ML20012C947
| ML20012C947 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/14/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20012C945 | List: |
| References | |
| NUDOCS 9003260171 | |
| Download: ML20012C947 (4) | |
Text
. _ _ -
T.a.
1-
?*
f[p28;togfr (k UNITED STATES
_g NUCLEAR REGULATORY COMMISSION
- ( _1 g
/c t WASHINGTON, D. C. 20555
'u SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CONTAINFLNT LINER LEAK CHASE CHANNEL VLNllNG UNION ELECTRIC COMPANY CALLAWAY PLANT, UNIT 1 DOCKET NO. STN 50-483
1.0 INTRODUCTION
The leak chase channels which cover the containment liner welds are welded to the liner plate.
In the Callaway Plant's containment there are leak chase channels on the floor plate over all welds and on the liner wall covering some welds of the liner and liner reinforcing inserts. Many of the leak chase channels are not accessible and cannot be vented during a containment integrated leak rate test.(CILRT).
By letter dated February 23, 19?0, Union Electric Company (UE), the-licensee of the Callaway Plant, reouested the HRR staff to cualify that the combined liner butt weld along with the associated pre-tested channel fillet welds and leak test connections constitute the actual containment boundary in post-accident conditions.
Consequently, this forms the basis that if the leak chases are acceptable for retaining design accident pressure, performing CILRT with the test pluasinstalled(i.e.,theleakchasesarenotvented)willtestthecontain-ment boundary in its accident condition.
The licensee has provided additional supporting information via letters dated July 10, 1987, March 20, 1989 and September 29,-1989.
E.0 D!SCUSSION The staff has reviewed the licensee's submittals and the justification for not venting the liner weld leak chase channels during a CILRT or Type A tests.
It is the staff's position that the channels need not be vented if the licensee can demonstrate that:
(a) the channel welds are qualitatively equivalent to or better than those for the primary containment liner welds, (b) the channels would maintain their integrity when subjected to the loading conditions of a postulated design basis accident as well as during normal operation, and (c) the inspection and reporting of tests as required in 10 CFR Part 50, Appendix-J has been implemented.
9003260171 900314 PDR 'ACOCK 05000403 P
=
T. 3.0- EVALUATION The containment structure is designed to house the reactor coolant system and is referred to as the reactor building.
It consists of-a prestressed, reinforced concrete cylindrical structure with a hemispherical dome and a conventionallyreinforcedconcretebaseslabwithacentralcavityand instrumentation tunnel to house the reactor vessel. Principal nominal dimensions of the reactor building are as follows:-
Interior diameter 140 ft.
Interior height 205 ft.
Height to s3 ring line 135 ft.
q Base slab t11ckness 10 ft.
Cylindrical wall thickness 4 ft.
Dome thickness 3 ft.
Liner plate thickness 0.25 in.6 internal free volume 2.5 x 10 cu. ft.
.A carbon steel liner plate covers the entire inside surface of the reactor a
building (excludingpenetrations). The liner is 0.25 inch thick but is thickened locally around the penetrations, large brackets and major attachments.. The liner plate, including the thickened plate, is anchored to the concrete structure.
Leak chase channels and angles are also atteched at seam welds where the welds are inaccessible to nondestructive i
examination after construction.
I
.The containment liner of Callaway Plant is designed such that the majority-of pressure boundary welds are exposed to the containment atmosphere. No urids.in the dome are covered with leak chases; less than 2% of the welds on the containment shr11 are covered with leek chase channel, but almost I
all welds on the containment floor are covered. The containment floor is L
- inished with 18 inches of concrete which will protect these leak chases from.the effects of accident loading.
The original purpose of the leak chase channels was to have the ability to i
pressure test the liner plate or penetration welds for leaks without-pressurizing the full containment structure.
Since these leak chase channels are not to be vented during subsequent Type A tests, they are 1
l considered as an integral part of the liner plate and therefore a part of E
the leak-tight containment pressure boundary.
The licensee has conducted an investioation to assess the ability of the.
liner plate leak chase channel systems to function as an integral part of the containment structure leak-tight pressure boundary. This investigation included the following:
A.
Construction Records in an engineering analysis dated September 29, 1989, the licensee stated that til leak chases installed were leak tested during installation of the b
i
i i
T '
containment liner as per construction specification and the applicable ASME Code. All leak chase channels are a minimum of 3/16-inch channel or angle with 3/16-inch seal welds to attach to the liner plate. This construction is sufficient to retain the accident pressure of 48.1 psig. The leak chase channel system was installed by Chicago Bridge and Iron (CBI) as a nonsafety related portion of the containment liner also constructed by CBI. The fabri-cation and installation of the leak chase system was performed under the same construction specification as the fabrication and erection of the containment.
liner.
Since these channels were installed as nonsafety related, there are no weld control records that document the actual material used.
- However, where portions of the liner required repair (including the repair of channel),
the repair plan specified the welding material to be used. This material was consistent with the general notes regarding permissible weld rod types.
The construction specifications for the containment liner also specified that pro)er controls would be taken for the storage of welding rods to ensure t1at there was no decradation of the material. Again, there are no exceptions stated allowing lesser controls for the welding materie.1 that was to be used on the leak chases. Consequently, it is reasonable to believe that the same welding material used for the pressure boundary.ioints of the i
liner was used for the fabrication of the leak chase channel system.
The licensee has provided a copy of " Technical Specification for Furnishing, l
Febricating and Delivering Reactor Building Liner Plate for the Standardized Nuch r Unit Power Plant System (ENUPPS)" which has been used by the Callaway Plant. This document demonstrates the fabrication and.ouality assurance program of the plant.
B.'
Structural Analysis The leak chase channels were primarily used for pressure testing the liner l
plate or penetration velds for leaks without pressurizing the full containment structure and therefore were not designed as safety-related structural 1
members. Since the leak chase channels now become part of the containment wall af ter relocation of the pressure boundary and are therefore considered e structurel element, the strength of the channel box and its welds should l
be able to resist all load combinations involving the tested loads and the loads of a postulated accident, including seismic loads. The design of the I
leak chase channel should meet the applicable requirements of steel containments; i.e., either ASME. Boiler and Pressure Vessel Code,Section III, Division 1, Subsections NE.2000, 3000 and 4000 for class MC Components (1983) and l
American Institute of Steel Construction for the Design, Fabrication and L
Erection of Structural Steel for Buildings (1978), or whatever comparable l
code that was used in design and construction.
l I
I
~#~
p 1
The licensee responded to this question by providing an engineering analysis of the leak chase channel system by submittal dated September 29, 1989.
3x4.1 channels are used on walls and floor, 2x2x1/4 angles on floor corner joints,.and 1-3/4 x 1-3/4x3/16 on wall joint around the transfer tube. Each channel is analyzed for the following different load cases:
1., Pressure loading (Design pressure = 60 psig) 2.
Dead load and superimposed loads 3.
Occasional loads, including wind and seismic forces, on the containnent structure 4
Thermal stresses Designs of welded connections have also been analyzed._ All welds have low stresses. Since all welds are 3/16 inch, the minimum requirements for weld size are met.
Besed on the results of the structural analysis, the leak chases of'the contain-ment liner meet the design requirements of Subsection NE of the 1974 ASME B&PV Section III. Division 1 Code.
4.0 'CONCLUS10NS' On tre basis of the above evaluation, the staff concludcs that:
(a) the channel welds at the redefined pressure boundary are qualitatively equivalent to those for the primary containment liner welds and l
are acceptable, l~
(b) the channels are capable to withstand the loading conditions of a postulated design basis accident as well as during normal operation l
and maintain their structural integrity at all times.
We therefere concur with the licensee that it is not necessary for the Callaway Plant to vent the containment linct weld leak chase channels during-a CILRT, provided that the licensee commits to comply with the recuirements of 10 CFR Part 60, Appendix J, including a visual inspection of readily accessible areas prior to each subsequent Type A test.
~
j Principal Contributor:
S. Chan Dated:
March 14,1990 l
l l
L f-