ML19257B285
| ML19257B285 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/20/1976 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19257B284 | List: |
| References | |
| TASK-15-05, TASK-15-5, TASK-RR NUDOCS 8001150480 | |
| Download: ML19257B285 (1) | |
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&r:I 2,199h Evaluation The use of the SAFE code represents an acceptable method of predicting reactor vessel inventory following a loss of Fif/FNCI. The heat source for SAFE, which represents heat input due to fission product decay following reactor scram, conservatively accounts for the previous operating history of Millstone Unit 1.
As mentioned above, the analysis in support of 40'4 power operation takes credit for water supplied by the CRD pumps. We find this to be acceptable since the CRD system has sufficient redundancy to represent a reliabic source of water.
Moreover, the reliability of the CRD system is further enhanced since it is in constant use during reactor operation to supply water for control rod operation.
Even in the event that a CRD pump is not availabic during a loss af FN/FNC1 transient from 40'e power, we estimate that peak clad te:'peratures will not exceed 1000"F; thus, no fuel clad perforation is predicted.
One of the najor assur.ptions made in the analysis is that the reactor operator is capabic of taking action to depressuri:e the reactor no later than 10 minutes after initiation of the loss of FW/FKCI transient.
We find this assun.ption acceptable since sufficient instrumentation and alarms exist to positively and promptly identify a loss of FK/FWC1.
In addition, the Mill.= tone Unit 1 operating procedures have been modified during the Isolation Condenser outage to require prompt operator action to the LPCI/CS pumps and depressuri:e the reactor in the event of a loss start o f Fll/ FECI.
Even in the event that operator action is delayed for one 0
hour, the peak transient fuel clad temperature would not exceed 619 F; thus, fuel integrity would still be maintained.
We concur with NNECO that following a loss of FW/FWCI from 40t power, no uncovery of the reactor core will take place. Consequently, even without the Isolation Condenser, which would normally serve to provide adequate core cooling in the event of a loss of FW/FECI, tl.c restriction to 40". pouer combined with operator action to depressurize the reactor and iniate core cooling with the LPCI and CS system will assure that no fuel damage will take place.
The operator has ampic time to carry out the required actions to depressuri:e the reactor even if no credit were to be taken for operation of a CRD punp.
Since the restriction is necessitated by the inoperability of the Isolation Condenser, it is appropriate that the restriction, contained in paragraph 3.E.2 of license DPR-21, be deleted upon return to service of the Isolation Condenser.
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