ML20209B410
| ML20209B410 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1999 |
| From: | Wen P NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| PROJECT-692 NUDOCS 9907060464 | |
| Download: ML20209B410 (8) | |
Text
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June 30, 1999 MEMORANDUM TO: FILE FROM:
/s/ Peter C. Wen, Project Manager Generic Issues, Environmental, Financial and Rulemaking Branch Division of Regulatory improvement Programs Office of Nuclear Reactor Regulation
SUBJECT:
DISCUSSION TOPICS FOR JULY 13,1999 MEETING WITH CE OWNERS GROUP REGARDING CE NPSD-1041, " JOINT APPLICATION FOR HPSI SYSTEM TECHNICAL SPECIFICATION MODIFICATIONS" The attached message was faxed today to Ray Schneider of the CE Owners Group (CEOG).
The sole purpose of the message is to prepare CEOG personnel for an NRC/CEOG meeting to be held on July 13,1999. The message itself does not constitute a formal request for information or represent a formal staff position; the message will be included in the meeting summary.
Project No. 692
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SUBJECT:
DISCUSSION TOPICS FOR JULY 13,1999 MEETING WITH CE
. OWNERS GROUP REGARDING CE NPSD-1041, " JOINT APPLICATION FOR HPSI SYSTEM TECHNICAL SPECIFICATION
' MODIFICATIONS"
. The attached message was faxed today to Ray Schneider of the CE Owners Group (CEOG).
The sole purpose of the message is to prepare CEOG personnel for an NRC/CEOG meeting to be held on July 13,1999. The message itself does not constitute a formal request for information or represent a farmal staff position; the message will be included in the meeting
- summary, Project No!692
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j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001 49 * * * * *,o June 30, 1999 MEMORANDUM TO: FILE FROM:
Peter C. Wen, Project Manager d C.
Generic issues, Environmental, Financial and Rulemaking Branch Division of Regulatory improvement Programs Office of Nuclear Reactor Regulation
SUBJECT:
DISCUSSION TOPICS FOR JULY 13,1999 MEETING WITH CE OWNERS GROUP REGARDING CE NPSD-1041, " JOINT APPLICATION FOR HPSI SYSTEM TECHNICAL SPECIFICATION MODIFICATIONS" The attached message was faxed today to Ray Schneider of the CE Owners Group (CEOG).
The sole purpose of the message is to prepare CEOG personnel for an NRC/CEOG meeting to be held on July 13,1999. The message itself does not constitute a formal request for information or represent a formal staff position; the message will be included in the meeting summary.
Project No. 692
Attachment:
As stated cc w/att: See next page
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l CE OWNERS GROUP' Project No. 692 '
cc:
Mr. Gordon C. Bischoff, Project Director CE Owners Group ABB Combustion Engineering Nuclear Power M.S. 9615-1932 2000 Day Hill Road Post Office Box 500 Windsor, CT 06095 Mr. Ralph Phelps, Chairman CE Owners Group Omaha Public Power District P.O. Box 399 Ft. Calhoun, NE 68023-0399 Mr. Ian C. Rickard, Director Nuclear Licensing ABB Combustion Engineering Nuclear Power 2000 Day Hill Road Post Office Box 500 Windsor, CT 06095 Mr, Charles B. Brinkman, Manager Washington Operations ABB Combustion Engineering Nuclear Power 12300 Twinbrook Parkway, Suite 330 Rockville, MD 20852
NRC CommentsIQuestions on CE NPSD-1041." Joint Apolication for HPSI System Technical Specification Modifications" to be discussed on 7/13/99 NRCICEOG Meetina i
CE NPSD-1041:
1.
Page 10 states "Many CE PWRs include three (3) HPSI pumps... " Two will meet licensing requirements. Why is an AOT relaxation necessary?
2.
Numerous qualifiers are provided in the writeup that weaken an argument that a generic approach is satisfactory. The above item 1 is an example. Page 14 provides another 4
example when it states ",.. a work plan is typically developed for completing the associated maintenance within an acceptable period that is normally shorter than the duration of the AOT." (Emphasis added.) Please address the implications of such i
statements with respect to existing and to requested AOTs.
3.
Much of the justification on Page 16 appears to reflect weakness in spare parts availability and plar,ning. Extending AOTs is not the correct solution.
4.
Mean times to repair on Page 18 vary from plant-to-plant and information is provided for half of the plants. Page 32 et. al. shows a wide variation that underscores the plant specificity of this issue.
5.
The statement of need on Page 19 provides two examples. Are there more? If so, how many and of what types?
6.
The CRMP requires ecternal event consideration, but Page 27 states "For consistency in comparison or (sic) results, Core Damage Frequencies (CDFs) presented represent internal events only." All contributors should be included or it should be shown that the omitted ones are not significant. Many of the CDFs presented on Page 32 et al illustrate this point since they are significant, but do not include potentially significant contributors.
7.
Page 27 states "In a PSA, the CDF is obtained using mean unavailabilities for all standby-system components." This is insufficient because the outliers could dominate.
At the least, such an assumption should be backed by sensitivity / uncertainty studies.
This problem is repeated on Page 30 in that mean downtime for corrective maintenance and preventative maintenance is used.
8.
Much of the AOT-allowed operation involves human involvement. There is no human error component to the described PRA work.
9.
Some of the risk results are questionable. For example, on Page 32 et al, the Palisades 4
mean downtime is shorter than most, but the increase in CDF is 10 / reactor-year. This is not uactly acceptable, and CDF would likely increase if downtime were longer or more initiators were included.
10.
Page 43 references NUREG/CR-6144 plant operating states and results. These results were so distorted by initial assumptions that they were not usable and were ignored when the contractors went on to the Phase 2 part of the study.
ATTACHMENT
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11.
Page 43 states "The methodology for evaluating transition risk makes use of the existing 1
full power PSA models with minimum changes beyond changing component failure rates and initiating event frequencies. This methodology calculates a transition risk that is realistic with respect to the known elements of transition risk and to the calculation of the risk of remaining at power." Aside from the previously identified limitations of the modeling, this modeling approach may not yield good transition results unless careful consideration is given to the unique aspects of transition problems. The discussion starting on Page 46 clearly establishes that this was not done. On the "plus" side, most I
of the error is a significant underprediction of transition CDF which leads to underprediction of the potential benefit of remaining at power.
l Concerns related to the May 3.1999 CEOG fetter:
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1.
Page 8 states "It is conceivable that steaming may be provided in Mode 5." The reactor coolant system temperature in Mode 5 is < 200 *F. How is steaming achieved when below 200 *F?
2.
Page 9 states " Entry into low temperature Mode 5 operation will invoke LTOP procedures... (which) increase.s the risk of a leak or LOCA... " (This " message"is repeated many times later, including attempted justifications for Mode 4 operation where LTOP is described as not needed.) LTOP procedures are entered prior to this.
3.
Pane 9 states " Technical Specifications restrict removal of safety equipment in Mode 4.
These restraints are largely lifted upon entry into Mode 5. Thus Mode 4 provides a mechanism for greater operational control." This " message"is repeated. A licensee operating under a philosophy that the TS provide sufficient coverage for safe shutdown operation is not operating safely - and no one operates this way.
4.
Page 9 states " SIT (safety injection tank) operability is also required (in Mode 4)." SITS must be isolated from the reactor coolant system (RCS) before RCS pressure reaches SIT pressure. Some CE SITS are roughly at 600 psi; others around 200 psi. Obviously, SIT operability is not required when RCS pressure approaches or goes below SIT pressure. It cannot be " required"in M9de 4 since one often operates with RCS pressure below that of the SITS. (Note there may be a few exceptions when SIT pressure is reduced as RCS pressure is reduced.)
5.
Page 9 states " Entry into Mode 5 will result in potential unavailability of all ECCS injection capability..." CE licensees committed to providing ECCS injection capabikty in asponse to GL 88-17.
6.
Page 11 states "An important insight that has resulted from these (licensee) PSAs is j
that the incremental risk of core damage associated with the inability to implement HLI j
(hot leg injection) is primarily due to an operator error or unavailability of necessary j
realignment valves, not unavailability of the HPSI pumps." These PSAs do not consider such failure modes as throttle valve erosion. Have such modes been addressed in CE plants and, if so, what were the findings?
7.
Page 11 states "Because HLI is proceduralized and sufficient time is available to perform this action..., unavailability of HLI for an otherwise successfully mitigated event is of low probability," How is HLI via HPSI pumps achieved if the pumps are not available?
F 8.
Page 14 states "The operation of one HPSI and a SIT can maintain the Appendix K criteria during a design basis large LOCA scenario." Please explain how this result was obtained.
9.
Page 19 states "Thus, even with the increased AOT flexibility, the frequency of occurrence of longer duration HPSI system maintenance that would fully disable a HPSI train beyond that already allowed currently by the Technical Specifications, is small."
What is the rationale leading to this conclusion?
10.
Page 19 states "The Conditional CDP of the full 7 day AOT is sufficiently low (between 4 x 10" to 6 x 104..) so as to not present a significant risk to the public." 6 x 104 is not sufficiently low especially when one considers the initiators that were omitted from the calculations.
11.
Page 20 states "As with the current technical specifications, Safety Margins are not affected by removing the HPSI from service." Please explain.
j 12.
Page 21 states "Since CE plants have relatively low pressure HPSI pumps, unavailability of HPSI rarely contributes to a high pressure core damage scenario (since for high pressure sequences HPSl flow could not be injected into the RCS)." CE plant HPSI pumps have shutoff heads ranging from 1200 to 2300 psig. The upper end is not a "relatively low pressure." How many high pressure sequences are avoided if HPSI is used before pressure exceeds the pump shutoff head?
13.
The large early release discussion starting on Page 54 contains a number of difficulties or potential difficulties, including:
a.
Containment bypass via ruptured steam generator tubes resulting from severe accident conditions do not appear adequately identified.
b.
Page 55 states "HPSI piping failure due to exposure to the full RCS pressure is very low. Therefora, no change in the ISLOCA frequency is expected." In light of the Wolf Creep event, pipe breaks are not the concern. Mistakes and valve failures are. Discuss further.
c.
Page 55 states "...the ISLOCA will progress into early core damage regardless of HPSI availability." This fails to recognize the contribution HPSI can make to preventing core damage while actions are taken to mitigate the ISLOu d.
Page 55 states "Thus, the impact of the unavailability of HPSI in respondin6 o a t
SGTR event on core damage frequency is expected to be small." Provide further justification.
e.
Page 55 states "Between 50 and 90% of the core damage sequences from CE PWRs are dominated by RCS transients that occur at high pressure." This has not been substantiated. (External events? Shutdown operation?)
f.
Page 55 states "Thus, increased unavailability of the HPSI system.. is expected to have a negligible to small impact on the large early release frequency (LERF) for CE PWRs with PORVs." HPSI is an important contributor to prevention of core damage, as is specifically stated on Pages 57 and 58. However, there is no discussion to address those plants without PORVs.
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s g.
Page 56 states "The fraction of the CDF due to HPSI pump unavailability leading to a high pressure core damage state is typically less than 20% for CE PWRs" l
This does not appear to be consistent with the Page 39 and 40 information and the related discussion.
h.
The Pages 57 and 58 discussion of compensatory measures is good, but there is no commitment that licensees will follow it. The maintenance rule will provide some of this, but the staff doesn't understand what ensure the remainder.
14.
The LOCA discussion of Page 60 completely misses the actual problems. It falls back on the historic picture of pipe rupture as opposed to the realistic valve and operator -
associated problems. This carries into the Pages 61 and 62 discussion, where a philosophy of not using LTOP is expanded. Such statements as "... the use of this end state... avoid the potential that other systems... will be deliberately or inadvertently placed in a degraded condition while repairs are being performed on the inoperable HPSI subtrains." Further, the quoted material appears to say that the risk-informed approach, the maintenance rule activities, and outage plans and implementation will be ineffective.
SUMMARY
i 1.
The calculated results, which omit potentially significant contributors, sometimes result in CDFs that exceed the guidelines.
2.
The material seems to contain numerous questionable and inaccurate statements, assumptions, and calculated results.
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