ML20140D627
| ML20140D627 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 01/20/1986 |
| From: | OMAHA PUBLIC POWER DISTRICT |
| To: | |
| Shared Package | |
| ML20140D621 | List: |
| References | |
| TAC-58000, NUDOCS 8602030085 | |
| Download: ML20140D627 (5) | |
Text
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Attachment A Technical Report in Support of Plant Specific Approval to Use Code Case N-408 omaha Public Power District has identified two portions of piping system at the Fort Calhoun facility that cannot be examined per the requirements of the Section XI Code.
These sections run from containment isolation valves HCV-383-3 and HCV-383-4 to openings in containment and are a section of the safety injection recirculation piping.
(These sections are labeled as 24-SI-2001 and 2002 on the ISI isometrics).
These sections are embedded in concrete, and thus inaccessible for weld examination.
As can be seen from the attached copy of USAR Section 5.1.1, Attachment B, the peak containment pressure for design purposes is regarded as 60 psig and the peak containment temperature as 305'F.
This combination of temperature and pressure does not allow the buried sections of 24-SI-2001 and 24-SI-2002 (see attached ISI isometrics) to be exempted under IWC-1220(A) of the vinter 1980 addenda to the ASME Section XI Code.
Under normal operating conditions, however, (exclusive of a LOCA or main steam line break) the containment recirculation line is exposed to no water, no temperature greater than containment ambient, and no pressure greater than containment ambient.
The ability of the buried sections to perform their safety function, when needed, is therefore, never impaired by normal operation.
- Thus, the only conditions we are concerned about are those of the post-accident situation, which have been analyzed.
The con-clusions regarding that situation are summarized in USAR Section 6.2.1 as follows:
"A portion of the recirculation piping shown in Figure 6.2-3 is buried directly in concrete.
Under post-accident conditions compressive thermal stresses will occur in the pipe.
These thermal stresses will not cause failure of the piping since the stainless steel is a ductilo material and the stresses are compressive.
Reinforcing bars will absorb the tensile stress in the surrounding concrete."
The question of exempting open ended systems otherwise rated as Class 2 has been addressed in the ASME B&PV Code Case N-408 (approved by ASME, July 12, 1984) where the following Question is answered:
Inquiry:
When determining the components subject to examination and establishing the examination requirements for Class 2 piping under Section XI, what alternative exemptions to those stated in IWC-1220 and what alternative examination require-monts to those stated in IWC-2500, Category C-F may be used?
0602030005 060120 PDR ADOCK 05000205 p
PDH
Attcchm0nt A (continusd) i i
1 The following is extracted from the NRC reply:
Paragraph (a) (6) of the reply exempts piping and other components of any size beyond the last shutoff valve in open ended portions of systems (or portion of systems) of RHR, ECC, and CHR systems that do not contain water during normal plant operating conditions from volume-tric and surface examination requirements of IWC-2500.
Thus, plant specific approval to use this code case, will result l
in an exemption for the sections of the containment recircu-lation lines from HCV-383-3 and HCV-383-4 to the open ended portion of thuse lines in the containment.
Omaha Public Power District believes that the standard Appendix i
J (of 10 CFR 50) integrated leak rate testing, and the assoc-lated individual penetration Type C test (our test number l
ST-CONT-3) which covers the buried sections in question, constitute alternate testing which, when combined with the analysis presented above will assure the functional integrity of l
the system.
Additionally, OPPD examined the welds that are physically accessible from the I.D.
in the buried sections of the line during the 1985 refueling outage.
OPPD examined these welds using the VT-1 technique as described in the Section XI code (IWA-2211, Visual Exam, VT-1).
Also, if accessible, an examination has been made of the first weld outside of the buried sections, which is located in the " submarine hull" pene-l trations in Room 23.
Such inspection activities were discussed with the NRC in a telephone conversation on September 12, 1985.
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SECTION 5 STRUCTl:RES 5.1 CONTAINMENT STRUCTURE 5.1.1 General Description The containment structure (see Figures 5.1-1 and 5.1-2) is a rein-forced concrete pressure vessel partially prestressed, with cylindrical walls, domed roof and a bottora mat incorporating a depressed center portion for the This structure is lined with a steel membrane forming a continuous reactor.
steel envelope located at the inner surface of cylinder, roof and mat to prcvide a vapor-tight container. The structure is designed to safely withstand all internal and external loadings which can be expected to occur during the life of the plant. The design raaxirnum leak rate 12 0.2 percent of the containnent free volume over a 24-hour period at the destgn pressure of 60 psig and design tenper-ature of 305'f.
The containment structure nteel envelope encompasses internal rein-forced concrete which is independent of the cylindrical wall above the founda-tion raat. The internal concrete houses the reactor coolant system, and certain engineered safeguards componentn; it also provides localized biological shielding, and the required missile protection for the liner, engineered e.afeguards equipment, piping, and instrumentation and controls. The refueling cavity is also part of the internal concrete structure.
5.1.2 Structural Featuren, The contairunent structure i:: supported on steel piles driven to bed-rock located approximately 70 feet below grade.
The concrete foundation rnat is reinforced with high strength reinforc-ing steel and has a permanent access gallery extending under the containment structure directly below the cylindrical wall.
The cylindrical concrete wall is conventionally reinforced and is...
prestrenced by a system of post-tensioned tendona inclined at 45 degrees to c'ach side of the vertical and follouing a helical pattern in two directions. The w'all tendons terrninate at the top of the wall and at the underside of the raat within the access gallery.
The domed roof is conventionally reinforced and is prestressed by a three way post-tensioned tendon nyntem; in plan, the three groups of tendon:: are natually inclined at 120 degreen.
Tendons are placed in steel conduits which are filled with a waterproof grease to prevent corrosion. The anchors of all tendons are located so that they are accessible for innpection, tenting and retensioning at all times during the life of the plant.
A temporary opening wa ; provided in the cylindrical wall for the entry of major equipment ecmponent. into the containment. This opening was closed prior to the str:ssing of the tendons.
5.1-1 Attachment B
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