ML20148D626
| ML20148D626 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/24/1964 |
| From: | Thornburg H US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20148D623 | List: |
| References | |
| 50-010-64-02, 50-10-64-2, NUDOCS 8010080799 | |
| Download: ML20148D626 (8) | |
Text
'1 U. S. ATOMIC ENERGY COMMISSION REGION TII DIVISION OF COMPLIANCE Fbreh 24, 1964 C0 REPORT NO 10/64-2
Title:
COMM0!NEALTH EDISON COMPANY LICENSE NO. DPR-2 Date of Visit:
March 11, 1964 By:
H. D. Thornburg, Reactor Inspector S 1.'."MA RY A visit was made to the Dresden Nuclear Power Station on March 11, 1964 The following items of interest were noted:
1.
One control drive has been locksd out in the fully inserted position because of a malfunction. Fe.raonnel at the site suspect that the problem is due to galling of the index tube.
2.
Af ter preliminary consideration cf the 1963 bio-assay results it would appear that ingestion of radionuclides has occurred in several instances. The majority of the results were negative.
3.
One of the post incident cooling eyetera inlet valves was found inoperative during a recent rcutir.e test.
Heat transfer calculations indicate that the system meets li: ente specifications with the valve closed and locked out.
No items cf noncompliance were noted, pETAILS I.
Scone of Visit A visit was mcde to the Dresden 'iuclear Powar Station on lurch 11, 1964 to obtain information about:
A.
Radioactive effluents and wsste diepozr.1 at the site. The infornation will be forwarded to P7 in complian:e with their recent l
request.
E.
Containment vessel leck rste cesting.
Don c i nu e O i
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A
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2 Scope of Visit (continued)-
H C.. An inoperable control. drive.
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D.- A: problem with the post incident cooling system.
y The following Commonwealth Edison personnel were contacted:
Mr._H. K. Hoyt Station Superintendent Mr. C. B. Zitek Assistant' Station Superintendent
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'Mr. N. A. K'.rshaw Manager of Erficiency Group g
Mr. G. Red An Operating Engineer, Mechanical E
Mr. F. Palmer Technical Supervisor
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'Mr. W. Kiedaisch
-Radiation Protection Engineer II.
Results of Visit A.
Discussion of Containment Vessel Leak Rate Testinc The inspector discussed the various aspects of containment vessel leak rate testing wi:h personnel at the site. They stated that they are currently performing an engineering evaluation of the problem and will make a proposal to RL as soon as the study has been concluded.
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5 The following general topics were covered:
j-1.
Vessel penetration design.
2.
Recent experience related to extrapolating leak rate f
data obtained at intermediate pressures to the peak j
accident pressure.
I-1 3.
Work which has been performed on leak mechanisms.
4.
The possible methods of perfcrming leak rate tests.
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Mr. Palmer and the inspector calculated the extrapolated leak
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rate from the 5 psig.. test performed in 1961 assuming laminar flow and arrived at a value of approximately 0.67. of the contained volume per day. _
Mr. Palmer stated that the four ventilation isolation valves were leak tested recently. The inspector reviewed a rough copy of the test
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report and noted that the test was performed at 20 psig. Both valves inside the containment vessel indicated no leakage.
One exterior valve indicated no leakage and one was found to leak at'the rate equivalent j
to 0.0015% of the contained volume / day.
Mr. Palmer indicated that the steam and ventilation isolation valves and the air locks are leak tested at least once per_ year. The inspector has reported the results j
in previous repcrts.
(continued)
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Results of Visit (cuntinued)
L.
Bin 31ne Control Rod Drive During the coarse of the routine daily exercising of all completely withdrawn control drives (a t 4: 25 a.m. on March 2,1964), it was noted the control drive K-4 did not respond to a normal insert signal.1/
At 7:35 a.m. on March 2, 1964 when drive K-2 was given another insertion signal with normal hydraulic systou pressures, it was inserted a single notch. Successive attempts to withdraw the drive resulted in progressive notch by notch insertion. Normal and greater thar normal hydraulic driving pressures were used during the above sequen:e.
Each notch of insertion required at least two withdraw s ignals, indica t: ag the drive w
'usert impulse.1/ as ratcheting in ur.dtr the influence of the preliminary While the drive was in the fully inserted position, the operation of the hydraulic system valves associated with the drive was investigated and appeared to function prcperly. The drive was then disarmed in the fully inserted position until subsequent tests were conducted during a previously scheduled outage on }brcli 6, 1964.
During the outage on March 6,1964, additional attempts to with-draw drive K-4 were again unsuccessful. Special gages were installed at i
critical points in the hydraulic system to ascertain if the problem was as'ociated with that part of the drive hydraulic system. The results of s
this test indicated normal hydraulie system pressures, valve action, etc.
The drive was again disarmed in the fully inserted position. At the time of the inspecticn the solenoid valves were dcactivated and the position indicator was tagged in the centrol room.
Commonwcalth Edisor. Company's evaluation of the problem, with the concurrence of G-E consultants, indicates that the inoperability of the drive was due to increased friction. The probable cause of the increased friction is considered to be galling of the index tube similar j
to the problem encountered on June 17, 1962 with control drive C-7.
Commonwealth Edison Ccmpany's justification for continuing operation with control drive K-5 fully insarted it.:o the ccre and deactivated was as follows:
(continued) 1/ Th-drive performed normally during e similar test on March 1, 1964.
2/ The preliminsry insert impulse is necesesry in the Dresden design to force the shuttle piston dcwn te ur.lotk the latch fingers, i
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Results of Visit (continued) i 1.
All other control drives are operating properly.
2.
Apparently the onset of maloperation can be detected by routine daily and weekly tests.
3.
Although increased fricticn in a drive may impair normal motica, it has n+ver been observed to prevent scram operation. Scram pressures are en the order of five times that necessary to insert K-4.
4.
The fact that drive K-4 was locked out in the fully inserted position has no effect es the stu;k rod criteria and will not impair t eactor control.
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5.
No indication of an impending massive failure of the control system was indicated.
6.
Axici flux dccc shoved thtt the ineertien of K-4 does net impeir ths contr:1 :f sxial flua.
It is pla nsd that the drive will ba removed, incpected, and replaced during the refeeling cuttgc in April.
0:2 other drive will j
be selected for inspection cisc, a:ccrding to ;criennel at the site.
C, Post Incident Sv=te -
i t
Mr. Hoyt notified the inepectcr on January 31, 1964 by telephone I
tha t a problee had been en:cuntered with the operation of ens of the inlet i
valves of the posc-incident system during the course. ci s routine test of the system performed on the weekend prior to the call. The valve, one of three valves in two ide.ntical systart vhie.h cor.ttin s teral of six similar 1
valves, was disabled and ic itd i: the fally closed pcaitier.
i An analysis of the situation by personnel at the site concluded that the system in the above-describcd conditien could mect the requirements of DPR-2, Appendix Ad# based on:
1.
Heat transfsr dsta eb:31:.e6 during preeptrational testing, t.
assuming a certervativs fe.uling fteter.
2.
Calculatices tFat 54rs cerrcated batsd on the der.sity and viscosity of water at the accide.t :crciticn.
3.
A conservstive vclue for the hest trarafer acefficient (approximately 200 Btu /hr f t." OT?.
It was calculated trat the heat rescsil capacit:, of-the system in the condition outlined above is appreximately 31 x 106 Btu /hr at an enclosure temperature of 2560r.
The valve will be repaired dur136 the for thcoming refueling outage, accor ding cc pet torz (1 at the eite.
(cr.tinued) i 3/ Iten L 11 ef ciM., Appenca A ite tt : h tu be st : c.reval capacity of 1
thic syster.
t litet ' O.- 10b Ett:h: Lt u
- _oftre ::.tc: a: tcrptrsrure of 2560?.
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4 s l Results"of Visit (continued) i D.
Personnel Exposure
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The. inspector reviewed the annual summary reports on the exposure of employees to direct radiatien and bio-assay program results for 1963. The following items were noted-i 1.
Radiation Exposure Summary a.
The exposure for 90 permanently assigned Dresden personnel averaged 890 mrem for the yect 1963.
b.
The average for the year 1962 was 874 mrem.
~I c.
The highest individual exposure for 1963 j
was 2313 mrem.
j d.
The highest individual exposure for the year 1962 was 1985 mrem.
e.
The highest exposures for a work group in 1963 were accumulated by maintenance personnel and appear to be attributable to maintenance jobs performed during overhaul periods. Approxi-mately 60% of the maintenance groups' exposure was accumulated in the first quarter, during which the refueling outage occurred.
f.
The expasures accumulated by the equipment operators, equipment attendants, and radiation protection men were above the average alsp.
There men are required to enter radiation areas frequently to operate equipment, take radiation measurements, etc.
Roughly 50% of the exposure for these groups was accumulated during the first quarter (refueling outage).
2.
Bio-assay Summary - 1963 a.
The average concentrations of 331 urine sample analyses was 0.03 d/m/ml.
b.
The results ranged from 0.94 d/m/ml to 0.02 d/m/ml.
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6-Results of Visit (continued)
- c..A limit of 4 d/m/ml has been established by Commonwealth Edison Company as the point where the contractor performing the analysis is instructed to notify the Commonwealth Edison Company Medical Director immediately.
(1) Subsequent sompics would be collected to
' I check the original result.
(2)
If a high concentration is confirmed and sustained in subsequent samples, the Medical Director vill prescribe the.necessary action.
i d.
The limit of 4 d/m/ml has been calculated as a value which epproaches 10 CPR 20 specifications for internal dose. Allowances were made on the.
basis of the critical organ which is influenced by the distribution of isotopes and their possible physiological effects.
i No limits are used other than the 4 d/m/ml upper limit l
.for consideration of bio-assay data.
Other facilities i
have two-intermediate values: nne which is considered' a positive threshold result and a second which is con-t sidered a varning limit. The absolute r.ombers depend i
on some of the following considerations:
. I a.
Isotopes considered.
1 b.
The critical organ associated with a given it.otope.
c.
Excretion rates.
1 d.
Asaay techniques.
Bio-assay 10:ite employed by various installations are 1
no comparable unless the assumptions, assay methods,
.etc., have been fully evaluated. The inspector.bss not fully analyzed these considerstions s.s yet at Dresden.
(continued) rw w -.
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' Results of Visit (c'ontinued) s.
E.
Operational and Test InformAtion 1.
The refueling outtgs is still scheduled for'about the middle of April despite the fact that the full insertion of control rod K-5 is worth approximately 8 MWe or one week of operation.
2.
System activit,- levels for March to the date of the visit are:
Stack effluent activity (after two hours)
'1i4,000 microcuries/sec.
Gross systez tetivity
'270.51 microcuries/ml.
5 Gross Iodine activity grl.4 x 10 ep,f,1, As one would expect, system activity is influenced by power level. The mtxixem capacity of the plant has been on the declins since Janut.ry of 1964.
3.
The results of-the recent test 9 performed during the
' March 6,1964, outage have not been fully evaluated as yet.
Ir was determincd that the temperature coefficient became negative tt 300 F.
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A test was perforced 7.t 155 MWe which involved tripping i
one of the mtin hett transfer pumps. A second pump,
?j vhich Iceds the core through a nozzle opposite that for
- ij the previously tripped pump was tripped several minutes later. The purpoes of the test was to obtain data for the evaluation of whether or not one or more main heat transfer pumps should be tripped b j
vhenever a turbine trip cecurs.4/ y the safety system It was suggested thtt the stfety system be so modified j
following a turbir.e trip in the-succer of 1963. The Dresden Revisv Concittee suggested thtt tests be per-formed before the zodifications vere performed.
Dresden 1
personnel performed c I.ntlysis of the harcrds presented
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4/ See CO. report dated 8-2-63.
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Results of Visit (continued) l r
by such a test and found'that it. did not involve I
hazards exceeding the magnitude of those encountered i
during full powcr operation ot previous test operations.
General Electric consultanta concurred in this view.
6 Three-pump flow was observed to be 29.0 x 10 lbs/hr,
. while two-pump flov.vass 21.0 x 106 lbs/hr. The burn-out ratio was. calculated to be'> 4.0 with both two and three-pump flow.
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4.
Extensive testing performed in January and February
.c has identified nine control cells as possibly containing failed fuel elements. The testing hos been performed at 110 MWe, 160 MWe and 190 MWe.
Rod pattern changes were made to assure that all rods were tested.
The flux-tilting method was used as was the case with Core 1.
The' data were not reproducible at all power levels. For I
example, the data obtained at 110 MWe did not exhibit the
.l large. leakers at 150 MWe, but did exhibit two leaker locations found during previous testing.
The series of tests provided more insight with respect to core power distribution in both the txial and radial directions.
F.
Plant Eff1r.nte trd kcste Distope.1 j
These da:t have been transmitted to C0 Headquarters as a separate memorandem addressed to B. H. Grier, dated Mtreh 13, 1964.
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