ML20214G453
| ML20214G453 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 12/18/1974 |
| From: | Tedesco R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| CON-WNP-0046, CON-WNP-46 NUDOCS 8605220159 | |
| Download: ML20214G453 (3) | |
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hoeket No. 50-397
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Roguested Completion hete: Boeseber 15, 1974 Teelenical Baview By: Containment Systems Breed Descripties of Task: Evaluate Submittal by WFEB en Bryss11-Wetuall Imdage moview status: Auraitias Additi===1 Inde===ri==
s' In roepense to your Techniaal Assistenes magneet of a m 7, 1974, the j
Centainment systema Branch hee revissed the appliment's admittal entitled
Dryuell to Wetwell Isakage Study" (WF$s-74-2-RS). Be Sand that addittaael information is required for me to esmpista car e==8W as specified in the encleeed quantion list. Me will aise requise the tapet from the Structural Engineertag Branch, enhaeaW for Eevester 25, 1974, regarding their evaluation of the magnitude of potential bypeos leek paths.
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REOUEST FOR ADDITIONAL INFOR>fATION Lrrss - 2 DOCKET NO. 50-397 1.
The analysis of allowable bypass leakage for small primary system breaks given in the Drywell to Netwell Leakage $tudy (17PPSS-74-2-R5) is an endpoint type calculation which does not track the pressure -
temperature transient in the drywell and wetwell. Current plants with pressure suppression containments (i.e., Mark III) do such a transient calculation which is based on a physically reasonable, yet still conservative, model and provides a more accurate estimate j
of the containment bypass capability. Therefore the results of such a similar analysis (wetwell pressure, wetwell temperature and suppression pool temperature as a function of time) should be provided.
Include the effect of heat sinks in the wetwell and indicate the allowable bypass capability of the containment for small breaks s
on the basis of this type of analysis.
s 2.
On pages III-26 and 27 of the above referenced report it is stated that the operators could actuate the drywell and wetwell sprays or depressurize the reactor vessel via the pressure relief valves to terminate the bypass leakage transient. Provide clarification of your position as follows:
(a) Justify that actuation of the spray system will terminate bypass leakage or mitigate its effects for the range of small primary system break sizes.
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i (b) Specify the suppression pool temperature at the time that it would be anticipated to actuate the primary system pressure L
relief valves and the incremental temperature rise of the pool due to relief valve operation. Discuss the acceptability of potential pool dynamic loads due to relief valve blowdown over the given range of pool temperature and relief valve discharge line mass flux.
3.
Page 1-4 of the above referenced report states that only 5% of the RHR System flow can be diverted to the wetwell spray header, whereas current Mark III plants provide full RHR flow to the containment (wetwell) spray headers af ter a 10-minute delay to allow the RHR System to fulfill its EccS function. Discuss the feasibility of providihg a similar design for your plant and indicate the increase t
in bypass capability that such a nodification would yield.
4.
Page IV-2 of the referenced report indicates that redundant position switches will be provided on each vacuum breaker. Specify the sen-sitivity of these switches and the total equivalent bypass area if each vacuum breaker was unseated by this amount.
5.
Discuss any proposed periodic drywell-wetwell leak testing for your plant.
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