ML19282D046
| ML19282D046 | |
| Person / Time | |
|---|---|
| Issue date: | 01/10/1978 |
| From: | Novak T Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19282D043 | List: |
| References | |
| FOIA-79-98 NUDOCS 7905110060 | |
| Download: ML19282D046 (2) | |
Text
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NUCLEAR REGULATOn s D:.".ilsslotJ r
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NOTE TO:
RSB Members
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T. M. flovak c,UBJ ECT :
LOOP SEALS Ifi PRESSURIZER SURGE lit 1E l
I
- t. cop seals in the pressurizer surge line are used in some plant designs
'noted in B&W).
Under ordinary circumstances, these configurations are inconsequential because the saturation' temperature in the pressurized
' 6500F) is the highest temperature in the primary system.
- However, under upset conditions (such as prolonged relief valve opening) and ccidents where significant voids are formed in the primary system, it l
.ay be possible to end up with a two-phase mixture in the pressurizer j
that is not at the'nighest temperature in the primary system.
Under j
these circumstances, additional loss of primary system inventory or i
shri.nkage in the primary system may not be ' indicated by pressurizer
'evel.
This situation has already occurred at Davis Besse I when a
.elier valvt stuck open.
'he loup seal results in a manometer effect as shown in Fig.1.
If there is satvated. team at 1200 psi in the hot leg pipe and the level in the i
. ressurizer is 60 feet, the pressurizer pressure, P, would only have to 2
te about 11N psi, which corresponds to saturation temperature about 50F
! elow that in the hot leg.
Thus, the pressurizer temperature does not nave to be significantly lower than the temperature in the primary
- ystem.
Although the safety anMyses do not require termination of the makeup vstem, operators would control makeup flow based on the pressurizer level as par t,if their normal procedures..As a result, under certain onditions where the pressurizer could behave as a manometer, the op'erator could erroneously shut off makeup flow when significant void occurs else-shere in the system or loss of inventory is continuing.
It is recommended that the bases for the design requirement be studied
.arefully for all CP reviews with the object of determining if the loop eal can be eliminated.
For OL reviews, procedures should be reviewed
.o ensure adequate information before the operator terminates makeup flow.
&};n :ci L Thomas M. !!ovak, Chief l
Reactor Systems Branch
Enclosure:
l Figure 1 cc:
D. Ross l
Contact:
Sandy Israel, t'RR 49-27591 7 90511 oc(30 7
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