B12902, Assessment of Reverse Direction Testing of Containment Isolation Valves
| ML20153B759 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 05/31/1988 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20153B723 | List: |
| References | |
| B12902, NUDOCS 8805060073 | |
| Download: ML20153B759 (12) | |
Text
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Docket No. 50-245 112H2 I
Attachment 2 Millstone Unit No. 1 Assessment of Reverse Direction Testing of Containment Isolation Valves i
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i May 1988 i
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i PDR8805060073 880502 P ADOCK 05000213 i
Attachment 2 B12902/Page 1 Assessment of Reverse Direction Testina of Containment Isolation Valves at Millstone Unit No. 1 In response to Inspection Report No. 50 245/87-18,II) a review of local leak rate tests (LLRTs) conducted at Millstone Unit No. I disclosed that the following containment penetrations and associated valves are subjected to reverse direction tests.
Penetrations Valves Reverse Direction Tested X-7A through 70 MS 1A through - ID X-8 HS 5 X-14 CU 2 and CU-2A X-25 AC-7 and AC-9 X-26 AC-5 X 202 AC-Il and AC-12 X-205 AC 3A, AC-38, and AC 6 X 211A & B LP-14A and - 148 X-10A IC-1 X-llA IC-4 X-12 50 1 The following valves can be eliminated from further concern with regard to the subject issue (reasons for elimination are provided in parenthesis):
o MS 1A through ID, MS 5, CU 2 and 2A, and LP-14A and 148 (these valves are all inside containment; packing leakage on reverse direction tested containment valves installed inside containment can not result in a breach of containment; see Figure 2).
o 10-1, IC 4, and SD 1 are not containment isolation valves (1C 2. IC-3 SD-2A, and SD-2B are considered the containment isolation valves in these closed loop systems; in addition, all of these valves are inside containment).
The remaining valves were checked for seat orientation during plant walkdowns. In all cases, it was concluded that the installations put actuator shaft seals, body to bonnet joints, or double 0 ring flange seals on the containment sides of these valves. These orientations do not permit these potential containment isolation boundaries to be leak checked during reverse direction LLRTs. Consequently, all of the following valves are subject to the concern discussed in Reference (1): AC 3A, AC 3B, AC-5, AC-6, AC-7, AC-9, AC-II, and AC-12.
Reversing the orientations of AC-3A, AC-3B, AC-5, AC-6, AC-7, AC-9, AC-II, and AC-12 will alleviate most of the concerns of Reference (1). Such re orientation will move actuator shaft seals and body to bonnet joints into LLRT pressurization boundaries. The bolted joints on the containment sides (1) W. V. Johnston letter to E. J. Mroczka, "Inspection No. 50 245/87-18,"
dated September 23, 1987.
Attachment 2 B12902/Page 2 of these valves will still be omitted by reverse direction testing. The affected Allis Chalmers butterfly valves (AC 3A, 3B, 5, 6, 7 and 11) have testable double 0 ring seals on both of their mounting faces. Performance >
of leakage tests on these seals (only potential containment boundary omitted by LLRT) will satisfy the requirements of Appendix J. The DeZurik plug valves (AC 9 and AC-12) have untestable gasketed mounting joints. These joints on the containment sides of these valves are leakage checked during integrated leak rate tests (ILRTs). These gasketed joints are no different than any other mechanical piping joint and are not subject to the LLRT ,
requirements of Appendix J.
Finally, it must be realized that reversing all of the valves subject to the NRC's concern to include actuator shaft seals does not meet Appendix J reverse direction testing conservatism criteria. This is because test pressure would tend to force the valve discs into their seats, which could improve their leak tightness. But DBA pressure would tend to force the discs away from their seats, which could result in more leakage than measured during reverse direction LLRTs.
The effect of system pressure on closing force and sealing can be accounted for in a valve's design. If the closing compressive force is large enough, sealing will be achieved regardless of the additive or subtractive effects of system pressure. This seems to be the case at Millstone Unit No. I since NNECO has tested atmospheric control system butterfly and plug valves of these types in all possible combinations of orientation and direction of pressuriz6 tion with consistent results (see Attachment 2A). In fact, the only test trend identifiable in historical data is that the soft seats in these valves deteriorate over several cycles of plant operation. Notice, on Attachment 2A, that there are no significant differences shown in the ranges of leakage measured for valve groupings AC-4, 5, 6 and 17 and AC 7 through 12 before 1980 and after 1980. The year 1980 is significant because it is the year in which valves AC 5, 6, 7, 9 and 12 were turned around to assure conservatism in reverse direction LLRTs.
Conclusion Based on the discussions provided above, NNECO proposes the following as a means of resolving the NRC's reverse direction LLRT concerns:
o Valves AC-3A, AC 38, AC 5, AC 6, AC-7, AC-9, AC-II, and AC-12 could be removed and turned around to include actuator shaft seals in LLRTs.
This could be performed during the next two refueling outages, a schedule consistent with our requirement to replace all the seats in the butterfly valves within this group (six of the eight) every two outages, o NNECO has proposed exemption from the requirements of Appendix J to permit reverse direction testing of three of the valves (AC 5, AC 6,
Attachment 2
.B12902/Page 3 and AC-7) to be turned around.(2) Additional exemption requests will be submitted to permit reverse direction testing of AC-3A, AC 3B, AC-7, AC-9, AC-11, and AC 12.
o The testable 0 ring seals on the containment sides of valves AC 3A, AC-38, AC-5, AC 6, AC-7, and AC-Il will be leak tested. Results will be reported steps with other have already beenAppendix J Type incorporated in B theand C test report 4 ffsults.
These of the 1987 refueling outage Appendix J test results, i
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l (2) E. J. Mroczka letter to U.S. Nuclear Regulatory Comission "Integrated Safety Assessment Program Topic Nos.1.14, ' Appendix J Modifications,'
and 2.33, 'RBCCW Leak Rate Testing'," dated April 29, 1988.
(3) E. J. Mroczka letter to W. T. Russell, "Reactor Containment Building j Integrated Leak Rate Test," dated November 20, 1987, f
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Docket No. 50 245 Illiu i
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a Attachment 2A i
Millstone Unit No. 1 Atmospheric Control System
. Containment Isolation Yalve Leakage History 3
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i May 1988 i
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. Attachment 2A
,812902/Page 1 MILLSTONE I ATMOSPHERIC CONTROL SYSTEM CONTAINMENT ISOLAT1QH VALVE LEAKAGE HISTORY Test Results o
The results reported are given in units of standard cubic feet per hour (scfh).
o Results are reported by atmospheric control (AC) system valve grouping; all valves in a grouping are tested simultaneously, o
The acceptance criterion for each valve grouping has varied from 18.8 scfh to 19.95 scfh due to impacts of torus configuration modifications, o Befor e 1984, "as found" AF results were not reported to the NRC; results in previous years a(re )"as left" (AL) unless otherwise indicat o
Most of these valves had excessive leakage in 1972 and 1976 that necessitated soft seat replacement; seats were replaced in AC-3A AC-8, AC-10, and AC-12 in 1987 as part of a NNECO commitment to change o,ut all AC system CIV soft seats every two refueling outages; additional seat maintenance may have been performed in other years- this was not researched because it was not necessary to compare the results shown, o
AC 2A and 2B are vacuum breakers tested simultaneously with AC 3A and 3B; since their leaka are listed here. ge is included with that reported for AC-3A and 38, they AC System Valve Grounino Test ltE AC-4. 5. 6. 17 AC-7 thru 12 AC-2A and 3A AC-2B and 3B 1972 6 (AL) 14.5(AL) --- - - -----
1973 6 14 1 3 1974 5 10.3 0 0 1975 5.8 14.75 0 1976 0 11.7 (AL) 6.8(AL) 0 0 1978 2.54 8.96 .85 1979 0.49 .42 6.25 2.97 2.55 1980* 5.23 (AL) 1982 5.60(AL) .63 1,56 16.32 2.62 4.60 1984 7.12 17.35 (AF & AL) 13.20(AF&AL) 1.05 (AF & AL) 1985 .19 (AF & AL 1.06 (AF & AL) 8.78 (AF & AL) .01 (AF & AL) .22 (AF & AL) 1987 .89(AF&AL)) 5.45(AL) .37(AF) .40 (AF & AL)
(AFindeterminate)
- Indicates year AC 5, 6, 7, 9 and 12 were turned around
,. . Attachment 2A
.812902/Page 2 Direction of Test Pressurization / Valve Tvoe o Direct pressure test is denoted as "DP'.
o Reverse direction pressure test is denoted as "RP".
o If test pressure tends to force the valve disc into its seat, the notation ' DIS' is used, o Years in which the test configuration is applicable are provided in parenthesis;e.g.(19821987).
Valve UDestr_lgtion Test Confiouration AC-3A/Allis Chalmers, butterfly RP, DOS,(1972-1987)
AC-3B/Allis Chalmers, butterfly RP, DOS,(1972-1987)
AC-4/Allis Chalmers, butterfly DP, DOS (1972-1987 AC-5/A111s Chalmers, butterfly RP, DOS I 1980 1987 AC-6/Allis Chalmers, butterfly RP, DOS I ,;1980-1987 AC-7/Allis Chalmers, butterfly RP, DOS I AC 8/Allis Chalmers, butterfly DP,OlS(;19801987) 1972-1987)
AC-9/De2urik, plug RP, DOS,(19801987)
Valve #/0escriotion Test Confiauration AC-10/Allis Chalmers, butterfly AC-11/Allis Chalmers, butterfly DP, DOS,I;197219871972 RP, DOS, I 1987)
AC 12/De2urik, plug RP, DOS, (,19801987 AC-5/Allis Chalmers, butterfly RP, DIS, I,1972 1979 AC 6/Allis Chalmers, butterfly RP, DIS, I;1972-1979l l AC-7/Allis Chalmers, butterfly RP, DIS, i AC 9/De2urik, plug 19721979 RP, DIS, i,1972 1979)
AC-12/DeZurik, plug RP, DIS, I,19721979)l AC-17/Allis Chalmers, butterfly DP, DIS,(1972-1987)
B12902 Sealingmechanism(e.g., packing)onthis shaft is outside of the test pressure boundary; but, it is exposed to post accident pressurization.
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[arrowsshowsealing surfaces l ~' ' *~ ,
Direction of Post + +
Accident containment g'V'F5' pressurization (i.e., Direction this is the containnent Test si.de. of the valve) ,
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'. # Pressure I
Section of An Eccentric Plug Valve (in closed position)
Figure 1: Illustration of lias an Ac:uator Shaf t Sc-1 0 .e., nackinc..
Can be Excluded f rom a W7 verse Directie. Le# iest I
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l Shaft seal leakage; this leakage is either fluid released to the containment atmosphere or is
' containment atmosphere leaking into the piping system (i.e., double headed arrows imply flow can be in either direction).
These arrows show the "true containment boundary" within I
this valce.
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This side of the valve 1
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faces toward the outside of containment; this side of the valve is pressurized Post Accident .--ge. during a reverse direction Pressure Appendix J Type C test.
6e Section Of A Closed Eccentric Plu_g_ Valve
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Figure __2: Illustration of How Leakage Past reverse Pressure Tested Valves can Not Result in a Breach of Containment (for valves installed inside containment).
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Figure 3: Figure of a Valve Similar to DH-TV-1843 %'
(difference is in flanged ends versus weld ends).
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3 c{h DH.A0V-554 (also called
' DH-TV-554) has body internals
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Containment side of valve ,
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- hhI : : direction of flow
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Containment side of valve ha I ,t i 1!')
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neveru spring paphreem W" Figu r e_. 5 : Figure of Valve similar to WC-TV-1845.