ML19206A426
| ML19206A426 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse, Midland, Crane  |
| Issue date: | 01/08/1979 |
| From: | Creswell J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Streeter J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML19206A398 | List: |
| References | |
| TASK-AS, TASK-BN-79-10, TASK-TF, TASK-TMR BN--79-10, BN-79-10, TAC-11050, NUDOCS 7904200027 | |
| Download: ML19206A426 (3) | |
Text
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Docket No. 50-500/501
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MEMOR!dLUM FOR:
J. F. Ctreeter, Chief, Nuclear Support Section 1 ad FROM:
J. S. Creswell, Reactor Inspector
SUBJECT:
CONVEYING NEW INFORMATION TO LICENSING BOARDS -
DAVIS-BESSE UNITS 2 5 3 AND MIDLAND UNITS 1 & 2 r
i During the course of my inspections at Davis-Besse, certain issues have come I
'to my attention which I am submitting f or consideration f or forwardir g to the Atomic Safety and Licensing Board which has proceedings pending for the aforementi)ned facilities.
This submittal is made pursuant to Regional Procedure. 530A (November 16,1978), step 3 and inforcation st.pplied to me per step 1.
The issues for censideration are:
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1.
Durit g a recent inspection at Davis-Besse Unit 1 inf ormation has been attained which inlicates that at certain conditions of reactor coola it viscosity (as a function of temperature) core lif ting may occur.
The licensee informed _.the inspector that this issue involves other B&W facilities.
The Dav5.s-Besse FSAR states in Section 4.4.2.7:
The hydraulic f orce on the fuel assembly receiving the most flow is shown as a function of system flow in Figure 4-39.
Additional forces acting on the f uel assembly are the assembly weight and a hold down spring force, which resulted in a net downward force at all times during normal station operation.
The licensee states that there is a 500 F interlock f or the starting
'of the fourth reactor coolant pump.
However, no Technical Specif1-cation requires that the pt=ip be r, tarted at or above this tempera-A concern regarding this matter would be if assemblies moved ture.
upward into a position such that control rod movement would be hindered.
2.
Inspection Report 50-346/78-06, paragraph 4, reported reactivity -
pouer oscillations in the Davis-Besse core.
These oscillations have also occurred at Oconee and are attributed to steam generator level oscillations.
BLU report BAU-1,0.027 states in A9.2:
2 January 8,1979 e
.J.
F. Streeter The OTSG laboratory model test results indicated that periodic oscillations in steam pressure, steam flow, and steam generctor primary outlet temperatures could occur under certain conditions.
It was shown that the oscillations were of the type associated with the relationships between feedvater heating chatber pres-sure drop and tube nest pressure drop, which are eliminated or reduced to levels of no consequence (no f eedback to reactor As system) by adjustment of the tube nest inlet resistance.
a result of the tests, an adjustable orifice has been installed in dbe downcomer section of the steam generators to provide for adjustment of the tube nest inlet resistance and to. provide the means for e3imination of oscillations if they should develop during the operating lif etime of the generators.
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The initial crifice setting is chosen conservatively to minimize the need for f urther adjustment during the startup test program.
We also note that the effect on the incore detector system for monitoring core parameters during the oscillations is not clear.
3.
Inspection and Enforcencut Report 50-346/78-06 documented C,at pre -
surizer level had gone of f scale for approxi=ately five minutes dur-ing the November 29, 1977 loss of offsite power event.
There are some indications that other B&W plants may have problems maintaining pressurizer level indications during transients.
In addition, under certain conditions such as loss of feedvatcr at 100% power with the reactor coolant pumps running.the pressurizer may void completely.
A special analysis has 'een performed concerning this event.
This analysis is attached as Enclosure 1.
Because of pressurizer level maintenance problems d a sizing of the pressurizer may require f urther review.
Also noted during the event was the fact that Teold went offscale (less than 520 F).
In addition, it was noted that the makeup flow monitoring is limited to less than 160 gpm and that makeup flow may be substantially greater than this value.
This infor=ation should be examined in light of the requirements of GDC 13.
4.
A memo from B&W regarding control rod drive system trip breaker maintenance is attached as Enclosure 2.
This memo should be evaluated in terms of shutdown margin maintenance and ATUS considerations par-ticularly in light of large,ositive moderator coef ficients allowable with B&W facilities.
J. F. Streeter 3
Jianuary 8, 1979 5.
Inspection and Enforcement Report 50-346/78-17, paragraph 6 refers to inspection findings regarding the capability of the incare detec-tor system to determine worst case thermal conditions.
The reactor can be operated per the Technical Specifications with the center incore string cut of service.
If the peak power locations is in the center of the core (this has been the case at Davis-Besse),
factors are not applied to conservatively monitor values such as Fq and F delta H.
- 6. describes an event that occurred at a B&W facility which resulted in a severe thermal t 'nsient and extreme dif ficulty in controlling the plant.
The aforementioned facilities should be reviewed in light of this information for possible safety implica-tions.
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J. S. Creswell Reactor Inspector
Enclosures:
As stated cc w/o enclosures:
G. Fiorelli R. C. Knop T. N. Tambling n
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