Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors

complicated crap written in the full knowledge that ECCS dont work:

http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/part050-0046.html

UNITED STATES NUCLEAR REGULATORY COMMISSION

50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
(a)(1)(i) Each boiling or pressurized light-water nuclear power reactor fueled with uranium oxide pellets within cylindrical zircaloy or ZIRLO cladding must be provided with an emergency core cooling system (ECCS) that must be designed so that its calculated cooling performance following postulated loss-of-coolant accidents conforms to the criteria set forth in paragraph (b) of this section. ECCS cooling performance must be calculated in accordance with an acceptable evaluation model and must be calculated for a number of postulated loss-of-coolant accidents of different sizes, locations, and other properties sufficient to provide assurance that the most severe postulated loss-of-coolant accidents are calculated. Except as provided in paragraph (a)(1)(ii) of this section, the evaluation model must include sufficient supporting justification to show that the analytical technique realistically describes the behavior of the reactor system during a loss-of-coolant accident. Comparisons to applicable experimental data must be made and uncertainties in the analysis method and inputs must be identified and assessed so that the uncertainty in the calculated results can be estimated. This uncertainty must be accounted for, so that, when the calculated ECCS cooling performance is compared to the criteria set forth in paragraph (b) of this section, there is a high level of probability that the criteria would not be exceeded. Appendix K, Part II Required Documentation, sets forth the documentation requirements for each evaluation model. This section does not apply to a nuclear power reactor facility for which the certifications required under § 50.82(a)(1) have been submitted.
(ii) Alternatively, an ECCS evaluation model may be developed in conformance with the required and acceptable features of appendix K ECCS Evaluation Models.
(2) The Director of Nuclear Reactor Regulation may impose restrictions on reactor operation if it is found that the evaluations of ECCS cooling performance submitted are not consistent with paragraphs (a)(1) (i) and (ii) of this section.
(3)(i) Each applicant for or holder of an operating license or construction permit issued under this part, applicant for a standard design certification under part 52 of this chapter (including an applicant after the Commission has adopted a final design certification regulation), or an applicant for or holder of a standard design approval, a combined license or a manufacturing license issued under part 52 of this chapter, shall estimate the effect of any change to or error in an acceptable evaluation model or in the application of such a model to determine if the change or error is significant. For this purpose, a significant change or error is one which results in a calculated peak fuel cladding temperature different by more than 50 °F from the temperature calculated for the limiting transient using the last acceptable model, or is a cumulation of changes and errors such that the sum of the absolute magnitudes of the respective temperature changes is greater than 50 °F.
(ii) For each change to or error discovered in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or holder of a construction permit, operating license, combined license, or manufacturing license shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission at least annually as specified in § 50.4 or § 52.3 of this chapter, as applicable. If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with § 50.46 requirements. This schedule may be developed using an integrated scheduling system previously approved for the facility by the NRC. For those facilities not using an NRC approved integrated scheduling system, a schedule will be established by the NRC staff within 60 days of receipt of the proposed schedule. Any change or error correction that results in a calculated ECCS performance that does not conform to the criteria set forth in paragraph (b) of this section is a reportable event as described in §§ 50.55(e), 50.72, and 50.73. The affected applicant or licensee shall propose immediate steps to demonstrate compliance or bring plant design or operation into compliance with § 50.46 requirements.
(iii) For each change to or error discovered in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or holder of a standard design approval or the applicant for a standard design certification (including an applicant after the Commission has adopted a final design certification rule) shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission and to any applicant or licensee referencing the design approval or design certification at least annually as specified in § 52.3 of this chapter. If the change or error is significant, the applicant or holder of the design approval or the applicant for the design certification shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with § 50.46 requirements. The affected applicant or holder shall propose immediate steps to demonstrate compliance or bring plant design into compliance with § 50.46 requirements.
(b)(1) Peak cladding temperature. The calculated maximum fuel element cladding temperature shall not exceed 2200° F.
(2) Maximum cladding oxidation. The calculated total oxidation of the cladding shall nowhere exceed 0.17 times the total cladding thickness before oxidation. As used in this subparagraph total oxidation means the total thickness of cladding metal that would be locally converted to oxide if all the oxygen absorbed by and reacted with the cladding locally were converted to stoichiometric zirconium dioxide. If cladding rupture is calculated to occur, the inside surfaces of the cladding shall be included in the oxidation, beginning at the calculated time of rupture. Cladding thickness before oxidation means the radial distance from inside to outside the cladding, after any calculated rupture or swelling has occurred but before significant oxidation. Where the calculated conditions of transient pressure and temperature lead to a prediction of cladding swelling, with or without cladding rupture, the unoxidized cladding thickness shall be defined as the cladding cross-sectional area, taken at a horizontal plane at the elevation of the rupture, if it occurs, or at the elevation of the highest cladding temperature if no rupture is calculated to occur, divided by the average circumference at that elevation. For ruptured cladding the circumference does not include the rupture opening.
(3) Maximum hydrogen generation. The calculated total amount of hydrogen generated from the chemical reaction of the cladding with water or steam shall not exceed 0.01 times the hypothetical amount that would be generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react.
(4) Coolable geometry. Calculated changes in core geometry shall be such that the core remains amenable to cooling.
(5) Long-term cooling. After any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.
(c) As used in this section: (1) Loss-of-coolant accidents (LOCA’s) are hypothetical accidents that would result from the loss of reactor coolant, at a rate in excess of the capability of the reactor coolant makeup system, from breaks in pipes in the reactor coolant pressure boundary up to and including a break equivalent in size to the double-ended rupture of the largest pipe in the reactor coolant system.
(2) An evaluation model is the calculational framework for evaluating the behavior of the reactor system during a postulated loss-of-coolant accident (LOCA). It includes one or more computer programs and all other information necessary for application of the calculational framework to a specific LOCA, such as mathematical models used, assumptions included in the programs, procedure for treating the program input and output information, specification of those portions of analysis not included in computer programs, values of parameters, and all other information necessary to specify the calculational procedure.
(d) The requirements of this section are in addition to any other requirements applicable to ECCS set forth in this part. The criteria set forth in paragraph (b), with cooling performance calculated in accordance with an acceptable evaluation model, are in implementation of the general requirements with respect to ECCS cooling performance design set forth in this part, including in particular Criterion 35 of appendix A.
[39 FR 1002, Jan. 4, 1974, as amended at 53 FR 36004, Sept. 16, 1988; 57 FR 39358, Aug. 31, 1992; 61 FR 39299, July 29, 1996; 62 FR 59726, Nov. 3, 1997; 72 FR 49494, Aug. 28, 2007]
Page Last Reviewed/Updated Wednesday, September 19, 2012

Obvious breaches of the above which occurred at Fukushima Diiachi on a repeat basis across multiple reactors at the same site at approximately the same time:

1. “Water injection commenced, using the various systems provide for this and finally the Emergency Core Cooling System (ECCS). These systems progressively failed over three days.” The World Nuclear Association http://www.world-nuclear.org/info/fukushima_accident_inf129.html this breaches para 5 as follows : “(5) Long-term cooling. After any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.”

Media and industry attributed the formation of hydrogen gas to the reaction of zircalloy with oxygen in water. The resulting explosions in all three reactors involves breaches of : (b)(1) Peak cladding temperature. The calculated maximum fuel element cladding temperature shall not exceed 2200° F. AND
(3) Maximum hydrogen generation. The calculated total amount of hydrogen generated from the chemical reaction of the cladding with water or steam shall not exceed 0.01 times the hypothetical amount that would be generated if all of the metal in the cladding cylinders surrounding the fuel, excluding the cladding surrounding the plenum volume, were to react.

Further the reactor cores are reliably reported to be blobs at the bottom of the reactor. These blobs are not amenable to cooling. This breaches :

(4) Coolable geometry. Calculated changes in core geometry shall be such that the core remains amenable to cooling.

and

(2) Maximum cladding oxidation. The calculated total oxidation of the cladding shall nowhere exceed 0.17 times the total cladding thickness before oxidation. As used in this subparagraph total oxidation means the total thickness of cladding metal that would be locally converted to oxide if all the oxygen absorbed by and reacted with the cladding locally were converted to stoichiometric zirconium dioxide. If cladding rupture is calculated to occur, the inside surfaces of the cladding shall be included in the oxidation, beginning at the calculated time of rupture. Cladding thickness before oxidation means the radial distance from inside to outside the cladding, after any calculated rupture or swelling has occurred but before significant oxidation. Where the calculated conditions of transient pressure and temperature lead to a prediction of cladding swelling, with or without cladding rupture, the unoxidized cladding thickness shall be defined as the cladding cross-sectional area, taken at a horizontal plane at the elevation of the rupture, if it occurs, or at the elevation of the highest cladding temperature if no rupture is calculated to occur, divided by the average circumference at that elevation. For ruptured cladding the circumference does not include the rupture opening.

The industry, the regulators and the media have failed to explain to the public why the ECCS in the afflicted reactors failed so miserably in three short days. From the time possibility of destructive failure realised to be possible (1967) industry and regulators commenced spending years claiming that ECCS would prevent containment failure and melt down. This, despite counter claims from equally verse independent scientists. The regulations imposed upon ECCS performance however were implemented even though there had any demonstration that they were sufficient.

In March 2011 a full scale demonstration of the ECCS in three reactors took place in Japan and the ECCS failed to comply with the performance parameters guaranteed for them. Multiple core breaches occurred, multiple hydrogen explosions occurred, multiple cladding failures occurred, multiple meltdowns occurred despite the regulatory edict by industry and regulators that such would be highly probable. Yet these same consequences occurred at the same site to 3 reactors at the same time from the same triggers. The best ECCS in each reactor could do was to hobble along for less than 3 full days before expiring.

Improbable or not. It happened. So shut them all down. The above regulatory requirement defines how close a reactor can come to explosion, containment breach, and melt down. The mechanism which allegedly (but not actually) prevents this terminal sequence is the ECCS. The whole story has not been explained and noone in the cheap seats, including me, has any real idea of why the ECCS failed to meet the above criteria. All I can say is the very grave concerns which were raised between 1967 and 1975 and later by opponents to the cobbled assurances of the regulators described in a detailed predictive fashion what would happen to a stricken reactor if the ECCS didnt work. Well, it happened. And nothing, not a dot, has changed one iota. GE comes out in public and says “Fukushima was an error”. Well, they have 30 days to write up the freaking correction. According to the above.

Finally, it can said that no matter how inadequate the above regulations are, the ECCS failed to meet them. The reactors were allowed to approach too close to containment failure by regulations in the first instance. The ECCS is defined as an independent self powered set of systems which are integral and separate from vulnerable systems. If in fact the ECCS SHARED any vulnerable, the whole idea of an ECCS as a last line of defence against containment breach (AEC) is a false one. No authority has explained why the ECCS failed. If it is because of “loss of ultimate heatsink” that is completely inadequate as the ECCS is stand alone, last line and fully independent. Including its heat sink. It is a complete fudge to invoke a technical jargon term to cover up the loss and failure of 3 ECCS units in the course of a multiple reactor disaster where those ECCS units were guaranteed to prevent such disaster in the first place. What lessons have been learned and implemented as result of the ECCS failures? Have any reactors fitted with ECCS been taken off line because of this clear multiple failure of ECCS to work as promised since 1967 and each day since?

The objective of nuclear reactors is to boil water to turn a turbine. Why is it then deemed appropriate to define an internal temperature of over 2,000 degrees F? Water boils at 212. Double that. That’s all that’s needed.
See also:

http://www.nrc.gov/about-nrc/short-history.html#core-cooling

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