ML19319B244
| ML19319B244 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/27/1973 |
| From: | Stello V US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8001130050 | |
| Download: ML19319B244 (42) | |
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R. C. DeYoung, Assistant Director for Pressurized Unter nesctors, L INTERIH REPO%r O'i OCONEE 2-3 ECCS In Inclosed is an interin report frc:a TR:ES on Oconee 2-3 ECCS.
accordance with your recent notice of schedule slippage on this application, we vill defer completion of the final report to nid-May, 1973. In the meanwhile, the substauce of the interim report cay be of general guidance to your staff in the conduct of reviews of this style BW plant.
In reSard to the.CFT line break accident for the 1967 BW product line, two technical issues have arisen lately which require further explanation. %e first issue concerns " abundant core cooling".
g For the postulated CFT line break with the worst single active
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failure, the ECC deliverf is 400-500 rpm, which more or less matches the boil-off rate for a matter of hours. This is not considered
'J acceptable for the fellowing reasons:
1.
Core hest transfer voald be by evaporation in the core, as the liquid level is only part-vay. up the core.
For plants which have additives such as sodium-thiosulfate or sodium-hydroxide in the ECC, there exists the potential for deposition of solids in the core af ter saturation is reached. To our knowledge, BW has been working on this analynis for sometime, but nothing has come of it.
2.
W e flow loop for HP1 injection, in the recirculation mode, does not include a decay heat (ER) exchanger. In response to staff requests in the past, a cystem design change was made to permit DH removal by a path from the recirculation oe p to a LP pump to. DH cooler and hence through a crosatie to the HP pump section.
If the single failure postulated removes the LP pu=p which is intended to supply recirculated, cooled water to the HP pump, then there would be no supply of cooled water to the core. This conclusion has several variations in the general theme, however.
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Specific designs may vary insofar as which LP pu=p feeds which HP pump. Also, the NPSH may not be sufficient for a HP pump to use uncooled recirculated water; this again is case-dependent.
Presuasbly each HP pump is connected to the P3 sump. Finally, there would be a potential for heat removal from the reactor building as a whole, which could gradually lover the recirculated water te=perature. In any case, it seems that the ECC syste:a itself should cool the fluid before returning it to the core.
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!3.1The plant operator has several key moves to make about i hour, post-LOCA, in: order to acco=plish the BWST injection-R3 zump recirculation switchover. It seems prudent to have a full
-vessel at.that eine. Boiloff is such that the vessel level
. could' drop 1 ft/ min if Ecc were interrupted. A previously stable'thernal condition could quickly degrade if operator error or equipment failure occurred at that-time.
For these three reasons we have recom ended on several plants in the'0L stage (Oconee, MI-1, P.ancho Seco) that the potential for using the one good LP pump be investigated. Generally, this means adjusting crossover valves so that half ( 1500 gpm) of a LP pu:np is now available to_ the vessel, although we understand -
SMUD is considering a variation.* Some estimates of the tima required to accomplish this valving' adjustment range up_to 15 minutes. The expectation on the clad t q erature transient is such that a peak is ' essentially reached at or before 15 minutes, and that diversion' of LP vater could be accomplished anytime in the first hour, insofar as remedying the three objections stated above. The
. feasibility of accomplishing the crossover is a case related matter and involves RO and TR:0SB consideration.
The desirability of ~ disengaging the operator action in future CP
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cases is not-the subject of this memo. Additions 1 discussion may f
be marited in this regard, for example on North Anna.
An additional technical issue, generic to the 1967 B&U product line, is that of level swell and heat transfer following a Crr line break. This is discussed in the enclosed report, nico. A recent memo, Stello to DeYoung, indicated acceptance by TR:RS of an interia power capability for Oconee Unit 1 of 757. of rated.
.primarily because of a pending fuel densification resolution.
-Duke Power has contracted for tests _ (to be run by E) to verify assumptions of level swell and heat transfer. In addition to the 5tN analysis, TR:CPB has'a new calculational technique (called SVELL) which it hopes to index on the E tests. Ticing esy be crucial
- in that test. completion, data analysis, transmittal of information to' REG, staff analysis, and report generation all appear to be squeezed into the April-May time frame. For this reason, TR:CPR expects to participate along the way, rather than at the end if schedules are to be met.
- ISMUD believes th'ey can detect which CFT line breaks by excessive
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flow in one loop, none in the other, for the first few minutes post-LOCA.
In~ this case, they would crosstie the whole 2500-3000 gpm
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-to the vessel.
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. e i rlease examine the attached' report for applicability to near-ter.s
' B&V-type SER's.
Ve will suppleant each case with coments fron TR:0SB on ' acceptability of the. crossover procedures. Ve will p*. ovide a generic report on the level;svell-heat transfer, presumbly in (May 1973',:if Duke meets its schedule. We will provide a supplemntal-report on Oconee 1 fuel densification by May 1, also if Duke meets
!its schedule.
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} Dddnal Signed by TIctorSte!!o L
Victor Stello, Jr., Assistant Director for Ecactor Safety Directorate-of Licensing ji
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T. Novak' W. Houston A. Schwencer D. Ross R.-Bernero D. Davis
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