ML20052F412
| ML20052F412 | |
| Person / Time | |
|---|---|
| Site: | 07601978 |
| Issue date: | 04/26/1979 |
| From: | Cromer S Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| ACRS-CT-1109C, NUDOCS 8205120435 | |
| Download: ML20052F412 (11) | |
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An *==ination of S.I.eted gX4 n
Licensee Event Reports 1976 through 1978 Two SasiItypes of Reactors are used for production of power within W United States.
The Boiling Water Reector h t produoos steam from domineralized water in direct contact with h Reactor fuel elements, and the Pressurized Water Reactor ht utilizes a secondary fluid (Reactor Coolant) to transfer heat from the Reactor to heat exchangers (Steam Generators) in which steam is produood. An electrically heated pressurizer is incorporated in the Reactor Coolant System to maintain the pressure of the Reactor Coolant high enough to prevent boiling in the Reactor.
Boron solutions are used with both types of Reactors. However in W Boiling Water Reactor it is used only in h Standby Liquid Control System. The function of this system is to provide a backup method, which is independent of h control rods, to make the Reactor sub-critical over it's full range of operating oonditions. This is accom-
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plished by injocting a poison solution of sodium pentaborate in dominera=
lized water into h Reactor Yessel through two explosively actuated valves connected in parallel. Metal diaphragms incorporated in these valves isolate W boron solution from the Reactor until they are sheared by the explosive actuators. This system has no other ibnotion and would
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be expected to remain in standby condition throughout the life of the e
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Reactor.
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- w Pressurized Water Reactors have three major Boron Systems:
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' Etno A.
Rosetor Coolant System OEo W
B.
Residual Heat Removal System DE-
't 3 ORIGINAL omi d
Certiflod Ey
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The Reactor Coohnt System includes W reactor coolant piumps that eirculate W coolant through the system, the steam generators, the pressurizer, piping and associated instruments and controls. The reactor coohnt, composed of denineralized water, sodium pentaborate and other chemicals added for Ph control, serves not only as a heat transfer media, but because of it's boron poison content, as a shim control to reduce the.mmber of control rods needed and to improve power distribution. The boron content of the coolant is decreased 1
from about 13,000 ppn with a new core to about 100 pp:n with spent j
i fuel.
i h Bnergency Core Cooling System is designed to coal b reactor
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core and provide shutdown capability in case of the m pture of any coohnt or steam pipe, a tube mpture in the steam generator, or a mpture of the control rod device mechanism causing a rod cluster oontrol assembly ejection accident. This is accomplished by injecting borated water into either the cold leg or the upper head of h reactor from hrge safety injection tanks in which the liquid is stored under nitrogen pressure. When these tanks are depleted additional borated water may be pumped from W rehling storage tank or from the reactor containment sump.
Chemical control of the boric acid solutions is accomplished by b cheadcal volume control iiysteu located outside the reactor i
containment building. It contains equipnent for continuously with-i i
i drawing a small side stream of reactor ooolant, purifyir.g it by ion exchange, adding chemicals and domineralized water as needed and returning it to W coolant system with high pressure c} urging pumps.
I
7 of A
lation of 234 Licensee Event Reports issued during 1976, 1977 and 1978 on Boron Systmawp. prepared by the Nuclear Safety Information Center,were reviewed. These reports are principally concerned with the Chemical Volume Control System and did not include the charging pumps and associated piping or any equipment located inside the Reactor Containment Building.
Causes for problems with the vstems reported i
are presented by Reactors in Table 1.
Pressurized Water Reactors, as might be expected because of the more extensive use of Boron Systems, were responsible for the major portion of the IER's. Information from j
Table 1 may be further sunriarized as follows:
t Licensee Event Reports Concerning Boron Systems Issued in 1976, 1977 and 1978 Itam Number Boron Concentration outside Technical Spec. Limits 72 30.8 Valves 59 25.2 Pumps-23 9.8 Heaters 22 9.4 I
Instruments & Controls 22 9.4 Pipe Leaks 17 7.3 Other E
M I
Totals
~ &34 100.00 As over 30% of the LER's, including eight of the nine IER's for
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l Boiling Water Reactors, were caused by boron concentrations found to be outside the technical specification limits. These 72 IER's were i
examined in an attempt to determine tha basic reasons for the problems encountered in this area. The reasons developed are as follows:
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r cause Number t
Defootive Procedures 41 56.9 i
Personnel Error 20 27.7 i
Valve Leaks 4
5.6 Design Errors 4
5.6 Analytical Errors 3
4.2
~
72 100.00 i
It may be observed that the sum of reportabla events, caused by defective procedures, personnel errors, and analytical errors contri-
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buting to boron concentrations reported outside technical spec. limits l
i is88.8%
Isaks through the seats in check valves and block valves affect boron concent:-ation by diluting strong solutions with domineralized f
water or by permitting concentrated solutions to mix with weaker ones, thereby increasing boron conoontration.
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In the few cases listed under Design Construction Errors, condi-
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tions wars encountered during operation where the tech, spec, could not be met with the equipment provided. In these cases equipment or proco-dures were modified t provide for safe operation.
VALVES A review of the 59 IER's on valves showed that seat leakage was I
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responsibleforover60%oftheproblems. In sovr.-al instances the j
l valves seated properly after flushing with domineralized water. This might indicate local oold spots that permitted boric acid crystals to I
form. Cracked or ruptured diaphraga's were reported for several Grinnell Valves indicating the need for routine replacement of diaphragms before the end of their servise life. One LER indicated an accumulation of
radioactive crud. Approximately one fifth of valve LER's were caused by Operator Error such as opening the wrong valve or employing an incorrect valve lineup. In a few cases valves constructed of materials unsuitable for the servioo were found and replaced. Ordy two lesia in valve bodies were reported.
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TABIE 1 UCENSEE EVENT REPORTS 8
8 5
b b
h
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3 ac e
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5 e1 2 8
L s.
g.
2
~
L y
a g
g u
Reactor d
A 5
- e S
1C M
5 0
W. S R.
Arnold WR 545 5/74 1
1 1
1 6
1 5
Big Rock Point BWR 70' 12/62 1
1 1
Beaver Vaney PWR 852 4/77 1
2 3
1 2
Bellefonte PWR 1213 1
1 1
Callaway PWR H50 1
1 1
Calvert Cliffs 1 WR 850 5/75 4
1 1
6 2
2 2
Calvert Cliffs 2 PWR 850 4/77 1
- 4 1
7 1
2 4
1 1
3 3
Cook 1 N R' 1054 8 75 1
1 Cook 2 WR 1094 6 8 4
1 5
5 Conneticut Yankee PWR 575 1
1 7.
1 2
2 Crystal River 3 PWR 825 3 77 2
3 4
1 10 1
6 3
Diablo Canyon 1 PWR 1060 5 76 1
1 1
Davis Besse 1 NR 906 n/77 4 1
6 H
1 4
6 Dresden 2 WR 800 8/70 1
1 1
l Farley 1 PWR 860 12/77 1 10 H
4 7
Calhoun 1 PWR 457 9 73 1
1 1
Ginna 1
PWR 490 3 70 1
1 1
Indian Point 2 PWR 873 7 74 1
3 1
2 7
3 2
2 Indian foint 3 PWR
%5 8/76 1
1 1
Iowaunee 1 PWR 535 6/74 1
1 1
Ia Crosse BWR 50 n/69 1
1 1
3 1
2
(
McGuire 1 & 2 PWR 1180 7/79 1
1 1
l Millstone 1 BWR 652 12/70 1
1 1
Millstone 2 PWR 828 12/75 3 1
1 2
7 2
3 2
N:rth Anna 1 PWR 934 4/78 2
3 1
6 2
4 Oconee 1 PWR 871 12/73 1
1 1
3 1
2 l
Coonee 2 PWR 8 71 9/74 2
2 2
Oconee 3 PWR 871 12/74 1
1 1
l Sub Total 15 13 3 51 5 14 5 106 17 35 Sh i
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TABLE 1 UCENSEE EVENT REPORTS e5 g
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b 2
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e t
e se
+
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g Reactor ES
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Palisades 1 PWR 700 12/71 4
1 5
3 2
}
Peach Bottets 2 BWR 1065 7/74 1
1 1
Peach Bottom 3 BWR 1065 12 74 2
2 1
1 Prairie Island 1 PWR 520 12 73 2
1 3
1 2
i Prairie Island 2 NR 52J 12 74 1 2
3 1
2 Pilgrim 1 Bia 670 12 72 1
1 1
Pdnt Brmoh 2 NR 497 12 72 1
1 1
E,B. Robinson 2 PWR 665 3/71 3
4 1
1 3
12 5
3 4
i St. Incie 1 PWR 802 12/76 1
1 1
3 1
1 1
i San Onofre 1 PJR 436 1/68 1
1 1
3 1
2 l
Salem 1 PWR 1090 12/76 1 9
10 3
5 2
Surry 1 PWR 775 12/72 5 5
1 1
12 4
1 7
Surry 2 PWR 775 5/73 7
3 5
1 1
1 1
19 3
7 9
Seabrook 1 & 2 PWR 1150 1
1 1
i hree Mile Ishnd 1 PWR 792 9 74 1
1 1
Three Mile Ishnd 2 PWR 880 5 78 1
1 2
2
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Trojan 1 PWR n30 5 76 1
3 4
2 1
1 hrkey Point 3 PWR 666 8 71 1
1 2
4 2
1 1
l hrkey Point 4 PWR 666 9 73 3
3 1
7 2
5 Yankee Rowe 1 PWR 175 6 61 5
3 8
3 3
2 Zion 1 PWR 1100 6 73 3
1 1
4 9
3 4
2 Zion 2 PWR 1100 12/73 14 1
1 1
17 5
12 Sub Totals this page 44 10 19 21 12 8 14 128 39 48 41 l
Sub Total Page 1 15133 51 5 14 5 106 17 35 54 j
Total 59 23 22 72 17 22 19 234 56 83 95 I
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Reactors l
WR's 8
8 1
9 3
5 1
PWR's 45 59 23 22 64 17 22 18 225 53 78 94 Total 53 i
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t Problems with charging pmaps not included in the above susmarv are as follows:
Design and Manufacturing Errors 13 Crac}:s & Imaks in Castings 10 i
Packing and Seal Isaks 9
Pipe Leaks 7
Maintenance 7
Procedures & Personnel Error 6
Elsetrical & Motors 5
l Instruments & Controls 4
Yalves 4
i Suetion Air Bound 3
Seal Water Pump Failures 3
Total 71 The causer reported for Licensee Events in the three major Pressur-ized Reactor Boron Systems may be sumarized as follows:
i Design Construction Errors 15 1
Seal Leaks 10 Isaks in Small Pipes Connected to System 9
l Instnaments & Controls 4
Defective Procedures & Personnel Errors 3
Electric Power l
Total M
t Residual Heat Removal System Procedures & Personnel Errors 31 Yalves 24 i
Pipe Imaks 19
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Pasps 8
Design Errors 6
Instnaments & Controls 6
Maintenance 4
Electric Power 3
Construction Errors 3
Airbound Pumps 1
Seal Water Isaks 2
Other l
L Total 106 Emergency Core Cooling System Procedures & Personnel Errors 54 Instruments & Controls 46 i
Valves 40 l
i Design Errors 15 Pipe Imaks 10 Defective Equipment 10 Electrical Power 8
Inadvertant Safety Injections 8
i Construction Errors 7
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Pumps 6
Other 5
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Maintenance 4
Seal Water Leaks J
l 215 k
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12 Discussion It appears that the most serious problem facing the Nuclear Industry is proper training of personnel, particularly in W handling of non-routine problems.
Considering the important role of boron solutions in the operation of the Pressurized Water Reactor, a great deal of effort is justified in developing proper procedures for better control of boron concentrations.
Control of concentration and proper attention to Heat Tracing Systems to prevent crystal formation in lines and valves is i
needed to minimize problems with plugged lines, airbound pumps and improperly seating valves, etc.
A well coordinated experimental development program on valves for servios with boric acid solutions should be undertaken to minimise the many problems reported. It is recognized ht this is a very difficult problem, however valves suitable for handling many very unconventional materials have been developed.
The positive displacement charging pumps appear to be responsible for many of the problems such as vibration and fatigue in pipes and equi ment. A number of these pumps have been installed without pulsa-l l
tion dampers on the suction and discharge lines. Several IERfs have indicated that these were being installed. NRC is compiling infomation on the Reactors ht have pulsation dampers and the dates that%y were
$nstalled. From this information it should be possible to determine their i
offect on minimizing the fatigue problem.
l Isaks have been reported in small diameter lines such as seal water lines that are connected to Reactor Cooh rt Pumps. Attention needs to be~
m en to these 11nes to minim 1.e fatigue and subse,uent fa m r..
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Attention needs to be given to the problem of prevention of water hanener in the steam generator,and for other causes for the inadvertant actuation of the Safety Injection' system.
Note: Statistical data presented in this Draft will be reviewed l
before the final report. Many equipment items and lines in the Boron System have a atitiple function, such as the Charging Pamps which may also serve as the Eigh Pressure Safety Injection Pumps. It is quite possible that the same Event may have been reported for several systems.
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t Sylvan Cromwr A ril 26, 1979 f
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