ML20206T564
| ML20206T564 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 08/10/1989 |
| From: | Lyon W Office of Nuclear Reactor Regulation |
| To: | Hodges R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20206S598 | List: |
| References | |
| FOIA-99-28 GL-88-17, NUDOCS 9902110421 | |
| Download: ML20206T564 (12) | |
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fM/VKW W4J M /.J / O aW NOTE FOR:
R. Wayne Hodges, Chief Reactor Systems Branch Division of Engineering & Systens Technology THRU:
Robert C. Jones, Section Chief Reactor Systems Branch Division of Engineering & Systens Technology FROM:
Warren C. Lyon, Senior Reactor Engineer Reactor Systems Branch Division of Engineering & Systems Technology SUBJECTS NEED FOR COMPLETE COVERAGE OF PMENTIAL EVENTS BY EMERGENCY OPERATING PROCEDURES (EOPs)
The Salem loss of residual heat removal (RHR) event of May 20, 1989 again illustrated a continuing problem - that operators do not have suitable guidance for conditions that nay place their plants in Jeopardy. The Salem operators used two procedures to respond
- one dealing with loss of RHR under different conditions and another dealing with procedures developed under generic letter 88-17.
The procedures contained contradictory instructions and neither was appropriate for the situation, other situations also exist where coverage is inadequate, such as aspects of non-power operation, response to a loss of all AC power, LOCA outside containment, and severe accidents. Examination of generic emergency operating procedures guidelines and plant EOPs identifies additional problems. There are significant differences in what is covered and in what is being done about it between vendors and between licensees. It is time for us to take a clear leadership role to alleviate the difficulties. We should, in conjunction with industry, define coverage that is to be provided by EOPs and formulate a plan to provide that coverage. The Attachment provides some thoughts to initiate thinking.
I feel some urgency with this topic. For example, consider a large, unisolable LOCA outside containment. If this were to happen today in a Westinghouse plant, the operator probably would reduce operating safety injection (SI) systems to one train, and continue to try to run this one train until the refueling water storage tank was empty. This might flood all intermediate and low head SI pumps, as well as containment spray punps, eliminating their availability.
(Plant geometries are quite variable.) Core nelt could quickly follow. The same accident in Babcock and Wilcox and Combustion Engineering plants would probably find the operators without guidance. I doubt they would reduce SI injection rate in violation of existing procedures and training. In some plants, one could easily get into a situation of core melt with much of the water still remaining in the refueling water storage tank or its equivalent - something that to my knowledge has not been considered.
There are no simple solutions to the LOCA problem. One could throttle back on SI to what is needed to keep the core covered and prevent core danage, but this could fill the aux building with radioactive stekm.
Or one could compromise and try to maintain the break under some water. This udght control the steam f or a short time, and probably would reduce offsite releases. Perhaps a rapid depressurization of the reactor coolant system (RCS) could be acconplished to reduce or even eliminate the loss outside of containment.
I'm not aware of any FWR that has "all out" RCS depressurization procedures. Some of this would be plant dependent. And can anything be done about hydrogen control if a core melt is in progress to prevent or minindte an explosion an the aux building? I expect the answer is yes.
Have we realistically looked into reasonable hardware modifications in conjunction with procedures? 7dl of this would need to be carefully thought through. We don't, for example, want an inadvertent entry into a LOCA response procedure nor do we want an unrecognized increased likelihood of some other accident due to a hardware modification. The important point is that, t o my knowledge, we haven't really looked at this, much less come up with reasonable responses to extend the time to core melt, control consequences, or decrease the 2ikelihood of core melt.
KELLY 99-28 PDR a
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l Warren C. Lyon, Senior Reactor Engineer Reactor Systems Branch Division of Engineering & Systems Technology
Attachment:
As stated cc: A Thadani I
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ATTACHMENT i
CONSIDERATIONS IN COMPLETING EMERGENCY PROCEDURES GUIDELINES (EPGs)
AND EMERGENCY OPERATING PROCEDURES (EOPs) COVERAGE I.
s?Atus Ann wrrn EPGs and EOPs presently cover the more likely aspects of events originating from power operation and limited work is ongoing to address generic letter (GL) 88-17 topics. Some discussions have been held within industry to extend non-power operation, but this is not, to my knowledge, industry-wide. Certain potentially high-risk accidents are not i
covered. EPGs and EOPs must be expanded to cover all operation, consistent with a philosophy that operators should never be forced into a position where they have no guidance.
I'll discuss EOPs in the remainder ~of this attachment. The discussion is 1
applicable to both EPGs and EOPs.
The depth and quality of EOPs is inconsistent. This should also be corrected.
(This is, in part, a result of our failure to adequately coordinate guidance and review of EPGs.)
II.
EXISTING WEAKNESSES Specific examples are provided in this section. This is not a recommendion for a procedure that necessarily addresses each. Excellent guidance from the TMI action plan was to use symptom oriented procedures. This should continue to be a primary ob]ective, supplemented by more specific guidance where sensible.
A.
Power coeration Existing ' holes" in EOPs for power operation must be closed. This includes:
1.
LOCA outside containment.
Much thinking is that this LOCA will lead to core melt.
This is not correct. Mitigation strategies are possible, and need exploration.
Procedures must be provided which, at worst, extend the time between initiation and core nelt. Minor (realistic) hardware changes may also be significant contributors to handling this accident. I am convinced that reasonable improvements can be l
achieved that will reduce this LOCA risk.
2.
ceveraoe ef containment.
We haven't given as much thought to containment coverage in EPGs and EOPs as is warranted. For example, venting philosophy and practice must i
be realistically addressed that includes the real strengths and limitations of containments.
l 3.
station blackout. EOP philosophy has always been that coverage is not lindted to i
plant capability as defined in the regulations. Station blackout is no exception, I
and operator guidance should be provided that covers conditions if power is not recovered during the time covered by the station blackout rule. Of course, the EOPs must cover the time as determined by the rule.
4.
Severe accidents. We identified the need for extending EOP coverage in the 1983 j
Babcock and Wilcox (B&W) safety evaluation report covering their EPGs. This need j
still exists.
5.
Steam eenerator tube ructure. A consistent approach needs to be developed that balances retaining control of the plant against release of radioactive naterial.
The problem is greatest with B&W plants.
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6.
Other safety sienificant areas.
Loss of instrument air, non-nuclear instrumentation, and similar conditions are of safety significance and need to be addressed. Initial emphasis on procedures may be best, with follow-up on reascnable hardware improvements.
B.
Non-Power creration i
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l Is In the non-power area, coverage of lowered inventory operation in PWRs is being partially addressed under the recommendations of generic letter 88-17.
The remainder of lowered inventory operation has not been comprehensively addressed by the staff or by industry.
EOP SCOPE AND DEVELOPMENT GUIDANCE A.
Scene of EOPm EOPs apply any time a barrier to release of radioactivity is in jeopardy or potentially in jeopardy.
There are three such barriers: the fuel cladding, the reactor coolant
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system pressure boundary, and the containment.
B.
EOP Entry cnnditions Entry is required whenever an item A condition occurs.
1.
Power eneration.
Entry is required for reactor trip, existence of conditions for which a reactor trip is necessary, and for a forced (unplanned) shutdown condition.
l Operators may enter EOPs at any time they judge the need exists.
2.
. Mon-cower eneration.
Entry criteria must be developed. During conditions where operation of decay heat removal (DHR) systems is appropriate, entry into EOPs might be required for conditions such as unplanned loss of a DHR system, failure to achieve DHR when an initiation attempt is made, and upon exceeding a pre-determined safety parameter limit such as temperature or water level.
C.
EOP Frit criteria EOPs may be exited when use of non-emergency procedures is appropriate. The EOP entry criteria, as appropriate, and violation of safety function criteria contained in EOPs still apply. If such criteria are violated, then EOPs are reentered.
Rarely, considered expert guidance may be used in place of pre-prepared EOPs. Alncst
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always, such guidance should be based upon newly prepared EOPs that apply to a rare, i
unique situation that could not be reasonable foreseen. Advice from the technical i
support center is not a substitute for adequate EOPs.
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D.
Deeth of covermae Coverage should be sufficient that operators do not have to deviate from the EOPs or invent major guidance regardless of the event.
CONTINUE WORKING FROM HERE 4.
Station blackout. EOP philosophy has always been that coverage is not lindted to j
the plant capability as defined in the regulations.. Station blackout is no exception, and operator guidance should be provided that covers conditions if power is not recovered during the time covered by the rule. Of course, the EOPs also must cover the time as determined by the rule.
5.
CoAtainment. Containment should be covered since it is one of the three barriers to release of radioactive material that I identified early in this talk.
6.
Severe accidents. We originally identified the need for extending EOP coverage in the 1983 B&W SER covering our review of ATOG. We anticipate a Commission policy a
statement soon that will provide guidance on this topic.
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Loss of instrument air, non-nuclear instrumentation, and other conditions. Some of 7.
our people are quite concerned that safety significant events can occur that involve such areas as instrument air.
I share this concern and believe appropriate coverage i
should be p;ovided. I don't believe it is important whether such procedures are called emergency procedures or some kind of plant procedure. What is important is i.
that they adequately cover the situation, that they interface properly with other e
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t EOPs and plant procedures, when necessary, and that they are consistent with a symptom oriented philosophy.
I have discussed a number of topics related to EPGs and their incorporation into EOPs.
Please remember that these are often my thoughts and I have tried to share some of our preliminary thinking with you. These do not always represent official staff policy.
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Assumptions Used by B&W to Calculate Dose Consequences of SGTRs Five transient configurations were discussed at th November 16,eeting.
The assumptions used in these analyses, and the dose conse cr.c;s e listed i
below:
Assumptions used for all transients:
1.
Fraction of failed fuel at start of transient - 0.05%.
Will perform calculations using range of failed fuel fractions (up to at least 0.1%
failed fuel) in subsequent analyses.
2.
29.2 factor on the Iodine spike occurs over 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 3.
For steaming to the condenser, used 50% Grand X/4 4.
For steaming through an ADV, used Chimney-effect X/4 5.
Wherever possible, used worst case X/q for chimney effect
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6.
Used most limiting plant site of B&W plants (Rancho Seco before SMUD shut down), then used next worst plant site (thought it might be TMI-1).
Assumed TMI-1 ground X/q was the most limiting. Will check and use k
worst case in future calculations.
7.
Assumed reactor operated long enough to achieve equilibrium fission product inventory 8.
Assumed that all of released fission productr. were at ground level at the Exclusion Area Boundary 9.
None of the fission products plated out in the plant (no DF) 10.
All Iodine released from fuel, still have Iodine in coolant in first 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> 11.
No credit for purification systems 4
12.
Partition factor of 10 in thE Condenser.
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l B&W performed the following analyses:
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I Case 1 - Historical SGTR -
i Assumptions RCPs not tripped (6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to DHR) 100 gal / min constant leak rate
)
Steamed to condenser 1
Dose at EAB - 0.4 mrem thyroid Case 2 - Double-Ended SGTR Assumptions RCPs not tripped (6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to DHR) 400 gal / min initial flow, flow rate a function of time after SGTR Steamed to condenser Dose at EAB - 0.5 mrem thyroid Note:
~B&W calculated the doses for both steaming the affected steam generator and isolating the affected steam generator for the first two cases. The differential increase obtained by steaming the affected steam generator was 0.3 mrem thyroid and 1.5 nRem whole body.
Case 3 - Double-Ended SGTR i
Assumptions
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Two loops on natural circulation cooldown (20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> to DHR) 400 gal / min initial flow, flow rate a function of time after SGTR Steamed through ADVs Dose at EAB - 900 mrem after 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />
't Case 4 - Double-Ended SGTR Assumptions Affected loop on t.C cooldown (50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> to DHR)
Affected loop steaming through ADV 400 gal / min initial flow, flow rate a function of time after SGTR Dose at EAB - 1 Rem thyroid after 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> i
Note: The whole body doses for the first 4 cases were less than 3 mrem Case 5 - Double-Ended SGTR with stuck open MSSV and water-solid SG j
Assumptions Affected SG initially isolated Ground level X/4 400 gal / min initial flow, flow rate a function of time after SGTR Dose at EAB - 7+ Rem thyroid, 6+ mrem whole body after 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> Futdre Plans - SGTR 1.
Will conduct analyses using other fractions of failed fuel (up to 0.1%)
2.
Recognizes the need for specifying bounding points for use of alternate cooling strategies.
3.
Will review E0Ps to see how they compare with the TBD.
4.
Will change TBD to reflect new TRACC limits (changing from 10CFR100 limits to l'OCFR20 limits).
5.
Will put recommendations for SGTR recovery into the TBD.
6.
Will provide tables, charts, etc. to assist operators.
7.
Will provide clear guidance for operators.
8.
Will account for individual plant configurations for determining times to limits.
l 9.
Expect to have followup meeting sometime between Thanksgiving and Christmas.
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Future Plans - TBD 1.
Ist Quarter of 90 RCS voiding & RCP restart Reestablishing NC from BCM f
l HPI cooling 2'.
3rd Quarter Statipn blackout text l
guideline review session with OSC j
Basis guidelines i
3.
4th Quarter Make Revs to TBD to benchmark E0P guideline 4.
Ist Quarter of 91 LOOP rev - guidelines Loss of HPI w/SBLOCA or LOFW guideline into TBD l
5.
3rd Quarter RCP restart w/ voids guideline 1
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