ML19319A963
| ML19319A963 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/13/1976 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Goller K Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7912300263 | |
| Download: ML19319A963 (3) | |
Text
.
_i SEP 131976 i
MEMORANDUti FOR:
X. Goller, Assistant Director, Operating Reactors, D0R FR0ft:
D. Eisenhut, Assistant Director, Operational Technology, MR SUBJLCT:
EVALUATION OF BORON DILUTI0il FLO!! INDICATION REQUIRE!!ENTS IN OCONEE tiUCLEAR STATION, UtilTS 1, 2, AND 3.
REFERENCE:
TAR No. CRB-1-252 Oconee-Units 1, 2, &.3 (50-269/270/287) ij By letter dated August 6,1976 (Reference 1) Duke Power Company has i
requested the NRC to remove the requirement for installation of i
positive flow indicators in the hot leg drain lines. This requirement was imposed by the NRC (Reference 2) in order to ascertain that boron dilution flow is achieved during the post-LOCA long tem cooling period.
As a part of the ECCS review, the NRC requested that the licensee providc procedures which would prevent boric acid from precipitating in the core region during post-LOCA long term cooling. The licensee j
responded to this request by letter dated October 31,1975 (Reference 3) in which he proposed the procedures for maintaining boric acid c concentration below the solubility limits.
According to these procedures for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of long tern cooling, dilution flow should be maintained by a natural circulation of coolant between the downcomer and the core through the internal vent valves. After that time, the dilution flow will be maintained by a forced circulation produced by draining the injected coolant through the decay heat drop line.
In order to make the systen single failure proof, the licensee proposed to modify the existing piping by the addition of two drain lines from the decay heat line to the sump: One line, installed upstream of the existing isolation valves, having two notor operated valves and the other, installed downstrean from the existing isolation valves, having one motor-operated valve.
The NRC evaluated the proposed design as a part of the review of the Oconee, Unit 1 ECCS analysis (Reference 4) and by letter dated I
February 17,1976 (Reference 2) advised the licensee that their proposed design was acceptable with the provision that positive flow I
indicators should be installed in the drain lines.
In the event that the flow indicators could not be provided prior to the plant startup, a preoperational test demonstratinc adequate flow thecuch the drain lines under post-LOCA conditions would constitute an accentable interin solution.
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> SEP L1 s 1976 DEisenhut' KParczewski
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1).the licensee has providedf('
ts performed on the boron dilution By letter dated August 6,1976.(Reference He also reiterated: his request the results of the preoperational.tes Oconee hould not be installed in the systems in Oconee Units-I and 2.that the drain line f f the passive ' nature and t-edu plants. -He argued that because.oof. cne system and a p In fact. for certain. types of hot leg h drain lines. no flow"' or. low flow" failure of t are not required. ~
. simulteneous flow in bot In r
indications would not necessarily mean i formation to the operator.asuring devices i
and they may provide ini.sleading _ naddition the in drain lines and contribute to the decreasepositi 1
The licensee has indicated.that a h
s in the drain lines and
. hydraulic resistance of t e low pressure injection flows should provide, l
of the f.ow - rates.of the open position of the isolation va ve.
existence of boron dilution flow.
continuous monitoring of the.. sufficient positive indica
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h st for dispensing with the flow The staff has reviewed the submittal anby the f the i.
ystem has sufficient
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l f and, as such, is acceptable to drain line indicated that the resulting s measuring devices.
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ff is-of the opinion that monitoring o redundancy to be single failure proo the staff. 'However, the sta Even with a full d
- the LPI. flow does not provi e su d in the core.in the drain lines may, under j
-dilution flow could be maintaine L
f Linsufficient dilution flowhe could injection flow, the lack of adequate flowcertain With this information available.to the operator, 1
lternate boron dilution modesrizer s 1
it take appropriate action to init a e a(eg.. injection in'.the core.
cid below the solubility limits.evio i
to keep the concentration of bor c a
- The staff, therefore. maintains its prindication of the fluid
. measure, a positive flow p
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. leg is required.
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.Darrell G. Eisenhut, Assistant D rec o -
for Operational Technology i
Division of Operating Reactors j-B
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REFERENCES _
from William O. Parker, Jr., (Duke Power: Company) to L t
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Rusche, (NRC). dated' August 6', 1976.
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Bernard C (2)[Let'terfromRobert'A.-Purple (NRC)-toWilliamO.Pa'rk i
17, 1976.
Power Company), dated February C
y) to
-(3): Letter.from William O. Parker, Jr., (Duke Power ompan Bernard C.' Rusche (NRC)', dated October-31, 1975.
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1, ller (NRC), dated
. (4) Letter. from~D. F. Ross L(NRC) to Karl R. Go
-January 16, 1976.
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