impactor stage.
A detailed look at the calculations raises a question regarding the gas flow rates used in the impactors.
The manufacturer's operating manual suggests a flow rate range up to 0.75 cfm; but GE used flow rates of 1.0 and 2.0 cfm.
The use of flow rates higher. than the normal range may introduce uncertainty due to calibration shifts and reentrainment.
A technical discussion that quantified impactor calibrations and reentrainment at higher-than-design flow is necessary.
The issue is important because the effects listed could cause a bias
~towards small particles leading-to erroneous interpretation of scrubbing efficiency versus particle size.
720.128 Question 720.55 (Material Balance) dealt with the possibility of making a material balance.
The GE answer indicates the measurements do not permit this.
The GE answer also alludes to differences between the inlet sample and the bubble formation orifice. More information on the isokinetic upstream sample (filter or impactor) is necessary to assess the degree to which the sample was representative of aerosols entering the pcol.
If the orifice and the sample location are different then serious questions are raised concerning the applicability of anythino measured by the inlet sampler.
- s..
720.129
~
Question 720.56 (Entrance Effect) was directed at an entrance effect (a DF due to removal processes occurring during bubble formation) that was included in the theoretical model for the single bubble tests.
It is agreed that removal processes would occur during bubble famation.
Three questions remain: 1. Did an integration over the size distribution yeild a DF of 10.0 for all of the experiments, or is 10 merely an average assigned by technical judgment?
- 2. Why was an entrance effect not included in the model used to predict the DF in the verification test?
- 3. What particle size distribution was used for scrubbing predictions for the rising bubbie, e.g. was the depletion of large particles by the entrance effect specifically accounted for, or was the factor of 10 DF applied to the entire aerosol mass?
.720.130 Question 720.57 (Particle Size Spectra) dealt with size distributions measured and used in the predictions. GE notes that actual measurements were used.
The example given for Test 12/2 shows that 0.1 of the mass is smaller than %2.5 pm, whereas in Table 15 DA.1-5 some 0.4 of the mass is smaller than 2.5 pm.
This variation indicates that the particle size spectrum varied significantly from test to test.
Since only one type of aerosol was used, this variation is not expected.
Futhermore, without a measured distribution for each test, no checks by the staff are possible.
See also the comment to question 720.46.
Provide an explanation of what mechanisms cause this large variation.
720.131 Question 720.58 (Particle Size for Cunningham Factor and Diffusivity) dealt with particle sizes and densities used to predict the Cunningham
. slip facter (CSF).
The GE answer asserts that the Cunningham factor depends on particle size, mean free path, and particle density, that ave; age values were used, and that use of the average CSF may result in an average increase in predicted DF by s20%. Two comments are offered.
(1) CSF does not depend explicitly on particle density as GE has suggested.
The problem is that the use of cascade impactor data for computing CSF and diffusivity requires one to choose a particle-density in order to compute. effective Predicted particle diameters (from impactor data) particle size.would vary by factors 1 to 1/C8.
- Thus, predicted diffusivities could be in error by as much as a factor of 2.8, potentially leading to predicted errors in DF due to diffusion of as much as exp (2.8)8 = 5.3.
(2) The use of average values of CSF for the whole particle size spectrum introduces unnecessary errors into DF predictions..Therefore, CSF should be computed for each discrete particle size range.
The problem is that particles reaching the pool surface are not those for which inertial deposition dominates the removal.
Provide the results of such an assessment, u
r 720.132 Question 720.59 (Predicted DF Versus Particle Diameter) asked for data to support a GE statement that experimental data supported the predicted trend of DF versus particle size. GE has submitted a graph of DF versus particle size.
Inspection of the " theoretical model" curve of the figure shows that it has a minimum DF of s20 at a particle diameter of a.O. 2 m.
The bubble scrubbing ocdels described by GE do not predict a minimum DF this high and it is evident that the " entrance effect" discuss"d earlier was used.
It appears that a constant DF of 10, applicable to all particle sizes was used.
The introduction of a
, constan DF of 10, if this was done, is highly questionable en technical grounds.
Therefors, provide detailed description of how the theoretical model lir:e was comcuted.
720.133 Question 720.61 (Particle Growth Due to Superheated Steam) asked for information to support a GE statement that superheated steam could cause particle growth.
In GE's response, it is pointed out that bubbles quickly reach thermal equilibrium with the pool so the steam becomes saturated.
Saturated steam can then condense on particles, as illustrated in the Figure supplied by GE.
It is agreed that soluble aerosols can grow in humid atmospheres.
Realistic predictions of particle growth require knowledge of particle solubility and of bubble humidity, factors which are not particularly easy to evaluate.
Two aspects of particle growth not addressed in the GE response are:
(1) soluble particles can grow in humidities less than 100% whefbas insoluble particles require a humidity >100% to nucleate water.
(2)
The degree of grcwth depends critically on the actual humidity inside a bubble.
Provide a discussion of your views on both aspects.
720.134 Question 720.62 (Thermal Effects on Scrubbing) asked why diffusiophoresis can be neglected compared to'thermophoresis, and how the low temperature tests can be considered conservative from a temperature effect.
The GE answer states that diffusiophoresis (which could impede particle capture) would cease after s0.1 seconds, hence would not be a significant factor in limiting scrubbing. While it is agreed that bubbles are expected to reach thermal equilibrium quickly, this does not stop the inward flow of steam.
Vapor-liquid equilibria dictate that steam will evaporate into rising bubbles because total pressure is decreasing with height.
The magnitude of the evaporation velocity depends strongly on water temperature, and for a saturated pool the effect is maximum.
Numerical calculations show the evaporation can be a significant impediment to the capture of particles in the intermediate size range (0.01 t; 3 pm).
Therefore, provide an analysis
,of steam evaporation into rising bubbles and its effect on particle capture.
We consider any "first principle" model deficient without specific inclusion of this effect.
720.135 Question 720.63 (Run to Run Variations in DF) asked for an explanation of DF variations of a factor of 4 for tests done under similar conditions.
GE responds that the tests had different particle concentrations and particle size distributions and further that typographical errors were present in the original table.
The attached table shcws that for the runs done on 12/11 and 12/J4 the particle 3
concentrations were 4.34 and 1.38 g/m respectively.
The measurea DF's were quite similar (2945 vs 2270) indicating that particle concentration had little effect on DF.
For the other run (12/15), concentration was not measured and the DF was 928. The particle size data alluded to in the response are not given, so no judgment with respect to particle size effects can be made.
In the absence of particle si:e data it is not possible to assess what part of the variations in measured DFs is attributable to differences in experimental conditions and what is due to experimental error.
See the two previous requests for all the data which is necessary to allow the staff to evaluate the tests, and justify your conclusions if particle size data is not available.
720.136 Question 720.64 (Bubble Shattering Distance) was aired at distances required for bubble shattering. The GE response notes that-bubbles shatter when the bottom overtakes the top, that Froude scaling applies, and that breakup distance is geometrically sinilar. No mention is made of the apparent conflicts on pages 49-C43 and 49-C45, as requested in the question.
From page 49-C45, it is stated that typically,12-inch diameter bubbles shatter about 18" above the vent (5.44-inch diameter).
If this result is sc4 ed to the plant, then the height to shattering is (18/5.44) x 1
27.5 = 91 inches or 7.6 feet.
If this shatter distance is correct, then the effective scrubbing height would be greatly diminished because the submergence of the horizontal vents varies from 8.4 to 13.5 feet (GE information supplied with question 720.65).
A discussion of'how one estimates effective scrubbing heights for the horizontal vents should be provided.
720.137 Question 720.65 (Submergence of vents) dealt with submergence of vents in tests and submergence in the plant. The response indicates that rise velocity and bubble size of stable bubbles would be the same in small and full scales, so that extrapolation to 14 feet is straight forward.
This response fails to deal with the important question involved here, the distance required for the large bubble to shatter into stable bubbles.
If the break-up distance is scaled linearly, as suggested by GE in response to question 720.64, then in the plant, break-up heights of the order of 8-feet may be predicted. This is a large fraction of L
r 720.137 cont.
submergence (8 ft. to 13.'5 ft.). -If the tests had used' geometric similarity a minimum submergence of (5.44/27.5)(8) = 1.6 ft. which is very close to the break-up distance quoted on page 49-C45.
Please address the question of effective scrubbing height for all applicable discharge conditions. GE is using the model to validate the tests and the tests to validate the model in this answer.
This is unacceptable.
720.138 Ouestion 720.66 (Bubble Rise Velocities) asked for clarification of rise velocities presented in Figure 15 DA.2.3.
The response is that the curve through the data is an " eye ball" trend fit, nothing more. Other parts of the _ question that dealt with the significance of the data, and how it was used, were not addressed. The significance of the data set remains in question. Thereforeprovide a discussion of both topics.
~
720.139
' Question 720.69 (Entrainment from Pool) asked how entrainnent carryover can be neglected.
The response is that the bursting bubbles are expected to be relatively free of suspended particles.
This response apears to be based on a surface cleaning theory that is r.ot well documented.. Rather than be particle-free, it is possible.that the interface would contain higher than average concentrations of particles.
Interfacial crud and foams that contain concentrated impurities are commonly founa in mass transfer processes.
While entrainnent would not be expected to be significant for low DFs (<100), carryover could dominate if large DFs (>10') are claimed.
In view of the above, provide further justification for your conclusions.
720.140 uestion720.70(Cs! Experiments)askedinformationonthetestsdone with Cs!.
The responso indicates that experimental difficulties prevented valid results from being obtained, a satisfact:ry answer. The' overall conclusion, that results were consistent with DFs of 2.5 as would be predicted for 0.1 - 0.2 um particles, appears to be reasonable.
The, fact that minimum calculated DFs are in the range of 2-5 is as expected, but is inconsistent with the theory line presented in response to question 720.59, which shows a minimum DF >10.
Please discuss this inconsistency.
720.141 Concerning Question A (Table 7.2-1 Rev. !!), based upon comunications with D. Hankins, the answer provided to this question on the direction and magnitude of the changes between Rev. 2 and Rev. ll cn early and l
latent fatalities is not exactly correct. Attached are copies of Table 7.2-1 from Rev. 2 and Rev. 11.
Indicate in the appropriate places the corrections'necessary for mi: typing, and discuss the direction and expected magnitude of any changes made between the two analyses.
7
.---..... 23S NUCLEAR S AND dA7007 GCNERAL CLECTRIC COMPANY Rav* 2 PROPRIETARY INFORMATION f,y Class III 2
- r-Table 7.2-1 ESTIMATED CORE DAMAGE AND RISK COMPARISON assessed Risk b
Frequency Early Latent of Event Fatalities Fatalities Per Reacter Per Reactor Per Reactor Event Year Year Year I.
CORE DA". AGE f;
RSS 3*mTR/4 Mark-I a
a
-5
-5
-2 e composite site
.4x10 six10 s5x10 RSS ENR/4 Mark I
-6
~
9 site 16C s4x10 1.2x10 y,y yg-2 BWR/6 Mark III C
~4 O site 96 5x10' O
2x10 r
- l
- L II.
U.S. NATURAL BACKGROUND Continuous 0
814' RADIATION "With WASH-1400 Methods (calculated from the reported curves).
bThe total accident-caused fatalities over. the. lifetime of the exposed population or the c. lculated excess cancers in the same population from one yea. of backcround radiation.
- Computed with the GE CRAC Code.
/
G 4
9 e
4 15.D.3-143
7 Class III
,7 Tablo 7.2-1
.\\
o@\\.
ESTIMATED COP 2 DAMAGE AND RISK COMPARISON Assessed Frequency R:.Lsk (Per Year) of Event Per.. Reactor Early,
.., Latent Event Year Fatalitids "Fatalitiesh
.s I.
COP 2 D7. MAGE RSS BWR/4 Mark I i
a a
-5 E composite site Nix 10 f Nix 10 c
~
N5x10"!c
-5 44x10 "
2.4x10 2.5x10~*
~
RSS 3nR/4 Mark.I
-5
-6 6 site (6C N4x10 7.8x10 2.1x10'. 2 3WR/6 Mark III
-6 5
6 site f6C 5x10 40
- 1. 75c10
~
~
II.
U.S.
NATURAL BACKGROUND Continuous 0
.814-RADIATION
~
S'ith WASE-14 00 Methods (balculated from the reForted curves).
The total accident-caused fatalities over the lifetini of the exposed population or the calculated excess cancers in the same population from one year of background radiation.
"Co: puted wit.k the GE CRAC Code.
15.D.3-143
T' l-*
720.142 Nowhere does GE give an example of exact inout values for their. DF model and an example calculation using those inputs.
To evaluate the GE model the staff needs the following:
1 1)
Final equation for DF with all coefficients defined.
- 2) A comolete listing of all input to that equ. tion.
3)
An evaluation for a single set of input of spherical and ellipsoidal bubble models 4). An evaluation, including an input listing, of DF versus particle size for a size range from 0.01 um to.1C pm.
720.143 The GE response to Questions 720.77 and 720.78 regarding uncertainties in the GESSAR-II PRA is not acceptable. The staff believes that a more compre-hensive treat =ent of uncertainties is essential toward establishing the L
credibility of 'the GESSAR PRA risk esticates. Since it is not practical or even possible to perform a completely co:prehensive assessment of uncertain-ties, GE should prepare a plan describing a proposed uncertainty analysis for presentation to the staff in the near future. The plan should include the assessment of the major types of uncertainties.affecting the accident 1 sequences contributing significantly to overall plant risk. Four types of uncertainty that.should be addressed include:
(1) statistical uncertainties in component and human failure rates and in other analysis input parameters, (2) approximations in physical phenonena modeling, (3) errors in completeness in considering possible failure modes, and (4) arithmetic errors The propagation of these errors should also be addressed.
References for uncertainty analyses: Indian Point and Li=erick risk assess-ment.
a_.