ML19319C384
| ML19319C384 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/18/1976 |
| From: | Ross D Office of Nuclear Reactor Regulation |
| To: | Deyoung R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002140771 | |
| Download: ML19319C384 (5) | |
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i FEB 18 TE Richard C. DeYoung, Jr., Assistant Director for L*iR's, D?M REQUEST FOR ADDITIO!LiL ECCS I!iFORMATIO!! O!' DAVIS-BESSE 1 ye are currently avaluating the sub:aitted ECCS analyses for Davis-3 esse 1.
In addition to topical report SK4-10lG5, "ECCS Evaluation of 34W's 177-FA Raised Loop 'ISS." ve are reviewing the centents of the letters from Toledo Edison Co::xpany dated July 9th, July 21st.
September 5th and October 3. 1975.
In addition to questions subviitted to 3&i'ppertaining to 3AW-10105, enclosed is a list of additional information that is required for our review.
Origir.21 OIE*'*2' D. 7.F.JS4 sd D. F. Ross. Assistant Director for Reactor Safety Division of Systems Safety Of fice of :inclear Reactor Rc;:lation
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Req'Jes t for.t:fditional Information ee:
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- 4. Minners C. Ma::etis (3)
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i DAVIS-BESSE 1 1
REQUEST FOR ADDITIONAL INFORMATION i
I 1.
Justify the selection of initial pin pressure and oxide layer-for the CFT line break (referenced in BAW-10103 to FSAR).
Ex-l plain not considering the Case 1 power shape previously shown to produce a higher PCT. What value of LHGR was assumed and why?
A l
2.
With regard to the single failure analysis in your letter dated September 5, 1975; f
a).
The core flooding line isolation valves CFIA and CFlB will be required to have power disconnected and breakers locked open.
i b). states that if valve HP1556 spuriously closed during the injection phase of a LOCA, there will c
be no effect on HPI capability. To confirm that your evaluation was complete, provide the -details of your 4
study which considered this spurious closure during a small break which allows RCS pressure to remain above the cut-off head of the HPI pumps for such a time as to ccapromise pump integrity (due to the loss of the 1 -inch bypass lines).
Provide the time that you assumed it would take before pump damage would occur and relate this situation to its affect on the capability to meet the criteria of 10 CFR 50.46.
3.
Your July 9, 1975 letter indicated that, with the exception of decay heat suction valves DH-ll and DH-12, no critical equipment is affected by post-LOCA flooding. Provide the level of water (above the con-tainment floor) assumed for the LOCA and include the calculations upon which this value is based. Also, the statement is made that a water-tight " trench" will enclose valves DH-ll and DH-12.
Pro-vide a description, with diagrams, of the trench and discuss the surveillance planned to ensure that this installation remains water-tight throughout the reactor lifetime.
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4.
With regard to the partial loop analyses in your October 8, 1975 letter; a).
Provide an analysis of a break in the idle pump discharge.
b)*
Explain the double peak in cladding temperature under 20 seconds and explain why the 1st peak is more pronounced in this analysis relative to the 4-pump break spectrum and relative to the 3-pur analyses for other category plants.
Ii i.
,.. 'l rt the PCT vers s al Provide assurance that alter d y par c).
BAW-10105 would not loop operation.
identified in the LOCA parameters of interest k Spectrum the " Minimum Requirements for ECCS Brea Submit d).
25, 1975.
Submittals," dated April j!
l aasumption Explain the basis for the initial power leve 3
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e).
of 777. for 3-pump operation.
i building pressure p
It is stated that the containment worst case in if calculated by CONTEMPT is similar to thethe lower initial core flow a f).
d BAW-10105. Why didn't in a lower power level for 3-pump operation result containment pressure?
3-pump Provide the core-wide metal-water reaction for g).
operation.
d oxide layers the values of initial pin pressure an values.
assumed and justify the selection of these Submit h).
d Technical Specifi-Provide your schedule for submitting the propose 1.0CA analysis.
5.
cations affected by the d for January (see Provide the passive f ailure analysis committe your September 5,1975 letter).
e with potentially 6.
With regard to the ability of, Davis-Besse 1 to co OCA, the staff d B&W topical report 7.
f notes that Toledo Edison Company has re erenceThe following add-21, 1975).
BAW-10105 (see letter dated July itional information is required:
h doc-More recent boron dilution design proposals on a.
ks simplicity relative to the multi-mode piping networis the staff's Also, it described in the topical report.
h h the decay position that Mode 1 (forced circulation t roug method to Jrop line) should not be attempted as a long-term con. col boron concentration in the core duringThe s hes' in the decay of the possibility of gas or steam entrainment cooling.
I
_3 heat suction nozzle. Such gas or steam entraint'nt can result in severe dam'ge to the decay heat removal pump.
Long-term heat re-,al requirements can exist for long durations (days.r months) after the accident and continuous operation of one train of the decay heat removal system is required.
In the event of equipment malfunction in this train, no method is available to remove the decay heat if the other train has been previously damaged.
For the same reason, step 7 on page 10-7 should also not be attempted.
It is preferred that a simple design exist for boron liilution whereby operator involvement with major ECCS components that fulfill the primary role of long-term heat removal is kept simple and to a minimum. Accordingly, discuss alternate means to provide dilution of boron during the long-term after a LOCA.
b.
Temperature indicators are not satisfactory instrumentation to verify that a minimum flow rate of 40 gpa is maintained.
The. staff requires flow rate indicators which will clearly show the operator that this minimum flow rate is achieved and maintained over the long term.
c, Discuss cor. mon power supply problems and the procedure to restore a loss of power to essential valves. Also, address possible access problems due to high doses should such a power loss occur after the shift to the recirculation mode.
11$[ Discuss the capability to test the dilution systems.
IEI. Discuss the feasibility of gravity draining from the hot leg
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to the sump.
f, Indicate the feasibility of monitoring boron concentration levels during the long term.
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1 8.
With regard to the REFLOOD code resistance values in Table 4-2 l
of BAW-10105 used for loop venting calculations, insufficient j
information exists to support the values selected, a.
Identify each parameter which has been derived from actual measurements made on plant systems, components, models and/or prototypes.
Provide calculations to show how these measured parameters were converted to the K-factors presented in Table 4-2.
j b.
For each flow path shown in Table 4-2, justify the appropriateness of the flow resistance for Davis-Besse 1.
For example, it is not clear that the most conservative areas were selected to serve as a generic calculation applicable to Davis-Besse 1-c.
To allow a greater understanding of the effect of these resistances on reflood rate, re-submit Table 4-2 with the flow paths listed in decreasing order of importance j
to peak cladding temperature calculation:. Provide the specific sensitivity study (peak cladding temperature versus K-factor) for the first, middle, and last value.
9.
It is noted that no additional flow resistance was added to the cold legs c : to the HPI pumps injecting ECC water during reflood.
l Evaluat the effect of an additional 0.25 psi cold leg AP upon the reflood rate and cladding temperature. For the LOCA limit analysis, i
compare the existing time at which the reflood rate goes below 4
1 in/see to the new time calculated using the additional cold leg resistance.
- 10. Justify that the assumed CFT line resistance is appropriate for Davis-Besse 1.
Provide the L/D's for the CFT line for Davis-Besse 1
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and include the entrance and exit losses, 4
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