ML20012G676
| ML20012G676 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 03/08/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20012G675 | List: |
| References | |
| NUDOCS 9303110308 | |
| Download: ML20012G676 (6) | |
Text
.
s.
'o UNITED STATES
~,
l' 7,
NUCLEAR REGULATORY COMMISSION g
l wAssincrow. o. c. 20sss s.,.... /
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION DRYWELL PENETRATION AND REINFORCEMENT OF OPENINGS GPU NUCLEAR CORPORATION l
OYSTER CREEK NUCLEAR GENERATING STATION l
DOCKET NO. 50-219
- 1. 0 INTRODUCTION AND BACKGROUND As part of the Systematic Evaluation Program (SEP), the staff of the U.S. Nuclear Regulatory Commission (NRC) reviewed the design of the drywell penetrations and reinforcement of openings at the Oyster Creek Nuclear Generating Station (OCNGS), to ensure that this design met the requirements specified in SEP Topic III-7.B. " Design Codes, Design Criteria, Load Combinations, and Reactor Cavity Design Criteria."
In this review, the staff identified 28 specific areas of design code changes that may apply to 0CNGS and for which the current codes require substantially greater safety margins than did the earlier version of the codes, or for which no original code provision existed.
The staff documented review findings in Section 4.12 of the OCNGS Integrated Plant Safety Assessment Report (Ref-erence 1).
In a letter dated October 29,1986, (Reference 2), the staff issued its safety evaluation on GPU Nuclear Corporation's (GPUN's, the licensee's) submittal of June 4,1984, (Reference 3), and concluded that 25 of the 28 issues are resolved. The remaining three issues required further responses from the licensee.
These three issues were:
1.
Assessment of differences from current criteria for the reinforcement of openings (Reinforcement of Openings),
2.
Confirmation that cyclic analysis is not required for openings at OCNGS in accordance with the code exclusion criteria (Penetration Openings Subject to Cyclic Loading), and 3.
Evaluation of the drywell concrete subject to high-temperature and thennal transients.
On May 25, 1990, GPUN submitted its responses to these tnree issues (Reference 4).
This safety evaluation documents the findings of the staff's review of GPUN's responses to Issues 1 and 2 above.
Issue 3 above is being reviewed by the staff and the results will be provided in a separate safety evaluation.
2.0 REVIEW APPROACH This safety evaluation is based on the staff's review of GPUN's letter dated May 25,1990 (Reference 4), an audit conducted at GPUN's offices on July 11-12, 1990, including a review of GPUN's calculations (References 8 and 9) and a review of a followup GPUN memorandum regarding the concerns 9303110308 930308 PDR ADDCK 05000219
> raised during the audit (Reference 10). The NRC staff reviewed the calcu-lations to assess the acceptability of the original design in comparison with the current code requirements.* The staff examined specific areas of design code changes that apply to Oyster Creek to ensure the acceptability of the approach adopted in justifying the opening reinforcement. The staff reviewed samples of the calculations and discussed the detailed workings of the calculations.
/
3.0 REVIEW
SUMMARY
3.1 Reinforcement of Openings In the staff's October 29, 1986, letter (Reference 2), the staff concluded that the existing placement of the reinforcement is in accordance with current criteria for some openings but not for others. The staff based this conclusion on a review that Chicago Bridge & Iron (CBI) (Reference 5) conducted of the drywell penetration design performed in 1983 for GPUN.
This review indicated that 16 penetrations designed according to the original design criteria (Reference 6) did not satisfy the current criteria at that time.
In addition, the staff concluded that for those openings that do not meet the 1980 ASME Code,Section III, Subsection NE, GPUN shoula provide an assessment of the impact of the differences from the 1980 Code and their bases for the acceptability of the existing design.
This assessment should consider the loadings on the penetrations and the safety significance of failure. Table 1 lists the 16 penetrations that did not satisfy the 1980 Code.
Table 1.
Outstanding Issues Regarding Containment Penetrations Penetration Outstanding Issue i
X-45 Needs fillet weld (neck to shell)
X-41 Neck-to-shell weld size too small X-52 Detail not permitted by ASME Code 1980 edition X-17 & 37 Partial penetration weld of pad-to-shell X-19 X-7 X-11 X-23-27 & X-61 X-40 & X-47 X-42 & X-43 X-20A & B X-21, X-28-34 & X-36 X-62 X-44, 46, 59, 60 X-67 X-66 For the SEP evaluation, " current code requirements" referred to the 1980 Edition of the ASME Boiler & Pressure Vessel Code (hereinafter referred to as the ASME Code).
h
W Io assess the opening reinforcement and associated details, GPUN perfomed a more detailed reanalysis (Referenct 8).
The reanalysis covered all of the 16 penetrations to show that the present reinforcement meets the requirements of the 198C ASME Code.
Staff Evaluation i
In the staff's letter dated October 29, 1986, it was stated that for some openings, the existing reinforcements do not conform to Subsection NE-3330,
" Opening and Reinforcement" of the 1980 ASME Code.
Specifically, the size of the area replaced was insufficient to meet the standards in NE-3332, and the welding did not meet the standards specified in NE-3352, l
In response tn these concerns, GPUN developed alternative calculations to 1
l show that the existing reinforcement is adequate around the opening when l
l the actual stresses adjacent to the penetration area are taken into accuunt, j
GPUN developed a manual calculation method to determine the approximate load distribution caused by the internal p essure loading between the nozzle (pipe), the vessel shell, and the existing reinforcements. The
{
forces exerted on each component were calculated on the basis of relative j
"exibilities of the shell and the pipe ir. ;onjunction with the reinforce-i
/
ment. Using this method, GPUN calculated the stresses in the reinforcement and in the welded connections between the components.
I 1
l The licensee computed stresses manually using design formulas provided by l
t -
the 1980 ASME Code,Section III, Subsection NE, Subarticle 3300, 6nd also I
by standard engineering textbook methods (Reference 11).
The licensee's approach to qualify the existing reinforcement area and openings through
. )
analysis is acceptable as provided in subsubparagraph NE-3331(c).
The NRC staff reviewed the licensee's calculation (Reference 8) as a part of an audit conducted at the licensee's office on July 11-12, 1990. The l
staff also verified tha:. the appropriate loadings and load combinations were used. As a result, the staff found that the licensee's reanalyses provides a reasonable basis for concluding that the reinforcement of openings at the OCNGS satisfy the applicable design requirements of the l
1980 ASME Code,Section III, Subsection NE.
l 3.2 Penetration Openings Subject to Cyclic loadings The 1980 ASME Code, Sec. tion III, Subsection NE, requires a fatigue analysis for the cyclic loads unless the vessel shtisfies the exclusion criteria specified in subsubparagraph NE-3221.5(d).
In the NRC staff's letter dated October 29, 1986, the staff concluded that the licensee should confirm that all openings in the containment vessel for which the cyclic I
I analysis was not performed satisfy these requirements.
The fatigue exclusion criteria provided in subsubparagraph NE-3221.5(d) stipulate various conditions for the specified service loadings that must l
all be satisfied.
The service loading is calculated from the temperature profile through the penetration durirg a thermal transient and from the number of cycles that the containme< endured as a result of themal transients and pressure transient',. Thus, to meet the exclusion criteria
I
.,y I
- l requirements of NE-3221.5(d), a considerable amount of plant operational-l data are required for each penetration opening.
Because these dale are i
not available for a large number of penetrations at OCNGS, GPUN evaluated i
17 penetrations typical of high-temperature and pressure fluctuations l
connected to safety-related systems. Based on a review of data on system oesign conditions, GPUN determined that 5 of the.17 penetrations will envelope the remaining 12. The following is a list of penetrations selected for the fatigue evaluation:
.{
1.
Isolation or emergency condenser penetrations (X-5 A/B)
I 2.
Cleanup demineralizer penetration (X-10) 3.
Shutdown cooling penetration (X-7)
{
4.
Main steam penetrations (X-2A/B)
E.
CRD scram discharge hydraulic penetrations (X-13 A/B)
The licensee performed detailed calculations for these penetrations (Reference 9).
The calculations show that the service loadings on all of these penetration openings, with the excepti_ ' of isolation condenser i
penetrations (ICPs), satisfy the fatigue exclusion criteria provided in subsubparagraph NE-3221.5(o).
Staff Evaluation j
The staff reviewed the licensee's calculations (Reference 9) during an audit at the licensee's offices on July 11-12, 1990.
The staff found that the calculations provide a reasonable basis for concluding that the loadings meet the cyclic exclusion criteria of NE-3221.5(d) for the j
following penetrations:-
j i
1.
Clean up demineralizer penetration (X-10),
2.
Shutdown cooling penetration (X-7),
i 3.
Main steam penetration (X-2 A/B), and t
4.
CRD scram discharge hydraulic penetration (X-13 A/B) j i
Because the loadings on these penetratiors comply with NE-32?1.5(d), an analysis for cyclic service is not required.
On this basis, the staff I
concludes that the licensee's analyses adequately demonstrate that the i
cyclic design of these penetrations meets the applicable requirements 1
of the 1980 ASME Code,Section III, Subsection NE.
Because loadings on ECPs X-SA and X-5B do not satisfy all the requirements I
of the cyclic exclusion criteria NE-3221.5(d), the licensee performed an
- j analysis to demonstrate the adequacy of these two penetrations with respect'
)
to cyclic loading as required by subsubparagraph NE-3221.5(e) of the 1980 l
ASME Code,Section III.
For penetration ECP X-5B, the stress range during the most severe i
thermal transient loading is greater than the maximum allowable stress amplitude. Therefore, GPUN performed the calculatiem to comply with the
.equirements of NE-3228.3 (simplified elastic-plas 41vsis).- In
-l addition, GPUN has shown that the allowable _ number "S e cycles
(
(calculated in accordance with NE-3221.5(e) taking t..,
- i *evere thermal l
5
t t -
P transient as the service loading cy la) is greater than the number of stress cycles expected during the 40-year life of the plant.
In this calculation, the number of stress cycles corresponding to a less severe thermal transient was reduced to an equivalent number of stress cycles corresponding to the most severe thermal transient.
Based ca these considerations, the staff concludes that the cyclic design of penetration X-5B meets the applicable requirements of the 1980 ASME Code,Section III, Subsection NE.
Penetration X-SA is due for a modification in the next planned refueling outage which would reduce the stress cycle due to high energy line break (HELB) to a negligible amount.
Contingent upon successful completion of the modification and analysis, the staff considers the issue closed for this penetration.
4.0 CONCLUSION
Based on the results of the review and audit performed by the NRC staff, the staff concludes that the two issues associated with Section 4.12 of the Integrated Plant Safet) Assessment Report for Oyster Creek concerning reinforcement of openings and penetration openings subject to cyclic loading have been adequately addressed by the licensee. The staff's conclusion is based on a review uf the licensee's analyses as discussed in t
this safety evaluation.
For the reinforcement of openings in penetrations, the licensee adequately demonstrated in a detailed reanalysis comparing the area of reinforcement to the requirements of the 1980 ASME Code,Section III, Subsection NE, that all the 16 penetrations met the applicable design l
requirements of the 1980 Code.
For the reinforcement of openings subject to cyclic loadings, the licensee adequately demonstrated that the penetrations satisfied the cyclic design requirements specified in the 1980 ASME Code,Section III, Subsection NE.
On these bases, the staff considers the two issues concerning (1) reinforcement of openings and (2) penetration openings subject to cyclic loading to be closed.
r b
4 P
I I
5.0 REFERENCES
l (1) NUREG-0822, " Integrated Plant Safety Assessment, Systematic Evaluation Program, Oyster Creek Nuclear Generating Station," January 1983.
j (2) Letter, J. A. Zwclinski (NRC) to P. B. Fiedler (GPUN), "0yster Creek Nuclear Generating Station - NUREG-0822 Section 4.12 Design Codes, Design Criteria and Loading Combination," October 29, 1986.
(3) Letter, P. B. Fiedle 9 PUN) to D. M. Crutchfield (NRC), "SEP Topic
'e !
III-7.B," June 4, 1981 (4) Letter, J. C. DeVine (GPUN) to hRC, "IPSAR (NUREG-0822) Section 4.12, Design Codes, Design Criteria and Load Combination (SEP Topic III-7.B),"
May 25, 1990.
(5) Report on Additional Design Information for Oyster Creek Primary Containment Vessel (Drywell), Prepared by Chicago Bridge & Iron Company for GPU Nuclear Corporation, November 1983.
(6) ASME Boiler and Pressure Vessl Code,Section VIII, 1962 Edition.
(7) ASME Boiler and Pressure Yessel Code,Section III, Subsection NE, 1980 Edition.
(8) GPUN Calc. No. C-1302-187-5320-007 Revision 0, "Drywell Penetratio'n Reinforcement," November 8, 1989.
(9) GPUN Calc. No. C-1302-243-5320-042, Revision 0, OCNGS SEP Topic III.7.B " Penetration Fatigue", January 1,1988.
Appendices 6.4 and 6.5, pages 303A-303G, July 26, 1990, and August 8, 1990, respectively.
Revision 2 to Sheets 2 and 290, August 21, 1990.
(10) GPUN Internal Memorandum from J. H. Horton (GPU), to Y. Nagai (GPU),
July 26, 1990.
(11) Formulas for Stress and Strain, Fifth Edition, R. J. Roark (McGraw-Hill).
Principal Contributor:
T. Cheng Date:
March 8, 1993 i
l l
-