ML21314A015
| ML21314A015 | |
| Person / Time | |
|---|---|
| Site: | 07109337 |
| Issue date: | 09/11/2021 |
| From: | Ashley Ferguson Croft Associates Limited |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML21314A013 | List: |
| References | |
| Download: ML21314A015 (7) | |
Text
Croft Associates Ltd F4 Culham Science Park Culham, Abingdon Oxon, United Kingdom OX14 3DB T:
F:
E:
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+44 (0)1865 407740
+44 (0)1865 407449 info@croftltd.com www.croftltd.com 3979A O-ring NCT Test Temperature Reduction -
SARP Impact Document Reference CTR 2021/22 Issue A Date 09/11/2021 File Name Document1 Client Reference
3979A O-ring NCT Test Temperature Reduction -
SARP Impact CTR 2021/22 Issue A Page i Document Verification Title 3979A O-ring NCT Test Temperature Reduction - SARP Impact Project Number Document Reference CTR 2021/22 Revision Issue A Date 09/11/2021 First issue.
Compiled Checked Approved Name A L Ferguson I Dingwall A L Ferguson Signature Revision Issue Date Basis and details of change Compiled Checked Approved Name Signature
CTR 2021/22 Issue A Page 1 of 5 3979A O-ring NCT Test Temperature Reduction -
SARP Impact Figure 1 - Safkeg LS-3979A
CTR 2021/22 Issue A Page 2 of 5 3979A O-ring NCT Test Temperature Reduction -
SARP Impact Contents 1
Introduction.................................................................................................................... 2 2
References.................................................................................................................... 3 Tables Table 1 - NCT Temperature Reduction - SARP 3979A Safety Impact Assessment................ 4 Figures Figure 1 - Safkeg LS-3979A..................................................................................................... 1 1 Introduction The Safety Analysis Report for Package (SARP) design No. 3979A contains a requirement to perform thermal ageing tests on batches of the O-ring seals procured for the Containment Vessel, as specified Chapter 8, section 8.1.5.2 of the SARP (CTR 2008/10: Docket No. 71-9337 [1]). This test requirement identifies two separate tests:
The temperature of the O-rings shall be maintained for 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> at 150°C to 155°C for the 150oC test or for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> at 200oC to 205oC for the 200oC test.
2 Change Proposal Due to material test repeatability issues, as identified and discussed in Test Report CTR 2021/24 [2], the NCT 1000 hour0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> 150oC test is to be reduced to 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> at a slightly reduced temperature, 130oC (with the test performed between 130 to 135oC), however, the HAC test requirement will remain unchanged.
3 SARP Temperature Impact Assessment The impact on the SARP assessment of reducing the NCT temperature test requirement is considered and assessed in Table 1, addressing each reference to the use of the 150oC seal temperature limit identified within the SARP and assessing its impact, if any, on safety functions.
The conclusion of the assessment performed is that there are no safety issues related to this change proposal, all assessments performed in the SARP employ bounding temperature limits in terms of structural, thermal, containment and pressure assessments.
The maximum NCT temperature assessed in the SARP was 116.4oC, therefore the temperature reduction continues to provide a safety margin over actual operating temperatures.
CTR 2021/22 Issue A Page 3 of 5 3979A O-ring NCT Test Temperature Reduction -
SARP Impact 4 References
[1] Croft, CTR 2008/10, Safety Analysis Report Safkeg-LS Design No. 3979A, Revision 7.
[2] Croft, CTR 2021/24, LS 3979A (3980) O-ring Seal, Issue A, 2021.
CTR 2021/22 Issue A Page 4 of 5 3979A O-ring NCT Test Temperature Reduction -
SARP Impact Table 1 - NCT Temperature Reduction - SARP 3979A Safety Impact Assessment SARP Section Subject Reference location NCT temperature reduction Safety Impact Justification/Comments 2, Table 2-12 Mechanical Properties of SA-320/A320 Grade L43 Bolting Steel Page 2-22 None, used to provide an upper bound on material properties.
The reduced NCT temperature range fits within the temperature range listed 2.3.2 Examination.
Material Tests Page 2-24 None, the second paragraph describes the proposed tests The reduced temperature NCT test continues to provide a safety margin over actual NCT temperatures 2.7.1.1 End Drop, Containment Vessel Evaluation Page 2-50, 2nd para None, used to provide an upper bound on material temperatures.
The reduced NCT temperature range fits within the bounding temperature range assessed.
2.7.1.2 Side Drop, Containment Vessel Evaluation Page 2-53, 2nd para None, used to provide an upper bound on material temperatures.
The reduced NCT temperature range fits within the bounding temperature range assessed.
2.7.1.3 Corner Drop, Containment Vessel Evaluation Page 2-56, 2nd para None, used to provide an upper bound on material temperatures.
The reduced NCT temperature range fits within the bounding temperature range assessed.
3.1.3 Summary Tables of Temperatures, Table 3-2 Summary of Calculated Package Temperatures with 10 W Internal Heat Load under NCT Page 3-4 None, an arbitrary Containment vessel lid seal seal material temperature limit of 150oC is referenced in the last column The reduced temperature NCT test of 130oC continues to provide a safety margin over actual NCT temperature of 116.4oC.
3.1.3 Summary Tables of Temperatures, Table 3-3 Summary of Package Temperatures for HAC Thermal Test Page 3-5, Table note 1
None, discussed temperature excursions above NCT during HAC.
The note references an upper NCT temperature of 150oC, however, the HAC seal material test requirement remains the same, test at 200oC (the most recent tests are reported in CTR 2021/24 [2]).
3.2.2 Component Specifications Page 3-10, 7th para None, quotes manufacturers temperature ranges The reduced temperature NCT test of 150oC to 130oC continues to provide a safety margin over actual NCT temperature of 116.4oC.
CTR 2021/22 Issue A Page 5 of 5 3979A O-ring NCT Test Temperature Reduction -
SARP Impact SARP Section Subject Reference location NCT temperature reduction Safety Impact Justification/Comments The subsequent leakage tests performed after the 1000 hour0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> NCT (and HAC) test are significantly more searching than manufacturers data.
3.2.2 Component Specifications Page 3-11, 1st para None, quotes an arbitrary upper temperature limit of 150oC, much higher than actual NCT temperatures.
The reduced temperature NCT test of 150oC to 130oC continues to provide a safety margin over actual NCT temperature of 116.4oC.
4.1 Description of the Containment System, Page 4-2, 3rd para None, references an upper NCT temperature of 150oC, but actual temperature is 116.4oC The reduced temperature NCT test of 150oC to 130oC continues to provide a safety margin over actual NCT temperature of 116.4oC. The 200oC test continues to demonstrate acceptable performance at temperature excursions above 130oC, as reported in CTR 2021/24 [2].
8.1.5.2 Containment Vessel O-rings Page 8-3, 1st, 2nd and 6th paras None. This section lists the NCT and HAC seal material test requirement only, the revised NCT test temperature of 130oC for 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> ensures a reliable and repeatable material test.
As noted in the above assessments, reducing the NCT seal material test from 150oC to 130oC retails a sufficient safety margin over actual NCT temperatures. As noted in CTR 2021/24 [2], additional tests were performed at 140oC, demonstrating that there are no potential failures just over the revised NCT temperature limit.